Background: Osteoarthritis (OA) is a highly degenerative joint disease, mainly companying with progressive destruction of articular cartilage. Adipose-derived stromal cells (ADSCs) therapy enhances articular cartilage repair, extracellular matrix (ECM) synthesis and attenuates joints inflammation, but specific mechanisms of therapeutic benefit remain poorly understood. This study aimed to clarify the therapeutic effects and mechanisms of ADSCs on cartilage damage in keen joint of OA rat model. Methods: In vivo study, destabilization of the medial meniscus (DMM) and anterior cruciate ligament transection (ACLT) surgery-induced OA rats were treated with allogeneic ADSCs by intra-articular injections for 6 weeks. The protective effect of ADSCs in vivo was measured using Safranin O and fast green staining, immunofluorescence and western blot analysis. Meanwhile, the miRNA-7-5p (miR-7-5p) expression was assessed by quantitative reverse transcription-polymerase chain reaction (qRT-PCR). The mechanism of increased autophagy with ADSCs addition through decreasing miR-7-5p was revealed using oligonucleotides, adenovirus in rat chondrocytes. The luciferase reporter assay were used to reveal the molecular role of miR-7-5p and autophagy related 4A (ATG4A). The substrate of mTORC1 pathway: (p-)p70S6 and (p-)S6 in OA models with ADSCs addition were detected by western blotting. Results: The ADSCs treatment repaired the articular cartilage and maintained chondrocytes ECM homeostasis through modulating chondrocytes autophagy in OA model, indicators of the change of autophagic proteins expression and autophagic flux. Meanwhile, the increased autophagy induced by ADSCs treatment was closely related to the decreased expression of host-derived miR-7-5p, negative modulator of OA progression. Functional genomics (overexpression of genes) in vitro studies demonstrates inhibition of host-derived miR-7-5p in mediating the benefit of ADSCs administration in OA model. Then ATG4A were defined as a target gene of miR-7-5p, and the negative relation between miR-7-5p and ATG4A were investigated in OA model treated with ADSCs. Furthermore, miR-7-5p mediated chondrocyte autophagy by targeting ATG4A in OA cell model treated with ADSCs was confirmed with the rescue trial of ATG4A/miR-7-5p overexpression on rat chondrocyte. Finally, the mTORC1 signaling pathways mediated by host-derived miR-7-5p with ADSCs treatment were decreased in OA rats. Conclusions: ADSCs promotes the chondrocytes autophagy through decreasing miR-7-5p in articular cartilage by targeting ATG4A and a potential role for ADSCs based therapeutics for prevention of articular cartilage destruction and extracellular matrix (ECM) degradation in OA.

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