BACKGROUND: Endothelial-to-mesenchymal-transition (EndMT) plays a major role in cardiac fibrosis, including endocardial fibroelastosis but the stimuli are still unknown. We developed an endothelial cell (EC) culture and a whole heart model to test whether mechanical strain triggers TGF-β-mediated EndMT. METHODS: Isolated ECs were exposed to 10% uniaxial static stretch for 8 h (stretch) and TGF-β-mediated EndMT was determined using the TGF-β-inhibitor SB431542 (stretch + TGF-β-inhibitor), BMP-7 (stretch + BMP-7) or losartan (stretch + losartan), and isolated mature and immature rats were exposed to stretch through a weight on the apex of the left ventricle. Immunohistochemical staining for double-staining with endothelial markers (VE-cadherin, PECAM1) and mesenchymal markers (αSMA) or transcription factors (SLUG/SNAIL) positive nuclei was indicative of EndMT. RESULTS: Stretch-induced EndMT in ECs expressed as double-stained ECs/total ECs (cells: 46 ± 13%; heart: 15.9 ± 2%) compared to controls (cells: 7 ± 2%; heart: 3.1 ± 0.1; p < 0.05), but only immature hearts showed endocardial EndMT. Inhibition of TGF-β decreased the number of double-stained cells significantly, comparable to controls (cells/heart: control: 7 ± 2%/3.1 ± 0.1%, stretch: 46 ± 13%/15 ± 2%, stretch + BMP-7: 7 ± 2%/2.9 ± 0.1%, stretch + TGF-β-inhibitor (heart only): 5.2 ± 1.3%, stretch + losartan (heart only): 0.89 ± 0.1%; p < 0.001 versus stretch). CONCLUSIONS: Endocardial EndMT is an age-dependent consequence of increased strain triggered by TGF- β activation. Local inhibition through either rebalancing TGF-β/BMP or with losartan was effective to block EndMT. IMPACT: Mechanical strain imposed on the immature LV induces endocardial fibroelastosis (EFE) formation through TGF-β-mediated activation of endothelial-to-mesenchymal transition (EndMT) in endocardial endothelial cells but has no effect in mature hearts. Local inhibition through either rebalancing the TGF-β/BMP pathway or with losartan blocks EndMT. Inhibition of endocardial EndMT with clinically applicable treatments may lead to a better outcome for congenital heart defects associated with EFE.
BACKGROUND: Endothelial-to-mesenchymal-transition (EndMT) plays a major role in cardiac fibrosis, including endocardial fibroelastosis but the stimuli are still unknown. We developed an endothelial cell (EC) culture and a whole heart model to test whether mechanical strain triggers TGF-β-mediated EndMT. METHODS: Isolated ECs were exposed to 10% uniaxial static stretch for 8 h (stretch) and TGF-β-mediated EndMT was determined using the TGF-β-inhibitor SB431542 (stretch + TGF-β-inhibitor), BMP-7 (stretch + BMP-7) or losartan (stretch + losartan), and isolated mature and immature rats were exposed to stretch through a weight on the apex of the left ventricle. Immunohistochemical staining for double-staining with endothelial markers (VE-cadherin, PECAM1) and mesenchymal markers (αSMA) or transcription factors (SLUG/SNAIL) positive nuclei was indicative of EndMT. RESULTS: Stretch-induced EndMT in ECs expressed as double-stained ECs/total ECs (cells: 46 ± 13%; heart: 15.9 ± 2%) compared to controls (cells: 7 ± 2%; heart: 3.1 ± 0.1; p < 0.05), but only immature hearts showed endocardial EndMT. Inhibition of TGF-β decreased the number of double-stained cells significantly, comparable to controls (cells/heart: control: 7 ± 2%/3.1 ± 0.1%, stretch: 46 ± 13%/15 ± 2%, stretch + BMP-7: 7 ± 2%/2.9 ± 0.1%, stretch + TGF-β-inhibitor (heart only): 5.2 ± 1.3%, stretch + losartan (heart only): 0.89 ± 0.1%; p < 0.001 versus stretch). CONCLUSIONS: Endocardial EndMT is an age-dependent consequence of increased strain triggered by TGF- β activation. Local inhibition through either rebalancing TGF-β/BMP or with losartan was effective to block EndMT. IMPACT: Mechanical strain imposed on the immature LV induces endocardial fibroelastosis (EFE) formation through TGF-β-mediated activation of endothelial-to-mesenchymal transition (EndMT) in endocardial endothelial cells but has no effect in mature hearts. Local inhibition through either rebalancing the TGF-β/BMP pathway or with losartan blocks EndMT. Inhibition of endocardial EndMT with clinically applicable treatments may lead to a better outcome for congenital heart defects associated with EFE.
Authors: Xingbo Xu; Ingeborg Friehs; Tachi Zhong Hu; Ivan Melnychenko; Björn Tampe; Fouzi Alnour; Maria Iascone; Raghu Kalluri; Michael Zeisberg; Pedro J Del Nido; Elisabeth M Zeisberg Journal: Circ Res Date: 2015-01-13 Impact factor: 17.367
Authors: Doff B McElhinney; Melanie Vogel; Carol B Benson; Audrey C Marshall; Louise E Wilkins-Haug; Virginia Silva; Wayne Tworetzky Journal: Am J Cardiol Date: 2010-12-15 Impact factor: 2.778
Authors: Sitaram M Emani; Doff B McElhinney; Wayne Tworetzky; Patrick O Myers; Brian Schroeder; David Zurakowski; Frank A Pigula; Gerald R Marx; James E Lock; Pedro J del Nido Journal: J Am Coll Cardiol Date: 2012-10-10 Impact factor: 24.094