Research Projects in Medical Sciences

A Cognitive Approach to Refine and Enhance Use of a Dental Diagnostic Terminology

Faculty: Elsbeth Kalenderian, DDS, MPH, PhD
Funder(s): National Institute of Dental and Craniofacial Research

The purpose of this study is to develop standardized and uniform diagnostic dental codes with distinct terms and synonyms that are easy to use, intuitive, and inclusive and that can be loaded in the electronic health record currently in use by 50 dental schools nationwide.

Research Projects in Medical Sciences

Assessing Patient Safety in Dentistry

Faculty: Elsbeth Kalenderian, DDS, MPH, PhD
Funder(s): OHPE Department

A variety of expensive and largely ineffective methods have been used in medicine to identify AEs, including chart audits and malpractice claims review. There is little knowledge about the type and frequency of adverse events (AEs) in dentistry, with particularly a dearth of information in academic settings. The goal of this research was to 1) assess patient safety culture of faculty, hygienists, students and staff from three dental schools, 2) analyze FDA MAUDE (Manufacturer and User Facility Device Experience) database that represents device-related AE reports, and 3) conduct trigger chart reviews to identify AEs that may occur in academic dental settings.
Overall, our adapted Medical Office Survey on Patient Safety Culture showed that dental settings rated ability preventing AEs as excellent/good at 31% while medical settings rate themselves at 64%.
Analysis of MAUDE (1994-2011) revealed 2,017,966 AEs, of which 29,427 were related to dental devices (1.45%). Of those, 72 (0.24 %) resulted in death, 20,139 (68.44 %) in injury and 7003 (23.80%) caused malfunction. Endoesseus implant-related devices were linked to the majority (61%) of the AE reports. 
Three triggers (I&D, failed implants, multiple restorative providers) were used as part of an electronic chart review tool. In total 87 charts were triggered, of which 54 were positive for one or more AEs. Most AEs caused temporary harm, but nine were considered to have caused permanent harm.
Our results suggest the need for dental institutions to improve the patient safety culture; focus on devices that may cause AEs; and the use “triggers,” or clues, to identify AEs from chart reviews may be a promising method for measuring the overall level of harm from care.
References
1. Taichman, R.S., et al., Prospective identification and skeletal localization of cells capable of multilineage differentiation in vivo. Stem Cells Dev, 2010. 19(10): p. 1557-70.
2. Agency for Healthcare Research and Quality, Medical Office Survey on Patient Safety Culture, J. Sorra, M. Franklin, and S. Streagle, Editors. 2008, Agency for Healthcare Research and Quality: Rockville, MD.
3. Gurtcheff, S.E., Introduction to the MAUDE database. Clin Obstet Gynecol, 2008. 51(1): p. 120-3.
4. Institute of Medicine, Crossing the Quality Chasm. A New Health System for the 21st Century. 2001, Washington: National Academy Press.
5. Leape, L.L., et al., Reducing adverse drug events: lessons from a breakthrough series collaborative. Jt Comm J Qual Improv, 2000. 26(6): p. 321-31.
6. Jha, A.K., et al., Identifying adverse drug events: development of a computer-based monitor and comparison with chart review and stimulated voluntary report. J Am Med Inform Assoc, 1998. 5(3): p. 305-14.
7. Resar, R.K., J.D. Rozich, and D. Classen, Methodology and rationale for the measurement of harm with trigger tools. Qual Saf Health Care, 2003. 12 Suppl 2: p. ii39-45.
8. Chambers, D.W., Risk management. The Journal of the American College of Dentists, 2010. 77(3): p. 35-45.
9. Trigger tool for measuring adverse events.  01/23/2012]; Available from: www.ihi.org.

Research Projects in Medical Sciences

Development of an Inter-University Oral Health Research Database

Faculty: Elsbeth Kalenderian, DDS, MPH, PhD
Funder(s): NLM G08 grant opportunity PAR-07-236

There is a paucity of high-quality large oral-health databases that can be used to conduct research. Many dental schools in the United States, Canada, and Europe have implemented or are about to implement electronic health records (EHRs). EHRs facilitate the secure storage and retrieval of health histories, diagnoses, procedures performed, student evaluations, billin, and other administrative data. There is an unprecedented opportunity to integrate these disparate data sources that are being collected in dental schools throughout the United States into a secure, de-identified repository that can be used to help research our most pressing oral-health problems. The dental schools participating provide an ideal resource for the establishment of an oral-health research database: the schools are geographically distributed; the patient population is generally underserved and of lower socioeconomic status; the schools all utilize the same electronic software system and standardized dental procedure codes. The study’s objective is to establish a consortium of dental schools in the United States, Canada, and Europe that actively share data from EHRs for clinical research. In the research, a pilot study was conducted to determine the feasibility of integrating data sources from three dental schools in the US.

The majority of dental schools in North America use the same EHR system (AxiUm, Exan Corporation, Vancouver, Canada). At their international users meeting, a group of researchers came together and agreed to share de-identified data from each institution. As a result, the Collaboration on Oral Health-Related Informatics (COHRI) was formed. Data was pooled between three institutions as a proof of principle study.

Tufts University School of Dental Medicine, the University of Texas Dental Branch at Houston, and the University of California, San Francisco, pooled demographic and health-history data from all new patient encounters, comprehensive examinations, and periodic oral examinations from predoctoral dental clinics at each institution from 8/1/06 to 7/31/07. Demographic and oral-health data were integrated into one large relational database.

 

Research Projects in Medical Sciences

Biogenesis of extracellular matrix

Faculty: Bjorn R. Olsen, MD, PhD
Funder(s): NIH/NIAMS

The long-term goal of these studies is to understand the cellular and molecular mechanisms that control bone development and homeostasis. During the past funding period, significant progress has been made in identifying the multiple roles of vascular endothelial growth factor (VEGF) in skeletal development. These roles include serving as chemotactic factor for vascular invasion into cartilage models of future bones, serving as survival factor for chondrocytes in hypoxic regions, promoting matrix production by osteoblasts and chondrocytes and stimulating osteoclast formation and migration. Through the use of conditional targeting techniques for cell-specific inactivation of VEGF and VEGF receptor genes in mice (Aims 1 and 2), the work proposed is aimed at identifying the cellular mechanisms by which VEGF exerts its skeletal functions. Experiments using inducible, conditional targeting strategies to inactivate both VEGF and VEGF receptors are also planned to find out whether VEGF is required for postnatal skeletal growth and homeostasis. In studies of a mouse model for cherubism, a genetic disorder in humans, the investigators seek to identify mechanisms in myeloid cells that are important for regulation of macrophage/osteoclast differentiation. Based on extensive studies of mice in which the most common mutation in cherubism families has been knocked into the mouse gene, the investigators believe that cherubism is a hematopoietic disorder and that mutant myeloid progenitor cells are hyper-responsive to cytokines that stimulate differentiation to macrophages and osteoclasts. Through a combination of in vitro and in vivo studies (Aim 3) the signaling pathways that are affected by the cherubism mutations will be identified. Bone marrow cells from control and cherubism mutant mice will be compared in cell signaling studies of osteoclast formation in vitro. In vivo studies of the mutant mice will test the hypothesis that the mutations in cherubism cause a combination of molecular gain-of-function and loss-of-function effects. The outcomes of the proposed work will provide insights into cellular mechanisms of bone formation and resorption that are altered in skeletal disorders of excess bone formation and inflammatory bone loss.

Research Projects in Medical Sciences

Collagen gene structure and expression

Faculty: Bjorn R. Olsen, MD, PhD
Funder(s): NIH/NIAMS

The long-term goals of this project are to gain insights into mechanisms by which extracellular matrix components contribute to assembly, maintenance and function of vascular and epithelial tissues. The work is focused on a component of basement membranes, the specialized structures that separate epithelial and endothelial cells from underlying connective tissues. This component, collagen XVIII, interacts with other basement membrane constituents and receptors on adjacent cells via one of its domains, endostatin. In humans, recessive mutations resulting in loss of collagen XVIII/endostatin cause Knobloch syndrome. Knobloch patients have abnormalities that include high myopia, vitreoretinal degeneration, retinal detachment and midline defects in bones of the skull; some patients have imaging abnormalities in the brain suggesting defects in neuronal migration. We have generated a mouse model of Knobloch syndrome and identified developmental and age dependent defects in eyes leading to dysfunction of retinal pigment epithelial cells and progressive loss of vision. Laser-induced choroidal neovascularization in mutant eyes is significantly enhanced compared to control eyes. Systemic administration of endostatin, normally released from collagen XVIII and circulating in blood, reduces the neovascularization response in mutant animals to that of controls; increasing endostatin levels in control animals also suppresses the response. A combination of cell biological, biochemical and genetic approaches are proposed to further study the mechanisms by which collagen XVIII supports the functions of epithelial and vascular endothelial cells. Molecular and functional changes in retinal pigment epithelial cells caused by loss of collagen XVIII will be characterized. Studies of mouse lines generated to restrict excision of the Col18a1 gene to retinal pigment epithelial or vascular endothelial cells will address the question of whether abnormalities in Knobloch patients and mice lacking collagen XVIII are caused by loss of collagen XVIII in eye tissues or are consequences of systemic effects. Experimental cell biological and genetic strategies will be used to determine by what process loss of collagen XVIII leads to accumulation of protein deposits behind the retina similar to what is seen in age- dependent macular degeneration. Genetic strategies will test hypotheses of how interactions between cell surface receptors and endostatin affect angiogenesis. The work is likely to generate not only new insights into mechanisms by which collagen XVIII/endostatin maintains retinal pigment epithelial function and a basis for therapeutic strategies for patients with Knobloch syndrome, it also will add significantly to broader efforts aimed at developing/refining anti-angiogenic therapies in diseases such as age dependent macular degeneration and cancer.

