A Large Mammalian Model of Myocardial Regeneration After Myocardial Infarction in Fetal Sheep.

Objective: Ischemic heart disease accounts for over 20% of all deaths worldwide. As the global population faces a rising burden of chronic diseases, such as hypertension, hyperlipidemia, and diabetes, the prevalence of heart failure due to ischemic heart disease is estimated to increase. We sought to develop a model that may more accurately identify therapeutic targets to mitigate the development of heart failure following myocardial infarction (MI). Approach: Having utilized fetal large mammalian models of scarless wound healing, we proposed a fetal ovine model of myocardial regeneration after MI. Results: Use of this model has identified critical pathways in the mammalian response to MI, which are differentially activated in the regenerative, fetal mammalian response to MI when compared to the reparative, scar-forming, adult mammalian response to MI. Innovation: While the foundation of myocardial regeneration research has been built on zebrafish and rodent models, effective therapies derived from these disease models have been lacking; therefore, we sought to develop a more representative ovine model of myocardial regeneration after MI to improve the identification of therapeutic targets designed to mitigate the development of heart failure following MI. Conclusions: To develop therapies aimed at mitigating this rising burden of disease, it is critical that the animal models we utilize closely reflect the physiology and pathology we observe in human disease. We encourage use of this ovine large mammalian model to facilitate identification of therapies designed to mitigate the growing burden of heart failure.

Early survival following in utero myocardial infarction.

Intrauterine myocardial infarction is a rare and frequently fatal diagnosis. It has been presented in the literature only as case reports and short series. We present a case report of a coronary occlusive intrauterine myocardial infarction and survival and present a systematic review of the literature. This is the first summative description of current data on intrauterine and perinatal myocardial infarction. We performed the systematic review based on the guidelines established by the PRISMA statement. Our population of intrauterine and perinatal myocardial infarction included published cases who presented as a live birth within the first 28 postnatal days, and had a diagnosis of myocardial infarction. We conducted descriptive statistics and regression analysis on short-term mortality as the primary outcome. After applying exclusion criteria we described 84 individual cases of myocardial infarction from 63 full-text articles including our own case. Presentation within the first 12 hours was associated with mortality (OR 3.90, p=0.004). Treatment modalities were varied and inconsistently recorded. The aetiologies and comorbidities are varied in our systematic review. We would have a low threshold to perform viral testing, consider anticoagulation early and coronary imaging if feasible. The use of extracorporeal membranous oxygenation may serve as a bridge to cardiac recovery.

Periodontitis Increases the Risk of a First Myocardial Infarction: A Report From the PAROKRANK Study.

BACKGROUND: The relationship between periodontitis (PD) and cardiovascular disease is debated. PD is common in patients with cardiovascular disease. It has been postulated that PD could be causally related to the risk for cardiovascular disease, a hypothesis tested in the Periodontitis and Its Relation to Coronary Artery Disease (PAROKRANK) study. METHODS AND RESULTS: Eight hundred five patients (<75 years of age) with a first myocardial infarction (MI) and 805 age- (mean 62±8), sex- (male 81%), and area-matched controls without MI underwent standardized dental examination including panoramic x-ray. The periodontal status was defined as healthy (≥80% remaining bone) or as mild-moderate (from 79% to 66%) or severe PD (<66%). Great efforts were made to collect information on possibly related confounders (≈100 variables). Statistical comparisons included the Student pairwise t test and the McNemar test in 2×2 contingency tables. Contingency tables exceeding 2×2 with ranked alternatives were tested by Wilcoxon signed rank test. Odds ratios (95% confidence intervals) were calculated by conditional logistic regression. PD was more common (43%) in patients than in controls (33%; P<0.001). There was an increased risk for MI among those with PD (odds ratio, 1.49; 95% confidence interval, 1.21-1.83), which remained significant (odds ratio, 1.28; 95% confidence interval, 1.03-1.60) after adjusting for variables that differed between patients and controls (smoking habits, diabetes mellitus, years of education, and marital status). CONCLUSIONS: In this large case-control study of PD, verified by radiographic bone loss and with a careful consideration of potential confounders, the risk of a first MI was significantly increased in patients with PD even after adjustment for confounding factors. These findings strengthen the possibility of an independent relationship between PD and MI.

