Biomineralization is one of the most widespread and important processes in both vertebrates and invertebrates. We have directed our efforts to study the mineralization of bone and dentin in which apatite crystals are specifically grown within type I collagen matrices. Although it is likely that the overall mechanisms involved in mineralization of the two tissues are similar, we have adopted the dentin system since it represents a relatively simpler system than bone. The basic working hypothesis has been that certain acidic, phosphorylated, non-collagenous extracellular matrix protein macromolecules (NCP) are first localized by interaction with the collagen I fibril surfaces, which then direct the nucleation of crystal deposits and orientation of certain specific crystallographic habit directions relative to the fibril axes. Further interactions of the NCP with the growing crystals are postulated to specifically regulate crystal growth in terms of habit, shape and size. Although there are many NCP present in dentin, we have focused our efforts on the primary phosphoprotein of dentin: Phosphophoryn ([PP]). PP is very acidic in nature and characterized by a very high content of serine residues, at about an 85 percent level of phosphorylation. In this proposal we plan to introduce the gene encoding for PP to over-express it in fibroblast, osteoblast and odontoblast cells, respectively. This will enable us to establish an in vivo system to study biomineralization. We will characterize the mineralization of the crystals in these three separate cells to ascertain the nucleation and crystal growth directions. This approach will allow us to address many important questions: Is the post-translationnal modification of PP similar in fibroblast in contrast to osteoblast and/or odontoblast cells? Will the mineralized crystal have the same crystallographic properties when the nucleating protein, such as PP, is expressed in a fibroblast without the rest of the NCP, which is usually expressed in an osteoblast or odontoblast? We will also study the effect of phosphorylation on the Mineralization process in vitro by expressing the recombinant PP and studying its in vitro phosphorylation on the mineral. These studies should yield new information related to the specific role of phosphoproteins in biomineralization. This knowledge will be extremely valuable in determining the mechanisms involved in the biomineralization process particularly since the studies are conducted in an in vivo model in comparison to the traditional approaches of in vitro studies of biomineralization. This data will also provide basic knowledge for designing treatment of ectopic mineralization specifically in diseases as such kidney stones or failing heart valve prosthesis.

Agency
National Institute of Health (NIH)
Institute
National Institute of Dental & Craniofacial Research (NIDCR)
Type
Research Project (R01)
Project #
5R01DE016123-04
Application #
7231485
Study Section
Skeletal Biology Development and Disease Study Section (SBDD)
Program Officer
Lumelsky, Nadya L
Project Start
2004-08-01
Project End
2010-05-31
Budget Start
2007-06-01
Budget End
2010-05-31
Support Year
4
Fiscal Year
2007
Total Cost
$283,113
Indirect Cost
Name
University of Pittsburgh
Department
Dentistry
Type
Schools of Dentistry
DUNS #
004514360
City
Pittsburgh
State
PA
Country
United States
Zip Code
15213
Sfeir, Charles; Fang, Ping-An; Jayaraman, Thottala et al. (2014) Synthesis of bone-like nanocomposites using multiphosphorylated peptides. Acta Biomater 10:2241-9
Beniash, Elia; Deshpande, Atul S; Fang, Ping An et al. (2011) Possible role of DMP1 in dentin mineralization. J Struct Biol 174:100-6
Deshpande, Atul Suresh; Fang, Ping-An; Zhang, Xiaoyuan et al. (2011) Primary structure and phosphorylation of dentin matrix protein 1 (DMP1) and dentin phosphophoryn (DPP) uniquely determine their role in biomineralization. Biomacromolecules 12:2933-45
Sfeir, Charles; Lee, Donghyun; Li, Jinhua et al. (2011) Expression of phosphophoryn is sufficient for the induction of matrix mineralization by mammalian cells. J Biol Chem 286:20228-38
Ko, Hsu-Feng; Sfeir, Charles; Kumta, Prashant N (2010) Novel synthesis strategies for natural polymer and composite biomaterials as potential scaffolds for tissue engineering. Philos Trans A Math Phys Eng Sci 368:1981-97
Li, Jinhua; Olton, Dana; Lee, Donghyun et al. (2009) Cell derived hierarchical assembly of a novel phosphophoryn-based biomaterial. Cells Tissues Organs 189:252-5
Jadlowiec, Julie A; Zhang, Xiaoyuan; Li, Jinhua et al. (2006) Extracellular matrix-mediated signaling by dentin phosphophoryn involves activation of the Smad pathway independent of bone morphogenetic protein. J Biol Chem 281:5341-7