[Comparative study of functional and structural changes produced in a porcine model of acute and chronic heart attack]. / Estudio comparativo de los cambios funcionales y estructurales producidos en un modelo porcino de infarto de miocardio agudo y crónico.

INTRODUCTION AND OBJECTIVES: Animal models are a useful tool for the evaluation of disease mechanisms and also for technologies for diagnosis and treatment. In this study we performed a descriptive analysis of the functional and structural cardiac changes occurred as a result of acute coronary occlusion in pigs and its evolution during 5 weeks. METHODS: 19-Large White pigs, weighing 20kg, randomized into 3-experimental series were used. After sternotomy, anterior descending coronary artery was occluded. Duration of occlusion: Series 1 (n=6) 60min; series 2 (n=8) 90min; series 3 (n=5) 60min followed for 5 weeks. The following parameters where then analyzed: global cardiac function (ECG, left ventricular and atrium pressures, aortic flow and cardiac echocardiography), regional contractility, troponin T and CK-MB levels, macroscopic and histological analyzes. RESULTS: Coronary occlusion transiently altered the global cardiac function and produced increased cell damage markers, impaired regional contractility and produced histological changes. The increment of ischemic time (60 vs. 90min) increased infarct size (13.4±5.4% vs. 22.9±7.8 S1 S2%; P=.04). After 5 weeks, morphological remodelling changes were evident. In 79% of cases ischemia triggered ventricular fibrillation. CONCLUSION: The porcine open chest model of acute myocardial infarction and reperfusion is valid for studying the pathophysiology of coronary ischemia, allows direct analysis of regional myocardial function and is easily retrievable in the event of serious arrhythmias.

miR-133a enhances the protective capacity of cardiac progenitors cells after myocardial infarction.

miR-133a and miR-1 are known as muscle-specific microRNAs that are involved in cardiac development and pathophysiology. We have shown that both miR-1 and miR-133a are early and progressively upregulated during in vitro cardiac differentiation of adult cardiac progenitor cells (CPCs), but only miR-133a expression was enhanced under in vitro oxidative stress. miR-1 was demonstrated to favor differentiation of CPCs, whereas miR-133a overexpression protected CPCs against cell death, targeting, among others, the proapoptotic genes Bim and Bmf. miR-133a-CPCs clearly improved cardiac function in a rat myocardial infarction model by reducing fibrosis and hypertrophy and increasing vascularization and cardiomyocyte proliferation. The beneficial effects of miR-133a-CPCs seem to correlate with the upregulated expression of several relevant paracrine factors and the plausible cooperative secretion of miR-133a via exosomal transport. Finally, an in vitro heart muscle model confirmed the antiapoptotic effects of miR-133a-CPCs, favoring the structuration and contractile functionality of the artificial tissue.

A comparison of electrospun polymers reveals poly(3-hydroxybutyrate) fiber as a superior scaffold for cardiac repair.

The development of biomaterials for myocardial tissue engineering requires a careful assessment of their performance with regards to functionality and biocompatibility, including the immune response. Poly(3-hydroxybutyrate) (PHB), poly(e-caprolactone) (PCL), silk, poly-lactic acid (PLA), and polyamide (PA) scaffolds were generated by electrospinning, and cell compatibility in vitro, and immune response and cardiac function in vitro and in vivo were compared with a noncrosslinked collagen membrane (Col) control material. Results showed that cell adhesion and growth of mesenchymal stem cells, cardiomyocytes, and cardiac fibroblasts in vitro was dependent on the polymer substrate, with PHB and PCL polymers permitting the greatest adhesion/growth of cells. Additionally, polymer substrates triggered unique expression profiles of anti- and pro-inflammatory cytokines in human peripheral blood mononuclear cells. Implantation of PCL, silk, PLA, and PA patches on the epicardial surface of healthy rats induced a classical foreign body reaction pattern, with encapsulation of polymer fibers and induction of the nonspecific immune response, whereas Col and PHB patches were progressively degraded. When implanted on infarcted rat heart, Col, PCL, and PHB reduced negative remodeling, but only PHB induced significant angiogenesis. Importantly, Col and PHB modified the inflammatory response to an M2 macrophage phenotype in cardiac tissue, indicating a more beneficial reparative process and remodeling. Collectively, these results identify PHB as a superior substrate for cardiac repair.

Hypoxia-inducible factor 1 alpha contributes to cardiac healing in mesenchymal stem cells-mediated cardiac repair.

Mesenchymal stem cells (MSC) are effective in treating myocardial infarction (MI) and previous reports demonstrated that hypoxia improves MSC self-renewal and therapeutics. Considering that hypoxia-inducible factor-1 alpha (HIF-1α) is a master regulator of the adaptative response to hypoxia, we hypothesized that HIF-1α overexpression in MSC could mimic some of the mechanisms triggered by hypoxia and increase their therapeutic potential without hypoxia stimulation. Transduction of MSC with HIF-1α lentivirus vectors (MSC-HIF) resulted in increased cell adhesion and migration, and activation of target genes coding for paracrine factors. When MSC-HIF were intramyocardially injected in infarcted nude rats, significant improvement was found (after treatment of infarcted rats with MSC-HIF) in terms of cardiac function, angiogenesis, cardiomyocyte proliferation, and reduction of fibrotic tissue with no induction of cardiac hypertrophy. This finding provides evidences for a crucial role of HIF-1α on MSC biology and suggests the stabilization of HIF-1α as a novel strategy for cellular therapies.

IL1ß induces mesenchymal stem cells migration and leucocyte chemotaxis through NF-κB.

Mesenchymal stem cells are often transplanted into inflammatory environments where they are able to survive and modulate host immune responses through a poorly understood mechanism. In this paper we analyzed the responses of MSC to IL-1ß: a representative inflammatory mediator. Microarray analysis of MSC treated with IL-1ß revealed that this cytokine activateds a set of genes related to biological processes such as cell survival, cell migration, cell adhesion, chemokine production, induction of angiogenesis and modulation of the immune response. Further more detailed analysis by real-time PCR and functional assays revealed that IL-1ß mainly increaseds the production of chemokines such as CCL5, CCL20, CXCL1, CXCL3, CXCL5, CXCL6, CXCL10, CXCL11 and CX(3)CL1, interleukins IL-6, IL-8, IL23A, IL32, Toll-like receptors TLR2, TLR4, CLDN1, metalloproteins MMP1 and MMP3, growth factors CSF2 and TNF-α, together with adhesion molecules ICAM1 and ICAM4. Functional analysis of MSC proliferation, migration and adhesion to extracellular matrix components revealed that IL-1ß did not affect proliferation but also served to induce the secretion of trophic factors and adhesion to ECM components such as collagen and laminin. IL-1ß treatment enhanced the ability of MSC to recruit monocytes and granulocytes in vitro. Blockade of NF-κß transcription factor activation with IκB kinase beta (IKKß) shRNA impaired MSC migration, adhesion and leucocyte recruitment, induced by IL-1ß demonstrating that NF-κB pathway is an important downstream regulator of these responses. These findings are relevant to understanding the biological responses of MSC to inflammatory environments.