Enhancement of vascularization and granulation tissue formation by growth factors in human platelet‐rich plasma‐containing fragmin/protamine microparticles

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. © 2011 Wiley Periodicals, Inc. J Biomed Mater Res Part B: Appl Biomater, 2011.