C-terminal variable AGES domain of Thymosin ß4: the molecule's primary contribution in support of post-ischemic cardiac function and repair.

Repairing defective cardiac cells is important towards improving heart function. Due to the frequency and severity of ischemic heart disease, management of patients featuring this type of cardiac failure receives significant interest. Previously we discovered that Thymosin ß4 (TB4), a 43 amino-acid secreted actin sequestering peptide, is beneficial for myocardial cell survival and coronary re-growth after infarction in adult mammals. Considering the regenerative potential of full-length TB4 in the heart, and that minimal structural variations alter TB4's influence on actin assembly and cell movement, we investigated how various TB4 domains affect cardiac cell behavior and post-ischemic mammalian heart function. We synthesized 17 domain combinations of full-length TB4 and analyzed their impact on embryonic cardiac cells in vitro, and after cardiac infarction in vivo. We discovered the domains of TB4 affect cardiac cell behavior distinctly. We revealed TB4 specific C-terminal tetrapeptide, AGES, increases embryonic cardiac cell migration and myocyte beating in culture, and improves adult mammalian heart function following ischemia. Investigating the molecular background and mechanism we discovered systemic injection of AGES enhances early myocyte survival by activating Akt-mediated signaling mechanisms, increases coronary vessel growth and inhibits inflammation in mice and pigs. Biodistribution analyses revealed cardiomyocytes uptake AGES efficiently in vitro and in vivo projecting a potential independent clinical utilization for the tetrapeptide. Our comprehensive domain investigations also suggest, preservation and/or restoration of cardiomyocyte communication is a target of TB4 and AGES, and critical to improve post-ischemic heart function in pigs. In summary, we identified the C-terminal four amino-acid variable end of TB4 as the essential and responsible domain for the molecule's full benefits in the hypoxic heart. Additionally, we introduced AGES as a novel, systemically applicable drug candidate to aid cardiac infarction in adult mammals.

Mammalian fetal cardiac regeneration after myocardial infarction is associated with differential gene expression compared with the adult.

BACKGROUND: In adults, myocardial infarction (MI) results in a brisk inflammatory response, myocardium loss, and scar formation. We have recently reported the first mammalian large-animal model of cardiac regeneration after MI in fetal sheep. We hypothesize that the ability of the fetus to regenerate functional myocardium after MI is owing to differential gene expression regulating the response to MI in the fetus compared with the adult. METHODS: Myocardial infarction was created in adult (n=4) or early gestation fetal (n=4) sheep. Tissue was harvested after 3 or 30 days, and RNA was extracted for microarray, followed by principal component analysis and global gene expression analysis for the following gene ontology terms: response to wounding, inflammatory response, extracellular matrix, cell cycle, cell migration, cell proliferation, and apoptosis. RESULTS: Principal component analysis demonstrated that the global gene expression pattern in adult infarcts was distinctly different from the uninfarcted region at 3 days and remained different at 30 days after MI. In contrast, gene expression in the fetal infarct was different from the uninfarcted region at 3 days, but by 30 days it returned to a baseline expression pattern similar to the uninfarcted region. Three days after MI there was an increase in the expression of genes related to all gene ontology terms in fetal and adult infarcts, but this increase was much more pronounced in adults. By 30 days, the fetal gene expression returned to baseline, whereas in the adult it remained significantly elevated. CONCLUSIONS: These data demonstrate that the global gene expression pattern is dramatically different in the fetal regenerative response to MI compared with the adult response and may partly be responsible for the regeneration.

