Effect of RGD coating on osteocompatibility of PLGA-polymer disks in a rat tibial wound

Osteocompatibility of porous polylactic-glycolic acid (PLGA) disks coated with synthetic peptides was assessed in 5-mm diameter unicortical tibial osseous wounds in rats. The coatings consisted of various ratios of peptides including the tripeptide arginine-glycine-aspartic acid (RGD) and the inactive arginine-glycine-glutamic acid (RGE). When left empty, the tibial wounds healed spontaneously with proliferation of intramedullary woven bone within 1 week. The reactive bone was resorbed, and by 3 weeks, the cortical wound was healed with lamellar bone, and the medullary space was repopulated with marrow. When PLGA disks were implanted there was a delay in repair with reduced bone fill and no bone bridging at 3 weeks. When disks were coated with increasing amounts of RGD peptide, there was a biphasic effect on osteocompatibility and on osseous ingrowth. Evaluation at 10 days showed a dose-dependent increase, with 1.5-fold greater osteocompatibility (p < 0.05) and 1.6-fold more osseous ingrowth into the polymer (p < 0.01) than uncoated disks. With more RGD and with undiluted RGE, osteocompatibility and osseous ingrowth were the same as with uncoated disks. At 3 weeks, there were no significant differences among all the groups. These data indicate that RGD coating enhanced early stages of osteocompatibility and ingrowth.