Hypoxia Inducible Factor (HIF) Adaptation After Mechanical Circulatory Unloading of the Heart. A Gene Expression Analysis Study of Paired Myocardial Samples

Background: Endothelial to Mesenchymal Transition (EndMT) and the reverse phenomenon of mesenchymal to endothelial transitioning (MET) has been shown to contribute to fibrosis in rodent models of heart failure. There are no studies documenting the same in human cardiac tissue. Methods: We performed immunofluorescence dual staining on end stage heart failure myocardial samples obtained from our bio repository. Staining for endothelial and mesenchymal markers were performed with Anti-VE-Cadherin (Santa Cruz Biotechnologies) and anti-Fibroblast specific protein 1 (Dako Antibodies) respectively using standard immunofluoresence techniques. Presence of dual staining on fluorescence microscopy was considered as positive for the presence of EndMT. Vascular density was assessed using a DAB (3-3’ Diaminobenzidine) technique with Anti-CD31 (PECAM, Abcam). Results: Of the end stage heart failure samples, 18 were from left ventricular core during LVAD implant and 5 during a direct transplant as status 1A (axillary intraaortic balloon pump). 10 hearts of patients bridged to transplant with a continuous flow LVAD (Days under support 3436228) were also studied. Mean age was 55y with 82% males and 74% white. 70% of all samples had evidence of EndMT. The number of cells ranged from 1 to 5 per high power field. There was no significant difference between patient characteristics between those with evidence of EndMT versus not, except a higher prevalence of diabetes in the latter group. (Fig 1B) 74% of the end-stage heart failure samples and 60% of the post-VAD samples showed the presence of EndMT cells. Vascular Density was higher in the samples exhibiting EndMT phenomenon. (Figure 1A). Conclusion: We have documented for the first time, the existence of endothelial-mesenchymal transition in human end stage myocardial samples corroborating earlier pioneering studies in rodents. Interestingly the existence of such dual staining cells in end stage hearts (which is highly fibrotic) suggests a possible role of ongoing fibrosis with endothelial to mesenchymal transitioning or potential antifibrotic mechanism though mesenchymal to endothelial transitioning. Further studies of the later process will be warranted to explore potential anti-fibrotic therapeutic implications.