Knobloch syndrome, improve clinical management of age-dependent macular degeneration, and suppress angiogenesis-dependent disease processes such as cancer.

Research Projects in Medical Sciences

BMP-3 signaling in the formation and regulation of bone

Faculty: Vicki Rosen, PhD; Laura W. Gamer, PhD
Funder(s): NIH/NIAMS

Although research on the bone morphogenetic proteins (BMPs) has expanded exponentially over the past decade, we actually know very little about the physiological roles that individual BMPs play in the skeleton. Our decision to focus this proposal on role the BMP3 in bone is based on several important findings. First, although BMP3 is the most abundant BMP in bone, accounting for 65% of the total BMP protein stored in bone matrix, little is known about its biology. A second reason for our interest in BMP3 are recent reports that correlate changes in BMP3 levels in vivo with fracture healing, mechanical loading of the skeleton, and the loss of endogenous bone formation with age. Finally, and perhaps most intriguing is our observation that BMP3 knockout mice display an unequivocal bone phenotype without a change in skeletal patterning. At five weeks of age, the total trabecular bone mass of BMP3 knockout animals is twice that of their wild-type littermates, demonstrating that BMP3 is a negative regulator of bone mass. In vitro, BMP3 is able to exert an inhibitory effect on osteoblast differentiation in the presence of potent osteogenic stimuli. The signaling pathway used by BMP3 to negatively regulate bone mass has not yet been identified. As osteogenic BMPs are now therapeutic agents used to augment bone formation in thousands of patients each year, understanding how BMP3 exerts its regulatory effects on bone mass has wide ranging clinical significance. In this proposal, we will: investigate what the lack of BMP3 signaling does to the formation, growth and maintenance of the skeleton (SA1); examine the effects of increased BMP3 expression on the formation, growth and maintenance of the skeleton (SA2); dissect the BMP3 signaling pathway (SA3), and define the function of BMP3 in regulating bone formation in the periosteum and bone collar (SA4). It is our belief that the information we obtain as a result of our experimental plan will be key to understanding how individual BMPs, alone and in combination with one another, function in skeletal patterning, bone formation, and the maintenance of bone mass.

Research Projects in Medical Sciences

BMP-2 regulation of bone homeostatis

Faculty: Vicki Rosen, PhD; Laura W. Gamer, PhD
Funder(s): NIH/NIAMS

Bone morphogenetic proteins (BMPs) were identified as potent bone forming agents based on their ability to induce de novo bone formation in adult animals and this unique feature of BMP activity has led to use of BMPs as therapeutic agents in bone repair. It has also generated intense interest in defining the role endogenous BMPs play in the skeleton. Removal of individual osteogenic BMPs (BMPs 2, 4, 5, 6, 7) during embryonic development shows that loss of any individual BMP can be compensated for by the other BMPs present. Mice in which combinations of osteogenic BMPs have been removed display a variety of skeletal phenotypes, consistent with idea that individual BMPs work in concert during skeletal development to provide the appropriate levels of BMP activity. BMP activity is also required to maintain normal bone function in adults, and increasing the levels of BMP antagonists in bone leads to osteopenia, bone fragility and spontaneous fracture.  Our recent data showing that loss of BMP2 from the limb skeleton leads to pervasive spontaneous fractures in the postnatal mice (Tsuji 2006) identifies BMP2 as a primary participant in skeletal homeostasis in adults. In this proposal, we hypothesize that BMP2 is required for skeletal homeostasis because it has a unique spatial and temporal expression pattern in the postnatal limb skeleton and so cannot be compensated for by other BMPs.  We address this hypothesis in three specific aims. In SA 1 we create a mouse in which the BMP2 gene is replaced by a visual reporter, providing a precise way to follow BMP2 expression. In SA 2 we investigate the role of BMP2 in maintaining the bone marrow stromal cell microenvironment that is required to support osteoblast differentiation in the adult skeleton. Loss of BMP2 would be of greater consequence if BMP2 were required for maintenance of the bone marrow stromal microenvironment that allows for osteoblast differentiation. In SA 3 we characterize the requirement for BMP2 in Wnt-mediated osteoblast differentiation. Loss of BMP2 would be of greater consequence if BMP2 were required for optimal Wnt signaling in bone. Completion of the experimental plan will allow us to define the role of BMP2 in bone homeostasis.

 

 

Research Projects in Medical Sciences

Molecular Rationale for the Use of BMP2 in Bone Regeneration

Faculty: Vicki Rosen, PhD
Investigators: Giuseppe Intini, ITI fellow
Funder(s): ITI Foundation

With the major goal of describing the BMP2-dependent molecular mechanisms leading to bone regeneration, Dr. Intini will utilize the Bmp2c/c;Prx1:cre mutant mice, which display a limb specific inactivation of Bmp2, to identify the genetic networks, the signal pathways, and the target genes that are specifically activated in the presence of BMP2. Dr. Intini will take advantage of new molecular technologies such as individual mRNA barcoding, ChIP-on-Chip, and ChIP-seq analyses. The discovery of the molecular mechanisms associated with the activation of BMP2 will suggest novel strategies for bone regeneration therapies whereby BMP2 may be administered together with other factors such as Platelet-Derived Growth Factor (PDGF) or Platelet-Rich Plasma (PRP). Because BMP2, PDGF, and PRP are presently available to periodontists, oral surgeons, and orthopaedic surgeons the outcome of this study may lead to more effective treatments in orthopaedics and dentistry.

Research Projects in Medical Sciences

Potential of a novel alginate-hydrogel scaffold as a platelet derived growth factor delivery system

Faculty: David M. Kim, DDS, DMSc
Funder(s): Osteology Foundation

Research Projects in Medical Sciences

T-regulatory cells in periodontitis

Faculty:
Funder(s): NIH/NIDCR

The goal of the proposed project is to elucidate the roles, mechanisms and features of a recently discovered immune suppressive T cell subset, T regulatory (Treg) cells, in the context of periodontal pathogenic adaptive immune responses (PPAIR). Treg cells are distinct from T effector cells (Th1-, Th2- or Th17-cells) based on their profiles of cytokine production (IL-10 and TGF-2) as well as their expressions of a unique transcription factor, FOXP3, and concomitantly expressed CD25. Importantly, Treg cells are known to suppress adaptive immune responses occurring in autoimmune and infectious diseases and in many other immune-response related outcomes. Thus, upon successful characterization of Treg’s molecular-immunological mechanisms, via our mouse model of periodontal disease (PD), we will have gained the understanding required for future human clinical trials. This translational strategy should lead to the development of novel drug-free and side- effect-free therapeutic approaches to the treatment human periodontal bone loss and tissue destruction, as well as other immune-associated oral diseases. One such approach, UV illumination, is summarized below. The pathogenic involvement of adaptive immune response was demonstrated by our recent discovery that the osteoclast differentiation factor, RANKL, is distinctively expressed by activated T cells and B cells in gingival tissues with periodontal disease, but not by these cells in healthy gingival tissues. We recently found that the prevalence of FOXP3 expression by CD25+ T cells, which do not express RANKL, was significantly lower in human gingival tissues with periodontal disease than in healthy tissues. Based on a mouse model of periodontal disease, our preliminary studies indicated that adoptive transfer of CD25+ Treg cells, which were ex vivo-expanded with Treg developing factor, TGF-2, could ameliorate the periodontal bone loss induced by PPAIR induction, as well as inhibit in vitro antigen-specific proliferation of Th1 effector cells and their production of RANKL. These conclusions have, in turn, led us to speculate that UV illumination in general, and UVB illumination in particular, could have a novel therapeutic use in the treatment of periodontal disease. That is, since UVB is used to augment the Treg cell population in the treatment of psoriasis, a skin disease hypothesized to be immune-mediated, then the same technique should up-regulate TGF-2 expression in mouse gingival epithelium, resulting in an increase of FOXP3+/CD25+ Treg cells in the gingivae. Such a previously optimized research platform will permit us to elucidate the as yet unstudied roles, features and mechanisms of Treg cells in the context of periodontal disease. Therefore, in the proposed project, we will investigate 1) the requirement of antigen specificity by Treg cells in their suppression function to PPAIR-induced bone resorption, 2) the roles and mechanisms of Treg cells on the regulation of PPAIR- induced periodontal bone resorption; and 3) the development of a promising phototherapeutic approach to PD, which utilizes the phenomenon of Treg induction by gingival UV illumination. PROJECT NARRATIVE: Our studies will generate empirical data confirming the prevalence and activity of a recently discovered immune suppressive lymphocyte subpopulation, T regulatory cells (Treg). To date, the immune suppressive function of Treg has only been sparsely studied, and its roles, mechanisms, and features, in terms of periodontal pathogenic adaptive immune response (PPAIR), have not been studied at all. Therefore, the proposed project will employ both a mouse model of periodontal disease, as well as periodontally diseased human gingival tissues, to illuminate our understanding of the commonalities between mouse and Treg-mediated immune intervention in the pathogenesis of PD. To the extent that these results are translational, we can begin to develop novel therapies. One such promising therapeutic modality is the application of phototherapy, in the form of UVB illumination, to the lesions of diseased tissue. This is the key therapeutic strategy that forms the foundation of our study. Augmentation of Treg-activity is implicated in the treatment of psoriasis by UVB illumination. Thus, we believe that the trials we plan for our mouse in vivo model will prove equally effective in inducing human in vivo Treg and thereby possibly ameliorating the bone destructive effects of PPAIR.

