Cells in the cardiovascular system are permanently subjected to mechanical forces due to the pulsatile nature of blood flow and shear stress, created by the beating heart. These haemodynamic forces play an important role in the regulation of vascular development, remodelling, wound healing and atherosclerotic lesion formation. Mechanical stretch can modulate several different cellular functions in VSMCs (vascular smooth muscle cells). These functions include, but are not limited to, cell alignment and differentiation, migration, survival or apoptosis, vascular remodelling, and autocrine and paracrine functions. Laminar shear stress exerts anti-apoptotic, anti-atherosclerotic and antithrombotic effects on ECs (endothelial cells). Mechanical stretch of cardiac myocytes can modulate growth, apoptosis, electric remodelling, alterations in gene expression, and autocrine and paracrine effects. The aim of the present review is primarily to summarize the cellular and molecular effects of mechanical stretch on vascular cells and cardiac myocytes, emphasizing the molecular mechanisms underlying the regulation. Knowledge of the impact of mechanical stretch on the cardiovascular system is vital to the understanding of the pathogenesis of cardiovascular diseases, and is also crucial to provide new insights into the prevention and therapy of cardiovascular diseases.

Myostatin, a negative regulator of muscle growth, is increased in hypertrophied and infarcted heart. However, the mechanism of regulation is not known. Mechanical stress is an important regulatory factor for cardiomyocyte growth. The aim of the study was to investigate the effect of cyclic stretch on the expression of myostatin gene in cardiomyocytes. Neonatal Wistar rat cardiomyocytes grown on a flexible membrane base were stretched by vacuum to 20% of maximum elongation at 60 cycles/min. An in vivo model of aorta-caval shunt in adult rats was used to investigate the myostatin expression. Cyclic stretch significantly increased myostatin protein and mRNA expression after 6 to 18 h of stretch. Addition of the p38 mitogen-activated protein (MAP) kinase inhibitor SB203580, insulin-like growth factor-1 (IGF-1) monoclonal antibody, and p38 siRNA 30 min before stretch inhibited the induction of myostatin protein. Cyclic stretch increased, while SB203580, IGF-1, and IGF-1 receptor antibody abolished, the phosphorylated p38 protein. Gel shift assays showed significant increase of DNA-protein binding activity of myocyte enhancer factor 2 (MEF2) after stretch, and transfection with p38 siRNA abolished the DNA-protein binding activity induced by cyclic stretch. Cyclic stretch significantly increased the IGF-1 secretion from myocytes. Both conditioned media from stretched myocytes and exogenous administration of IGF-1 recombinant protein to the non-stretched myocytes increased myostatin protein expression similar to that seen after cyclic stretch. An in vivo model of aorta-caval shunt in adult rats also demonstrated the increased myostatin expression in the myocardium. Cyclic mechanical stretch enhances myostatin expression in cultured rat neonatal cardiomyocytes. The stretch-induced myostatin is mediated by IGF-1 at least in part through a p38 MAP kinase and MEF2 pathway.

Acute coronary syndrome (ACS) patients have a wide spectrum of risks for subsequent cardiovascular events and death. However, there is no simple, convenience scoring system to identify risk of adverse outcomes. We investigated whether CHADS₂ and CHA₂DS₂-VASc scores were useful tools to assess the risk for adverse events among ACS patients. This observational prospective study was conducted at 39 hospitals. Totally 3,183 patients with ACS were enrolled, and CHADS₂ and CHA₂DS₂-VASc scores were calculated. The primary endpoint was occurrence of adverse event, including subsequent myocardial infarction, stroke, or death, within 1 year of discharge. CHADS₂ and CHA₂DS₂-VASc scores were significant predictors of adverse events in separate multivariate regression analyses. A Kaplan-Meier analysis of CHADS₂ and CHA₂DS₂-VASc scores of ≥2 showed a higher rate of adverse events as compared with scores of <2 (P<0.001;log-rank test). CHA₂DS₂-VASc score was better than CHADS₂ score in predicting subsequent adverse events; the area under the receiver operating characteristic curve increased from 0.66 to 0.70 (p<0.001). Patients with CHADS₂ scores of 0 or 1 were further classified according to CHA₂DS₂-VASc score, using a cutoff value of 2. The rate of adverse events significantly differed between those with a score of <2 and those with a score of ≥2 (4.1% vs.10.7%, P<0.001). CHADS₂ and CHA₂DS₂-VASc scores were useful predictors of subsequent adverse events in ACS patients.

Vascular smooth muscle cells (VSMCs) are exposed to hormonal and mechanical stress in vivo. Hormonal factors have been shown to affect hypoxia-inducible factor-1α (HIF-1α). How mechanical stress affects the regulation of HIF-1α in VSMCs has not been reported previously, and therefore we sought to investigate the regulation of HIF-1α by cyclical mechanical stretch in cultured rat VSMCs. Rat VSMCs grown on a flexible membrane base were stretched by vacuum to 20% of the maximum elongation at 60 cycles/min. The levels of HIF-1α protein began to increase as early as 2 h after stretch was applied and reached a maximum of 2.8-fold over the control by 4 h. Real-time PCR showed that the levels of HIF-1α mRNA increased 2.1-fold after cyclical stretch for 4 h. Cyclical mechanical stretch also increased the immunohistochemical labelling of HIF-1α in VSMCs after cyclical stretch for 4 h. The phosphorylation of p42/p44 mitogen-activated protein kinase (MAP kinase) increased after stretch and this was inhibited by the MAP kinase kinase inhibitors PD98059 and U0126. PD98059 and U0126 also blocked HIF-1α gene expression induced by cyclical stretch. In conclusion, cyclical mechanical stretch activates the gene expression of HIF-1α in cultured VSMCs and this mechanical effect is possibly mediated by the p42/p44 MAP kinase kinase pathway.