Integrin β-3 is required for the attachment, retention and therapeutic benefits of human cardiospheres in myocardial infarction

PEX3 promotes regenerative repair after myocardial injury in mice through facilitating plasma membrane localization of ITGB3

The peroxisome is a versatile organelle that performs diverse metabolic functions. PEX3, a critical regulator of the peroxisome, participates in various biological processes associated with the peroxisome. Whether PEX3 is involved in peroxisome-related redox homeostasis and myocardial regenerative repair remains elusive. We investigate that cardiomyocyte-specific PEX3 knockout (Pex3-KO) results in an imbalance of redox homeostasis and disrupts the endogenous proliferation/development at different times and spatial locations. Using Pex3-KO mice and myocardium-targeted intervention approaches, the effects of PEX3 on myocardial regenerative repair during both physiological and pathological stages are explored. Mechanistically, lipid metabolomics reveals that PEX3 promotes myocardial regenerative repair by affecting plasmalogen metabolism. Further, we find that PEX3-regulated plasmalogen activates the AKT/GSK3β signaling pathway via the plasma membrane localization of ITGB3. Our study indicates that PEX3 may represent a novel therapeutic target for myocardial regenerative repair following injury.

Possible Treatment of Myocardial Infarct Based on Tissue Engineering Using a Cellularized Solid Collagen Scaffold Functionalized with Arg-Glyc-Asp (RGD) Peptide

Currently, the clinical impact of cell therapy after a myocardial infarction (MI) is limited by low cell engraftment due to low cell retention, cell death in inflammatory and poor angiogenic infarcted areas, secondary migration. Cells interact with their microenvironment through integrin mechanoreceptors that control their survival/apoptosis/differentiation/migration and proliferation. The association of cells with a three-dimensional material may be a way to improve interactions with their integrins, and thus outcomes, especially if preparations are epicardially applied. In this review, we will focus on the rationale for using collagen as a polymer backbone for tissue engineering of a contractile tissue. Contractilities are reported for natural but not synthetic polymers and for naturals only for: collagen/gelatin/decellularized-tissue/fibrin/Matrigel™ and for different material states: hydrogels/gels/solids. To achieve a thick/long-term contractile tissue and for cell transfer, solid porous compliant scaffolds are superior to hydrogels or gels. Classical methods to produce solid scaffolds: electrospinning/freeze-drying/3D-printing/solvent-casting and methods to reinforce and/or maintain scaffold properties by reticulations are reported. We also highlight the possibility of improving integrin interaction between cells and their associated collagen by its functionalizing with the RGD-peptide. Using a contractile patch that can be applied epicardially may be a way of improving ventricular remodeling and limiting secondary cell migration.

Key Roles of RGD-Recognizing Integrins During Cardiac Development, on Cardiac Cells, and After Myocardial Infarction

Cardiac cells interact with the extracellular matrix (ECM) proteins through integrin mechanoreceptors that control many cellular events such as cell survival, apoptosis, differentiation, migration, and proliferation. Integrins play a crucial role in cardiac development as well as in cardiac fibrosis and hypertrophy. Integrins recognize oligopeptides present on ECM proteins and are involved in three main types of interaction, namely with collagen, laminin, and the oligopeptide RGD (Arg-Gly-Asp) present on vitronectin and fibronectin proteins. To date, the specific role of integrins recognizing the RGD has not been addressed. In this review, we examine their role during cardiac development, their role on cardiac cells, and their upregulation during pathological processes such as heart fibrosis and hypertrophy. We also examine their role in regenerative and angiogenic processes after myocardial infarction (MI) in the peri-infarct area. Specific targeting of these integrins may be a way of controlling some of these pathological events and thereby improving medical outcomes.