Research Projects in Medical Sciences

Innovative Mouse Model to Study Parathyroids and an Application to Human Disease

Faculty: Beate Lanske, PhD
Funder(s): NIH/National Institute of Diabetes and Digestive and Kidney Diseases

Parathyroid glands produce parathyroid hormone (PTH), one of the most important regulators of calcium and phosphate homeostasis, and of bone metabolism. FGF23, secreted from bone, is another crucial regulator of phosphate homeostasis. Recent data have suggested a bone-parathyroid axis in which FGF23 and PTH regulate each other; however, the existing data are contradictory and require clarification. Progress in understanding the molecular regulation of parathyroid cells is very slow because no cell line exists, the glands are very small, and in vivo molecular analysis is almost impossible. Since dysfunction of the parathyroid gland leads to severe consequences such as soft-tissue calcification, fragile bones, chronic renal failure, myopathy, cardiac dysfunction, hematological abnormalities, rickets, and osteomalacia, a new approach is needed to address this question.

The overall goal of this proposal is to generate an innovative and unique mouse model with a retroviral receptor stably expressed on the surface of parathyroid cells. This mouse can then be induced to express different genes including siRNAs exclusively in the parathyroid glands through simple intraperitoneal injection of retroviral constructs. Targeting different genes alone or in combination to the parathyroids is then possible without the need to generate new transgenic mice for each construct. We will also apply this new model to a specific genetic form of hypoparathyroidism (HP). Novel heterozygous mutations in GCMB were identified in two families with a genetic, autosomal dominant form of hypoparathyroidism that have a dominant-negative effect (dnGCMB). We will express either wild type or dnGCMB in the parathyroids to identify its role in postnatal parathyroid glands.

Understanding the actions of GCMB might help in the development of therapeutic agents affecting parathyroid gland function and thus could be used for a wide range of diseases, including primary hyperparathyroidism, a much more common disorder than HP, and secondary hyperparathyroidism related to chronic kidney disease. This innovative in vivo model will not only help us understand the regulatory network in the parathyroid glands but will serve as a useful model for similar research in other systems.

Research Projects in Medical Sciences

In Vivo Analyses of Fibroblast Growth Factor-23 Function

Faculty:
Funder(s):

A major focus of our research is to determine the roles and interactions of key molecules controlling mineral homeostasis, particularly phosphate homeostasis. Phosphate is essential, not only for signaling and energy metabolism, but also for normal skeletal growth and development. Disturbances in phosphate homeostasis can affect the functional activities of almost any organ system.

Despite its wide biological importance and significance, the regulation of phosphate homeostasis is not yet clearly understood. Recent studies have identified a number of molecules that have phosphaturic activities, including fibroblast growth factor-23 (FGF-23, a circulating phosphaturic factor), frizzled-related protein 4 (FRP4), and the matrix extracellular phosphoglycoprotein (MEPE). Among these newly identified molecules, only FGF-23 has been implicated in various human diseases, including autosomal dominant hypophosphatemic rickets (ADHR), autosomal recessive hyposphosphatemic rickets (ARHR), X-linked hypophosphatemia (XLH), oncogenic osteomalacia (OOM), chronic kidney disease, and familial tumoral calcinosis (FTC).

We are using genetically altered mouse models to modulate FGF-23 actions in order to determine (1) the in vivo mechanism of abnormal phosphate homeostasis; (2) the in vivo effects of circulating Fgf-23; (3) the in vivo role of vitamin D in mediating Fgf-23 actions; (4) the consequence of hyperphosphatemia on cell death and tissue atrophy; and (5) the function of Fgf-23 as an inhibitor of mineralization in vitro. We are also investigating possible autocrine functions of FGF-23 on skeletal mineralization and bone cell differentiation in vitro, and are examining interactions between Fgf-23, klotho, and Wnt signaling. The lab is currently establishing new methods to manipulate the expression of various genes simultaneously in any specific tissue. These new methods will allow us to examine interactions among various molecules, and will help avoid systemic effects. Our research not only aims to improve our understanding of normal regulation of phosphate homeostasis, but also aims to designate selective interventions of disorders associated with abnormal phosphate homeostasis, including chronic renal diseases, XLH, ADHR, ARHR, FTC, diabetic ketoacidosis, and osteomalacia.

Research Projects in Medical Sciences

Complications with Implant Supported Fixed Bridges in Edentulous Patients

Faculty: German Gallucci, Dr. med. dent., PhD
Investigators: Panos Papaspyridakos, DMD, ITI fellow; Marl Chen, DMD, ITI fellow
Funder(s):

The objective of this systematic review is to assess the long-term complication ratio of fixed-implant rehabilitations for edentulous patients. A number of implant and prosthetic variables will be analyzed in order to avoid preventable complications for this particular clinical situation.

Research Projects in Medical Sciences

Treatment of Edentulous Mandible with Implant Supported Fixed Bridges

Faculty: German Gallucci, Dr. med. dent., PhD
Investigators: Goran Benic, DMD, research fellow; Muiz Mokti, DMD, implant resident; Coralie Schneider, DMD, implant resident
Funder(s):

The objective of this systematic review is to assess the long-term outcomes of fixed-implant rehabilitations for the edentulous mandible. A number of implant and prosthetic variables will be analyzed in order to determine the most suitable treatment modality for this particular clinical situation.

Research Projects in Medical Sciences

Splinted vs. Nonsplinted Implant Impression Techniques

Faculty: German Gallucci, Dr. med. dent., PhD
Investigators: Panos Papaspyridakos, DMD, ITI fellow; Virginia Hogsett (DMD 2013)
Funder(s):

This retrospective clinical study includes 13 fully edentulous jaws, in which five to eight implants were placed in each jaw to support stress imposed by a permanent prosthesis. Implants for all patients were placed by one of two prosthodontists using a computer-guided system that standardizes the surgical procedures, as well as the placement and angulation of the implants. Two different implant impression techniques were used on each patient, one in which the abutments were splinted with acrylic resin and one in which they were not. Working casts were made from each type of impression to serve as the two test groups. Jigs serve as controls of the patients’ mouth, and were fabricated intraorally by connecting the abutments together will acrylic resin.

The hypothesis is that there is no clinically significant difference in the accuracy of different implant impression techniques. We will test this hypothesis by comparing splinted versus nonsplinted impression techniques using patient models. Accuracy will be determined by fit, as measured both macroscopically using an explorer tool and microscopically using microtomography (microCT).

 

Research Projects in Medical Sciences

Dimensions of Peri-Implant Bone and Mucosa: A Cone Beam CT (CBCT) and Clinical Pilot Evaluations of Immediately Placed Anterior Implants in Humans

Faculty: German Gallucci, Dr. med. dent., PhD; Bernard Friedland, BCh, MSc, JD
Investigators: H-P Weber, DMD, Dr. Med. Dent.; Goran Benic, DMD, research fellow; Muiz Mokti, DMD, implant resident; Marl Chen, DMD, ITI fellow
Funder(s): Department of Restorative Dentistry and Biomaterials Sciences

The aim of this study is to evaluate the soft-tissue and bone dimensions around implants that have been placed immediately after the tooth extraction and have been in function for five years.

