TRIM3 exacerbates chondrocyte apoptosis through suppression of AKT/mTOR signaling pathway in osteoarthritis

As a leading cause of disability worldwide, osteoarthritis (OA) progressively degrades articular cartilage. The incomplete understanding of OA's molecular mechanisms hinders development of disease-modifying treatments.

We analyzed GEO database knee OA datasets to track TRIM3 expression dynamics throughout disease progression. Western blot and IHC quantified TRIM3 protein differences between OA and normal cartilage. TRIM3-knockdown chondrocytes showed altered Bcl-2/Bax ratios via qRT-PCR/Western blot, with p-AKT/p-mTOR levels indicating AKT/mTOR activation. To establish functional dependency, siTRIM3 cells were treated with mTOR inhibitor followed by reevaluation of Bcl-2/Bax balance. Apoptotic responses to IL-1β stimulation were quantified by flow cytometry, while collagen II (COL2A1) preservation was visualized via immunofluorescence.

Integrated bioinformatics and IHC analyses demonstrated significant TRIM3 upregulation in OA cartilage compared to healthy controls (P = 0.043). TRIM3 depletion exerted dual protective effects: (1) modulating apoptotic regulators by decreasing Bax while increasing Bcl-2 expression, and (2) enhancing AKT/mTOR pathway activation evidenced by elevated p-AKT/p-mTOR levels.Notably, mTOR inhibition abolished these effects, restoring pro-apoptotic Bax expression and suppressing anti-apoptotic Bcl-2 (p < 0.01), confirming pathway mediation. Functionally, siTRIM3 conferred 40% reduction in IL-1β-induced apoptosis (P = 0.0081) and remarkably preserved COL2A1 integrity, exhibiting 2.3-fold higher fluorescence intensity versus controls.

Our findings establish TRIM3 as a novel regulator of OA pathogenesis that exacerbates disease progression through AKT/mTOR pathway suppression, thereby promoting chondrocyte apoptosis and extracellular matrix degradation. Therapeutic targeting of TRIM3 may represent a promising strategy to attenuate cartilage degeneration in OA.