The role of bifurcation angles on collective smooth muscle cell biomechanics and the implication in atherosclerosis development.

Vascular smooth muscle cells (SMCs) are located in the middle of the tunica media and regulate the vasodilation and vasoconstriction of the blood vessels. SMCs also play a critical role during the development of atherosclerotic lesions, which are mainly found at sites of disturbed blood flow such as arterial branch points and bifurcations. Although the migratory and proliferative activities of SMCs and their phenotypic switch have been widely studied, the mechanotransduction of the SMC layer underlying atherosclerotic plaques remains unclear. In this study, bifurcate micropatterns with different angles were fabricated with polydimethylsiloxane and polyacrylamide gel for SMC culture and characterization of cell traction force. The cellular morphology, density and orientation-specific adaptation during branched cell layer formation on this platform were monitored until they became confluence. The results indicated that the characteristic cell traction forces and the von Mises stresses were dependent on bifurcation angles, which might provide important geometrical cues associated with the development of atherosclerosis. Immunofluorescence staining and gene analysis further revealed the proliferative and migratory states of SMCs in response to different bifurcation angles, which might elucidate the localization and progression of atherosclerotic lesions.