PRP treatment effects on degenerative tendinopathy - an in vitro model study

Platelet-rich plasma (PRP) has become a popular option for the treatment of injured tendons. However, the efficacy of PRP treatment is a matter of heated debate in orthopaedics and sports medicine. In this study, we used a cell culture model to evaluate the potential effects of PRP treatment on degenerative tendinopathy. The in vitro model, which uses the current concept of "diseases-in-a-dish", consisted of tendon stem/progenitor cells (TSCs) that were derived from rabbit tendons and cultured in differentiating media with and without autologous platelet-rich clot releasate (PRCR). We found that 10% PRCR treatment of TSCs blocked their non-tenogenic differentiation, as evidenced by the marked decrease in lipid droplets, proteoglycan accumulation, and calcium deposition on cell surfaces. Moreover, the protein markers for non-tenocytes (adiponectin, collagen type II, and osteocalcin) were either minimally expressed or greatly reduced. However, after TSCs underwent non-tenogenic differentiation by pre-treatment in non-tenogenic media for two days, PRCR only slightly reduced adipogenesis and osteogenesis of TSCs, although chondrogenesis was markedly suppressed. Finally, PRCR treatment after pre-treatment of TSCs in non-tenogenic media for one week had little effect on any of the three nontenogenic differentiations of TSCs. These findings suggest that the injection of PRP in clinics may not be able to effectively reverse the degenerative conditions of late-stage tendinopathy, which are characterized by lipid depositions, proteoglycan accumulation, and calcification, either alone or in combination.