Abstract: Objective The aim of the present study is to investigate whether frozen could influence platelet-rich plasma (PRP) releases growth factors, and whether frozen PRP could protect chondrocyte from IL-1β-induced injury. Methods PRP concentrates were obtained from healthy subjects by apheresis and were divided into 4 groups, then were frozen for as long as 3 months. The storage condition was -20 ℃ without preservation agent, -80 ℃ without preservation agent, -20 ℃ in 5% DMSO and -80 ℃ in 5% DMSO. The growth factors (PDGF-AB, VEGF and IGF-1) in PRP releasates were quantified by ELISA. The effect of PRP on the proliferation of IL-1β induced chondrocytes’inflammation was detected by CCK-8. The levels of IL-6 in cells were detected by ELISA. Results No significant difference was observed in PDGF-AB levels among fresh PRP group and frozen PRP groups. VEGF and IGF-1 levels were significantly decreased in the PRP samples stored at frozen conditions. No obvious difference with CCK-8 assay was observed between the PRP stored in -80 ℃ in 5% DMSO group and fresh PRP group. They both can promote IL-1β-induced inflammatory chondrocyte' s proliferation. The other three experimental groups can’t promote IL-1β-induced chondrocyte proliferation. After PRP treatment, IL-6 production of inflammatory chondrocyte was decreased. No statistically significant differences were found in IL-6 production between fresh PRP and frozen PRPs. Conclusions ome growth factor levels of PRP were reduced after frozen storage. But the frozen PRP can protect IL-1β-induced chondrocyte injury by inhibiting inflammatory response.

Key words: Platelet-rich plasma, PRP gel, Frozen storage, Chondrocyte inflammation