EFFECTS OF HETERODIMERIC ISOFORM OF PLATELET-DERIVED GROWTH-FACTOR PDGF-AB ON WOUND-HEALING IN THE RAT

Earlier wer reported a positive effect of platelet-derived growth fact or (PDGF-BB) on rat wound healing while corresponding doses of PDGF-AA were not as effective. The present work was undertaken to study the e ffects of the heterodimeric form of PDGF (PDGF-AB) on wound healing in rats. Subcutaneously implanted hollow cylindrical cellulose sponges s erved as an inductive matrix for the granulation tissue. Fifty microli ters of solutions containing 0, 5, 50 or 500 ng of PDGF-AB heterodimer were injected daily into the sponges. The analyses of the granulation tissue in the sponge cylinders were carried out 7 days after implanta tion. Injections of 500 ng of PDGF-AB stimulated significantly the acc umulation of collagen and proteins, indicated by the elevated hydroxyp roline and nitrogen content of the sponge (+ 51%, p < 0.01 and + 48%, p < 0.001, respectively). Similarly, the amounts of DNA, RNA, hexosami nes and uronic acids were significantly higher, reflecting a PDGF-AB-i nduced increase in the cellularity and glycosaminoglycans. Analyses of wound fluid showed a marked decrease in the number of polymorphonucle ar leukocytes in response to PDGF-AB treatment. Injections of a lower dose, 50 ng, of PDGF-AB increased significantly the mean amounts of ni trogen, RNA and uronic acids but no significant changes were observed in other parameters. The lowest dose of PDGF-AB, 5 ng daily, induced n o essential effect. In vitro PDGF-AB increased the number of rat granu lation tissue-derived fibroblasts and collagen accumulation per cultur e dish at concentrations of 10 and 30 ng/ml. To conclude, PDGF-AB acce lerates dose-dependently granulation tissue formation in experimental wounds. Correspondingly, PDGF-AB stimulates the proliferation of granu lation tissue-derived fibroblasts in culture.