 

Research Projects in Medical Sciences

Accuracy Outcomes of Closed-Tray and Open-Tray Impression Techniques for Bone-Level Implants: A Clinical Study

Faculty: German Gallucci, Dr. med. dent., PhD
Investigators: Ahy Linah, DMD, implant resident; Connie Kim (DMD 2012)
Funder(s): Straumann

This clinical study compares the accuracy outcomes of two impression techniques, in cases where two bone-level (BL) implants are placed adjacent to each other for a multiunit bridge. In addition, the effect of implant angulations on the choice of impression technique will be assessed on stone models obtained from closed-tray and open-tray impressions. A correlation between the accuracy outcomes and the implant angulations will be sought in order to establish clinical recommendations.

Research Projects in Medical Sciences

A Comparison of Zirconia CAD/CAM to Conventionally Fabricated Single Implant Restorations in the Esthetic Zone: A Randomized Controlled Clinical Trial

Faculty: German Gallucci, Dr. med. dent., PhD
Investigators: Ahy Linah, DMD, implantology resident; Coralie Schneider, DMD, implantology resident
Funder(s): ITI Foundation

This is a randomized clincal study with two groups of patients receiving implant restorations fabricated using two different techniques. ZirconiCa AD/CAM (ZCC) implant abutments and restorations will be compared to conventional, prefabricated titanium (TCF) implant abutments and porcelain-fused-to-metal restorations using reproducible aesthetic (objective/subjective) and biologic parameters.

Research Projects in Medical Sciences

Oral Cancer Detection Methods in a Community Setting

Faculty:
Investigators: Sook-Bin Woo, DMD, MMSc; Kathy Myers, RDH, MBA, project manager
Funder(s): National Institute of Dental and Craniofacial Research

The purpose of the study is to evaluate the efficiency of a risk-assessment algorithm in identifying subjects with suspicious precancerous or cancerous lesions in a high-risk population, as compared to broad screening in the general population.

Background

The Preventive Services Task Force of the United States does not recommend broad population screening of asymptomatic adults for oral cancer based on lack of evidence in support of such screening. The decision is due to several unknown parameters that have to do with resource allocation as well as the accuracy of the employed methods. A community-based method targeting high-risk individuals would theoretically be more efficient, as it would maximize the output (number of identified lesions) for any given number of inputs (health-care personnel and/or monetary resources). While efficiency is an important attribute of successful public-health programs, it has not been evaluated in the context of oral cancer screening. To test the efficiency of risk assessment in a community setting, we propose to interview 2,000 individuals to calculate their oral cancer risk score, followed by intraoral examination using visual/tactile examination, and biopsy of suspicious lesions. Along with calculating the sensitivity and specificity of risk assessment, the results will be analyzed using the nonparametric Data Envelopment Analysis (DEA) methodology, a statistical methodology we have used successfully in the past in the evaluation of a national primary care network.

 

Research Projects in Medical Sciences

Multigenic Dissection of Nonsyndromic Oral Clefts

Faculty: Rachel Badovinac Ramoni, DMD, ScD
Funder(s): NIH/National Institute of Dental and Craniofacial Research

Cleft lip and/or cleft palate are among the most common birth defects and have serious physical, psychological, and financial consequences for those affected. Nevertheless, little is known about the causes of these anomalies because clefts are the result of genetic and environmental risk factors, rather than a single factor. This research has the potential to make a unique contribution to our understanding of clefts, as it employs novel analytical approaches that allow the simultaneous examination of many potential risk factors.

Using DNA from mothers and infants enrolled in a large-scale birth defects surveillance study, Dr. Badovinac-Ramoni is investigating the multigenic origins of nonsyndromic oral clefts (NOC) using a novel application of Bayesian networks, a proven analytical approach. First, she will identify and validate the most probable network linking the phenotype of isolated NOC to the candidate maternal and subject single nucleotide polymorphisms and environmental exposures among the majority race/ethnicity.

Second, Dr. Badovinac-Ramoni will validate two approaches to phenotyping nonisolated NOC. Finally, she will determine whether the model(s) generated in the first two analyses can be generalized to minority race/ethnicity groups. As the first investigation to concurrently consider the candidate environmental exposures and SNPs in several candidate genes previously associated with NOC in association studies, this work has the potential to move the study of NOC dramatically forward. 

 

 

Research Projects in Medical Sciences

Clinical and Radiographic Evaluation of Titanium-Zirconium Narrow-Diameter Dental Implants: A Multicenter Randomized, Controlled Clinical Trial

Faculty: German Gallucci, Dr. med. dent., PhD
Investigators: Goran Benic, DMD, research fellow; Muiz Mokti, DMD, implant resident
Funder(s): ITI Foundation

This multicenter, prospective, controlled, randomized clinical study will compare the outcomes of titanium-zirconium narrow-diameter implants and titanium regular-diameter implants. One study-implant per patient will be placed and restored with a single crown. Outcome parameters will be intraoperative time for the implant bed preparation, dimensions of the residual buccal bone and of the osseous defects immediately after the implant placement, operator’s perception of the procedure, patient’s morbidity, soft-tissue healing, radiographic marginal bone level, quantitative and qualitative measurements of the peri-implant soft tissue, implant and suprastructure survival, and rate of biological and technical complications.

Research Projects in Medical Sciences

Pathophysiologic Regulation of FGF-23 in Phosphate Homeostasis: Role of Vitamin D

Faculty: Beate Lanske, PhD
Investigators: Quan Yuan, PhD, Research Fellow, Michael Densmore, Research Associate
Funder(s): NIH/National Institute of Diabetes and Digestive and Kidney Diseases

Fibroblast growth factor-23 (FGF-23) is a recently identified molecule, which is implicated in the pathogenesis of various human diseases, including in X-linked hypophosphatemia (XLH), oncogenic osteomalacia (OOM), autosomal dominant hypophosphatemic rickets (ADHR), familial tumor calcinosis (FTC), and chronic renal diseases. FGF-23 is one of the most important and determinant factors in maintaining phosphate homeostasis and skeletal mineralization.

The long-term objective of this grant proposal is to determine in-vivo function and regulation of FGF-23 in physiological and pathophysiological conditions. As a preliminary step of obtaining such objectives, we have recently generated mice in which the Fgf-23 gene has been successfully ablated by homologous recombination. These Fgf-23 null mice exhibit hyperphosphatemia, increased vitamin-D activities, excessive mineralization in bone, and abnormal calcifications in the soft tissues. In this study, we are analyzing the effects and interrelationship of three essential components-phosphate, Fgf-23, and vitamin D-using Fgf-23 null mice. To determine the in-vivo roles and regulations of Fgf-23, we are defining the role of sodium-phosphate cotransporters (NaPi) in abnormal phosphate homeostasis in Fgf-23 null mice by generating Fgf-23-/- / NaPi 2a-/- double mutant mice.

In further studies we will determine the effects of lowering serum phosphate by nicotinamide in Fgf-23 null animals. We will also investigate whether circulating FGF-23, exclusively derived from ?1(l) collagen (2.3 kb promoter) expressing osteoblasts, is sufficient to rescue the abnormal systemic phenotype of Fgf-23 null animals. We are therefore generating a mouse model that is completely ablated for endogenous Fgf-23, but expresses FGF-23 in osteoblasts, which is then released into circulation. Furthermore, we plan to study the role of vitamin D in Fgf-23-mediated functions, by generating and molecular characterization of Fgf-23/1a hydroxylase and Fgf-23/vitamin D receptor double mutant mice (Fgf-23-/-/1a(OH)ase-/-; Fgf-23-/- / /DR-/-). In addition, we will examine the in-vivo bioactivities of Fgf-23 in a normocalcemic/normophosphatemic microenvironment that are independent of vitamin D signaling. Finally, we will analyze the autocrine function of Fgf-23 in vitro using calvarial osteoblasts and explants and will investigate its role as an inhibitor of mineralization. Successful completion of this study will generate data that will form the basis to design strategies to manipulate abnormal phosphate homeostasis and defective skeletal mineralization in patients suffering from a wide range of diseases including rickets, XLH, ADHR, OOM, FTC, and chronic renal failure, using FGF-23 or its interacting molecules as a potential therapeutic tool.

 

 

Research Projects in Medical Sciences

Role of Indian Hedgehog in Endochondral Bone Formation

Faculty: Beate Lanske, PhD
Investigators: Yukiko Maeda, PhD, research associate; Dutmanee Seriwatanachai, PhD,research fellow; Michael Densmore, research associate
Funder(s): NIH/National Institute of Diabetes and Digestive and Kidney Diseases

Indian hedgehog (Ihh) has multiple functions during skeletogenesis. Mice lacking the Ihh gene exhibit severe skeletal abnormalities, including markedly reduced chondrocyte proliferation and abnormal maturation, with absence of mature osteoblasts. Since Ihh and its receptor, smoothened (smo), are expressed in chondrocytes as well as in osteoblasts, current animal models do not provide sufficient information about whether Ihh has a direct effect on osteoblasts, or whether the effects on bone are indirectly mediated through chondrocytes during endochondral ossification.

In this study, we are selectively ablating, in vivo, the Ihh gene from collagen type II expressing cells, pre- and postnatally, and from a subset of collagen type X expressing cells. In addition, we are deleting smo selectively from chondrocytes and compare the phenotypes. This will allow us to determine the specific role of chondrocyte-derived Ihh on endochondral bone formation.

