Vascular smooth muscle cells direct extracellular dysregulation in aortic stiffening of hypertensive rats

Abstract

SummaryAortic stiffening is an independent risk factor that underlies cardiovascular morbidity in the elderly. We have previously shown that intrinsic mechanical properties of vascular smooth muscle cells (VSMCs) play a key role in aortic stiffening in both aging and hypertension. Here, we test the hypothesis that VSMCs also contribute to aortic stiffening through their extracellular effects. Aortic stiffening was confirmed in spontaneously hypertensive rats (SHRs) vs. Wistar‐Kyoto (WKY) rats in vivo by echocardiography and ex vivo by isometric force measurements in isolated de‐endothelized aortic vessel segments. Vascular smooth muscle cells were isolated from thoracic aorta and embedded in a collagen I matrix in an in vitro 3D model to form reconstituted vessels. Reconstituted vessel segments made with SHR VSMCs were significantly stiffer than vessels made with WKY VSMCs. SHR VSMCs in the reconstituted vessels exhibited different morphologies and diminished adaptability to stretch compared to WKY VSMCs, implying dual effects on both static and dynamic stiffness. SHR VSMCs increased the synthesis of collagen and induced collagen fibril disorganization in reconstituted vessels. Mechanistically, compared to WKY VSMCs, SHR VSMCs exhibited an increase in the levels of active integrin β1‐ and bone morphogenetic protein 1 (BMP1)‐mediated proteolytic cleavage of lysyl oxidase (LOX). These VSMC‐induced alterations in the SHR were attenuated by an inhibitor of serum response factor (SRF)/myocardin. Therefore, SHR VSMCs exhibit extracellular dysregulation through modulating integrin β1 and BMP1/LOX via SRF/myocardin signaling in aortic stiffening.

Recombinant Human Soluble Thrombomodulin Suppresses Monocyte Adhesion by Reducing Lipopolysaccharide-Induced Endothelial Cellular Stiffening

“…Recent studies strongly suggest that stiff vascular vessels in aging-related arterial stiffening and atherosclerotic plaques promote monocyte adhesion and, subsequently, the progression of atherosclerosis [13,14]. We confirmed that human aortic endothelial cells enhance the formation of focal adhesion and stress fibers ( Figure S2), leading to cellular stiffening in response to LPS stimulation, as has similarly been observed with HUVECs.…”

“…Vascular stiffness has been primarily determined by the reconstitution of extracellular matrix components, fibrosis, and calcification in vascular vessels [12]. In addition, the increased stiffness of vascular smooth muscle cells and endothelial cells has similarly been observed in aging-related arterial stiffening and atherosclerotic plaques, respectively [13,14]. Our recent studies have also shown that endothelial cells increase their stiffness in response to proinflammatory stimuli [15].…”

Serum response factor‐cofactor interactions and their implications in disease

“…In addition, some in vitro and in vivo animal studies have shown that some drug compounds have been found to be effective in the treatment of pathological conditions related to the upregulation of SRF. For example, a group of small-molecule inhibitors of RhoA transcriptional signaling (CCG-100602, CCG-203971, CCG-1423, CCG222740, and CCG222740) has been found to be able to inhibit MRTF/SRF-mediated upregulation of the gene transcription caused by several environmental (mechanical stress) and cytokine (TGF-b) stimuli and repressed fibrosis and ECM stiffness as well as the VSMC stiffness [37,79,81,[85][86][87][88][89]. Although the results remain contradictory and the mechanisms involved are still not fully identified, they provide a promising strategy for the development of a therapeutic drug for clinical application.…”

“…Recent studies have also established a link between upregulation of SRF/myocardin pathways and the pathogenesis of aortic stiffness in age-related hypertension [37,[79][80][81]. Aortic stiffness is known as an independent risk factor for hypertension and cardiovascular morbidity in the elderly, and it is associated with intrinsic mechanical properties of VSMCs [79]. The underlying molecular mechanisms contributing to this condition is not known.…”

“…The underlying molecular mechanisms contributing to this condition is not known. Recent studies discovered that the RhoA/ROCK/SRF/myocardin plays a major role in the onset and progression of aortic stiffness and the development of hypertension by mediating a series of alterations including the VSMC intrinsic mechanical property, extracellular matrix (ECM) remodeling, and interaction between VSMC and ECM [37,[79][80][81]. Importantly, these regulations by SRF are specific in VSMCs in large conduct vessel but not in small arteries.…”