Survivin modulates stiffness-induced vascular smooth muscle cell motility.

Arterial stiffness is a contributor to cardiovascular diseases (CVDs) and is associated with the aberrant migration of vascular smooth muscle cells (VSMCs). However, the mechanisms driving VSMC migration in stiff environments remain unclear. We recently demonstrated that survivin is upregulated in mouse and human VSMCs cultured on stiff hydrogels, where it modulates stiffness-mediated cell proliferation. However, its role in stiffness-dependent VSMC migration remains unknown. To assess its impact on migration, we performed time-lapse microscopy on VSMCs seeded on fibronectin-coated soft and stiff hydrogels, mimicking the physiological stiffness of normal and diseased arteries. We observed that VSMC motility increased under stiff conditions, while pharmacologic or siRNA-mediated inhibition of survivin reduced stiffness-stimulated migration to rates similar to those observed under soft conditions. Further investigation revealed that cells on stiff hydrogels exhibited greater directional movement and robust lamellipodial protrusion compared to those on soft hydrogels. Interestingly, survivin-inhibited cells on stiff hydrogels showed reduced directional persistence and lamellipodial protrusion. We also found that survivin overexpression modestly increased cell motility and partially rescued the lack of directional persistence compared to green fluorescent protein (GFP)-expressing VSMCs on soft hydrogels. Mechanistically, stiffness- and survivin-dependent cell migration involves focal adhesion kinase (FAK) and actin dynamics, as stiffness increases phosphorylated FAK recruitment to focal adhesions and promotes actin organization and stress fiber formation-effects that are disrupted by survivin inhibition. In conclusion, our findings establish that mechanotransduction through a survivin-FAK-actin cascade converts extracellular matrix stiffness into stiffness-sensitive motility, suggesting that targeting this pathway may offer therapeutic strategies for CVD.