We are using animals that we generated and cross-bred with col2alpha1-cre, col2alpha1-creER*, and col10alpha1-cre mice, obtained from our collaborators. In the first aim of this study, we are selectively deleting either the Ihh or the smo gene from chondrocytes, before birth, and analyzing and comparing the mutant phenotypes to define the role of Ihh during the process of endochondral bone formation.

In the second aim, we are analyzing mice in which the Ihh gene has been selectively deleted from chondrocytes after birth. We are taking advantage of a tamoxifen-inducible ere that is under the control of the collagen type II promoter to determine the acute effects of Ihh on established endochondral bone. In the third aim, we are generating a hypomorph mouse model, in which only a subset of chondrocytes in the growth plate will be deleted for the expression of Ihh. For this purpose, collagen type X cre knock-in mice will be bred with floxed Ihh animals. Using this model we will be able to detect the response of chondrocytes to reduced Ihh expression. We expect a less-severe phenotype in these mice, and will perform a comparative analysis between animals lacking the Ihh gene in collagen type II and collagen type X expressing cells.

The innovative mouse models will generate a novel in-vivo system that will help us to clarify the role of Ihh, not only during endochondral bone formation, but also in maintaining endochondral bones. This new information will give us a more secure framework for understanding how Ihh regulates chondrocyte and osteoblast development and function. Such in-vivo molecular studies, could, therefore, lead to the discovery of other human skeletal diseases involving the Ihh gene and to novel therapeutic strategies aimed at modulating skeletal anomalies.

 

 

Research Projects in Medical Sciences

In Vivo Interactions of Fgf-23, Klotho, and Vitamin D

Faculty:
Funder(s): NIH/National Institute of Diabetes and Digestive and Kidney Diseases

Recent studies have shown crucial roles of fibroblast growth factor-23 (FGF-23) and klotho in regulating calcium and phosphate homeostasis. FGF-23 is an important in vivo regulator of phosphate homeostasis, while klotho is involved in regulating calcium homeostasis by interacting with the epithelial calcium channel transient receptor potential-vanilloid-5 (TRPV5). Interestingly, Fgf-23- and klotho-ablated (kl/kl, klotho-/-) mice have very similar physical, biochemical, and morphological phenotypes; in vivo genetic manipulation of Fgf-23 and klotho resulted in altered mineral ion homeostasis in these mutant mice. It is, however, not yet known how FGF-23, klotho and vitamin-D coordinately regulate mineral ion homeostasis.

In this study, we are using Fgf-23-/- , Fgf-23-/-1 a-hydroxylase mutant mice, and klotho-ablated and transgenic (Tg) mice as in vivo model systems to study possible in-vivo interactions of these molecules and their coordinated effects on mineral ion homeostasis. We are examining the effects of exogenous and endogenous FGF-23 on the induction of klotho in Fgf-23V and Fgf-23-/-1 a-hydroxylase mice, and whether such interaction is a vitamin-D dependent process.

Our preliminary results suggest an in-vivo interaction of FGF-23 and klotho. Furthermore, we found decreased renal expression of klotho in Fgf-23 mice; whether such decreased expression of klotho is partly responsible for premature aging-like features and abnormal mineral ion homeostasis in Fgf-23 mice is not known. Therefore, we will determine the effects of restoration of klotho levels in Fgf-23-/- mice by generating Fgf-23-/-klotho-Tg mutant mice. Finally, to determine klotho-dependent and -independent functions of FGF-23, we plan to study Fgf-23-/-/klotho-/- mice, and Fgf-23 transgenic/klotho-/- mice.

The long-term objective of this study is to determine in vivo function and regulation of FGF-23 and klotho in physiological and pathological conditions. As a preliminary step of obtaining such objectives, we have recently generated and partially characterized both Fgf-23-/- , and Fgf-23-/-1 a-hydroxylase double mutant mice. To study the effects of circulating FGF-23 on the induction of klotho to rescue the abnormal phenotypes of Fgf-23-/- , we generated another mouse model that is completely ablated for endogenous FGF-23, but expresses FGF-23 in osteoblasts, which is then released into circulation (Fgf-23-/-/Col1-FGF-23Tg mice). We will analyze the interrelationship of FGF-23, klotho, and vitamin D, and their effects on essential renal calcium and phosphate regulating molecules, including TRPV5, NaPi2a, Calbindin28k, NCX1, and PMCAbl and their effect on skeletogenesis. Successful completion of this study would generate data that will form the basis to design strategies to manipulate abnormal mineral ion homeostasis and defective skeletal mineralization in wide range of diseases, including rickets/osteomalacia, tumoral calcinosis, and chronic renal failure, by developing novel therapies and fine-tuning of the existing therapeutic modalities.

 

 

Research Projects in Medical Sciences

Early Performance of the Patient-Doctor Relationship As a Predictor of Success in Dental Education

Faculty: Elsbeth Kalenderian, DDS, MPH, PhD
Funder(s): Joint Commission of the American Dental Association

The objective of this study is to ascertain if it is possible to predict future (third year) academic performance of dental students through the assessment of their performance in a patient-centered course (Patient-Doctor I) offered during the first year. If so, can early educational interventions in the form of peer mentoring lead to better student performance, improved student satisfaction, and/or early realization that dentistry is not an appropriate match for certain students.

The faculty of the Patient-Doctor I (PDI) course has remained remarkably stable over the last 10 years, and the majority of the senior tutors responsible for guiding the students in their clinical years are also still affiliated with HSDM, in touch with each other, and stationed in the greater Boston area. Over the years, many anecdotal stories have given rise to the idea that instructors of PDI can easily predict who will be “stars” and who will be “laggards” once those students enter the clinical years of their education. If this is indeed true, it is the responsibility of the institution to intervene early (and reassess) to try to improve academic success and satisfaction among its students.

Students’ performance in PDI is assessed through a standardized assessment, which has been in use for 10 years. Students’ performance during their clinical years is assessed through formative and normative manual skills testing, as well as through a qualitative written report, which assesses their attitude, behavior, and patient-interaction skills. We plan to collect the assessments from the PDI course of the last 10 years for a total of 350 students and identify the stars and laggards. Of those students, we will then collect the qualitative reports of their clinical performance and confirm our interpretation of those qualitative reports with the relevant senior tutors through an interview process. We will then compare the two datasets for a positive correlation. If such a correlation is found to be present, we plan to implement a well-defined peer-mentoring program, in which the stars of the PDI course are matched with the laggards. The emphasis of the mentor will be on discussing with, showing, and providing feedback to the mentee regarding specific patient-doctor interpersonal skills that may be innate to the mentor but need to be expressively learned by the mentee. Being able to early on (first semester of the first year) predict significant poor academic performance will allow faculty to provide early meaningful remediation.

 

 

 

Research Projects in Medical Sciences

Using Inuit Qaujimajatuqangit, Traditional Knowledge, to Guide the Development of Hypothses on Narwhal Tusk Function

Faculty: Martin T. Nweeia, DMD, DDS
Funder(s): National Science Foundation

The narwhal remains one of the least-understood marine mammals on the planet, and its extraordinary tooth, a mystery. Mythical legends of the unicorn are only surpassed by the reality of an elusive whale that has challenged scientific minds for the past 500 years. Dr. Martin Nweeia combines an interdisciplinary team of scientists and Inuit elders and hunters to better understand the anatomy, behavior, and neurophysiology of nature’s most perplexing tooth.

The left canine of the male narwhal defies many principles and properties of tooth expression, from its architecture to its unique spiraled form. Why this tusk has become the exception to many of the evolutionary rules of teeth has been the subject of Dr. Nweeia’s 10-year investigation. Results from this study will uncover the knowledge recorded in the interviews of 55 hunters and elders from more than 12 communities in the High Arctic regions of Northeastern Baffin Island and Northwestern Greenland. These interviews will be translated and then integrated with scientific findings to bring a more complete understanding of the narwhal. By analyzing aspects of narwhal migration, distribution, behavior, anatomy, diet, and effects of global warming trends that are described in this collection of interviews, a more complete picture of this whale and its extraordinary tusk will be uncovered.

Dr. Nweeia’s research keeps children of all ages curious. Three television documentaries, 15 radio programs, and hundreds of magazine and newspaper articles and Internet sites demonstrate the public appetite for knowledge about the narwhal, its tusk, and this ongoing study. Findings from this work will be published in a book that includes the findings of the Traditional Knowledge and the ongoing scientific studies. Original art and graphic plates describing narwhal anatomy, physiology, migration, and behavior will also be completed and incorporated in to the book, as well as Museum exhibits.

