Platelet-derived growth factor enhancement of a mineral-collagen bone substitute

Anorganic bovine bone-collagen matrix is commercially available for bone regeneration procedures. Platelet-derived growth factor-BB (PDGF-BB) has been demonstrated to stimulate bone formation in vivo and in vitro. It was the aim of these studies to examine 1) the interaction of this mineral-collagen matrix with PDGF-BB and 2) determine if the adsorption of PDGF-BB to the mineral-collagen matrix stimulates osteoblastic cell proliferation above that of the untreated matrix.

Measurement of PDGF-BB adsorption and release was accomplished using 125I radiolabeled growth factor. The PDGF-BB was incubated with the anorganic bovine bone-collagen matrix and the amount which adsorbed was determined. In the release studies, radiolabeled PDGF-BB was adsorbed to the matrix material, then the samples were incubated in buffer for various time periods. The amount of PDGF-BB retained on the matrix was measured and the percent of growth factor released calculated. The biological activity was tested in an in vitro assay with primary culture neonatal rat osteoblastic cells. Osteoblastic cells were cultured on bone mineral-collagen matrix with known amounts of adsorbed PDGF-BB. Proliferation of the cells was assessed by 3H-thymidine incorporation and cell attachment measured by prelabeling cells with 3H-leucine.

PDGF-BB adsorbed to the mineralized-collagen matrix material in a rapid, concentration-dependent fashion. The growth factor was slowly released from the matrix such that approximately 30% of the adsorbed protein was liberated over 10 days. PDGF-BB treated mineralized-collagen matrix displayed significantly (P < 0.05, ANOVA) enhanced proliferation of cultured osteoblastic cells compared to the mineralized-collagen matrix alone.

These results suggest that PDGF-BB is rapidly adsorbed then slowly released from the anorganic bovine bone-collagen matrix. PDGF-BB adsorbed to this material is able to stimulate proliferation of the attached osteoblastic cells. These data suggest that it may be clinically feasible to adsorb PDGF to this bone-collagen matrix and that this combination of bone growth factor and mineral-collagen matrix has the potential for clinical applications.