Hypoxia induced the differentiation of Tbx18-positive epicardial cells to CoSMCs.

Xiaodong Jing,Yuling Yan,Qiang She,Songlin Xiao,Xiaoming Wei,Jianlin Du,Qin Qin,Ling Wu,Songbai Deng,Yajie Liu,Yulin Gao

doi:10.1038/srep30468

Abstract

Understanding the origin and differentiation mechanism of coronary vascular smooth muscle cells (CoSMCs) is very important to cardiovascular biology. The early cardiovascular system is formed in a hypoxic microenvironment, and Tbx18-positive epicardial cells are a source of CoSMCs. However, the effects of hypoxia on the differentiation of Tbx18-positive epicardial cells to CoSMCs and the primary regulatory mechanism are insufficiently understood. Using Tbx18:Cre/R26REYFP/LacZ fate-tracing mice, we cultured highly purified Tbx18-positive epicardial cells. We further showed that hypoxia induced Tbx18-positive epicardial cells to differentiate into CoSMCs and promoted the epithelial-mesenchymal transition (EMT) process of the cells in vitro. The induction of differentiation was primarily achieved via the hypoxia inducible factor-1α (HIF-1α)-mediated effects exerted on Snail. Using a cell migration assay, we showed that hypoxia enhanced the motility of Tbx18-positive epicardial cells. By constructing a hypoxic model of the embryonic epicardium in vivo, we showed that hypoxia led to premature in situ differentiation of Tbx18-positive epicardial cells to CoSMCs. Furthermore, hypoxia was sufficient to induce Snail expression in Tbx18-positive epicardial cells in vivo. Our study suggests that hypoxia intervention was sufficient to induce the differentiation of Tbx18-positive epicardial cells to CoSMCs. Furthermore, this differentiation was achieved primarily via HIF-1α-mediated regulation of Snail.

Highlights

Coronary vascular smooth muscle cells (CoSMCs) provide structural support for the contraction of coronary vessels and play important roles in the pathophysiological process of cardiovascular disease
The literature has confirmed that Snail contains hypoxia response element (HRE) fragments in its gene promoter, and hypoxia can regulate the expression of Snail via HIF-1αto induce EMT27
The increases of myh[11] protein levels after hypoxia exposure were inhibited by blocking hypoxia inducible factor-1α (HIF-1α)(Supplementary Fig. S5). These results suggested that hypoxia induced Tbx18-positive epicardial cells to differentiate into coronary vascular smooth muscle cells (CoSMCs) and that HIF-1αwas likely to be a key regulator of this hypoxia-induced differentiation

Summary

Introduction

Coronary vascular smooth muscle cells (CoSMCs) provide structural support for the contraction of coronary vessels and play important roles in the pathophysiological process of cardiovascular disease. Lineage tracing studies have demonstrated that a certain subset of epicardial cells undergo the epithelial-mesenchymal transition (EMT) process to generate a population of epicardium-derived cells (EPDCs) that differentiate to CoSMCs and fibroblasts[2,3,4]. Tbx18-positive epicardial cells migrate into the heart via the EMT process and differentiate into CoSMCs and fibroblasts. Research with chicken embryos confirmed the expression of HIF-1αin the early embryonic heart and its association with coronary vascular development[25]. We hypothesized that hypoxia may be one of the mechanisms that can induce the EMT process and the differentiation of Tbx18-positive epicardial cells to CoSMCs. Genetic lineage tracing techniques, such as the Cre-LoxP system, have been widely used in the field of development. We further exposed Tbx18-positive epicardial cells to hypoxia and studied the role of hypoxia in their differentiation to CoSMCs and the EMT process

Methods

Results

Conclusion