Mechanosensitive smooth muscle cell phenotypic plasticity emerging from a null state and the balance between Rac and Rho
Shefali Talwar,
Aayush Kant,
Tina Xu,
Vivek B. Shenoy,
Richard K. Assoian
Affiliations
Shefali Talwar
Center for Engineering MechanoBiology, University of Pennsylvania, Philadelphia, PA 19104, USA; Departments of Systems Pharmacology and Translational Therapeutics, University of Pennsylvania, Philadelphia, PA 19104, USA
Aayush Kant
Center for Engineering MechanoBiology, University of Pennsylvania, Philadelphia, PA 19104, USA; Materials Science and Engineering, University of Pennsylvania, Philadelphia, PA 19104, USA
Tina Xu
Departments of Systems Pharmacology and Translational Therapeutics, University of Pennsylvania, Philadelphia, PA 19104, USA
Vivek B. Shenoy
Center for Engineering MechanoBiology, University of Pennsylvania, Philadelphia, PA 19104, USA; Materials Science and Engineering, University of Pennsylvania, Philadelphia, PA 19104, USA
Richard K. Assoian
Center for Engineering MechanoBiology, University of Pennsylvania, Philadelphia, PA 19104, USA; Departments of Systems Pharmacology and Translational Therapeutics, University of Pennsylvania, Philadelphia, PA 19104, USA; Corresponding author
Summary: Reversible differentiation of vascular smooth muscle cells (VSMCs) plays a critical role in vascular biology and disease. Changes in VSMC differentiation correlate with stiffness of the arterial extracellular matrix (ECM), but causal relationships remain unclear. We show that VSMC plasticity is mechanosensitive and that both the de-differentiated and differentiated fates are promoted by the same ECM stiffness. Differential equations developed to model this behavior predicted that a null VSMC state generates the dual fates in response to ECM stiffness. Direct measurements of cellular forces, proliferation, and contractile gene expression validated these predictions and showed that fate outcome is mediated by Rac-Rho homeostasis. Rac, through distinct effects on YAP and TAZ, is required for both fates. Rho drives the contractile state alone, so its level of activity, relative to Rac, drives phenotypic choice. Our results show how the cellular response to a single ECM stiffness generates bi-stability and VSMC plasticity.