 

Research Projects in Medical Sciences

Calcitonin Regulation of Osteoclast Integrin Functions

Faculty: Roland Baron, DDS, PhD
Funder(s): NIH/National Institute of Arthritis and Musculoskeletal and Skin Diseases

Calcitonin (CT) is the most potent and rapidly acting known inhibitor of bone resorption that targets the osteoclast (OC) directly. CT was the first therapeutic agent used to inhibit excessive bone resorption in osteoporosis and other conditions. It is still used, and new formulations for treating osteoarthritis and osteoporosis are currently in development, despite the fact that a reported loss of efficacy with time has somewhat limited clinical use. Thus, new information about the mechanisms by which CT affects OC function has potential therapeutic importance. In vitro, CT rapidly inhibits OC motility and disrupts the podosome belt, the cytoskeletal attachment feature of mature resorbing OCs, accounting for much of CT’s inhibition of bone resorption.

In past research, we showed that CT inhibits OC spreading, motility, and bone resorption in large part by inhibiting the protease calpain, and that inhibiting calpain also promotes the recycling of the CT receptor to the cell surface by filamin. These results are a major breakthrough in understanding how CT regulates OC cytoskeleton organization and podosome function. This current work seeks to characterize the calpain-dependent mechanisms of CT action, focusing on how CT regulates calpain activity in OCs and how calpain regulates OC attachment and motility, which will provide novel insights into the regulation of osteoclast function in bone remodeling. 

The aims of this study are to: (1) further elucidate the mechanisms by which calpain modulates podosome function, cytoskeletal organization, cell adhesion, and motility, specifically focusing on proteins (cortactin, talin, Pyk2, filamin) that we or others have identified as calpain substrates that play key functional roles in adhesion complexes in osteoclasts; (2) further characterize the coupling of the CTR to calpain in OCs and the calpain- independent effects of CTR-induced signaling effectors on the function of podosome components; and (3) further characterize the molecular basis of the CTR-filamin interaction, and determine how that interaction affects CTR function, and more specifically, CT’s regulation of OC attachment and motility. These studies will reveal previously unappreciated features of CT’s mechanisms of inhibiting bone resorption and thereby possibly increase CT’s therapeutic potential by creating the possibility of rapidly and potently inhibiting bone resorption while avoiding the loss of response.

 

 

 

Research Projects in Medical Sciences

Duration of Behavioral Counseling Treatment Needed to Optimize Smoking Abstinence

Faculty:
Investigators: Christine Armour, Research Assistant; Sarah Kupper, Research Assistant
Funder(s): NIH/National Institute on Drug Abuse

Nicotine dependence is increasingly recognized as a complex and chronic condition. Only 10% to 20% of smokers receiving smoking-cessation interventions are able to maintain abstinence for one year. Poor outcomes from smoking-cessation programs may be due to the brevity and limited intensity of most existing behavioral treatments that supplement pharmacologic treatment. In our laboratory we have found very low quit rates (14%) for smokers given intensive, high-dose individualized nicotine patch therapy accompanied by only very minimal behavioral counseling.

This study examines, using a randomized, carefully controlled experimental design, whether use of extended-duration counseling protocols of moderate intensity will significantly improve cessation rates. Our study will provide the first information to our knowledge regarding the optimal duration of counseling needed to maximize cessation rates among those receiving nicotine-replacement treatment. We will recruit a sample of 450 smokers and provide nicotine patch treatment for 12 weeks. Subjects will be randomly assigned to one of the following post-quit counseling conditions: (a) 12 weeks, (b) 24 weeks, or (c) 52 weeks of counseling. Our study will provide a replication and significant extension of the recent seminal work of Hall et al. (Hall et al., Am J Psychiatry 2004;161:2100-2107) that found, in a small sample, that an extended counseling protocol of 52 weeks’ duration produced one-year quit rates of 50% to 55%. We will determine whether use of extended-duration counseling protocols can obtain similar quit rates at one year postcessation among a large, representative sample of more heavily dependent smokers. We will also determine whether a 52-week treatment protocol is necessary to produce optimal cessation rates, or whether a shorter-duration treatment (six months), perhaps more acceptable to smokers, might be as effective, or nearly as effective.

In addition, we will examine mechanisms (e.g., social support) through which extended-duration counseling may increase cessation rates, and follow smokers for two years to assess the durability of the assumed higher quit rates at year one among those randomized to the more extended-duration counseling conditions. Secondary aims will examine whether extended-duration counseling may be especially beneficial for certain subgroups such as women, those of lower education, and those with depressive symptoms. We will also provide information on the difficulties that smokers experience at different postcessation periods of the quit attempt, which may be useful for the development of future time-specific treatment interventions.

If our prime hypothesis concerning the efficacy of extended-duration counseling is supported, this would suggest that a new treatment model, involving more frequent and structured contact, longer periods of observation, and renewed quit attempts in the event of relapse, may be necessary to reduce the prevalence of cigarette smoking among the increasingly recalcitrant population of smokers in the United States. Project narrative relapse (return to smoking) occurs for the majority of smokers (approximately 80% to 95%) who try to quit. Our study will test the efficacy of using an extended-duration counseling procedure for improving long-term cessation outcomes among more heavily dependent smokers. The ultimate goal of this line of research is to develop treatments that will increase the likelihood that smokers will succeed in their quit attempts.

 

 

Research Projects in Medical Sciences

Molecular and Cellular Mechanisms of Vascular Anomalies

Faculty: Bjorn R. Olsen, MD, PhD
Funder(s): NIH/National Institute of Arthritis and Musculoskeletal and Skin Diseases

This program project (P01) aims to elucidate pathogenetic mechanisms of human vascular anomalies, to generate mouse models and identify therapeutic targets. These common vascular disorders belong to the group of childhood conditions popularly known as vascular birthmarks. One in about 100 children born have a vascular birthmark, and although significant progress has been made in identifying the genetic basis for many of the more rare forms of these anomalies, they are frequently misdiagnosed and effective therapies are unavailable. Hemangiomas usually appear a few days after birth, grow rapidly for a few weeks to months, and then slowly regress over a five- to 10-year period. Malformations do not regress, but grow with the child and can become life threatening.

Building on discoveries made during a previous grant period and taking advantage of exceptional patient-data, tissue, cell, and nucleic-acid resources that have been collected in two cores-one in Boston and one in Brussels-the investigators plan to use genetic, cell-biological, and protein-chemistry techniques to gain deeper understanding of how gene mutations that are associated with hemangioma and venous malformations affect endothelial and smooth muscle cell differentiation and function. Animal models comprising human cells transplanted into immunocompromised mice and genetically modified mice carrying hemangioma and venous malformation-associated mutations will be characterized and used for testing hypotheses and explored for preclinical trials of disease-modifying drugs.

Please visit the Vascular Anomalies Program Project website for more information about this study. Read an article about the study, “Genetic Switch Found for Growth of Common Childhood Tumor,” in Focus, the newsletter of HMS, HSDM, and HSPH.

 

 

Research Projects in Medical Sciences

Molecular Mechanisms of Choroidal Neovascularization and Vascular Homeostasis

Faculty: Bjorn R. Olsen, MD, PhD
Funder(s): NIH/NEI

Choroidal neovascularization (CNV) in age-related macular degeneration (AMD) is one of the leading causes of blindness worldwide. Our long-term goal is to elucidate the molecular mechanisms that regulate choroidal vascular development, choroidal vascular homeostasis in the adult, and CNV. Understanding these mechanisms is likely to provide the basis for a more targeted therapeutic approach in patients with neovascular AMD.

Recent experimental and clinical data have provided strong evidence for a pathogenetic role of VEGF signaling in CNV. Anti-VEGF treatments have shown clinical benefit in reducing CNV in patients with neovascular AMD. However, the molecular mechanisms through which VEGF stimulates CNV in the eye are only poorly understood. Our proposed experiments are directed toward a comprehensive analysis of the individual contributions of VEGF and the VEGF-receptors Flt1 and Flk1 for choroidal vascular functions, and toward exploring these signaling pathways as molecular targets for novel therapeutic approaches in the treatment of neovascular AMD. For this purpose, we will perform experiments that use a combination of conditional gene targeting approaches and treatments with blocking antibodies in mice. We will test the role of VEGF, Flt1 and Flk1 for choroidal endothelial cell functions. Furthermore, we will use an established experimental model for CNV in mice to investigate the role of VEGF and its receptors for CNV. In addition, we will perform GFP-positive bone marrow transplantation experiments and macrophage depletion experiments in order to determine the cellular composition of experimental CNV lesions and to study the effect of antibodies that target VEGF signaling pathways on these cells in this model. 

 

 

Research Projects in Medical Sciences

Molecular Mechanisms of Temporomandibular Joint Disorders by Use of Genetic and Nongenetic Mouse Models

Faculty: Lin Xu, MD, PhD
Funder(s): The Eleanor and Miles Shore 50th Anniversary Fellowship Program for Scholars in Medicine

The objective of this research study focuses on the pathogenesis of temporomandibular joint disorders (TMJD) that affect millions of people around the world. Dr. Xu has identified two mutant mouse models for TMJD and established a surgically induced mouse TMJD model by partial discectomy. Dr. Xu has been investigating risk factors that are responsible for trauma-induced TMJD by use of these mouse models. Results from these studies will provide information for search of novel therapeutic targets for the prevention and treatment of TMJD.

