Generation of Cardiomyocytes From Vascular Adventitia-Resident Stem Cells.

RATIONALE: Regeneration of lost cardiomyocytes is a fundamental unresolved problem leading to heart failure. Despite several strategies developed from intensive studies performed in the past decades, endogenous regeneration of heart tissue is still limited and presents a big challenge that needs to be overcome to serve as a successful therapeutic option for myocardial infarction. OBJECTIVE: One of the essential prerequisites for cardiac regeneration is the identification of endogenous cardiomyocyte progenitors and their niche that can be targeted by new therapeutic approaches. In this context, we hypothesized that the vascular wall, which was shown to harbor different types of stem and progenitor cells, might serve as a source for cardiac progenitors. METHODS AND RESULTS: We describe generation of spontaneously beating mouse aortic wall-derived cardiomyocytes without any genetic manipulation. Using aortic wall-derived cells (AoCs) of WT (wild type), αMHC (α-myosin heavy chain), and Flk1 (fetal liver kinase 1)-reporter mice and magnetic bead-associated cell sorting sorting of Flk1+ AoCs from GFP (green fluorescent protein) mice, we identified Flk1+CD (cluster of differentiation) 34+Sca-1 (stem cell antigen-1)-CD44- AoCs as the population that gives rise to aortic wall-derived cardiomyocytes. This AoC subpopulation delivered also endothelial cells and macrophages with a particular accumulation within the aortic wall-derived cardiomyocyte containing colonies. In vivo, cardiomyocyte differentiation capacity was studied by implantation of fluorescently labeled AoCs into chick embryonic heart. These cells acquired cardiomyocyte-like phenotype as shown by αSRA (α-sarcomeric actinin) expression. Furthermore, coronary adventitial Flk1+ and CD34+ cells proliferated, migrated into the myocardium after mouse myocardial infarction, and expressed Isl-1+ (insulin gene enhancer protein-1) indicative of cardiovascular progenitor potential. CONCLUSIONS: Our data suggest Flk1+CD34+ vascular adventitia-resident stem cells, including those of coronary adventitia, as a novel endogenous source for generating cardiomyocytes. This process is essentially supported by endothelial cells and macrophages. In summary, the therapeutic manipulation of coronary adventitia-resident cardiac stem and their supportive cells may open new avenues for promoting cardiac regeneration and repair after myocardial infarction and for preventing heart failure.

Percutaneous edge-to-edge repair of severe mitral regurgitation using the MitraClip XTR versus NTR system.

BACKGROUND: Transcatheter mitral valve repair (TMVR) has shown to improve symptoms and functional capacity in patients with severe mitral valve regurgitation (MR). Novel device developments provide the technology to treat patients with complex anatomies and large coaptation gaps. Nevertheless, the question of superiority of one device remains unanswered. We aimed to compare the MitraClip XTR and MitraClip NTR system in a real world setting. HYPOTHESIS: TMVR with the MitraClip XTR system is equally effective, but associated with a higher risk of leaflet injury. METHODS: We retrospectively analyzed peri-procedural and mid-term clinical and echocardiographic outcomes of 113 patients treated for severe MR between March 2018 and August 2019 at the University Hospital of Munich. RESULTS: Postprocedural MR reduction to ≤2+ was comparable in both groups (XTR: 96.1% vs. NTR: 97.6%, p = .38). There was a significant difference in a composite safety endpoint of periprocedural Major adverse cardiac and cerebrovascular events (MACCE) including leaflet injury between groups (XTR 14.6% vs. NTR 1.7%, 95% CI [2.7, 24.6], p = .012). After a median follow-up of 8.5 (4.4, 14.0) months, durable reduction of MR was confirmed (XTR: in 91.9% vs. NTR: 96.8%, p = .31) and clinical and symptomatic improvement was comparable in both groups accordingly. CONCLUSION: While efficacy was comparable in both treatment groups, patients treated with the MitraClip XTR systems showed more events of acute leaflet tear and single leaflet device attachment (SLDA). A detailed echocardiographic assessment should be done to identify risk candidates for acute leaflet injury.