Transient receptor potential vanilloid 4 calcium channel contributes to valve stiffening in aortic stenosis

Aortic valve stenosis (AVS) is a progressive disease characterized by fibrosis, inflammation, calcification, and stiffening of the aortic valve leaflets, which leads to impaired blood flow and left ventricular pressure overload. If left untreated, symptomatic AVS can result in heart failure and death within 2 to 5 years. Understanding the molecular mechanisms driving AVS is critical for developing noninvasive therapies. Emerging evidence suggests that extracellular and intracellular matrix stiffness influences gene expression, inflammation, and cell differentiation, with myofibroblast activation of valvular interstitial cells (VICs) and extracellular matrix remodeling being central to AVS progression. This study investigates the role of mechanosensitive transient receptor potential vanilloid 4 (TRPV4) channels as cellular stiffness sensors in AVS. TRPV4 has been shown to regulate macrophage and fibroblast activation in other fibrotic conditions, and its potential role in AVS is explored here. Using human aortic valve biopsies from AVS patients, we observed increased expression of TRPV4, CD68+ macrophages, and α-SMA+ myofibroblasts compared to healthy controls, with a strong correlation between TRPV4 expression and tissue stiffness. To detect TRPV4, CD68, and α-smooth muscle actin (α-SMA) proteins in human AVS valve tissues, we obtained 5 μm sections of aortic valve biopsies from AVS patients (n = 5) and healthy subjects (n = 2). Double immunofluorescence staining was performed on these sections to identify α-SMA-positive (α-SMA + ) myofibroblasts and CD68-positive (CD68 + ) macrophages expressing TRPV4 proteins (TRPV4 + ). Atomic force microscopy (AFM) analysis confirmed a 12-fold increase in aortic valve stiffness in AVS tissues compared to healthy valves. In a murine model of AVS, ten-micrometer aortic root sections from hypercholesterolemic ApoE -/- and ApoE -/- Trpv4 -/- mice (C57BL/6, both genders, 6-8 weeks) were analyzed to obtain force curves. We found a 7-fold increase in aortic valve stiffness in ApoE -/- mice compared to ApoE -/- TRPV4 -/- mice after 6 months on a high-fat diet (21% fat, 0.15% cholesterol; Harlan Teklad), suggesting TRPV4's role in regulating valve stiffness. Additionally, AFM analysis of VICs showed significantly higher stiffness in wildtype VICs compared to TRPV4 knockout VICs, particularly when stimulated by TGF, a critical profibrotic factor. These findings indicate that TRPV4 mechanosensing contributes to cellular and tissue matrix stiffening and AVS progression, suggesting that targeting TRPV4 could offer a novel therapeutic approach for AVS. This work was supported by an NIH (R01EB024556) grant to Shaik O. Rahaman. This abstract was presented at the American Physiology Summit 2025 and is only available in HTML format. There is no downloadable file or PDF version. The Physiology editorial board was not involved in the peer review process.