 

 

Research Projects in Medical Sciences

Role of Two Zinc Finger Proteins, ZFP521 and ZFP423

Faculty: Roland Baron, DDS, PhD
Investigators: Kei Yamana, PhD, visiting research fellow, principal investigator
Funder(s): Teijin Pharma Limited

This research focuses on the role of two zinc finger proteins (Zfp521 and Zfp423), which have been shown to play an important role in osteoblasts and chondrocytes and are induced by PTH, in the bone anabolic response to PTH in vivo and in vitro.            

 

 

Research Projects in Medical Sciences

Regulation of Osteoclastic Bone Resorption: Role of Cb1b

Faculty: Roland Baron, DDS, PhD
Funder(s): NIH/National Institute of Arthritis and Musculoskeletal and Skin Diseases

In this study, we pursue our research on the molecular mechanisms of the differentiation of osteoclasts and bone resorption. The understanding osteoclast (OC) differentiation and activity has been revolutionized by the discovery that (1) the activation of RANK by RANK ligand is absolutely required for osteoclast formation and activity, and (2) stimulation of myelomonocytic precursors with M-CSF and RANK ligand is sufficient to induce the formation of OCs. Less publicized, but in our eyes important as well, have been the findings that the Cbl family of proteins is both involved in osteoclast biology and in the down-regulation and/or signaling activity of RANK and M-CSF, as well as other activated tyrosine kinase receptors. Because of the central importance, on the one hand, of RANK and M-CSF in osteoclast biology, particularly differentiation, and, on the other hand, of the Cbl family of proteins in the regulation of signaling and degradation of these receptors, including recent and exciting findings from our group we plan to focus our efforts on the functional role of Cbl-b in the regulation of OC differentiation and bone resorption by RANK and the M-CSF receptor, c-Fms.

We have recently observed that both c-Cbl and Cbl-b knockouts have osteoclastic phenotypes, but very different ones, with only the absence of Cbl-b resulting in a several-fold increase in the expression of RANK on the OC surface, increased OC differentiation and bone resorption and osteopenia. We are therefore working to identify the molecular mechanisms by which Cbl-b regulates signaling by RANK and c-Fms and OC biology. Consequently, the aims of this study are to (1) further analyze the phenotype of the Cbl-b knockout at the bone, osteoclast, and molecular levels (focusing particularly on NKL- and M-CSF-induced signaling); (2) analyze in vitro the molecular mechanisms involved, mimicking, or rescuing the osteoclast phenotype in single KO cells and identifying the domains and signaling pathways responsible for the Cbl-b phenotype; and (3) express the mutated Cbl-b proteins that rescue/mimic the Cbl-b phenotype in vitro in single knockout transgenic mice. This work ] will increase our understanding of the regulation of bone resorption, potentially identifying novel targets for therapeutic intervention to control bone loss related to osteoporosis, arthritis, bone metastasis, and periodontal diseases.

 

 

Research Projects in Medical Sciences

From Adhesion to Bone Resorption: The Role of Dynamin in Osteoclasts

Faculty: Roland Baron, DDS, PhD
Funder(s): NIH/National Institute of Arthritis and Musculoskeletal and Skin Diseases

 

Bone resorption is performed by the mature osteoclast. To resorb bone, osteoclasts require both the presence of dynamic actin adhesion structures in the sealing zone (podosomes) and very efficient endocytosis in the ruffled-border domain. Data generated in our laboratory within the last five years has clearly established that two signaling enzyme activities are directly involved in the regulation of both bone resorption and actin dynamics in the osteoclast. On the one hand, we have shown that both Src tyrosine kinase activity and the binding of Src to Pyk2 are required, for bone resorption and for the dynamic assembly and disassembly of podosomes. On the other hand, we have also shown that dynamin 2 and its GTPase activity are involved in the dynamic assembly and disassembly of podosomes and are required for bone resorption by osteoclasts. Further, we have shown that dynamin, itself a substrate of Src, interacts with Pyk2 and with Cbl.

 This current study therefore explores the role of dynamin in the integrin-dependent signaling cascade that regulates podosome assembly and disassembly and the initiation of endocytosis at the ruffled border, and how dynamin 2 GTPase activity and the Pyk2 and Src tyrosine kinase activities regulate bone resorption in a coordinated manner. The first aim focuses on the early integrin signaling events involving dynamin/Pyk2 interaction and taking place upstream of Cbl, their regulation, and their link to actin dynamics and/or endocytosis in osteoclasts. The second aim explores the signaling events involving the dynamin/Cbl interaction that take place downstream of Cbl, their regulation, and their link to both actin dynamics and endocytosis. The third aim focuses on determining the role of dynamin in genetic experiments in vitro and in vivo: analyzing the skeletal and osteoclastic effects of dynamin knockouts/knockdowns and transgenic expression of mutants, selected from the results obtained in aims 1 and 2. This project explores a novel concept, based on strong (and partially published) preliminary data, which we believe will help further understand the mechanisms that regulate bone resorption.

 

 

Research Projects in Medical Sciences

Mechanism of Action of Halofuginone As a Novel Therapeutic

Faculty: Malcolm R. Whitman, PhD
Investigators: Maja Edenius, PhD, Research Fellow, Chang-Yeol Yeo, PhD, Research Fellow
Funder(s): NIH/National Institute of Arthritis and Musculoskeletal and Skin Diseases

The use of small molecules to manipulate metabolic function in vivo has emerged as an important new approach to therapy for a wide range of disease pathologies. The amino acid starvation response (AAR) is a signaling pathway that controls a variety metabolic and cytoprotective functions in response to the restriction of amino acid availability. In our preliminary experiments we have found that halofuginone, a small molecule with efficacy in a variety of animal disease models involving fibrosis and angiogenesis, is a potent and specific activator of the AAR. We have also found that halofuginone activates the AAR through a novel mechanism, and acts independently of the best characterized mediator of AAR signaling. Through this novel signaling mechanism, HF regulates a variety of previously described cell behaviors associated with disease pathology or pathogenesis. We have also identified a novel, specific effect of HF on the differentiation in vitro and in vivo pro-inflammatory T-cells. HF alters T-cell populations in vivo in a way predicted by its effects in vitro. HF reduces inflammatory pathology in a mouse model of autoimmunity, indicating that HF has strong potential as a new class of therapeutic for autoimmune and chronic inflammatory disease. These observations open an exciting new set of opportunities for understanding how HF, and other small molecules with similar molecular targets, may have new and unexpected uses for the treatment of pathology associated with chronic inflammatory disease.

 

 

 

Research Projects in Medical Sciences

Regulation of Osteoblast Differentiation by Delta FosB

Faculty: Roland Baron, DDS, PhD
Funder(s): NIH/National Institute of Arthritis and Musculoskeletal and Skin Diseases

The purpose of this study is to further understand how DeltaFosB (DFosB) increases bone formation (BF) in adult mice. Unlike most other transcription factors involved in osteoblast (OB) differentiation, DFosB increases BF postnatally, at any point in time, while not affecting skeletal development. This mimics the desired effects of a true bone anabolic therapeutic agent. We have now shown that the further truncated D2DFosB isoform recapitulates the phenotype of DFosB in bone. Like Fra1 and DNJunD, which induce a similar phenotype, D2DFosB does not have intrinsic transcriptional activity and antagonizes AP1. D2DFosB’s action may be primarily within the transcriptional machinery, since all interactions we have identified are with transcription factors or cofactors (Juns, Runx2, C/EBPb, Smad6, and Zfp521, a novel key player in the regulation of BF). In contrast to FosB, D2DFosB fails to repress beta-catenin transactivation in response to Wnt3a or to induce the inhibitory Smad6 inresponse to BMP2. These are major breakthroughs in our understanding of the DFosB osteosclerotic phenotype: the increased BF when DfosB, and therefore D2DFosB, is expressed may result not only from its positive effects on BMP signaling and Runx2 but also from the loss of the negative effects that full-length FosB exerts on BMP and Wnt signaling.

The current study aims to further explore the mechanisms by which D2DFosB affects BF, focusing on the AP-1 machinery and BMP and Wnt signaling. The specific aims are therefore to: (1) further explore the physiological roles of the FosB isoforms in vivo through analysis of - A (FosB + (2(FosB “knockout” mouse, expressing only FosB, by knocking-in an unspliceable mutant form of FosB - A (FosB “knock-in” mouse, expressing only (FosB and (2(FosB, - A transgenic mouse overexpressing an unspliceable mutant of FosB in osteoblasts, overexpressing only FosB;  (2) identify the FosB domains required to affect osteoblast differentiation and function; and (3) characterize the role of FosB proteins and their domains and interactions in the BMP and Wnt signaling pathways.