Novel PET/CT tracers for targeted imaging of membrane receptors to evaluate cardiomyocyte apoptosis and tissue repair process in a rat model of myocardial infarction

The purpose of this study was to employ novel tracers PET imaging approach to define the time course and intensity of myocardial repair after apoptosis and to correlate the imaging signal to immunohistochemical staining in myocardial infarction (MI). We designed novel α_Vβ₃-targeted and radio-functionalized tracers for detection of apoptosis in H9C2 cells and myocardial tissue. MI rats were imaged with [¹⁸F]FDG, [¹⁸F]ANP-Cin or [¹⁸F]ANP-RGD₂ using a small-animal PET/CT device. Rats were sacrificed, and tissue samples from viable and injured myocardial areas were sectioned for TUNEL assay and histology. The uncorrected radiochemical yield of [¹⁸F]ANP-Cin and [¹⁸F]ANP-RGD₂ were 41.3 ± 5.4% and 21.17 ± 4.7%, respectively. Two tracers meet many criteria for cardiac imaging, including high stability, high binding, no toxicity, fast renal clearance and excellent biodistribution in rat models. The uptake of [¹⁸F]ANP-Cin was significantly higher on the 1st and 3rd day than the 7th or 28th day after MI induction, a timeframe associated with increased cardiomyocyte apoptosis. Higher uptake of [¹⁸F]ANP-Cin was observed in MI rats than in N-acetylcysteine (NAC)-treated rats on the 3rd days. In contrast with [¹⁸F]ANP-Cin, no hot-spots was observed with [¹⁸F]ANP-RGD₂ on the 1st day and more hot-spots was observed from the 3rd day to the 7th day, then less on the 28th days in the high apoptotic site. There was no uptake of [¹⁸F]FDG in or around the apoptotic region. On the 7th day the uptake of [¹⁸F]ANP-RGD₂ was higher in NAC-treated rats than MI rats. [¹⁸F]ANP-Cin and [¹⁸F]ANP-RGD₂ are superior to [¹⁸F]FDG for PET/CT imaging for evaluation of cardiomyocyte apoptosis and tissue repair processes in the MI rats.

Exploration and validation of hub genes and pathways in the progression of hypoplastic left heart syndrome via weighted gene co-expression network analysis

Background

Despite significant progress in surgical treatment of hypoplastic left heart syndrome (HLHS), its mortality and morbidity are still high. Little is known about the molecular abnormalities of the syndrome. In this study, we aimed to probe into hub genes and key pathways in the progression of the syndrome.

Methods

Differentially expressed genes (DEGs) were identified in left ventricle (LV) or right ventricle (RV) tissues between HLHS and controls using the GSE77798 dataset. Then, weighted gene co-expression network analysis (WGCNA) was performed and key modules were constructed for HLHS. Based on the genes in the key modules, protein–protein interaction networks were conducted, and hub genes and key pathways were screened. Finally, the GSE23959 dataset was used to validate hub genes between HLHS and controls.

Results

We identified 88 and 41 DEGs in LV and RV tissues between HLHS and controls, respectively. DEGs in LV tissues of HLHS were distinctly involved in heart development, apoptotic signaling pathway and ECM receptor interaction. DEGs in RV tissues of HLHS were mainly enriched in BMP signaling pathway, regulation of cell development and regulation of blood pressure. A total of 16 co-expression network were constructed. Among them, black module (r = 0.79 and p value = 2e−04) and pink module (r = 0.84 and p value = 4e−05) had the most significant correlation with HLHS, indicating that the two modules could be the most relevant for HLHS progression. We identified five hub genes in the black module (including Fbn1, Itga8, Itga11, Itgb5 and Thbs2), and five hub genes (including Cblb, Ccl2, Edn1, Itgb3 and Map2k1) in the pink module for HLHS. Their abnormal expression was verified in the GSE23959 dataset.

Conclusions

Our findings revealed hub genes and key pathways for HLHS through WGCNA, which could play key roles in the molecular mechanism of HLHS.

The Future of Direct Cardiac Reprogramming: Any GMT Cocktail Variety?

