Abstract
The molecular mechanism that regulates epicardial development has yet to be understood. In this study, we explored the function of CDX1, a Caudal-related family member, in epicardial epithelial-to-mesenchymal transition (EMT) and in the migration and the differentiation of epicardium-derived progenitors into vascular smooth muscle cells. We detected a transient expression of CDX1 in murine embryonic hearts at 11.5 days post coitum (dpc). Using a doxycycline-inducible CDX1 mouse model, primary epicardium, and ex vivo heart culture, we further demonstrated that ectopic expression of CDX1 promoted epicardial EMT. In addition, a low-dose CDX1 induction led to enhanced migration and differentiation of epicardium-derived cells into α-SMA+ vascular smooth muscles. In contrast, either continued high-level induction of CDX1 or CDX1 deficiency attenuated the ability of epicardium-derived cells to migrate and to mature into smooth muscles induced by TGF-β1. Further RNA-seq analyses showed that CDX1 induction altered the transcript levels of genes involved in neuronal development, angiogenesis, and cell adhesions required for EMT. Our data have revealed a previously undefined role of CDX1 during epicardial development, and suggest that transient expression of CDX1 promotes epicardial EMT, whereas subsequent down-regulation of CDX1 after 11.5 dpc in mice is necessary for further subepicardial invasion of EPDCs and contribution to coronary vascular endothelium or smooth muscle cells.
Highlights
The formation of heart is a complicated morphogenetic process that requires participation of cells from different embryonic origins [1]
Ectopic expression of CDX1 promotes epicardial epithelial-to-mesenchymal transition (EMT) and epicardium-derived cells (EPDCs) formation As CDX1 is highly expressed in epicardium at 11.5 dpc, a time window during which epicardial EMT occurs [2,3,20], and the defects of transgenic embryos upon CDX1 induction mimics Wt1 null mutants [4], we investigated whether CDX1 participated in epicardial function
We demonstrated that CDX1 was temporarily expressed in hearts at 11.5 dpc, a time period that coincides with epicardial development
Summary
The formation of heart is a complicated morphogenetic process that requires participation of cells from different embryonic origins [1]. The epicardial cells which cover both the heart and the intrapericardial part of the great arteries are originally derived from the proepicardium with different developmental potentials [2,3]. In mice around 11.5 days post coitum (dpc), epicardium undergoes EMT to become developmentally plastic mesenchymal cells [2,3]. These epicardium-derived cells (EPDCs) invade into subepicardial layers and further generate cardiac fibroblasts, vascular smooth muscles, and a fraction of coronary endothelial cells [2,3]. Research on epicardial EMT regulation may offer novel therapeutic strategies to prevent or to treat heart diseases
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