Abstract
Objective: Major cause of low-back pain is intervertebral disc degeneration (IVDD), with mechanical stress playing a crucial role in its progression. A mechanosensitive ion channel, PIEZO1, is involved in various musculoskeletal tissues, but its role in the annulus fibrosus (AF) remains unclear. This study aimed to elucidate the function of PIEZO1 in AF cells under mechanical stimulation. Methods: Primary rat AF cells were subjected to cyclic tensile strain (CTS) at low (2%) and high (12%) strain levels to investigate strain-dependent effects on osteogenic gene expression. We evaluated the effects of Piezo1, Piezo2, and Trpv4 knockdown by RNA interference to identify the upstream mechanotransducer. Furthermore, PIEZO1 was activated using the agonist Yoda1, followed by RNA-sequencing analysis and evaluation of its effects on BMP2-induced osteogenesis in rat AF cells. We also examined the effects of Yoda1 in primary human AF cells. Results: Low-strain CTS significantly suppressed osteogenic marker expression, which was not observed with high strain. Piezo1 knockdown reversed this suppression, whereas Piezo2 and Trpv4 had no effect. Piezo1 activation by Yoda1 produced similar anti-osteogenic effects in both rat and human AF cells. RNA sequencing revealed the enrichment of ossification and calcineurin signaling pathways in rat cells. Furthermore, Piezo1 activation inhibited BMP2-induced osteogenesis and nuclear translocation of p-Smad1/5/9. Conclusions: Piezo1 maintains AF cell homeostasis under mechanical stress by suppressing osteogenic changes via calcineurin-mediated inhibition of BMP signaling, which may represent a novel therapeutic target for IVDD.