Wnt Site Signaling Inhibitor Secreted Frizzled‐Related Protein 3 Protects Mitral Valve Endothelium From Myocardial Infarction–Induced Endothelial‐to‐Mesenchymal Transition

Abstract

Background The onset and mechanisms of endothelial‐to‐mesenchymal transition (EndMT) in mitral valve (MV) leaflets following myocardial infarction (MI) are unknown, yet these events are closely linked to stiffening of leaflets and development of ischemic mitral regurgitation. We investigated whether circulating molecules present in plasma within days after MI incite EndMT in MV leaflets. Methods and Results We examined the onset of EndMT in MV leaflets from 9 sheep with inferior MI, 8 with sham surgery, and 6 naïve controls. Ovine MVs 8 to 10 days after inferior MI displayed EndMT, shown by increased vascular endothelial cadherin/α‐smooth muscle actin–positive cells. The effect of plasma on EndMT in MV endothelial cells (VECs) was assessed by quantitative polymerase chain reaction, migration assays, and immunofluorescence. In vitro, post‐MI plasma induced EndMT marker expression and enhanced migration of mitral VECs; sham plasma did not. Analysis of sham versus post‐MI plasma revealed a significant drop in the Wnt signaling antagonist sFRP3 (secreted frizzled‐related protein 3) in post‐MI plasma. Addition of recombinant sFRP3 to post‐MI plasma reversed its EndMT‐inducing effect on mitral VECs. RNA‐sequencing analysis of mitral VECs exposed to post‐MI plasma showed upregulated FOXM1 (forkhead box M1). Blocking FOXM1 reduced EndMT transcripts in mitral VECs treated with post‐MI plasma. Finally, FOXM1 induced by post‐MI plasma was downregulated by sFRP3. Conclusions Reduced sFRP3 in post‐MI plasma facilitates EndMT in mitral VECs by increasing the transcription factor FOXM1. Restoring sFRP3 levels or inhibiting FOXM1 soon after MI may provide a novel strategy to modulate EndMT in the MV to prevent ischemic mitral regurgitation and heart failure.

CD45 Is Sufficient to Initiate Endothelial-to-Mesenchymal Transition in Human Endothelial Cells—Brief Report

“…We anticipate that although CD45 is sufficient to induce EndMT, there are likely other mediators and pathways that induce EndMT in certain settings. For example, we did not find CD45 coexpressed in αSMA/VE-cadherin–positive mitral VECs at 8 to 10 days post-myocardial infarction, 23 suggesting that expression of CD45 in vivo may develop over a longer time period, as we originally observed. 4 The context(s) under which CD45 is implemented to drive EndMT will require further studies.…”

“…Recently, we showed SFRP3 in plasma blocks EndMT in mitral VECs. 23 However, SFRP3 transcripts were not detected in the bulk RNA-seq analysis; SRFP2, 4, and 5 were detected but not differentially expressed. ADAMTS18 (ADAM metallopeptidase with thrombospondin type 1 motif 18), recently implicated in angiogenesis, 28 was also strongly downregulated in ECFC-CD45 cells compared with ECFC-control (log2fold decrease, −4.48; adjusted P =0.0002), which could indicate a loss of endothelial function.…”

Challenges and Opportunities in Valvular Heart Disease: From Molecular Mechanisms to the Community

“…19 The potential to inhibit valve fibrosis in ischemic mitral regurgitation via pharmacological inhibition of CD45 was also demonstrated. Circulating factors activating serotonin receptors 20 and releasing molecular brakes on proliferative Wnt/β-catenin 21 can also provide therapeutic clues.…”

Endothelial to mesenchymal transition: at the axis of cardiovascular health and disease

“…sFRP3 plasma levels were negatively correlated with the size of MI and positively correlated with ejection fraction in sheep with MI. 103 When promoting EndMT, the WNT and TGF-β signalling cascades can synergize via β-catenin that upon translocation interacts with LEF/TCF and forms SMAD-associated transcriptional complexes to transcriptionally regulate shared target genes. However, WNT3a and WNT7a have an opposite effect on EndMT.…”