Excessive mechanical stress mediated Piezo1 activation regulates lysosomal membrane permeabilization-induced chondrocyte apoptosis in mouse osteoarthritis model

Abstract Excessive mechanical stress is closely associated with progression of osteoarthritis (OA). Pathological mechanical stress can lead to chondrocyte apoptosis and subsequent cartilage degeneration. Piezo1 is a recently identified mechanosensitive ion channel that mediates chondrocyte response to mechanical stress. Here, we investigated the potential role of Piezo1 in chondrocyte apoptosis and cartilage degeneration induced by excessive mechanical stress. The primary mouse chondrocytes were subjected to mechanical stretch stress for 0, 6, 12 and 24 h, respectively. Western blot, quantitative real-time polymerase chain reaction, immunofluorescence, lysosomes and acridine orange staining were applied to examine levels of Piezo1, lysosomal function, chondrocyte apoptosis and cartilage degeneration. In vivo studies, DMM mouse model was performed to explore the protective effects and underlying mechanisms of Piezo1 inhibition on chondrocyte apoptosis and articular cartilage degradation. Exposure of chondrocytes to excessive mechanical loading caused lysosomal membrane permeabilization (LMP), which increased chondrocyte apoptosis and cartilage degeneration. Moreover, Piezo1 was upregulated in mechanical stress treated chondrocytes, and Piezo1 inhibition by siRNA or pharmacological inhibitor attenuated LMP, chondrocyte apoptosis and cartilage degeneration. We also found that Piezo1 activated cPLA2 through the calcium signaling, and cPLA2 subsequently caused the occurrence of LMP. Finally, the DMM mouse model revealed that Piezo1 inhibition reduced cPLA2 induced LMP, thereby ameliorated the surgery induced chondrocyte apoptosis and cartilage degradation, and attenuated OA pathological process. In summary, our study indicates that activity of Piezo1 was the culprit in the excessive mechanical stress-induced LMP and cartilage degradation, and Piezo1 inhibition may be a promising strategy for OA treatment.