Platelet-derived growth factor (PDGF) is a potent activator for cells of mesenchymal origin. PDGF stimulates chemotaxis, proliferation, and new gene expression in monocytes-macrophages and fibroblasts in vitro, cell types considered essential for tissue repair. Therefore, we analyzed the influence of exogenously administered recombinant B chain homodimers of PDCF (PDCF-BB) on two experimental tissue repair paradigms, incisional and excisional wounds. In both types of wounds, as little as 20-200 picomoles applied a single time to wounds significantly augmented the time dependent influx of inflammatory cells and fibroblasts and accelerated provisional extracellular matrix deposition and subsequent collagen formation. In incisional wounds, PDCF-BB augmented wound breaking strength 50-70% over the first 3 weeks; in excisional wounds, PDGF-BB accelerated time to closure by 30%. PDCF-BB exaggerated, but did not alter, the normal course of soft tissue repair, resulting in a significant acceleration of healing.
Long term observations established no apparent differences between PDCF-BB treated and non-treated wounds. Thus, the vulnerary effects of PDGF-BB were transient and fully reversible in both wound healing models. Furthermore, analysis of PDCF-treated and non-treated wounds has provided important insights into mechanisms of normal and deficient tissue repair processes. PDCF appears to transduce its signal through wound macrophages and may trigger the induction of positive autocrine feedback loops and synthesis of endogenous wound PDGF and other growth factors, thereby enhancing the cascade of tissue repair processes required for a fully-healed wound. Thus, PDCF and other wound produced polypeptide growth factors may be the critical regulators of extracellular matrix deposition within healing wounds.