Cell-Free Fat Extract Attenuate Osteoarthritis via Chondrocytes Regeneration and Macrophages Immunomodulation

Abstract

Background: The prevalence of osteoarthritis (OA) is increasing, yet clinically effective and economical treatments are unavailable. We have previously proposed a cell-free fat extract (CEFFE) containing multiple cytokines, which possessed anti-apoptotic, anti-oxidative, and proliferation promotion functions, as a “cell-free” strategy. In this study, we aimed to evaluate the therapeutic effect of CEFFE in vivo and in vitro . Methods: In vivo study, sodium iodoacetate-induced OA rats were treated with CEFFE by intra-articular injections for 8 weeks. Behavioral experiments were performed every two weeks. Histological analyses, anti-type II collagen, and toluidine staining provided structural evaluation. Macrophage infiltration was assessed by anti-CD68 and anti-CD206 staining. In vitro study, the effect of CEFFE on macrophage polarization and secretory factors was evaluated by flow cytometry, immunofluorescence, and quantitative reverse-transcription polymerase chain reaction (qRT-PCR). The effect of CEFFE on cartilage regeneration was accessed by cell counting kit-8 assay and qRT-PCR. The generation of reactive oxygen species (ROS) and levels of ROS-related enzymes were investigated by qRT-PCR and western blotting. Results: In rat models with sodium iodoacetate (MIA)-induced OA, CEFFE increased claw retraction pressure while decreasing bipedal pressure in a dose-depend manner. Moreover, CEFFE promoted cartilage structure restoration and increased the proportion of CD206 + macrophages in the synovium. In vitro , CEFFE decreased the proportion of CD86 + cells and reduced the expression of pro-inflammatory factors in LPS + IFN-γ induced Raw 264.7. In addition, CEFFE decreased the expression of interleukin-6 and ADAMTs-5 and promoted the expression of SOX-9 in mouse primary chondrocytes. Besides, CEFFE reduced the intracellular levels of reactive oxygen species in both in vitro models through regulating ROS-related enzymes. Conclusions: CEFFE inhibits the progression of OA by promoting cartilage regeneration and limiting low-grade joint inflammation.