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The purpose of this study was to evaluate effects of human platelet-rich plasma (PRP)-containing fragmin/protamine microparticles (F/P MPs) as a protein carrier on neovascularization and granulation tissue formation. Frozen and thawed PRP contains high concentrations of various growth factors (GFs) and F/P MPs effectively adsorb those GFs. Human microvascular endothelial cells (MVECs) and dermal fibroblast cells (DFCs) were optimally grown in medium containing 4% PRP and the addition of F/P MPs significantly maintained and protected the proliferative activity of PRP incubated at 37°C for more than 10 days. When PRP-containing F/P MPs were subcutaneously injected into the back of mice, significant neovascularization was induced near the injected site with enhanced filtration of inflammatory cells from day 3 to day 30, compared with controls (injections of PRP, F/P MPs, and saline). Both PRP-containing F/P MPs and PRP alone induced significant formation of granulation tissue at the injected site. However, thickness of induced granulation tissues was well maintained for 30 days only in PRP-containing F/P MP-injected group. Those bound GFs may be gradually diffused and released from F/P MPs in vitro and in vivo. Thereby, PRP-containing F/P MPs offer significantly higher inductions of vascularization and fibrous tissue formation in vivo than PRP alone.

We evaluated the effects of fragmin/protamine micro-particles (F/P MPs) containing FGF-2 (F/P MP-F) as carriers for the controlled release of FGF-2 for adipocyte-survival and capillary formation in inbred rats with subdivided free fat grafts. F/P MPs could immobilize FGF-2, thereafter gradually releasing the bound FGF-2. Inbred Fisher 344 rats weighing around 150 g were anesthetized and implanted with paste comprising harvested fat combined with F/P MP-F. The effect of F/P MP-F on the survival, granulation, and capillary formation in fat grafts was histologically compared with control grafts containing either FGF-2, F/P MPs or PBS. The control fat grafts became attached to tissues adjacent to the implantation site and were significantly resorbed after 30 days. In contrast, pink, soft, supple grafts were compressible and were little resorbed in the group given F/P FP MP-F at 30-120 days. Normal adipocytes were obviously decreased in the control groups with increased granulation tissues, whereas normal adipocytes with capillary formations were maintained in the F/P MP-F group. Thus, adding F/P MP-F to subdivided fat grafts helps to improve graft volume retention and survival in soft-tissue reconstruction through accelerating adipocyte-survival rates and angiogenesis.