Beclin 1 overexpression inhibits chondrocyte apoptosis and downregulates extracellular matrix metabolism In osteoarthritis

Abstract

In the present study, the expression of Beclin 1 in osteoarthritis (OA) cartilage tissue was investigated, and also its role in proliferation, apoptosis and expression of matrix metalloproteinases (MMPs) in chondrocytes obtained from patients with OA. Beclin 1 expression in cartilage tissue from OA patients, and in the age- and sex-matched controls, was detected by immunohistochemistry, semi-quantitative polymerase chain reaction and western blotting. Chondrocytes were divided into control and Beclin 1-overexpressed groups. After transfection for 48, 72 and 96 h, cell viability, apoptosis, the phosphatidylinositol-3-kinase (PI3K)/protein kinase B (Akt)/mammalian target of rapamycin (mTOR) signaling pathway and MMPs were examined. The mRNA and protein expression levels of Beclin 1 were significantly decreased in cartilage tissue from OA patients compared with the sexand age-matched controls (P<0.05). In chondrocytes from OA patients, Beclin 1 overexpression significantly increased cell viability (P<0.05). Beclin 1 overexpression additionally decreased the degree of apoptosis, as demonstrated by Hoechst staining and flow cytometric analysis. B-cell lymphoma-2 (Bcl-2) was upregulated, and Bcl-2 associated X was downregulated, following Beclin 1 overexpression (P<0.05). The PI3K/Akt/mTOR signaling pathway was mitigated following Beclin 1 overexpression (P<0.05). In addition, MMP1, MMP3 and MMP13 were downregulated after Beclin 1 overexpression (P<0.05). Taken together, low expression levels of Beclin 1 may contribute towards the degeneration of chondrocytes. Beclin 1 overexpression increased cell viability, inhibited apoptosis and MMPs, likely via the PI3K/Akt/mTOR signaling pathway.