Stem cell therapies are promising strategies to regenerate human injured tissues, including ischemic myocardium. Here, we examined the acquisition of properties associated with vascular growth by human umbilical cord blood-derived mesenchymal stem cells (UCBMSCs), and whether they promoted vascular growth in vivo. UCBMSCs were induced in endothelial cell-specific growth medium (EGM-2) acquiring new cell markers, increased Ac-LDL uptake, and migratory capacity as assessed by qRT-PCR, Western blotting, indirect immunofluorescence, and invasion assays. Angiogenic and vasculogenic potentials could be anticipated by in vitro experiments showing self organization into Matrigel-mediated cell networks, and activation of circulating angiogenic-supportive myeloid cells. In mice, following subcutaneous co-injection with Matrigel, UCBMSCs modified to co-express bioluminescent (luciferases) and fluorescent proteins were demonstrated to participate in the formation of new microvasculature connected with the host circulatory system. Response of UCBMSCs to ischemia was explored in a mouse model of acute myocardial infarction (MI). UCBMSCs transplanted using a fibrin patch survived 4 weeks post-implantation and organized into CD31⁺network structures above the infarcted myocardium. MI-treated animals showed a reduced infarct scar and a larger vessel-occupied area in comparison with MI-control animals. Taken together, the presented results show that UCBMSCs can be induced in vitro to acquire angiogenic and vasculogenic properties and contribute to vascular growth in vivo.

Right ventricular fibrosis is a stress response, predominantly mediated by cardiac fibroblasts. This cell population is sensitive to increased levels of pro-inflammatory cytokines, pro-fibrotic growth factors and mechanical stimulation. Activation of fibroblasts results in the induction of various molecular signaling pathways, most notably the mitogen-activated protein kinase cassettes, leading to increased synthesis and remodeling of the extracellular matrix. While fibrosis confers structural protection in response to damage induced by ischemia or (pressure and volume) overload, it simultaneously contributes to increased myocardial stiffness and right ventricular dysfunction. Here, we review state-of-the-art knowledge of the development of right ventricular fibrosis in response to pressure overload and provide an overview of all published preclinical and clinical studies in which right ventricular fibrosis was targeted to improve cardiac function.

Coronary artery occlusion is associated with the risk of ventricular remodelling, heart failure, and cardiogenic shock. Novel strategies are sought to treat these ominous complications. We examined the effect of a pericardial-derived fat flap secured over an acute infarct caused by coronary occlusion. A novel intervention consisting of the pericardial isolation of a vascularized adipose flap and its transposition fully covering acute infarcted myocardium was developed in the swine model of coronary artery ligation (n= 52). Left ventricular (LV) ejection fraction and LV end-diastolic and end-systolic volumes were assessed using magnetic resonance imaging (MRI). Infarct size and gene expression analysis were performed on Day 6 and 1 month. Histological changes, collagen volume fraction (CVF), and vascular density were also evaluated on postmortem sections. One month after the intervention, a 18.8% increase in LV ejection fraction (P= 0.007), and significant reductions in LV end-systolic (P= 0.009) and LV end-diastolic volumes (P= 0.03) were found in treated animals compared with the control-MI group. At Day 6, histopathology confirmed a significant infarct size reduction (P= 0.018), the presence of vascular connections at the flap-myocardium interface, and less apoptosis in the infarct border zone compared with control animals (P< 0.001). Up-regulation of genes involved in cell cycle progression, cellular growth and proliferation, and angiogenesis were identified within the flap. Our results indicate that a vascular fat flap exerts beneficial effects on LV function and limits myocardial remodelling. Future studies must confirm whether these findings provide an alternative therapeutic approach for myocardial salvage after infarction.