Objective To investigate whether the supernatants of thrombin-activated platelet-rich plasma could be used as a substitute for the isolation and culture-expansion of human mesenchymal stem cells.Methods Human marrow mesenchymal stem cells(MSC) were cultured in media containing the supernatants of thrombin-activated platelet-rich plasma (tPRP) and fecal calf sera(FCS) selected from lots.Their proliferation status was evaluated by MTT and carboxyfluorescence diacetatesuccinimidyl ester-labeling assays.Furthermore,the phenotypic characteristics were analyzed by flow cytometry and the differentiations along adipogenic and osteogenic pathways were assessed by histological staining.Results MSC cultured in medium containing tPRP displayed a typical fibroblast-like morphology and,compared with(FCS),tPRP exhibited more potent activities to support the expansion of MSC.Flow cytometry showed that they were homogenously positive for CD29, CD73,CD166 and HLA-ABC and negative for CD31,CD34,CD45 and HLA-DR.Differentiation assays showed that of MSC cultured with tPRP occupied the capacities of in vitro osteogenesis and adipogenesis.Conclusion It is concluded that human tPRP might be an optional substitute to FCS for MSC proliferation.