Substrate Topography Modulate Human Vascular Smooth Muscle Cell Proliferation and Phenotype in Proinflammatory...

The clinical efficacy of "off the shelf" synthetic small-diameter vascular grafts (sSDVG) remains limited due to rapid occlusion from thrombosis and intimal hyperplasia (IH), driven by dysregulated vascular smooth muscle cell (VSMC) behavior after vascular injury. While luminal topography has been used to improve endothelialization, understanding the VSMC responses to topographies under proinflammatory conditions such as platelet-derived growth factor-BB (PDGF-BB) exposure is critical for improving sSDVG patency. We hypothesized topographies could modulate VSMC behavior, even with PDGF-BB stimulation, and that the responses would vary by feature size and shape. An initial screening of 16 micropatterns on polydimethylsiloxane identified five patterns for analyses of VSMC proliferation, phenotype switching (desmin-vimentin), and expression of α-smooth muscle actin (α-SMA) under normal and PDGF-stimulated conditions. The 2 μm grating reduced proliferation by half (49% to 24 ± 2%), doubled contractile phenotype expression (0.8% to 1.6 ± 0.11%), and elevated α-SMA expression. When incorporated into fucoidan-modified poly(vinyl alcohol) (PVA) hydrogels, previously shown to promote endothelialization, the 2 μm grating retained its ability to suppress PDGF-induced proliferation while enhancing contractile phenotype and directional motility. A 4-week in vivo study in a rabbit carotid artery model showed no increase in IH at anastomoses with 2 μm grating compared to unpatterned and ePTFE controls. Mechanistic studies showed the 2 μm gratings enhanced focal adhesion (FA) maturation, increased phosphorylated myosin light chain kinase (pMLCK) expression, and promoted cytoplasmic YAP localization, suggesting the topographical modulation of FA signaling promoted cytoskeletal contractility and reduced proliferation. Conversely, unpatterned and 1.8 μm convex lens substrates induced nuclear YAP and reduced pMLCK, favoring proliferation. These findings highlight that substrate topography, beyond aiding endothelialization, could also modulate VSMC responses in a proinflammatory environment, offering a promising strategy for improving sSDVG design.