The experiments could lead to the identification of novel pathways regulating bone formation and novel targets for drug discovery, potentially allowing new approaches for anabolic therapeutic intervention in osteoporosis, osteogenesis imperfecta, and other diseases where bone mass is decreased. 

 

 

Research Projects in Medical Sciences

Role of the c-Src Proto-Oncogene in Osteoclasts

Faculty: Roland Baron, DDS, PhD
Funder(s): NIH/National Institute of Arthritis and Musculoskeletal and Skin Diseases

The aim of this multiyear study is to pursue our program identifying the function of c-Src that, in the osteoclast, is required for bone resorption (src- mutants develop osteopetrosis) and is unique to c-Src (i.e., cannot be compensated by other Src family of kinases in this cell). During the first 11 years of this program, we have made very significant progress toward understanding the functions of c-Src in bone resorption. Although the mechanism(s) by which src deletion leads to a decrease in bone resorption is not yet fully characterized, it is now clear, in part through our work, that Src regulates integrin-dependent osteoclast adhesion and motility.

Two central questions remain unanswered: 1) What is the molecular basis for Src’s “uniqueness” in osteoclast function? and 2) Why would the phosphorylation of Cbl be so important in the osteoclast? The current study aims to identify the molecular basis for Src’s unique function in osteoclasts; explore the mechanisms by which phosphorylation of Cbl regulates its functions, linking integrins to actin, podosome turnover and osteoclast function; and extend these in-vitro studies to in-vivo models by generating new transgenic mice that express relevant mutated versions of Src or Cbl. The specific aims are: 1) to identify the specific domains of Src that are responsible for the osteoclast phenotype (i.e., cannot be compensated by other members of the Src family of nonreceptor tyrosine kinases); 2) to further characterize the mechanisms by which Src-mediated phosphorylation of Cbl regulates osteoclast function; i.e., the ability of Cbl to ubiquitinate and/or interact with other molecules [upstream components (Pyk2) and downstream components (dynamin and PI3-kinase)]; and 3) to translate the in-vitro results obtained during previous research and in aims 1 and 2 into in-vivo studies by creating new transgenic mice that express mutated Src or Cbl proteins that alter osteoclast function in vitro. The current study will increase understanding of the regulation of osteoclast function and bone resorption, potentially identifying novel targets for therapeutic intervention to control bone loss related to osteoporosis and other diseases with increased bone resorption such as bone metastasis and periodontal and joint diseases.

 

 

Research Projects in Medical Sciences

Role of DDR2 in OA-Like Pathogenesis in Osteochondrodysplasias

Faculty: Yefu Li, MD, PhD
Funder(s): NIH/National Institute of Arthritis and Musculoskeletal and Skin Diseases

The long-term goal of this study is to understand the pathogenesis of osteoarthritis (OA)-like changes in articular cartilage that are associated with osteochondrodysplasias caused by mutations in extracellular matrix proteins. This research is based on findings that

  • type IX collagen-deficient (Col9a1-/-) or type XI collagen haploinsufficient mice (heterozygous chondrodysplasia, cho/+) mice develop progressive OA-like changes in knee and temporomandibular (TM) joints;
  • the levels of expression and activity of matrix metalloproteinase 13 (MMP-13, collagenase 3), a major cartilage collagen-degrading proteinase, are increased in the articular cartilage of knee joints in both mutant mice;
  • the expression of a collagen receptor, the discoidin domain receptor tyrosine kinase 2 (DDR2), is also increased in the articular cartilage of knee joints in both mutant mice;
  • the expression and activity of MMP-13 and the expression of DDR2 are increased in a surgically induced mouse OA model and in human hip OA cartilages;
  • increased MMP-13 expression in chondrocytes results from type II collagen-induced activation of DDR2 in vitro; and
  • the Ras/Raf/MEK/ERK pathway is involved in the DDR2-dependent up-regulation of MMP-13 expression in human chondrocytes.

These findings form the basis of the hypothesis that cartilage collagen mutations lead to degenerative changes in articular cartilage in a process characterized by two phases. In an early phase. alterations in chondrocyte metabolism result in proteoglycan degradation and changes in the composition of the pericellular matrix including more collagen II fibrils in the vicinity of the cells. In a late phase, en

hanced interactions between type II collagen fibrils and resident chondrocytes lead to activation of DDR2, increased expression of DDR2 and MMP-13, and a progressive and irreversible destruction of the collagen network. To test the late phase aspect of our hypothesis, we plan to investigate the role of increased DDR2 expression as a factor leading to early-onset OA-like pathology; investigate whether inhibition of DDR2 signaling will delay the onset of OA in Col9a1-/- and cho/+ mice; and investigate the mechanism by which DDR2 induces the expression of MMP-13 in human chondrocytes. This study should not only provide novel insights into the role of DDR2 in the progression of genetic forms of OA, but may shed light on aspects of disease progression in nongenetic forms as well.

 

 

Research Projects in Medical Sciences

Identification of Specific C-Cbl and Cbl-B Functions in Osteoclasts Biology

Faculty: Roland Baron, DDS, PhD
Investigators: Fabienne Coury, Research Fellow, principal investigator
Funder(s): Gideon and Sevgi Rodan Fellowship

The Gideon and Sevgi Rodan Fellowship from the International Bone and Mineral Society is given annually to support the research activities of a deserving young investigator in the bone field. Support is a one-year, nonrenewable grant. Dr. Coury received this fellowship based on her work on c-Cbl and Cbl-b, which are two widely expressed mammalian members of a family of adaptor proteins that are involved in various biological processes, ranging from defense against infection to osteoclast biology. The goal of Dr. Coury’s study is to identify specific c-Cbl and Cbl-b functions in osteoclasts biology; in particular, to characterize the differential roles of Cbl-b and c-Cbl in the regulation of RANK and c-Fms expression and signaling and to elucidate the role of Cbl-b and c-Cbl in the differentiation and survival of osteoclasts downstream of these two receptors.

 

 

Research Projects in Medical Sciences

Development of a New Family of Small Molecule Therapeutics for the Treatment of Chronic Inflammation

Faculty: Malcolm R. Whitman, PhD; Tracy Leigh Keller, PhD
Investigators: Maja Edenius, PhD, Research Fellow
Funder(s): Harvard University Technology Development Accelerator Fund

Drs. Whitman and Keller are working as co-principal investigators in collaboration with Anjana Rao, of the Immune Disease Institute at Children’s Hospital Boston. They are developing a new family of small molecule therapeutics for the treatment of chronic inflammatory conditions and autoimmune diseases.

Established by the Office of the Provost and Office of Technology Development, the Accelerator Fund is an innovative program designed to fund early-stage applied and translational research with manifest commercial potential. Providing critical support to advance potentially important but nascent technologies is key, given the absence of early-stage funding from industry sources.

Research Projects in Medical Sciences

Regulation of Xenopus Embryonic Development by TGFbeta

Faculty: Malcolm R. Whitman, PhD
Investigators: Maja Edenius, PhD, research fellow; Chang-Yeol Yeo, PhD, research fellow
Funder(s): NIH/National Institute of Child Health and Human Development

Our long-term goal is to understand how members of the TGFa superfamily act to exert a wide range of cell-type specific actions during development. Our current focus is on the role of TGFa ligands and their primary signal transducers, the Smads, in two sets of developmental events: 1) the regulation of migration of cell populations that establish the craniofacial skeleton and the body wall musculature; 2) the normal growth of the tail and the regeneration of this structure following surgical extirpation.

Migration of cell populations over extended distances in the embryo prior to their terminal differentiation is a critical component of the establishment of embryonic pattern. These migrations involve cell behaviors and regulatory programs that may be recapitulated during tumor metastasis, making an understanding of their regulation important for tumor biology as well as embryology. The craniofacial skeleton is made up primarily of neural crest cells that migrate from the edge of the anterior neural plate into the craniofacial region, where they differentiate into cartilage and bone. The muscle of the body wall is made up of muscle precursor cells that migrate from the somites to the ventro-lateral body wall, where they differentiate into muscle. In each case, preliminary work implicates BMP signals as regulators of the cell migration and/or the subsequent differentiation of the migratory cell. We will use a novel conditional inhibitor developed in our lab to understand how BMPs regulate these processes.

The Xenopus tail has been shown to be a powerful system for studying the molecular basis of complex regenerative events. We have identified a TGFa superfamily ligand, GDF11, that controls outgrowth of the normal tail through the activation of Smad2. We plan to explore how GDF11 and Smad2 activation during tail regeneration interacts with other signaling pathways to establish the regenerative program. Understanding how extracellular factors control cell and tissue migration during normal development, during regenerative healing following extensive tissue damage, and during pathological processes such as tumor metastasis provides a basis for new paths to therapeutic regulation of these events. The study of TGFa superfamily ligands provides a common approach, and a common set of molecular tools, with which to understand the regulation of these important physiological processes.