OBJECTIVE: To investigate the changes in autophagy of mesenchymal stem cells (MSCs) from patients with ankylosing spondylitis and explore the mechanism for decreased autophagy in ASMSCs. METHODS: MSCs collected from 14 patients with AS (ASMSCs) and from 15 healthy donors (HDMSCs) were cultured in the absence or presence of 25 ng/mL TNF-α for 6 h. Autophagy of the cells was determined by immunofluorescence staining of GFP-LC3B, and the results were confirmed by detecting the protein expressions of autophagy markers LC3 II/LC3 I and P62. The mRNA expressions of the related genes were detected using qRT-PCR, and the protein expressions of the autophagy markers and signaling pathway-related molecules were determined with Western blotting. TG100713 was used to block the PI3K/AKT/mTOR signal pathway, and its effect on autophagy of ASMSCs was evaluated. RESULTS: ASMSCs showed significantly weaker GFP-LC3B puncta staining and lower protein expression levels of LC3 II/LC3 I but higher levels of P62 protein (P < 0.05), indicating a decreased autophagy capacity as compared with HDMSCs. TNF-α-induced ASMSCs showed significantly higher protein expressions of p-PI3K/ PI3K, p-AKT/AKT and p-mTOR/mTOR than HDMSCs (P < 0.05), suggesting hyperactivation of the PI3K/AKT/mTOR signaling pathway in ASMSCs. Blocking PI3K/AKT/mTOR signaling with TG100713 eliminated the difference in TNF-α-induced autophagy between HDMSCs and ASMSCs. CONCLUSION In patients with AS, hyperactivation of the PI3K/AKT/mTOR signaling pathway results in decreased autophagy of the MSCs and potentially contributes to chronic inflammation.
Autophagy ; Humans ; Mesenchymal Stem Cells/metabolism* ; Phosphatidylinositol 3-Kinases/metabolism* ; Proto-Oncogene Proteins c-akt/metabolism* ; Signal Transduction ; Spondylitis, Ankylosing ; TOR Serine-Threonine Kinases/metabolism* ; Tumor Necrosis Factor-alpha/metabolism*