Autologous Platelet-rich Clot Releasate Stimulates Proliferation and Inhibits Differentiation of Adult Rat Tendon Stem Cells Towards Nontenocyte Lineages

OBJECTIVE: To explore the effects of autologous platelet-rich clot releasate (PRCR) on proliferation and differentiation of adult rat tendon stem cells (TSCs) in vitro, following intense mechanical stretching. METHODS: TSCs were subjected to 8% mechanical stretching and subsequently incubated in control medium or medium supplemented with 2% or 10% PRCR. Collagen types I and III, peroxisome proliferator-activated receptor-gamma (PPAR gamma), sex determining region Y-box 9 (SOX-9) and runt-related transcription factor 2 (RUNX2) concentrations were assessed via Western blotting and flow cytometry. Transforming growth factor (TGF)-beta(1) and vascular endothelial growth factor concentrations were measured using enzyme-linked immunosorbent assay. Treated TSCs were also cultured in adipogenic, chondrogenic or osteogenic culture media. RESULTS: PRCR increased the number of TSCs, and the concentrations of collagen types I and III and TGF-beta(1). In contrast, PRCR significantly reduced PPAR gamma, SOX-9 and RUNX2-positive cell numbers, and significantly reduced the numbers of TSC-derived adipocytes, chondrocytes and osteocytes. CONCLUSION: PRCR induced tenocyte differentiation while suppressing the adipocyte, chondrocyte and osteocyte lineages believed to impede tendon healing.