Direct cardiac reprogramming has emerged as a novel therapeutic approach to treat and regenerate injured hearts through the direct conversion of fibroblasts into cardiac cells. Most studies have focused on the reprogramming of fibroblasts into induced cardiomyocytes (iCMs). The first study in which this technology was described, showed that at least a combination of three transcription factors, GATA4, MEF2C and TBX5 (GMT cocktail), was required for the reprogramming into iCMs in vitro using mouse cells. However, this was later demonstrated to be insufficient for the reprogramming of human cells and additional factors were required. Thereafter, most studies have focused on implementing reprogramming efficiency and obtaining fully reprogrammed and functional iCMs, by the incorporation of other transcription factors, microRNAs or small molecules to the original GMT cocktail. In this respect, great advances have been made in recent years. However, there is still no consensus on which of these GMT-based varieties is best, and robust and highly reproducible protocols are still urgently required, especially in the case of human cells. On the other hand, apart from CMs, other cells such as endothelial and smooth muscle cells to form new blood vessels will be fundamental for the correct reconstruction of damaged cardiac tissue. With this aim, several studies have centered on the direct reprogramming of fibroblasts into induced cardiac progenitor cells (iCPCs) able to give rise to all myocardial cell lineages. Especially interesting are reports in which multipotent and highly expandable mouse iCPCs have been obtained, suggesting that clinically relevant amounts of these cells could be created. However, as of yet, this has not been achieved with human iCPCs, and exactly what stage of maturity is appropriate for a cell therapy product remains an open question. Nonetheless, the major concern in regenerative medicine is the poor retention, survival, and engraftment of transplanted cells in the cardiac tissue. To circumvent this issue, several cell pre-conditioning approaches are currently being explored. As an alternative to cell injection, in vivo reprogramming may face fewer barriers for its translation to the clinic. This approach has achieved better results in terms of efficiency and iCMs maturity in mouse models, indicating that the heart environment can favor this process. In this context, in recent years some studies have focused on the development of safer delivery systems such as Sendai virus, Adenovirus, chemical cocktails or nanoparticles. This article provides an in-depth review of the in vitro and in vivo cardiac reprograming technology used in mouse and human cells to obtain iCMs and iCPCs, and discusses what challenges still lie ahead and what hurdles are to be overcome before results from this field can be transferred to the clinical settings.

Integrin β3 promotes cardiomyocyte proliferation and attenuates hypoxia-induced apoptosis via regulating the PTEN/Akt/mTOR and ERK1/2 pathways

Objective: Integrin β3 is one of the main integrin heterodimer receptors on the surface of cardiac myocytes. Our previous studies showed that hypoxia induces apoptosis and increases integrin β3 expression in cardiomyocytes. However, the exact mechanism by which integrin β3 protects against apoptosis remains unclear. Hence, the present investigation aimed to explore the mechanism of integrin β3 in cardiomyocyte proliferation and hypoxia-induced cardiomyocyte apoptosis. Methods: Stable cells and in vivo acute and chronic heart failure rat models were generated to reveal the essential role of integrin β3 in cardiomyocyte proliferation and apoptosis. Western blotting and immunohistochemistry were employed to detect the expression of integrin β3 in the stable cells and rat cardiac tissue. Flow cytometer was used to investigate the role of integrin β3 in hypoxia-induced cardiomyocyte apoptosis. Confocal microscopy was used to detect the localization of integrin β3 and integrin αv in cardiomyocytes. Results: A cobaltous chloride-induced hypoxic microenvironment stimulated cardiomyocyte apoptosis and increased integrin β3 expression in H9C2 cells, AC16 cells, and cardiac tissue from acute and chronic heart failure rats. The overexpression of integrin β3 promoted cardiomyocyte proliferation, whereas silencing integrin β3 expression resulted in decreased cell proliferation in vitro. Furthermore, knocking down integrin β3 expression using shRNA or the integrin β3 inhibitor cilengitide exacerbated cobaltous chloride-induced cardiomyocyte apoptosis, whereas overexpression of integrin β3 weakened cobaltous chloride-induced cardiomyocytes apoptosis. We found that integrin β3 promoted cardiomyocytes proliferation through the regulation of the PTEN/Akt/mTOR and ERK1/2 signaling pathways. In addition, we found that knockdown of integrin αv or integrin β1 weakened the effect of integrin β3 in cardiomyocyte proliferation. Conclusion: Our findings revealed the molecular mechanism of the role of integrin β3 in cardiomyocyte proliferation and hypoxia-induced cardiomyocyte apoptosis, providing new insights into the mechanisms underlying myocardial protection.