Crosstalk of human coronary perivascular adipose-derived stem cells with vascular cells: role of tissue factor

The coronary perivascular adipose tissue (cPVAT) has been associated to the burden of cardiovascular risk factors and to the underlying vessel atherosclerotic plaque severity. Although the "outside to inside" hypothesis of PVAT-derived-adipokine regulation of vessel function is currently accepted, whether the resident mesenchymal stem cells (ASCs) in PVAT have a regulatory role on the underlying vascular arterial smooth muscle cells (VSMCs) is not known. Here, we investigated the interactions between resident PVAT-ASCs and VSMCs. ASCs were obtained from PVAT overlying the left anterior descending (LAD) coronary artery of hearts removed at heart transplant operations. PVAT was obtained both from patients with non-ischemic and ischemic heart disease as the cause of heart transplant. ASCs were isolated from PVAT, phenotypically characterized by flow cytometry, functionally tested for proliferation, and differentiation. Crosstalk between ASCs and VSMCs was investigated by co-culture studies. ASCs were detected in the adventitia of the LAD-PVAT showing differentiation capacity and angiogenic potential. ASCs obtained from PVAT of non-ischemic and ischemic hearts showed different tissue factor (TF) expression levels, different VSMCs recruitment capacity through the axis ERK1/2-ETS1 signaling and different angiogenic potential. Induced upregulation of TF in ASCs isolated from ischemic PVAT rescued their angiogenic capacity in subcutaneously implanted plugs in mice, whereas silencing TF in ASCs decreased the proangiogenic capacity of non-ischemic ASCs. The results indicate for the first time a novel mechanism of regulation of VSMCs by PVAT-ASCs in angiogenesis, mediated by TF expression in ASCs. Regulation of TF in ASCs may become a therapeutic intervention to increase cardiac protection.

Stem cells from human cardiac adipose tissue depots show different gene expression and functional capacities

BACKGROUND

The composition and function of the adipose tissue covering the heart are poorly known. In this study, we have investigated the epicardial adipose tissue (EAT) covering the cardiac ventricular muscle and the EAT covering the left anterior descending artery (LAD) on the human heart, to identify their resident stem cell functional activity.

METHODS

EAT covering the cardiac ventricular muscle was isolated from the apex (avoiding areas irrigated by major vessels) of the heart (ventricular myocardium adipose tissue (VMAT)) and from the area covering the epicardial arterial sulcus of the LAD (PVAT) in human hearts excised during heart transplant surgery. Adipose stem cells (ASCs) from both adipose tissue depots were immediately isolated and phenotypically characterized by flow cytometry. The different behavior of these ASCs and their released secretome microvesicles (MVs) were investigated by molecular and cellular analysis.

RESULTS

ASCs from both VMAT (mASCs) and the PVAT (pASCs) were characterized by the expression of CD105, CD44, CD29, CD90, and CD73. The angiogenic-related genes VEGFA, COL18A1, and TF, as well as the miRNA126-3p and miRNA145-5p, were analyzed in both ASC types. Both ASCs were functionally able to form tube-like structures in three-dimensional basement membrane substrates. Interestingly, pASCs showed a higher level of expression of VEGFA and reduced level of COL18A1 than mASCs. Furthermore, MVs released by mASCs significantly induced human microvascular endothelial cell migration.

CONCLUSION

Our study indicates for the first time that the resident ASCs in human epicardial adipose tissue display a depot-specific angiogenic function. Additionally, we have demonstrated that resident stem cells are able to regulate microvascular endothelial cell function by the release of MVs.

