Piezo1‐mediated regulation of smooth muscle cell volume in response to enhanced extracellular matrix rigidity

Abstract

Background and PurposeDecreased aortic compliance is a precursor to numerous cardiovascular diseases. Compliance is regulated by the rigidity of the aortic wall and the vascular smooth muscle cells (VSMCs). Extracellular matrix stiffening, observed during ageing, reduces compliance. In response to increased rigidity, VSMCs generate enhanced contractile forces that result in VSMC stiffening and a further reduction in compliance. Mechanisms driving VSMC response to matrix rigidity remain poorly defined.Experimental ApproachHuman aortic‐VSMCs were seeded onto polyacrylamide hydrogels whose rigidity mimicked either healthy (12 kPa) or aged/diseased (72 kPa) aortae. VSMCs were treated with pharmacological agents prior to agonist stimulation to identify regulators of VSMC volume regulation.Key ResultsOn pliable matrices, VSMCs contracted and decreased in cell area. Meanwhile, on rigid matrices VSMCs displayed a hypertrophic‐like response, increasing in area and volume. Piezo1 activation stimulated increased VSMC volume by promoting calcium ion influx and subsequent activation of PKC and aquaporin‐1. Pharmacological blockade of this pathway prevented the enhanced VSMC volume response on rigid matrices whilst maintaining contractility on pliable matrices. Importantly, both piezo1 and aquaporin‐1 gene expression were upregulated during VSMC phenotypic modulation in atherosclerosis and after carotid ligation.Conclusions and ImplicationsIn response to extracellular matrix rigidity, VSMC volume is increased by a piezo1/PKC/aquaporin‐1 mediated pathway. Pharmacological targeting of this pathway specifically blocks the matrix rigidity enhanced VSMC volume response, leaving VSMC contractility on healthy mimicking matrices intact. Importantly, upregulation of both piezo1 and aquaporin‐1 gene expression is observed in disease relevant VSMC phenotypes.

A microtubule stability switch alters isolated vascular smooth muscle calcium flux in response to matrix rigidity

“…VSMCs are known to possess multiple stretch-activated ion channels, and these can vary depending on phenotype. We have previously shown that piezo1 is upregulated in disease relevant phenotypes (Johnson et al, 2024). It remains unknown whether the VSMC tensegrity equilibrium can be altered in healthy contractile differentiated VSMCs, but microtubule agents alter VSMC contractile function in isolated aortic rings, suggesting that this is the case (Zhang et al, 2000).…”

“…In this study, we used Ca 2+ flux as a readout of stretch-activated channel function. One of these, piezo1, is emerging as an important regulator of VSMC dysfunction (Johnson et al, 2024; Luu et al, 2023; Qian et al, 2022; Retailleau et al, 2015; Swiatlowska et al, 2023). Our findings further implicate piezo1, as a critical regulator of VSMC behaviour and suggest that changes in piezo1 opening drive altered VSMC behaviour in response to enhanced matrix stiffness.…”

“…Increases in volume and protein synthesis are key components in VSMC hypertrophy, which is known to increase aortic wall thickness and rigidity and decrease aortic compliance (Owens and Schwartz, 1983; Rizzoni et al, 2000; Schiffrin, 2012; Sehgel et al, 2013; Zhang et al, 2005). Importantly, we have recently shown that activation of piezo1 drives a sustained Ca 2+ influx, resulting in an increase in VSMC volume, via the membrane translocation of the water channel aquaporin-1, in response to matrix rigidity (Johnson et al, 2024). Increased matrix rigidity and hypertension are known to promote VSMC dedifferentiation, where they switch from a contractile phenotype to disease associated synthetic phenotypes (Cao et al, 2022; Hayashi and Naiki, 2009; Xie et al, 2018).…”

“…Increased matrix rigidity and hypertension are known to promote VSMC dedifferentiation, where they switch from a contractile phenotype to disease associated synthetic phenotypes (Cao et al, 2022; Hayashi and Naiki, 2009; Xie et al, 2018). Both aquaporin-1 and piezo1 gene expression is enhanced during VSMC dedifferentiation in atherosclerosis, during carotid remodelling and during aortic ageing (Johnson et al, 2024; Luu et al, 2023). Whether increased volume drives increased VSMC stiffness in response to matrix rigidity and the VSMC phenotypes involved remain unknown.…”

“…For example, in response to enhanced matrix rigidity, VSMCs generate increased actomyosin derived traction forces and increased deformational stresses are placed upon the cell membrane (Petit et al, 2019; Sanyour et al, 2019). These deformational stresses drive the opening of stretch-activated ion channels in VSMCs (Johnson et al, 2024). Microtubules exist in a mechanical balance with actomyosin activity, serving as pre-stressed compression bearing struts capable of resisting actomyosin generated deformational stresses (Brangwynne et al, 2006; Johnson et al, 2021; Stamenović, 2005).…”