AbstractRationaleThe extracellular matrix (ECM) initiates mechanical cues and transduces intracellular signaling through matrix-cell interactions. In the blood vessels, additional mechanical cues derived from the pulsatile blood flow and pressure play a pivotal role in homeostasis and disease development. Currently, the nature of the cues from ECM and how they coordinate with a mechanical microenvironment in large blood vessels to maintain the integrity of the vessel wall are not fully understood.ObjectiveThe aim of this study was to elucidate the crucial mediator(s) and molecular signaling pathway(s) involved in matrix mechanotransduction during remodeling of the vessel wall.Methods and ResultsWe performed secretome analysis using rat vascular smooth muscle cells (SMCs) under cyclic stretch and examined matrix-cell interactions and cell behavior. We found that the matricellular protein thrombospondin-1 (Thbs1) was secreted upon cyclic stretch and bound to integrin αvβ1, thereby recruiting vinculin and establishing focal adhesions. RNA-sequence (RNA-seq) analysis revealed that deletion of Thbs1 in vitro markedly affected the target gene expression of Yes-associated protein (YAP). Consistently, we found that Thbs1 promotes nuclear shuttling of YAP in response to cyclic stretch, which depends on the small GTPase Rap2 and Hippo pathway, and is not influenced by alteration of actin fibers. Deletion of Thbs1 in mice inhibited Thbs1/integrin/YAP signaling, leading to maladaptive remodeling of the aorta in response to pressure overload by transverse aortic constriction (TAC), whereas it suppressed neointima formation upon carotid artery ligation, exerting context-dependent effects on the vessel wall.ConclusionsThbs1 serves as a mechanical stress-triggered extracellular mediator of mechanotransduction that acts via integrin αvβ1 to establish focal adhesions and promotes nuclear shuttling of YAP. We thus propose a novel mechanism of matrix mechanotransduction centered on Thbs1, connecting mechanical stimuli to YAP signaling during vascular remodeling in vivo.Subject codesVascular DiseaseGenetically Altered and Transgenic ModelsVascular BiologyCell Signaling/Signal Transduction