Protein extracts of dentin affect proliferation and differentiation of osteoprogenitor cells in vitro

PROTEINS ASSOCIATED WITH THE MINERAL PHASE Of dentin are considered to have the potential to alter cell function within the local environment, during development and regeneration of tooth/periodontal tissues. Cells that may b e altered include osteoblasts, ameloblasts, periodontal ligament cells, odo ntoblasts, and cementoblasts. However, specific factors within dentin contr olling cell activity have not been elucidated. To investigate further the r ole of dentin proteins in regulating cell behavior, MC3T3-E1 cells, a mouse osteoprogenitor cell line, were exposed to guanidine/EDTA extracts of dent in (G/E-D) prepared from bovine teeth. Cells, with or without G/E-D (2 to 5 0 mu g/ mi), were evaluated for proliferative activity and for mRNA express ion of bone-associated genes. Results indicated that G/E-D suppressed cell proliferation and caused striking morphological changes, including the conv ersion of cuboidal cells into fibroblastic, spindle-shaped cells. Markers o f osteoblast differentiation, osteocalcin and bone sialoprotein mRNA were d ecreased, while osteopontin mRNA was enhanced in cells exposed to G/E-D. Si nce transforming growth factor beta (TGF beta(1)) has been reported to infl uence cells in a similar fashion, G/E-D were examined for the presence of a nd concentration of TGF beta using slot blot analysis and enzyme immunoassa y (ELISA), respectively. These analyses demonstrated that G/E-D contained 6 .6 ng/mg of TGF beta(1). Next, cells were exposed to G/E-D in conjunction w ith anti-TGF beta(1,2,3) antibody. When cells were exposed to antibody, G/E -D-mediated changes in morphology and gene expression were blocked. These r esults suggest that TGF beta(1) and perhaps other factors in dentin can reg ulate cell behavior and, therefore, can influence development, remodeling, and regeneration of mineralized tissues.