Nitric oxide synthase-3 deficiency results in hypoplastic coronary arteries and postnatal myocardial infarction.

AIMS: Hypoplastic coronary artery disease is a rare congenital abnormality that is associated with sudden cardiac death. However, molecular mechanisms responsible for this disease are not clear. The aim of the present study was to assess the role of nitric oxide synthase-3 (NOS3) in the pathogenesis of hypoplastic coronary arteries. METHODS AND RESULTS: Wild-type (WT), NOS3(-/-), and a novel cardiac-specific NOS3 overexpression mouse model were employed. Deficiency in NOS3 resulted in coronary artery hypoplasia in foetal mice and spontaneous myocardial infarction in postnatal hearts. Coronary artery diameters, vessel density, and volume were significantly decreased in NOS3(-/-) mice at postnatal day 0. In addition, NOS3(-/-) mice showed a significant increase in the ventricular wall thickness, myocardial volume, and cardiomyocyte cell size compared with WT mice. Lack of NOS3 also down-regulated the expression of Gata4, Wilms tumour-1, vascular endothelial growth factor, basic fibroblast growth factor and erythropoietin, and inhibited migration of epicardial cells. These abnormalities and hypoplastic coronary arteries in the NOS3(-/-) mice were completely rescued by the cardiac-specific overexpression of NOS3. CONCLUSION: Nitric oxide synthase-3 is required for coronary artery development and deficiency in NOS3 leads to hypoplastic coronary arteries.

Mammalian cardiac regeneration after fetal myocardial infarction requires cardiac progenitor cell recruitment.

BACKGROUND: In contrast to the adult, fetal sheep consistently regenerate functional myocardium after myocardial infarction. We hypothesize that this regeneration is due to the recruitment of cardiac progenitor cells to the infarct by stromal-derived factor-1α (SDF-1α) and that its competitive inhibition will block the regenerative fetal response. METHODS: A 20% apical infarct was created in adult and fetal sheep by selective permanent coronary artery ligation. Lentiviral overexpression of mutant SDF-1α competitively inhibited SDF-1α in fetal infarcts. Echocardiography was performed to assess left ventricular function and infarct size. Cardiac progenitor cell recruitment and proliferation was assessed in fetal infarcts at 1 month by immunohistochemistry for nkx2.5 and 5-bromo-2-deoxyuridine. RESULTS: Competitive inhibition of SDF-1α converted the regenerative fetal response into a reparative response, similar to the adult. SDF-inhibited fetal infarcts demonstrated significant infarct expansion by echocardiography (p < 0.001) and a significant decrease in the number of nkx2.5+ cells repopulating the infarct (p < 0.001). CONCLUSIONS: The fetal regenerative response to myocardial infarction requires the recruitment of cardiac progenitor cells and is dependent on SDF1α. This novel model of mammalian cardiac regeneration after myocardial infarction provides a powerful tool to better understand cardiac progenitor cell biology and to develop strategies to cardiac regeneration in the adult.

Association of age and CKD with prognosis of myocardial infarction.

BACKGROUND AND OBJECTIVES: CKD is a well known poor prognostic factor in myocardial infarction (MI). This study evaluated the prognostic significance of CKD, particularly in association with increasing age, in MI patients. DESIGN, SETTING, PARTICIPANTS, & MEASUREMENTS: This study was based on a retrospective cohort, the Korean Acute Myocardial Infarction Registry. Patients with a discharge diagnosis of MI were analyzed to investigate the association of CKD with mortality risk according to age. A total of 11,268 patients (mean age 63.0±12.6 years) were included and followed for 1 year. RESULTS: In the full cohort, 26% of patients had CKD (n=2929). The prevalence of CKD was higher with advancing age. Eight hundred sixty-one patients (7.6%) died and the interaction for 1-year mortality between age strata and estimated GFR (eGFR) strata was significant (P<0.001). Within each age category, the absolute 1-year mortality was higher in patients with a low eGFR. However, the adjusted relative mortality risk for a low eGFR was lower with increasing age (adjusted hazard ratio [95% confidence interval] for 1-year mortality at eGFR <30 ml/min per 1.73 m(2): 4.84 [1.93-12.15], 4.53 [2.42-8.47], 3.51 [2.42-5.09], and 3.30 [2.41-4.52] for patients aged <55, 55-64, 65-74, and ≥75 years compared with those with eGFR ≥60 ml/min per 1.73 m(2), respectively). CONCLUSIONS: For all age categories, the overall mortality was significantly higher as eGFR declined. The association of a lower eGFR with mortality was weaker with increasing age, indicating that the prognostic significance of CKD in MI patients is age dependent.

