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Background The immune system plays a pivotal role in myocardial homeostasis and response to injury. Interleukins‐4 and ‐13 are anti‐inflammatory type‐2 cytokines, signaling via the common interleukin‐13 receptor α1 chain and the type‐2 interleukin‐4 receptor. The role of interleukin‐13 receptor α1 in the heart is unknown. Methods and Results We analyzed myocardial samples from human donors (n=136) and patients with end‐stage heart failure (n=177). We found that the interleukin‐13 receptor α1 is present in the myocardium and, together with the complementary type‐2 interleukin‐4 receptor chain Il4ra , is significantly downregulated in the hearts of patients with heart failure. Next, we showed that Il13ra1 ‐deficient mice develop severe myocardial dysfunction and dyssynchrony compared to wild‐type mice (left ventricular ejection fraction 29.7±9.9 versus 45.0±8.0; P =0.004, left ventricular end‐diastolic diameter 4.2±0.2 versus 3.92±0.3; P =0.03). A bioinformatic analysis of mouse hearts indicated that interleukin‐13 receptor α1 regulates critical pathways in the heart other than the immune system, such as extracellular matrix (normalized enrichment score=1.90; false discovery rate q=0.005) and glucose metabolism (normalized enrichment score=−2.36; false discovery rate q=0). Deficiency of Il13ra1 was associated with reduced collagen deposition under normal and pressure‐overload conditions. Conclusions The results of our studies in humans and mice indicate, for the first time, a role of interleukin‐13 receptor α1 in myocardial homeostasis and heart failure and suggests a new therapeutic target to treat heart disease.

While microRNAs have been shown to copurify with polysomes, their relative fraction in the translation pool (polysome occupancy) has not yet been measured. Here, we introduce a high-throughput method for quantifying polysome occupancies of hundreds of microRNAs and use it to investigate factors affecting these occupancies. Analysis in human embryonic stem cells (hESCs) and foreskin fibroblasts (hFFs) revealed microRNA-specific preferences for low, medium, or high polysome occupancy. Bioinformatics and functional analysis based on overexpression of endogenous and chimeric microRNAs showed that the polysome occupancy of microRNAs is specified by its mature sequence and depends on the choice of seed. Nuclease treatment further suggested that the differential occupancy of the microRNAs reflects interactions with their mRNA targets. Indeed, analysis of microNRA•mRNA duplexes showed that pairs involving high occupancy microRNAs exhibit significantly higher binding energy compared to pairs with low occupancy microRNAs. Since mRNAs reside primarily in polysomes, strong interactions lead to high association of microRNAs with polysomes and vice versa for weak interactions. Comparison between hESCs and hFFs data revealed that hESCs tend to express lower occupancy microRNAs, suggesting that cell type–dependent translational features may be affected by expression of a particular set of microRNAs.

While experimentally induced arrest of human embryonic stem cells (hESCs) in G1 has been shown to stimulate differentiation, it remains unclear whether the unperturbed G1 phase in hESCs is causally related to differentiation. Here, we use centrifugal elutriation to isolate and investigate differentiation propensities of hESCs in different phases of their cell cycle. We found that isolated G1 cells exhibit higher differentiation propensity compared with S and G2 cells, and they differentiate at low cell densities even under self-renewing conditions. This differentiation of G1 cells was partially prevented in dense cultures of these cells and completely abrogated in coculture with S and G2 cells. However, coculturing without cell-to-cell contact did not rescue the differentiation of G1 cells. Finally, we show that the subset of G1 hESCs with reduced phosphorylation of retinoblastoma has the highest propensity to differentiate and that the differentiation is preceded by cell cycle arrest. These results provide direct evidence for increased propensity of hESCs to differentiate in G1 and suggest a role for neighboring cells in preventing differentiation of hESCs as they pass through a differentiation sensitive, G1 phase. Disclosure of potential conflicts of interest is found at the end of this article.

Inflammation has been implicated in the initiation, progression and manifestation of hypertensive heart disease. We sought to determine the role of monocytes/macrophages in hypertension and pressure overload induced left ventricular (LV) remodeling.We used two models of LV hypertrophy (LVH). First, to induce hypertension and LVH, we fed Sabra salt-sensitive rats with a high-salt diet. The number of macrophages increased in the hypertensive hearts, peaking at 10 weeks after a high-salt diet. Surprisingly, macrophage depletion, by IV clodronate (CL) liposomes, inhibited the development of hypertension. Moreover, macrophage depletion reduced LVH by 17% (p0.05), and reduced cardiac fibrosis by 75%, compared with controls (p=0.001). Second, to determine the role of macrophages in the development and progression of LVH, independent of high-salt diet, we depleted macrophages in mice subjected to transverse aortic constriction and pressure overload. Significantly, macrophage depletion, for 3 weeks, attenuated LVH: a 12% decrease in diastolic and 20% in systolic wall thickness (p0.05), and a 13% in LV mass (p=0.04), compared with controls. Additionally, macrophage depletion reduced cardiac fibrosis by 80% (p=0.006). Finally, macrophage depletion down-regulated the expression of genes associated with cardiac remodeling and fibrosis: transforming growth factor beta-1 (by 80%) collagen type III alpha-1 (by 71%) and atrial natriuretic factor (by 86%).Macrophages mediate the development of hypertension, LVH, adverse cardiac remodeling, and fibrosis. Macrophages, therefore, should be considered as a therapeutic target to reduce the adverse consequences of hypertensive heart disease.