Bone Marrow Cell Transplant From Donors With Cardiovascular Risk Factors Increases the Pro-atherosclerotic Phenotype in the Recipients

Improvement of long-term survival after hematopoietic stem cell transplantation has revealed that these patients have an increased appearance of de novo cardiovascular risk factors. Even though in these clinical studies no relation to transplant-related factors has been found, no attention has been paid to the influence of cardiovascular risk factors affecting the bone marrow donors on the cardiovascular risk of the recipients. Thus, the aim of this study was to analyze, using an animal model, whether transplantation of bone marrow from donors with cardiovascular risk factors increases cardiovascular risk in healthy recipients. Results from transplantation experiments have shown that bone marrow from donors with cardiovascular risk factors induced pro-atherogenic modifications in the cholesterol profile of healthy recipients, increasing the low-density lipoprotein cholesterol fraction in comparison to those transplanted with control bone marrow. Moreover, bone marrow from donors with cardiovascular risk factors induced significant alterations in liver pro-inflammatory state and lipid metabolism-related gene expression that could contribute to alter cholesterol homeostasis. Altogether, these results suggest that cardiovascular risk factors in the donor confer a cardiometabolic alteration to their bone marrow cells that is transferred to noncardiovascular disease transplant recipients, affecting their liver function and increasing their cardiovascular risk.

LRP5/canonical Wnt signalling and healing of ischemic myocardium

LRP5 (low-density lipoprotein receptor-related protein 5) activates canonical Wnt signalling. LRP5 plays multiple roles including regulation of lipoprotein and cholesterol homeostasis as well as innate immunity cell function. However, it is not known whether LRP5 has a role in the myocardium. The aim of this study was to investigate LRP5 and Wnt signalling in myocardial remodelling after acute myocardial infarction (MI). Wnt protein levels were determined in a hypercholesterolemic porcine model of MI, in Lrp5 ^-/- C57Bl6 mice, in cultured cardiomyocytes and in human explanted hearts with previous MI episodes. 21 days post-MI, there was upregulation of LRP5 in the ischemic myocardium of hypercholesterolemic pigs as well as an upregulated expression of proteins of the Wnt pathway. We demonstrate via overexpression and silencing experiments that LRP5 induces Wnt pathway activation in isolated cardiomyocytes. Hypoxia and lipid-loading induced the expression of Wnt proteins, whereas this effect is blocked in LRP5-silenced cardiomyocytes. To characterize the function of the LRP5-Wnt axis upregulation in the heart, we induced MI in wild-type and Lrp5 ^-/- mice. Lrp5 ^-/- mice had significantly larger infarcts than Wt mice, indicating a protective role of LRP5 in injured myocardium. The LRP5 upregulation in post-MI hearts seen in pigs and mice was also evident in human hearts as dyslipidemic patients with previous episodes of ischemia have higher expression of LRP5 and Wnt-signalling genes than non-ischemic dilated hearts. We demonstrate an upregulation of LRP5 and the Wnt signalling pathway that it is a prosurvival healing response of cardiomyocytes upon injury.

Inhibition of Notch rescues the angiogenic potential impaired by cardiovascular risk factors in epicardial adipose stem cells

The epicardial adipose tissue (EAT) is a reservoir of adipose-derived stem cells (ASCs), with as yet unknown effects on myocardial and coronary arteries homeostasis. The purpose of this study was to investigate the angiogenic function of epicardial ASCs and their regulation by the common cardiovascular risk factors (CVRFs) affecting heart disease. Epicardial fat was obtained from a rodent model with clustering of CVRFs [Zucker diabetic fatty (ZDF)-Lepr(fa)] rats and from their lean control (ZDF-Crl) littermates without CVRFs, ASCs were isolated, and their function was assessed by proliferation and differentiation assays, flow cytometry, gene expression, and in vivo Matrigel angiogenesis analysis. Epicardial ASCs from both groups showed adipogenic and osteogenic differentiation capacity; however, epicardial ASCs from CVRF animals had a lesser ability to form tubular structures in vitro after endothelial differentiation, as well as a reduced angiogenic potential in vivo compared to control animals. Epicardial ASCs from CVRF rats showed up-regulation of the downstream Notch signaling genes Hes7, Hey1, and Heyl compared with control animals. The inhibition of Notch signaling by conditioning epicardial ASCs from CVRF animals with a γ-secretase inhibitor induced a reduction in Hes/Hey gene expression and rescued their angiogenic function in vivo We report for the first time the impact of CVRF burden on the ASCs of EAT and that the defective function is in part caused by increased Notch signaling. Conditioning ASCs by blocking Notch signaling rescues their angiogenic potential.-Bejar, M. T., Ferrer-Lorente, R., Peña, E., Badimon, L. Inhibition of Notch rescues the angiogenic potential impaired by cardiovascular risk factors in epicardial adipose stem cells.

