基于自噬途径的骨髓间充质干细胞促进老龄大鼠受损跟腱愈合的作用机制OA

Objective To investigate the mechanism of autophagy in bone marrow mesenchymal stem cells(BMSCs)in repairing Achilles tendon injuries in aged rats.Methods Partial rupture mod-els of the Achilles tendon were established in young and aged rats.At 28 days postoperatively,repair was evaluated by histological staining(HE and Masson staining),immunohistochemistry[cell prolifer-ation antigen Ki67(Ki67),type Ⅰ collagen(COL Ⅰ),and type Ⅲ collagen(COL Ⅲ)],and bio-mechanical testing.Meanwhile,BMSCs were isolated from young and aged rats,and the expressions of autophagy-related proteins[microtubule-associated protein 1 light chain 3(LC3),autophagy-related protein 5(ATG5),P62,and lysosome-associated membrane protein 1(Lamp1)]were detected by Western blot to assess autophagy levels.Autophagy-enhanced BMSCs(BMSCATG5+)were constructed by transfecting the ATG5 gene using a lentiviral vector and transplanted into the Achilles tendon injury sites of aged rats.Histological and biomechanical differences between the BMSCATG5+rats and the BMSCvector rats were compared.Additionally,the expressions of tendon-forming-related proteins COL Ⅰ,tenascin C(TNC),and tenomodulin(TNMD)were detected to explore the effect of enhanced auto-phagy on tendon-forming differentiation of BMSCs.Results The repair capacity after Achilles ten-don injury was significantly reduced in aged rats(P＜0.05 or P＜0.01),characterized by disor-ganized collagen fiber arrangement,marked inflammatory cell infiltration,decreased expression of Ki67 and COL Ⅰ,increased expression of COL Ⅲ,and decreased failure load and stiffness.Com-pared with BMSCs from the young rats,expressions of ATG5 and Lamp1 protein were decreased,P62 protein accumulated,and LC3-Ⅱ/LC3-Ⅰ levels decreased in BMSCs from the aged group(P＜0.05),suggesting impaired autophagic flux.Overexpression of ATG5 significantly enhanced the au-tophagy level of BMSCs(P＜0.01).Transplantation of BMSCATG5+improved the histological struc-ture of the Achilles tendon in aged rats,reduced the inflammatory response,significantly increased the expression of Ki67 and COL Ⅰ,decreased the expression of COL Ⅲ,and significantly in-creased the failure load and stiffness(P＜0.05 orP＜0.01).Further detection showed that the ex-pression of COL Ⅰ,TNC,and TNMD in BMSCATG5+cells was significantly upregulated(P＜0.01),suggesting that enhanced autophagy promotes tendon-forming differentiation of BMSCs.Conclusion Enhancing ATG5-dependent autophagy can restore the tendon-forming differentiation potential of BMSCs and significantly improve tendon repair and biomechanical properties in aged rats.ATG5-mediated autophagy activation can directly drive tendon-forming differentiation of BMSCs and is an important mechanism for promoting Achilles tendon healing in the aged,providing poten-tial insights for exploring biological regulatory strategies for tendon regeneration.