SIRT6 enhances the therapeutic potential of extracellular vesicles in mitigating osteoarthritis in rat models.

Abstract

Background: Extracellular vesicles (EVs) derived from human umbilical cord mesenchymal stem cells (hUCMSCs) have emerged as promising therapeutic candidates for osteoarthritis (OA). Sirtuin 6 (SIRT6), a class III histone deacetylase, exerts protective effects by preventing cellular senescence, reducing inflammation, and promoting longevity. This study aims to generate immortalized hUCMSCs with SIRT6 and telomerase reverse transcriptase (TERT) overexpression and investigate the therapeutic potential of their secreted EVs (EVs@SIRT6) in OA.

Methods: hUCMSCs were genetically engineered using lentiviral transduction to overexpress SIRT6 and TERT, referred to as SIRT6/TERT-hUCMSCs. Natural EVs and EVs@SIRT6 were isolated via differential ultracentrifugation and characterized by morphology, size distribution, marker expression, and proteomic signature. Their effects on IL-1β stimulated chondrocytes were assessed in vitro, including cell viability, apoptosis, scratch closure, inflammatory cytokine secretion, and oxidative stress. Transcriptomic alterations were analyzed by RNA sequencing. Therapeutic efficacy in vivo was evaluated in a rat anterior cruciate ligament transection (ACLT) model via micro-computed tomography, histological analyses, and immunohistochemistry.

Results: SIRT6/TERT-hUCMSCs preserved mesenchymal identity, trilineage differentiation potential, and sustained proliferative capacity up to passage 60, accompanied by longer telomeres and reduced senescence compared to parental cells. EVs@SIRT6 maintained typical EV features but were enriched in SIRT6 protein and displayed a distinct proteomic signature, comprising 1,440 unique proteins associated with nuclear/chromatin repair. In vitro, EVs@SIRT6 more effectively enhanced chondrocyte viability and wound healing while reducing apoptosis compared with natural EVs. EVs@SIRT6 also markedly alleviated inflammatory response, promoted anabolism, suppressed catabolism, and mitigated oxidative stress in chondrocytes. The protective effects of EVs@SIRT6 on chondrocytes were associated with the suppression of the JAK-STAT signaling pathway. Studies in a rat ACLT model further confirmed that EVs@SIRT6 outperformed natural EVs in attenuating subchondral osteosclerosis, reducing osteophyte formation, and mitigating cartilage damage.

Conclusions: Engineered EVs@SIRT6 outperform natural EVs in preserving chondrocytes homeostasis and reducing OA progression, establishing an efficient platform for preparing engineered EVs for clinical application.