Senior Member of the Staff
Head, Department of Biomineralization
Associate Professor, Department of Developmental Biology,
Harvard School of Dental Medicine
email:
Worcester Polytechnic Institute, B.S., 1972, Chemistry
University of Vermont, Ph.D., 1976, Chemistry
The substances that make up hard biological structures, from bones to seashells, are formed through a process called biomineralization. The Margolis laboratory is finding out how one essential mineralized tissue, dental enamel, acquires its distinctive properties. Each tooth must have precisely the right composition, structure, hardness and durability to function effectively without significant breakdown. By studying enamel formation and the factors that affect its stability, we hope to learn more about how to preserve and restore teeth for a lifetime of use.
Each of the mineralized tissues of the human body derives its functional capabilities from its unique structure and composition. As a result of differences in mineral and matrix protein content, crystal sizes and crystal organization, mineralized tissues vary significantly with respect to physical properties. Research in our laboratory is currently focused on elucidating mechanisms involved in the formation (amelogenesis), preservation and repair (regeneration) of dental enamel. Much of this work is built upon a fundamental understanding of the kinetic and thermodynamic factors that control crystal growth and dissolution of enamel mineral and prototype mineral phases (e.g., hydroxyapatite) that are associated with the hard tissues of the human body.
Currently, we are using in vitro approaches to elucidate the structure and mechanism of formation of higher-order assemblies of enamel matrix proteins and their influence on mineralization and crystal organization. Our working hypothesis is that through cooperative mechanisms involving protein self-assembly and mineral formation, higher order assemblies of amelogenin, in possible association with other matrix molecules, regulate the growth, shape, and organization of initial enamel mineral crystals. Under appropriate mineralizing conditions, such assemblies support the formation of parallel arrays of very thin ribbons of enamel mineral. To improve our understanding of how matrix proteins regulate mineralization in tissues like enamel, we are conducting studies to characterize specific enamel matrix components with respect to their ability to form higher-order assemblies that ultimately regulate organized mineralization. In addition, we are testing the ability of key enamel matrix proteins to bind to mineral surfaces and regulate crystal shape and kinetics of crystal growth. Importantly, these findings are being obtained using multiple biophysical and imaging approaches (in collaboration with investigators from the Max Planck Institute and the University of Pittsburgh) designed to aid in the determination of the structure and mechanism of formation of proposed higher-order assemblies of the full-length amelogenin and the mechanism by which such assemblies regulate the formation of organized mineral structures. Long term, such information should provide new insights for the development of bio-inspired materials and novel approaches for mineralized tissue repair and regeneration.
Building on our knowledge of calcium phosphate chemistry and our current understanding of how mineral deposition and organization are regulated in developing mineralized tissues, we are currently carrying out research to investigate novel approaches to the repair (regeneration) of diseased or damaged dental tissues. These studies are designed to improve our understanding of how biomimetic approaches can be used to regenerate enamel and properly restore normal tooth enamel structure and properties. Our overall working hypothesis is that the regeneration of proper tooth structure and function can be achieved through the regulation of mineral ion diffusion, crystal growth kinetics and crystal orientation. For example, we are presently exploring the use of stabilized supersaturated calcium phosphate solutions, where mineralization can be regulated by an enzyme. We propose to extend these studies to include the use of other biologically relevant molecules to regulate the rate, crystal shape, and orientation of growing enamel crystals in the repair of damaged dental enamel. These latter studies will be carried out in collaboration with Dr. Elia Beniash (University of Pittsburgh).
Summary
Our research is designed to find out how nature produces a highly functional mineralized tissue (i.e., dental enamel) and to use this insight to develop new approaches for the repair and/or regeneration of damaged or diseased mineralized tissue.
Wiedemann-Bidlack FB, Kwak S-Y, Beniash E, Yamakoshi Y, Simmer JP, Margolis HC (2011) . Effects of phosphorylation on the self-assembly of native full-length porcine amelogenin and its regulation of calcium phosphate formation in vitro. J. Struct. Biol. 173: 250-60.
