Donor Mesenchymal Stromal Cells (MSCs) Undergo Variable Cardiac Reprogramming in Vivo and Predominantly Co-Express Cardiac and Stromal Determinants after Experimental Acute Myocardial Infarction

We previously showed the emergence of predominantly non-fused murine cells co-expressing cardiac and stromal determinants in co-cultures of murine mesenchymal stromal cells (MSCs) and rat embryonic cardiomyocytes. To determine whether a similar phenotype is detectable in vivo in ischemic myocardium, we infused green fluorescence protein (GFP)-marked MSCs intravenously into wild-type mice in an acute myocardial infarction (AMI) model generated by ischemia/reperfusion (I/R) or fixed coronary artery ligation. We found that infused GFP+ cells were confined strictly to ischemic areas and represented approximately 10% of total cellularity. We showed that over 60% of the cells co-expressed collagen type IV and troponin T or myosin heavy chain, characteristic of MSCs and cardiomyocytes, respectively, and were CD45(-). Nonetheless, up to 25% of the GFP+ donor cells expressed one of two cardiomyocyte markers, either myosin heavy chain or troponin T, in the absence of MSC determinants. We also observed a marked reduction in OCT4 expression in MSCs pre-infusion compared with those lodged in the myocardium, suggesting reduced stem cell properties. Despite the low frequency of lodged donor MSCs, left-ventricular end-diastolic pressure was significantly better in experimental versus saline animals for both AMI (12.10±1.81 vs. 20.50±1.53 mmHg, p=0.001) and I/R models (8.75±2.95 vs. 17.53±3.85 mmHg, p=0.004) when measured 21 days after MSC infusion and is consistent with a paracrine effect. Our data indicate that donor MSCs undergo variable degrees of cardiomyocyte reprogramming with the majority co-expressing cardiomyocyte and stromal markers. Further studies are needed to elucidate the factors mediating the extent of cardiomyocyte reprogramming and importance of the cellular changes on tissue repair.Fil: Yannarelli, Gustavo Gabriel. University of Toronto; Canadá. Consejo Nacional de Investigaciones Científicas y Técnicas; ArgentinaFil: Tsoporis, James N.. St. Michael’s Hospital. Li Ka Shing Knowledge Institute. Keenan Research Centre. Department of Medicine. Division of Cardiology; CanadáFil: Desjardins, Jean Francois. St. Michael’s Hospital. Li Ka Shing Knowledge Institute. Keenan Research Centre. Department of Medicine. Division of Cardiology; CanadáFil: Wang, Xing Hua. University of Toronto; CanadáFil: Pourdjabbar, Ali. St. Michael’s Hospital. Li Ka Shing Knowledge Institute. Keenan Research Centre. Department of Medicine. Division of Cardiology; CanadáFil: Viswanathan, Sowmya. University of Toronto; CanadáFil: Parker, Thomas G.. St. Michael’s Hospital. Li Ka Shing Knowledge Institute. Keenan Research Centre. Department of Medicine. Division of Cardiology; CanadáFil: Keating, Armand. University of Toronto; Canad

Repeated, but not single, VEGF gene transfer affords protection against ischemic muscle lesions in rabbits with hindlimb ischemia

Vascular endothelial growth factor (VEGF) gene transfer-mediated angiogenesis has been proposed for peripheral artery disease. However, protocols using single administration have shown little benefit. Given that the transient nature of VEGF gene expression provokes instability of neovasculature, we hypothesized that repeated administration would provide efficient tissue protection. We thus compared single vs repeated transfection in a rabbit model of hindlimb ischemia by injecting a plasmid encoding human VEGF165 (pVEGF165) at 7 (GI, n=10) or 7 and 21 (GII, n=10) days after surgery. Placebo animals (GIII, n=10) received empty plasmid. Fifty days after surgery, single and repeated administration similarly increased saphenous peak flow velocity and quantity of angiographically visible collaterals. However, microvasculature increased only with repeated transfection: capillary density was 49.4±15.4 capillaries per 100 myocytes in GI, 84.6±14.7 in GII (P<0.01 vs GI and GIII) and 49.3±13.6 in GIII, and arteriolar density was 1.9±0.6 arterioles per mm2 in GI, 3.0±0.9 in GII (P<0.01 vs GI and GIII) and 1.5±0.6 in GIII. Muscle lesions were reduced only within repeated transfection. With single administration, gene expression peaked at 7 days and declined rapidly, but with repeated administration, it remained positive at 50 days. At 90 days of repeated transfection (additional animals), gene expression decreased significantly, but neovessel densities did not. Thus, repeated, but not single, VEGF gene transfection resulted in increased microvasculature, which, in turn, afforded effective protection against ischemic muscle damage.Fil: Olea, Fernanda Daniela. Universidad Favaloro. Área de Investigación y Desarrollo; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas; ArgentinaFil: Vera Janavel, G.. Universidad Favaloro. Área de Investigación y Desarrollo; ArgentinaFil: Cuniberti, Luis Alberto. Universidad Favaloro. Área de Investigación y Desarrollo; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas; ArgentinaFil: Yannarelli, Gustavo Gabriel. Universidad Favaloro. Área de Investigación y Desarrollo; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas; ArgentinaFil: Cabeza Meckert, Patricia. Universidad Favaloro. Área de Investigación y Desarrollo; Argentina. Provincia de Buenos Aires. Gobernación. Comisión de Investigaciones Científicas; ArgentinaFil: Cors, J.. Universidad Favaloro. Área de Investigación y Desarrollo; ArgentinaFil: Valdivieso, L.. Universidad Favaloro. Área de Investigación y Desarrollo; ArgentinaFil: Lev, G.. Universidad Favaloro. Área de Investigación y Desarrollo; ArgentinaFil: Mendiz, O.. Universidad Favaloro. Área de Investigación y Desarrollo; ArgentinaFil: Bercovich, A.. Universidad Favaloro. Área de Investigación y Desarrollo; ArgentinaFil: Criscuolo, M.. Biosidus S. A.; ArgentinaFil: Melo, C.. Biosidus S. A.; ArgentinaFil: Laguens, R.. Universidad Favaloro. Área de Investigación y Desarrollo; ArgentinaFil: Crottogini, Alberto José. Universidad Favaloro. Área de Investigación y Desarrollo; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas; Argentin