Linking In Vitro Models of Endothelial Dysfunction with Cell Senescence.

Endothelial cell dysfunction is the principal cause of several cardiovascular diseases that are increasing in prevalence, healthcare costs, and mortality. Developing a standardized, representative in vitro model of endothelial cell dysfunction is fundamental to a greater understanding of the pathophysiology, and to aiding the development of novel pharmacological therapies. We subjected human umbilical vein endothelial cells (HUVECs) to different periods of nutrient deprivation or increasing doses of H2O2 to represent starvation or elevated oxidative stress, respectively, to investigate changes in cellular function. Both in vitro cellular models of endothelial cell dysfunction-associated senescence developed in this study, starvation and oxidative stress, were validated by markers of cellular senescence (increase in ß-galactosidase activity, and changes in senescence gene markers SIRT1 and P21) and endothelial dysfunction as denoted by reductions in angiogenic and migratory capabilities. HUVECs showed a significant H2O2 concentration-dependent reduction in cell viability (p < 0.0001), and a significant increase in oxidative stress (p < 0.0001). Furthermore, HUVECs subjected to 96 h of starvation, or exposed to concentrations of H2O2 of 400 to 1000 µM resulted in impaired angiogenic and migratory potentials. These models will enable improved physiological studies of endothelial cell dysfunction, and the rapid testing of cellular efficacy and toxicity of future novel therapeutic compounds.

Opposite Effects of Moderate and Extreme Cx43 Deficiency in Conditional Cx43-Deficient Mice on Angiotensin II-Induced Cardiac Fibrosis.

Abstract: Connexin 43 (Cx43) is essential for cardiac electrical coupling, but its effects on myocardial fibrosis is controversial. Here, we analyzed the role of Cx43 in myocardial fibrosis caused by angiotensin II (AngII) using Cx43fl/fl and Cx43Cre-ER(T)/fl inducible knock-out (Cx43 content: 50%) mice treated with vehicle or 4-hydroxytamoxifen (4-OHT) to induce a Cre-ER(T)-mediated global deletion of the Cx43 floxed allele. Myocardial collagen content was enhanced by AngII in all groups (n = 8-10/group, p < 0.05). However, animals with partial Cx43 deficiency (vehicle-treated Cx43Cre-ER(T)/fl) had a significantly higher AngII-induced collagen accumulation that reverted when treated with 4-OHT, which abolished Cx43 expression. The exaggerated fibrotic response to AngII in partially deficient Cx43Cre-ER(T)/fl mice was associated with enhanced p38 MAPK activation and was not evident in Cx43 heterozygous (Cx43+/-) mice. In contrast, normalization of interstitial collagen in 4-OHT-treated Cx43Cre-ER(T)/fl animals correlated with enhanced MMP-9 activity, IL-6 and NOX2 mRNA expression, and macrophage content, and with reduced -SMA and SM22 in isolated fibroblasts. In conclusion, our data demonstrates an exaggerated, p38 MAPK-dependent, fibrotic response to AngII in partially deficient Cx43Cre-ER(T)/fl mice, and a paradoxical normalization of collagen deposition in animals with an almost complete Cx43 ablation, an effect associated with increased MMP-9 activity and inflammatory response and reduced fibroblasts differentiation.