TRPV4 mediates cell damage induced by hyperphysiological compression and regulates COX2/PGE2 in intervertebral discs

Abstract

Background Aberrant mechanical loading of the spine causes intervertebral disc (IVD) degeneration and low back pain. Current therapies do not target the mediators of the underlying mechanosensing and mechanotransduction pathways, as these are poorly understood. This study investigated the role of the mechanosensitive transient receptor potential vanilloid 4 (TRPV4) ion channel in dynamic compression of bovine nucleus pulposus (NP) cells in vitro and mouse IVDs in vivo. Methods Degenerative changes and the expression of the inflammatory mediator cyclooxygenase 2 (COX2) were examined histologically in the IVDs of mouse tails that were dynamically compressed at a short repetitive hyperphysiological regime (vs sham). Bovine NP cells embedded in an agarose‐collagen hydrogel were dynamically compressed at a hyperphysiological regime in the presence or absence of the selective TRPV4 antagonist GSK2193874. Lactate dehydrogenase (LDH) and prostaglandin E2 (PGE2) release, as well as phosphorylation of mitogen‐activated protein kinases (MAPKs), were analyzed. Degenerative changes and COX2 expression were further evaluated in the IVDs of trpv4‐deficient mice (vs wild‐type; WT). Results Dynamic compression caused IVD degeneration in vivo as previously shown but did not affect COX2 expression. Dynamic compression significantly augmented LDH and PGE2 releases in vitro, which were significantly reduced by TRPV4 inhibition. Moreover, TRPV4 inhibition during dynamic compression increased the activation of the extracellular signal‐regulated kinases 1/2 (ERK) MAPK pathway by 3.13‐fold compared to non‐compressed samples. Trpv4‐deficient mice displayed mild IVD degeneration and decreased COX2 expression compared to WT mice. Conclusions TRPV4 therefore regulates COX2/PGE2 and mediates cell damage induced by hyperphysiological dynamic compression, possibly via ERK. Targeted TRPV4 inhibition or knockdown might thus constitute promising therapeutic approaches to treat patients suffering from IVD pathologies caused by aberrant mechanical stress.

Impact of TRP Channels on Extracellular Matrix Remodeling: Focus on TRPV4 and Collagen

“…In a mouse model, TRPV4 regulated the expression of COX2/PGE2, which in turn promoted cell-mediated loss of physiological function induced by excessive dynamic compression of the disc. The authors suggested that targeted TRPV4 inhibition may provide a new approach to treat patients suffering from intervertebral disc pathologies caused by excessive mechanical stress [53]. In addition, cyclic-tensile-strain-induced expression of the proteoglycans Acan and Prg4 in annulus fibrosus cells was abrogated after pharmacological inhibition of TRPV4.…”

Intervertebral Disc-on-a-Chip as Advanced In Vitro Model for Mechanobiology Research and Drug Testing: A Review and Perspective

“…TRP channels are non-selective calcium-permeable transmembrane channels that can be activated by different stimuli, including changes in temperature, pH, osmolarity, as well as oxidative and mechanical stress, either directly by mechanical forces applied to the cell membrane or indirectly via multistep signaling cascades that induce conformational changes, which in turn generate mechanical force on the cell membrane (Walter et al, 2016;Krupkova et al, 2017;Franco-Obregón et al, 2018;Kameda et al, 2019;Sadowska et al, 2019). The TRP vanilloid 4 (TRPV4) ion channel was recently identified as a mediator of stretchinduced inflammation and compression-induced cell damage and degeneration in IVD cells and tissues in the context of hyperphysiological mechanical loading (Cambria et al, 2020a;Cambria et al, 2021).…”