Adipose-derived stem cells induce autophagic activation and inhibit catabolic response to pro-inflammatory cytokines in rat chondrocytes.

OBJECTIVE: Adipose-derived stem cells (ADSCs) have been demonstrated to have an anti-apoptosis effect on chondrocytes; However, their effect on autophagic activation remains unclear. We sought to explore whether ADSCs can activate autophagy and inhibit IL-1β- and lipopolysaccharide (LPS)-induced catabolism in chondrocytes.

METHODS: ADSCs and chondrocytes were collected from SD rats. The biologic characteristics of ADSCs were analyzed by flow cytometric analysis, Oil red O and Alizarin Red staining. Autophagic level and autophagic flux were revealed by Western blotting for LC3-II and SQSTM1/P62, MDC (monodansylcadaverine) staining and mRFP-GFP-LC3 analysis. The mTOR pathway was investigated by Western blotting for p-mTOR. The mRNA level of matrix metalloproteinases (MMPs) and thrombospondin motifs (ADAMTSs) was detected by real-time PCR.

RESULTS: The typical surface markers and differentiation potentials of ADSCs were proved. ADSCs enhanced the expression of LC3-II/LC3-I and reduced SQSTM1 levels in IL-1β-induced chondrocytes after 24 and 48 h co-culturing and in LPS-induced chondrocytes after 48 h co-culturing respectively. mRFP-GFP-LC3 analysis suggested that autophagosomes and autolysosomes were formed earlier in IL-1β-treated chondrocytes than in LPS-treated chondrocytes. Bafilomycin A1 treatment further increased the LC3-II/LC3-I level in chondrocytes in co-culture with ADSCs. The mTOR pathway was inhibited in the chondrocytes in co-culture with ADSCs. Finally, ADSCs inhibited the increase of MMPs and ADAMTSs in chondrocytes induced by IL-1β and LPS.

CONCLUSIONS: ADSCs seem able to activate autophagy and inhibit catabolism in chondrocytes in an inflammation environment, and the mTOR pathway might be involved in the autophagy activation.