MSRB2 Ameliorates HO-induced Chondrocyte Oxidative Stress and Suppresses Apoptosis in Osteoarthritis.

Background: Chondrocyte oxidative stress and apoptosis are critical factors contributing to the pathogenesis of osteoarthritis (OA). Methionine sulfoxide reductase B2 (MSRB2) is a mitochondrial protein that protects cells from oxidative stress and is involved in apoptosis. This study aimed to investigated the expression of MSRB2 in articular cartilage tissues and elucidated its effect on HO-stimulated chondrocytes.

Methods: Human chondrocytes were cultured in Dulbecco's modified Eagle's medium (DMEM)/F12. MSRB2 overexpression in chondrocytes was achieved by transfecting with an MSRB2 overexpression plasmid. Western blot, quantitative RT-PCR, Immunofluorescence staining, and TUNEL assay were employed in this study.

Results: MSRB2 expression was found to be reduced in OA patients. Furthermore, overexpression of MSRB2 in HO-induced chondrocytes mitigated apoptosis and enhanced cell viability. Elevated MSRB2 expression diminished chondrocyte ROS contents, decreased cytochrome C (Cyc) in the cytoplasm, and regulated mitochondrial membrane potential to maintain mitochondrial homeostasis. Interestingly, knockdown of charged multivesicular body protein 5 (CHMP5) led to a decreased inMSRB2 expression in chondrocytes. Additionally, protein levels of CHMP5 and MSRB2 were reduced in HO-stimulated chondrocytes, and silencing CHMP5 reduced MSRB2 expression. Knockdown of CHMP5 increased cleaved caspase-3 expression in HO-induced chondrocytes and elevated TUNEL-positive chondrocytes.

Conclusion: MSRB2 decreased in OA, and overexpression of MSRB2 alleviated oxidative stress and apoptosis of chondrocyte.