β-galactosidase-targeted senolytic prodrug ameliorates preclinical models of post-traumatic osteoarthritis

BACKGROUND: Cellular senescence is involved in the pathogenesis of osteoarthritis (OA). This study aimed to identify prodrug SSK1 as a senolytic strategy for alleviating OA. METHODS: An oxidative stress-induced cellular senescence model was established to evaluate cell viability, replication, and genotoxicity after SSK1 treatment. Human OA chondrocytes and explants were collected to evaluate the therapeutic effect of prodrug SSK1 in vitro. In vivo evaluation was performed in young and aged male murine models. SSK1 (intra-articular injection every 3 days) was administrated 2 weeks after anterior cruciate ligament transection (ACLT) surgery. Animals were sacrificed 8 weeks after surgery. OA phenotype was analysed by micro-computerised tomography (μCT), histology and pain-related behaviour tests. FINDINGS: SSK1 showed precise, efficient, and broad-spectrum elimination of senescent chondrocytes. When co-cultured with human osteoarthritic chondrocytes and cartilage explants, the senolytic SSK1 prevented the generation of senescence-associated secretory phenotype factors, enhanced production of extracellular matrix (ECM) molecules, and promoted a regenerative chondral environment. Intra-articular administration of SSK1 showed improved pain response, enhanced retention of ECM, and remodelled subchondral bone homeostasis in both young and aged ACLT-induced OA murine model. INTERPRETATION: SSK1 is an effective candidate for senolytics in alleviating OA. The anti-ageing therapeutic effect of SSK1 lies in restoring a regenerative phenotype by improving the proliferation microenvironment, and reducing the accumulation of apoptotic signals in the joint microenvironment. FUNDING: Funded by the Regional Innovation Joint Fund of the National Natural Science Foundation of China (Integrated Project) (U23A6009), the National Natural Science Foundation of China (82202687, 82172420, and 82072486), the Beijing Municipal Natural Science Foundation (7222213), and the Capital's Funds for Health Improvement and Research (2022-4-20511), and Beijing Tongren Hospital Seed Funds (2021-YJJ-ZZL-008).