Inhibition against p38/MEF2C pathway by Pamapimod protects osteoarthritis chondrocytes hypertrophy.

Background: The p38 mitogen-activated protein kinase pathway plays an important role in the pathogenesis of osteoarthritis (OA) involving in hypertrophy, calcification, and apoptosis of chondrocytes (CHs). In this study, we focused on a p38 inhibitor named Pamapimod (PAM) in the effect of CH hypertrophy degeneration.

Methods: CHs were isolated from the cartilage collected from OA patients. Insulin-Transferrin-Selenium (ITS) medium was used as a hypertrophic inducer to establish CH hypertrophy model. Asiatic acid (AA) was used to activate p38 phosphorylation. We transfected CHs with myocyte enhancer factor 2C (MEF2C)-plasmid to upregulate MEF2C expression. Chondrogenic gene expression such as type II collagen and SOX-9, and hypertrophic genes such as type X collagen, MMP-13, and Runx-2 were analyzed by western blot, real-time polymerase chain reaction or immunofluorescence.

Results: ITS and AA all contributed to the CHs hypertrophy with an upregulation of p-p38 and MEF2C protein expression. PAM treatments significantly inhibited p-p38 and MEF2C expression, down-regulated type X collagen, MMP-13, and Runx-2 expression and upregulated type II collagen and SOX-9 levels. PAM indirectly affected MEF2C expression and resulted in CHs hypertrophy suppression.

Conclusions: PAM protects CHs hypertrophy by the inhibition of the p38/MEF2C pathway.