p53 mediated mesenchymal-to-endothelial transition is a novel mechanism of vasculogenesis after ischemic cardiac injury Public Deposited

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  • March 20, 2019
Creator
  • Ubil, Eric Scott
    • Affiliation: College of Arts and Sciences, Department of Biology
Abstract
  • The mammalian heart displays limited regenerative capacity after acute ischemic injury and heals primarily through fibrosis. Recent therapeutic research has focused on increasing vasculature at the site of injury as a means of preserving remaining myocardium and improving cardiac function after injury. Other research has focused on the ability to reprogram cardiac fibroblasts using exogenous transcription factors to achieve a similar goal. However, the ability of cardiac fibroblasts to adopt alternate cellular fates in the absence of exogenous factors is unclear. Here, we demonstrate that a subset of cardiac fibroblasts adopts the physiological and anatomical characteristics of native endothelial cells after ischemic cardiac injury in the absence of any added factors. Using mice harboring genetically labeled fibroblasts (Col1a2-CreERT:R26RtdTomato), we show that approximately 30% of labeled cardiac fibroblasts in the injury border zone express endothelial markers such as VE-cadherin, eNOS, Occludin, and Claudin 5. Fibroblast derived endothelial cells comprised 25+/-2% of total luminal endothelial cells at the border zone 3 days after injury. To better understand fibroblast-endothelial transition we subjected cardiac fibroblasts to cellular stress (serum starvation) and found that they formed endothelium-like structures on Matrigel and up-regulated endothelial specific genes (e.g. VE-cadherin, Flk1, Flt1) 6-20 fold. We show that transition of fibroblasts to endothelial-like cells ex vivo is p53 dependent. Pharmacological inhibition of p53 using Pifithrin-α or genetic deletion in fibroblasts (Col1a2-CreERT:p53fl/fl) led to a 94% mean decrease in Matrigel tube formation and 90% reduction in endothelial gene expression. Moreover, using semi-quantitative immunofluorescent staining, we observed that p53 levels in cardiac fibroblasts were more than 6 fold higher at the injury border zone. Injection of a p53 activator, RITA, after injury doubled p53 levels in cardiac fibroblasts and increased the degree of mesenchymal-to-endothelial transition (MEndoT) by 43%. Enhanced MEndoT was also associated with decreased collagen deposition and improved heart function 7 days post injury. In summary, we show that cardiac fibroblasts adopt endothelial cell like fates after cardiac injury and contribute to the neovascularization of the injured region. Manipulation of MEndoT could represent a novel therapeutic strategy to increase post infarct angiogenesis and enhance function in the injured heart.
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  • In Copyright
Advisor
  • Deb, Arjun
Degree
  • Doctor of Philosophy
Graduation year
  • 2013
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