A microtubule stability switch alters isolated vascular smooth muscle Ca²⁺ flux in response to matrix rigidity

During ageing, the extracellular matrix of the aortic wall becomes more rigid. In response, vascular smooth muscle cells (VSMCs) generate enhanced contractile forces. Our previous findings demonstrate that VSMC volume is enhanced in response to increased matrix rigidity, but our understanding of the mechanisms regulating this process remain incomplete. In this study, we show that microtubule stability in VSMCs is reduced in response to enhanced matrix rigidity via Piezo1-mediated Ca²⁺ influx. Moreover, VSMC volume and Ca²⁺ flux is regulated by microtubule dynamics; microtubule-stabilising agents reduced both VSMC volume and Ca²⁺ flux on rigid hydrogels, whereas microtubule-destabilising agents increased VSMC volume and Ca²⁺ flux on pliable hydrogels. Finally, we show that disruption of the microtubule deacetylase HDAC6 uncoupled these processes and increased α-tubulin acetylation on K40, VSMC volume and Ca²⁺ flux on pliable hydrogels, but did not alter VSMC microtubule stability. These findings uncover a microtubule stability switch that controls VSMC volume by regulating Ca²⁺ flux. Taken together, these data demonstrate that manipulation of microtubule stability can modify VSMC response to matrix stiffness.