Novel approaches to determine the functional role of cardiomyocyte specific E3 ligase, Pellino-1 following myocardial infarction

OBJECTIVES

Ubiquitination plays a vital role in controlling vascular inflammation, cellular protein quality control, and minimizing misfolded protein toxicity. Pellino-1 (Peli1), a type of E3 ubiquitin ligase, has emerged as a critical regulator of the innate immune response; however, its role in the repair and regeneration of ischemic myocardium remains to be elucidated.

METHODS

Mice (8-12 weeks old, male and females) were divided into (i) Wild type (ii) cardiomyocyte-specific Peli1 overexpressed (AMPEL1Tg/+), (iii) cardiomyocyte-specific Peli1 knockout (CP1KO) and were subjected to sham and left anterior descending artery ligation. The tissues were collected at various time points after surgery for Western blot, and immunohistochemical analyses. Echocardiography is performed 30 days after myocardial infarction. Cardiomyocytes isolated from wild-type, Peli1 overexpressed and knockout mice were used to study the interaction between cardiomyocytes and endothelial cells in vitro under oxidative stress and cells were used for Western blot, flow cytometric analysis, and scratch assay.

RESULTS

We observed faster wound closure and increased expression of angiogenic factors with MCECs treated with conditioned media obtained from the AMPEL1Tg/+ cardiomyocytes compared to CPIKO and WT cardiomyocytes. Again, AMPEL1Tg/+MI mice showed preserved systolic function and reduced fibrosis compared to the CPIKOMI and WTMI groups. Capillary and arteriolar density were found to be increased in AMPEL1Tg/+MI compared to CP1KOMI. Increased survival and angiogenic factors such as p-Akt, p-MK2, p-IkBα, VEGF, cIAP2, and Bcl2 were observed in AMPEL1Tg/+ compared to CP1KO and WT mice subjected to MI.

CONCLUSION

The present study uncovers the crucial role of cardiac Peli1 as a regulator of the repair and regeneration of ischemic myocardium by using multiple genetically engineered mouse models.

Atorvastatin protects myocardium against ischemia-reperfusion arrhythmia by increasing Connexin 43 expression: A rat model

Atorvastatin has protective effects against myocardial ischemia-reperfusion injuries and ischemia-reperfusion arrhythmia. This study was designed to investigate whether atorvastatin is able to protect against myocardial ischemia-reperfusion injury by enhancing the expression of Connexin 43 (Cx43) via the activation of the phosphatidylinositol-3-kinase (PI3K)/Akt pathway and mitochondrial ATP-sensitive potassium (K(ATP)) channels. Isolated perfused rat hearts were treated with classic ischemia postconditioning (IPOST), atorvastatin, and atorvastatin combined with inhibitor of PI3K and K(ATP) channels, respectively, after 30min of LAD ischemia and then subjected to reperfusion for 120min. The QRS duration and the ischemia-reperfusion ventricular arrhythmia were assessed. The lactate dehydrogenase (LDH) and creatine kinase isoenzyme (CK-MB) levels were measured and the Cx43 expression was assessed by immunoblotting and immunohistochemistry. After 120min of reperfusion, atorvastatin and IPOST significantly decreased the QRS duration and inhibited ventricular arrhythmia. They also decreased the levels of LDH and CK-MB. Meanwhile, atorvastatin and IPOST also significantly enhanced the Cx43 expression and the phosphorylation of Cx43. Such protective effects were abolished in the presence of the inhibitor of PI3K or the inhibitor of mitochondrial K(ATP) channels. This study suggests that atorvastatin protected against myocardial ischemia-reperfusion injury and enhanced the expression of Cx43 by activating the PI3K/Akt pathway and mitochondrial K(ATP) channels.

Adipose-derived stem cell adhesion on laminin-coated microcarriers improves commitment toward the cardiomyogenic lineage

For tissue-engineering studies of the infarcted heart it is essential to identify a source of cells that may provide cardiomyocyte progenitors, which is easy to amplify, accessible in adults, and allowing autologous grafts. Preclinical studies have shown that human adipose-derived stem cells (ADSCs) can differentiate into cardiomyocyte-like cells and improve heart function in myocardial infarction. We have developed pharmacologically active microcarriers (PAMs) which are biodegradable and biocompatible polymeric microspheres conveying cells on their biomimetic surface, therefore providing an adequate three-dimensional (3D) microenvironment. Moreover, they can release a growth factor in a prolonged manner. In order to implement ADSCs and PAMs for cardiac tissue engineering we first defined the biomimetic surface by studying the influence of matrix molecules laminin (LM) and fibronectin (FN), in combination with growth factors present in the cardiogenic niche, to further enhance the in vitro cardiac differentiation of ADSCs. We demonstrated that LM increased the expression of cardiac markers (Nkx2.5, GATA4, MEF2C) by ADSCs after 2 weeks in vitro. Interestingly, our results suggest that the 3D support provided by PAMs with a LM biomimetic surface (LM-PAMs) further enhanced the expression of cardiac markers and induced the expression of a more mature contractile protein, cardiac troponin I, compared with the 2D differentiating conditions after only 1 week in culture. The enrichment of the growth-factor cocktail with TGF-β1 potentiated the cardiomyogenic differentiation. These results suggest that PAMs offering a LM biomimetic surface may be efficiently used for applications combining adult stem cells in tissue-engineering strategies of the ischemic heart.