FRI0530 ADIPOSE DERIVED STEM CELLS TRANSPLANTATION AMELIORATES OSTEOARTHRITIS THROUGH AUTOPHAGY INDUCING VIA PI3K/AKT/MTOR SIGNALING

Background Osteoarthritis is characterized by joint inflammation and cartilage degradation. Adipose derived stem cells (ADSCs), as a source of adult mesenchymal stem cells, display similar multiple-linage differentiating potentials to bone marrow MSCs, only are much more abundant, much easier to isolate and expand, have been suggested for suppressing inflammatory responses and repairing cartilage damage. Autophagy are known to be take part in the pathogenesis of OA. Aging related changes of chondrocytes were related to increased mammalian target of rapamycin (mTOR) signaling and defective autophagy (1). We aim to determine the effect of ADSC on autophagy and its underlying mechanism. Objectives To investigate the effect of ADSCs on autophagy in a rat osteoarthritis model and IL-1-induced chondrocytes, and to ascertain whether it regulates autophagy via PI3K/AKT/mTOR signaling. Methods ADSCs and chondrocytes were isolated from SD rats. Flow cytometry was performed for ADSC phenotypic characterization. ADSCs and chondrocytes coculture were established in the presence of IL-1β. A rat anterior cruciate ligament transection (ACLT) OA model were established. ADSCs or irrelevant cell lines of similar number were injected in the osteoarthritis-affected joints. Autophagic activation was determined by Western blotting for LC3-II, p62, MDC (monodansylcadaverine) staining and GFP-LC3 fluorescence microscopy. Autophagy inhibition was mediated by siRNA knockdown of ATG5. Relevant proteins in the PI3K/AKT/mTOR signaling pathway were detected by western blotting. IL-1β, IL-6, TNFα, IFN-γ, Col2, MMP-1, 3 and -13 were measured. Histology of the target joints were evaluated. Results Application of ADSCs resulted in downregulation of MMP13 and upregulation of Col2 in OA model cartilage and IL-1β induced chondrocytes. ADMSCs decreased pro-inflammatory cytokines IL-1β, IL-6, and TNF-α in rat OA and IL-1β-induced chondrocytes. Autophagy was inhibited in OA model and IL-1β induced chondrocytes. ADSCs increased cell viability and autophagy-related proteins levels in vitro and in vivo. In IL-1β induced chondrocytes with ATG5 knockdown by siRNA, the effect of ADSCs on autophagy activation and its function as suppression of IL-1β induced pro-inflammatory cytokines was undermined. Furthermore, ADSCs remarkably decreased the expressions of phosphorylated (p)-PI3K, p-AKT and p-mTOR in IL-1β induced chondrocytes. Conclusion ADSCs inhibited the progression of cartilage degeneration in a rat OA model and provide an effective approach to decrease the pro-inflammatory cytokines secretion. ADSCs’ anti-inflammatory effect was associated with cell autophagy and these roles of ADSCs may be associated with PI3K/AKT/mTOR signaling pathway. References [1] Alvarez-Garcia O, Olmer M, Akagi R, Akasaki Y, Fisch KM, Shen T, Su AI, Lotz MK. Suppression of REDD1 in osteoarthritis cartilage, a novel mechanism for dysregulated mTORsignaling and defective autophagy.Osteoarthritis Cartilage. 2016; 24(9):1639-47. Disclosure of Interests None declared