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.
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.
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).
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.
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.
This is a preview of subscription content, access via your institution
Subscribe to Journal
Get full journal access for 1 year
only $9.15 per issue
All prices are NET prices.
VAT will be added later in the checkout.
Tax calculation will be finalised during checkout.
Get time limited or full article access on ReadCube.
All prices are NET prices.
The original data set used and analyzed during the current study is readily available from the corresponding author on reasonable request.
Sumpio, B. E., Riley, J. T. & Dardik, A. Cells in focus: endothelial cell. Int J. Biochem. Cell Biol. 34, 1508–1512 (2002).
Traub, O. & Berk, B. C. Laminar shear stress: mechanisms by which endothelial cells transduce an atheroprotective force. Arterioscler. Thromb. Vasc. Biol. 8, 677–685 (1998).
Zeisberg, E. M. et al. Endothelial-to-mesenchymal transition contributes to cardiac fibrosis. Nat. Med. 13, 952–961 (2007).
Arciniegas, E. et al. Endothelial-mesenchymal transition occurs during embryonic pulmonary artery development. Endothelium 12, 193–200 (2005).
Zeisberg, E. M. et al. Fibroblasts in kidney fibrosis emerge via endothelial-to-mesenchymal transition. J. Am. Soc. Nephrol. 19, 2282–2287 (2008).
Xu, X. et al. Endocardial fibroelastosis is caused by aberrant endothelial to mesenchymal transition. Circ. Res. 116, 857–866 (2015).
Pusztaszeri, M. P., Seelentag, W. & Bosman, F. T. Immunohistochemical expression of endothelial markers CD31, CD34, von Willebrand Factor, and Fli-1 in normal human tissues. J. Histochem. Cytochem. 54, 385–395 (2006).
Yoshimatsu, Y. & Watabe, T. Roles of TGF-β signals in endothelial-mesenchymal transition during cardiac fibrosis. Int. J. Inflam. 2011, 724080 (2011).
Illigens, B. M. W. et al. Vascular endothelial growth factor prevents endothelial-to-mesenchymal transition in hypertrophy. Ann. Thorac. Surg. 104, 932–939 (2017).
Weixler, V. et al. Flow disturbances and the development of endocardial fibroelastosis. J. Thorac. Cardiovasc. Surg. 159, 637–646 (2020).
Emani, S. M. et al. Staged left ventricular recruitment after single-ventricle palliation in patients with borderline left heart hypoplasia. J. Am. Coll. Cardiol. 60, 1966–1974 (2012).
McElhinney, D. B. et al. Assessment of left ventricular endocardial fibroelastosis in fetuses with aortic stenosis and evolving hypoplastic left heart syndrome. Am J Cardiol. 106, 1792–1797 (2010).
Friehs, I. et al. Impaired glucose transporter activity in pressure-overload hypertrophy is an early indicator of progression to failure. Circulation 100, II187–II193 (1999).
Friehs, I. et al. Promoting angiogenesis protects severely hypertrophied hearts from ischemic injury. Ann. Thorac. Surg. 77, 2004–2010 (2004).
Kalluri, R. & Zeisberg, M. Fibroblasts in cancer. Nat. Rev. Cancer 6, 392–401 (2006).
Suzuki, M. et al. Up-regulation of integrin β3 expression by cyclic stretch in human umbilical endothelial cells. Biochem. Biophys. Res. Commun. 239, 372–376 (1997).
Rieder, F. et al. Inflammation-induced endothelial-to-mesenchymal transition: a novel mechanism of intestinal fibrosis. Am. J. Pathol. 179, 2660–2673 (2011).
Wu, B. et al. Endocardial cells form the coronary arteries by angiogenesis through myocardial-endocardial VEGF signaling. Cell 151, 1083–1096 (2012).
Kong, P. et al. Lack of specificity of fibroblast-specific protein 1 in cardiac remodeling and fibrosis. Am. J. Physiol. 305, H1363–H1372 (2013).
Shimada, S. et al. Distention of the immature left ventricle triggers development of endocardial fibroelastosis: An animal model of endocardial fibroelastosis introducing morphopathological features of evolving fetal hypoplastic left heart syndrome. Biomed. Res. Int. 2015, 46469 (2015).
Lopez, D. et al. Tumor-induced upregulation of Twist, Snail, and Slug represses the activity of the human VE-cadherin promoter. Arch. Biochem. Biophys. 482, 77–82 (2009).
Watabe, T. et al. TGF-β receptor kinase inhibitor enhances growth and integrity of embryonic stem cell–derived endothelial cells. J. Cell Biol. 163, 1303–1311 (2003).
Wu, M. et al. Losartan attenuates myocardial endothelial-to-mesenchymal transition in spontaneous hypertensive rats via inhibiting TGF-β/Smad signaling. PLoS ONE 11, e0155730 (2016).
This research did not receive any specific grant from funding agencies in the public commercial or not-for-profit sectors but was supported by discretionary departmental funds.
The authors declare no competing interests.
Publisher’s note Springer Nature remains neutral with regard to jurisdictional claims in published maps and institutional affiliations.
About this article
Cite this article
Vorisek, C., Weixler, V., Dominguez, M. et al. Mechanical strain triggers endothelial-to-mesenchymal transition of the endocardium in the immature heart. Pediatr Res 92, 721–728 (2022). https://doi.org/10.1038/s41390-021-01843-6