New insights into lipid raft function regulating myocardial vascularization competency in human idiopathic dilated cardiomyopathy.

OBJECTIVE: Idiopathic dilated cardiomyopathy (IDCM) affects myocardial vascularization. Whether a lack of demand for increased myocardial vascularization and/or an impaired response of circulating angiogenic-supportive cells are responsible for the vascular derangements found in IDCM is unknown. METHODS AND RESULTS: Left ventricle (LV) samples obtained at transplant from IDCM hearts were compared to control hearts from non-cardiac decedents. Peripheral colony-forming myeloid cells were extracted from age- and sex-matched IDCM patients and healthy volunteers. At the tissue level, no differences were detected in stromal cell-derived factor (SDF)-1α expression, but integrin-linked kinase (ILK) levels and activity were increased in IDCM. A marked co-localization of SDF-1α and the specific marker of cholesterol-enriched lipid rafts Flotillin (Flot)-1 was found in IDCM. SDF-1α was also highly distributed into IDCM lipid rafts. Non-adherent pro-angiogenic cells from both groups, which were found increased in patients but showed similar surface levels of CXCR-4, equally supported Matrigel-mediated cell network formation. However, SDF-1-mediated migration was reduced in IDCM-derived cells, which also exhibited decreased ILK activity and downstream ERK activation. CONCLUSIONS: Taken together, our results point out that myocardial competency to increase vascularization is not altered in IDCM, but dysfunctional SDF-1-mediated migration by peripheral pro-angiogenic cells through ILK and downstream ERK signaling may compromise endothelial recovery in patients. We provide new insights into lipid raft function in human IDCM and envision more effective treatments.

Human umbilical cord blood-derived mesenchymal stem cells promote vascular growth in vivo.

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.

CTLA-4 polymorphisms and clinical outcome after allogeneic stem cell transplantation from HLA-identical sibling donors.

CTLA-4 is an inhibitory molecule that down-regulates T-cell activation. Although polymorphisms at CTLA-4 have been correlated with autoimmune diseases their association with clinical outcome after allogeneic hematopoietic stem cell transplantation (allo-HSCT) has yet to be explored. A total of 5 CTLA-4 single-nucleotide polymorphisms were genotyped on 536 HLA-identical sibling donors of allo-HSC transplants. Genotypes were tested for an association with patients' posttransplantation outcomes. The effect of the polymorphisms on cytotoxic T-lymphocyte antigen 4 (CTLA-4) mRNA and protein production were determined in 60 healthy control participants. We observed a reduction in the mRNA expression of the soluble CTLA-4 isoform in the presence of a G allele at CT60 and +49. Patients receiving stem cells from a donor with at least 1 G allele in position CT60 had worse overall survival (56.2% vs 69.8% at 5 years; P = .001; hazard ratio [HR], 3.80; 95% confidence interval [CI], 1.75-8.22), due to a higher risk of relapse (P = .049; HR, 1.71; 95% CI, 1.00-2.93). Acute graft-versus-host disease (aGVHD) was more frequent in patients receiving CT60 AA stem cells (P = .033; HR, 1.54; 95% CI, 1.03-2.29). This is the first study to report an association between polymorphisms at CTLA-4 and clinical outcome after allo-HSCT. The CT60 genotype influences relapse and aGVHD, probably due to its action on CTLA-4 alternative splicing.