Background Human mesenchymal stromal cells ( hMSC s) from adipose cardiac tissue have attracted considerable interest in regard to cell‐based therapies. We aimed to test the hypothesis that hMSC s from the heart and epicardial fat would be better cells for infarct repair. Methods and Results We isolated and grew hMSC s from patients with ischemic heart disease from 4 locations: epicardial fat, pericardial fat, subcutaneous fat, and the right atrium. Significantly, hMSC s from the right atrium and epicardial fat secreted the highest amounts of trophic and inflammatory cytokines, while hMSC s from pericardial and subcutaneous fat secreted the lowest. Relative expression of inflammation‐ and fibrosis‐related genes was considerably higher in hMSC s from the right atrium and epicardial fat than in subcutaneous fat hMSC s. To determine the functional effects of hMSC s, we allocated rats to hMSC transplantation 7 days after myocardial infarction. Atrial hMSC s induced greatest infarct vascularization as well as highest inflammation score 27 days after transplantation. Surprisingly, cardiac dysfunction was worst after transplantation of hMSC s from atrium and epicardial fat and minimal after transplantation of hMSC s from subcutaneous fat. These findings were confirmed by using hMSC transplantation in immunocompromised mice after myocardial infarction. Notably, there was a correlation between tumor necrosis factor‐α secretion from hMSC s and posttransplantation left ventricular remodeling and dysfunction. Conclusions Because of their proinflammatory properties, hMSC s from the right atrium and epicardial fat of cardiac patients could impair heart function after myocardial infarction. Our findings might be relevant to autologous mesenchymal stromal cell therapy and development and progression of ischemic heart disease.

Introduction: Human mesenchymal stromal cells (hMSCs) from adipose cardiac tissue have attracted considerable interest for cell-based therapies. However, the best source of hMSCs for infarct repair is still unknown. Hypothesis: We aimed to test the hypothesis that, because of their proximity to the heart, hMSCs from the heart and epicardial fat would be better cells for infarct repair. Methods and Results: We isolated and grew hMSCs from patients with ischemic heart disease (IHD) from four different sources: 1) epicardial fat 2) pericardial fat 3) subcutaneous fat and 4) the right atrium. hMSCs from the right atrium and epicardial fat secreted the highest amounts of trophic and inflammatory cytokines, while hMSCs from pericardial and subcutaneous fat secreted the lowest (pin vivo , we allocated rats to hMSC transplantation 7 days after myocardial infarction (MI) (n=8-10 per group). Atrial hMSCs induced the highest number of vessels in the infarct, together with the highest inflammation score and macrophage accumulation 27 days after their injection. However, left ventricular (LV) dysfunction was worst after therapy with atrium and epicardial fat hMSCs, and minimal after subcutaneous fat hMSC therapy. Notably, there was a correlation between levels of tumor necrosis factor-α and hepatocyte growth factor, in vitro , and post-transplantation LV systolic dilatation. These surprising findings were supported by gene expression analysis in hMSCs from different sources of a patient with IHD. We found that the relative expression of inflammation and fibrosis-related genes was considerably higher in hMSCs from the right atrium and epicardial fat than in subcutaneous fat hMSCs. Conclusions: The origin of hMSCs affects their reparative and immunomodulatory properties. Because of their pro-inflammatory properties, hMSCs from the right atrium and epicardial fat of IHD patients could impair heart function after MI. Our findings might be relevant to autologous MSC therapy and pathogenesis and progression of IHD.

Studies with diverse teratogens implicated the transcription factor NF-kappaB in mechanisms determining teratological susceptibility of embryos. Here, a teratogen such as cyclophosphamide (CP) was used to test whether teratogenic insult alters the classical NF-kappaB activation pathway, and how these alterations correlate with the ability of mouse embryos to resist the teratogen-induced process of maldevelopment. We observed that embryos tested 24 h after the exposure of females to 40 mg/kg CP exhibited a dramatic decrease in the level of NF-kappaB (p65 subunit)-DNA binding, IkappaB kinase beta (IKKbeta) activity, expression of p65 and IKKbeta proteins, as well as NF-kappaB inhibitory proteins (IkappaBs) such as IkappaBalpha, IkappaBbeta, and IkappaBepsilon, and died within the next 24 h. Embryos of females exposed to 15 mg/kg CP exhibited only a decrease in NF-kappaB-DNA binding and IKKbeta activity at 24 h. However, at 48 h, a more prominent decrease in NF-kappaB activity was observed, accompanied by a decreased expression of p65 and IKKbeta proteins. These embryos died within the next 24 h. After treatment with 10 mg/kg CP, embryos survived until the end of the antenatal period of development, demonstrating a transient decrease in NF-kappaB-DNA binding activity and no alterations in NF-kappaB signaling. These results suggest that the classical NF-kappaB activation pathway may be among targets that teratogens engage to initiate abnormal development. Besides, the observation that embryos destined to be dead exhibited a dramatically decreased rate of cell proliferation suggests a pathway, whereby teratogen-induced alterations in NF-kappaB signaling may culminate in such a final effect as embryonic death.