Le Norcy E, Kwak S-Y, Wiedemann-Bidlack FB, Beniash E, Yamakoshi Y, Simmer JP, Margolis HC (2011). Potential Role of the Amelogenin N-terminus in the Regulation of Calcium Phosphate Formation In Vitro. Cells Tissues Organs 194:188-193.
Fang P-A, Margolis HC, Conway JF, Simmer JP, Dickinson GH, Beniash E (2011). Cryo-EM study of amelogenin self-assembly at different pH. Cells Tissues Organs 194:166-170.
Le Norcy E, Kwak S-Y, Wiedemann-Bidlack FB, Beniash E, Yamakoshi Y, Simmer JP, Margolis HC (2011). Leucine-rich Amelogenin Peptides Regulate Mineralization In Vitro. J. Dent. Res. J. Dent. Res. 90:1091-7.
Fang P-A, James F. Conway JF, Margolis HC, Simmer JP, Beniash E (2011). Hierarchical Self-Assembly of Amelogenin and the Regulation of Biomineralization at the Nanoscale. Proc. Nat. Acad. Sci. USA. 108:14097-102
Le Norcy E, Kwak S-Y, Allaire M, Yamakoshi Y, Simmer JP, Margolis HC (2011). Effect of phosphorylation on the interaction of calcium with leucine-rich amelogenin peptide. Eur. J. Oral Sci. (In press).
Kwak S-Y, Green S, Wiedemann-Bidlack FB, Beniash E, Yamakoshi Y, Simmer JP, Margolis HC (2011). Regulation of calcium phosphate formation by amelogenins under physiological conditions. Eur. J. Oral Sci. (In press).
Cao H, Wang J, Li X, Florez S, Huang Z, Venugopalan SR, Elangovan S, Skobe Z, Margolis HC, Martin JF, Amendt BA (2010). MicroRNAs Play a Critical Role in Tooth Development. J. Dent. Res. 89:779-84.
Deshpande AS, Fang PA, Simmer JP, Margolis HC, Beniash E (2010). Amelogenin-collagen interactions regulate calcium phosphate mineralization in vitro. J. Biol. Chem. 285:19277-19287.
Margolis HC, Beniash E (2010). The Role of Amelogenin in Dental Enamel Formation: A Universal Strategy for Protein-Mediated Biomineralization, In: Amelogenins: Multifaceted Proteins for Dental and Bone Formation and Repair, Bentham Science Publishers, pp 133-142.
Kwak, SY. Wiedemann-Bidlack FB, Beniash E, Yamakoshi Y, Simmer JP, Litman A, Margolis HC (2009). Role of 20-kDa amelogenin (P148) phosphorylation in calcium phosphate formation in vitro. J Biol Chem. 284:18972-9.
Aichmayer B, Wiedemann-Bidlack FB, Gilow C, Simmer JP, Yamakoshi Y, Emmerling F, Margolis HC and Fratzl P (2009). Amelogenin nanoparticles in suspension: deviations from spherical shape and pH-dependent aggregation. Biomacromolecules 11:369-376
Yamazaki H, Margolis HC. 2008. Enhanced enamel remineralization under acidic conditions in vitro. J Dent Res. 87:569-74.
Wiedemann-Bidlack FB, Beniash E, Yamakoshi Y, Simmer JP, Margolis HC. 2007. pH triggered self-assembly of native and recombinant amelogenins under physiological pH and temperature in vitro. J Struct Biol 160:57-69.
Felicitas Bidlack, Ph.D. *
Seo-Young Kwak, PhD.
* and Manager, Biostructure Core Facility
Min Kyeong Lee, D.M.D.
Shankar Rengasamy Venugopalan, B.D.S., Ph.D.
Amy E. Litman, M.S.
Hajime Yamazaki, M.S.
