Platelet-rich plasma contains high concentrations of growth factors that stimulate proliferation and migration of various cell types. Earlier experiments demonstrated that local platelet-rich plasma administration activates Schwann cells to improve axonal regeneration at a transected peripheral nerve lesion. However, the optimal concentration of human platelet-rich plasma for activation of human Schwann cells has not been determined, and mechanisms by which platelet-rich plasma activates Schwann cells remain to be clarified.