Abstract
Background and Purpose Decreased aortic compliance is a precursor to numerous cardiovascular diseases. Compliance is regulated by the stiffness of the aortic wall and the vascular smooth muscle cells (VSMCs) within it. During ageing, the extracellular matrix of the aortic wall stiffens, reducing compliance and leading to conditions such as hypertension. In response, VSMCs generate enhanced contractile forces and undergo hypertrophy, promoting VSMC stiffening and further reducing compliance. Due to a lack of suitable in vitro models, the mechanisms driving VSMC hypertrophy in response to matrix stiffness remain poorly defined.
Experimental Approach Human VSMCs were seeded onto polyacrylamide hydrogels whose stiffness mimicked either healthy or aged/diseased aortae. VSMC response to contractile agonist stimulation was measured through changes in cell area and volume. VSMCs were pre-treated with pharmacological agents prior to agonist stimulation to identify regulators of VSMC contractility and hypertrophy.
Key Results VSMCs undergo a differential response to contractile agonist stimulation based on matrix stiffness. On pliable hydrogels, VSMCs contract, decreasing in cell area whereas on rigid hydrogels, VSMCs undergo a hypertrophic response, increasing in area and volume. Microtubule stabilisation prevented hypertrophy whilst leaving VSMC contraction on pliable hydrogels unimpeded. Conversely, microtubule destabilisation inhibited contraction and induced hypertrophy within VSMCs on pliable hydrogels.
Conclusions and Implications In response to enhanced matrix rigidity, VSMC undergo a hypertrophic response as result of decreased microtubule stability. Using standard biological techniques and equipment, we present a screening assay capable of identifying novel regulators of matrix rigidity induced VSMC hypertrophy. This assay can identify both beneficial and deleterious effects of pharmacological agents to cardiovascular health.
Following contractile agonist stimulation, isolated VSMCs seeded on pliable substrates undergo a contractile response, decreasing in cell area whilst maintaining a consistent volume. VSMCs seeded on rigid substrates fail to undergo a contractile response following contractile agonist stimulation and instead undergo a hypertrophic response, increasing in area and volume. VSMC hypertrophy can be prevented on rigid substrates through microtubule stabilisation. In VSMCs seeded on pliable substrates, microtubule destabilisation inhibits the contractile response and promotes VSMC hypertrophy.
Competing Interest Statement
The authors have declared no competing interest.