Notch signaling pathway activation in normal and hyperglycemic rats differs in the stem cells of visceral and subcutaneous adipose tissue

The precise mechanisms underlying the differential function and cardiometabolic risk of white adipose tissue (WAT) remain unclear. Visceral adipose tissue (VWAT) and subcutaneous adipose tissue (SCWAT) have different metabolic functions that seem to be ascribed to their different intrinsic expansion capacities. Here we have hypothesized that the WAT characteristics are determined by the resident adipose-derived stem cells (ASCs) found in the different WAT depots. Therefore, our objective has been to investigate adipogenesis in anatomically distinct fat depots. ASCs from five different WAT depots were characterized in both healthy lean and diabetic obese rats, showing significant differences in expression of some of genes governing the stemness and the earlier adipogenic differentiation steps. Notch-target genes [Hes (hairy and enhancer of split) and Hey (hairy/enhancer of split related with YRPW motif) families] were upregulated in ASCs derived from visceral depots. Upon adipogenic differentiation, adipocyte cell markers were downregulated in ASCs from VWAT in comparison to ASCs from SCWAT, revealing a lower adipogenic capacity in ASCs of visceral origin than in those of SCWAT in accordance with the differential activation of Notch signaling. Notch upregulation by its activator phenethyl isothiocyanate attenuated the adipogenic differentiation of ASCs from SCWAT whereas Notch inhibition by N-[N-(3,5-difluorophenacetyl-L-alanyl)]-S-phenylglycine t-butyl ester (DAPT) increased the adipogenic differentiation of ASCs from visceral origin. In conclusion, the differential activation of Notch in ASCs is the origin of the different intrinsic WAT expansion capacities that contribute to the regional variations in WAT homeostasis and to its associated cardiometabolic risk.

Systems biology approach to identify alterations in the stem cell reservoir of subcutaneous adipose tissue in a rat model of diabetes: effects on differentiation potential and function

AIMS/HYPOTHESIS

Autologous progenitor cells represent a promising option for regenerative cell-based therapies. Nevertheless, it has been shown that ageing and cardiovascular risk factors such as diabetes affect circulating endothelial and bone marrow-derived progenitor cells, limiting their therapeutic potential. However, their impact on other stem cell populations remains unclear. We therefore investigated the effects of diabetes on adipose-derived stem cells (ASCs) and whether these effects might limit the therapeutic potential of autologous ASCs.

METHODS

A systems biology approach was used to analyse the expression of genes related to stem cell identification in subcutaneous adipose tissue (SAT), the stromal vascular fraction and isolated ASCs from Zucker diabetic fatty rats and their non-diabetic controls. An additional model of type 2 diabetes without obesity was also investigated. Bioinformatic approaches were used to investigate the biological significance of these changes. In addition, functional studies on cell viability and differentiation potential were performed.

RESULTS

Widespread downregulation of mesenchymal stem cell markers was observed in SAT of diabetic rats. Gene expression and in silico analysis revealed a significant effect on molecules involved in the maintenance of pluripotency and self-renewal, and on the alteration of main signalling pathways important for stem cell maintenance. The viability and differentiation potential of ASCs from diabetic rats was impaired in in vitro models and in in vivo angiogenesis.

CONCLUSIONS/INTERPRETATION

The impact of type 2 diabetes on ASCs might compromise the efficiency of spontaneous self-repair and direct autologous stem cell therapy.