Proteasome inhibition during myocardial infarction.

The ubiquitin-proteasome system (UPS) plays a central role in protein degradation and regulates a variety of critical cellular processes. During recent years, the cardiac UPS has become increasingly recognized as a key regulator of cardiac function under both physiological and pathological conditions. Numerous studies have demonstrated that altered UPS function is involved in the pathogenesis of cardiac disease including myocardial ischaemia or infarction. The expression and activity of the E3 ubiquitin ligases, which confer substrate specificity in the UPS pathway, affect the apoptosis and severity of disease in myocardial ischaemia and reperfusion. Although impaired proteasome function is commonly associated with myocardial ischaemic injury, recent evidence also supports a cardioprotective role for proteasome inhibitors in myocardial ischaemia. We will review these studies and data, discuss controversies regarding the UPS alterations and use of proteasome inhibitors in myocardial ischaemia, and attempt to identify strategies that may enhance their clinical application.

Cardiomyocyte proliferation in rat fetuses under normal conditions and after heart injury.

Heart injury was inflicted to outbred albino rat fetuses on day 16 of prenatal development and cardiomyocyte proliferation was evaluated in the left ventricular zones adjacent to the wound and distant from it. The mitotic index of experimental animals was higher than in intact controls only for zones distant from the injury on day 10 after the intervention. The percentage of pathological metaphases gradually increased in all experimental groups, which causes doubt in the viability of postmitotic cardiomyocytes.

Transplantation of fetal cardiomyocytes into infarcted rat hearts results in long-term functional improvement.

Studies have demonstrated the feasibility of transplanting cardiomyocytes after myocardial infarction (MI). However, persistence and effects on left ventricular (LV) function have not been elucidated in long-term studies. Ventricular fetal cardiomyocytes from embryos of both sexes were injected into marginal regions of MI 4 weeks after suture occlusion of the left anterior descending artery in adult female rats. Two and 6 months after transplantation (Tx), engrafted cells were traced by immunohistochemical in situ hybridization for Y chromosomes or bromodeoxyuridine (BrdU) staining, LV dimensions and function were assessed by echocardiography, and LV pressure was assessed ex vivo in a Langendorff perfusion system. Immunohistochemistry for alpha-sarcomeric actin and Y chromosomes revealed the presence of transplanted cells in infarcted host myocardium at both 2 and 6 months. End-diastolic LV diameter markedly decreased after Tx and fractional shortening gradually increased after Tx (31.3 +/- 4.5% before Tx, 45.4 +/- 4.2% at 6 months; p<0.005). Wall area fraction and MI size were unaffected by Tx. In hearts with MI, but not in normal hearts, Tx led to the development of higher pressures (87 +/- 18 versus 38 +/- 8 mmHg, 6 months post-Tx versus nontreated). After catecholamine stimulation, both infarcted and normal hearts developed higher pressures after Tx (p<0.005), ultimately associated with reduced mortality after Tx versus nontreated. Transplanted cardiomyocyte-rich graft cells persist in host myocardium and mediate continuous improvement of LV function and survival in a rat model of MI even during long-term follow-up, possibly involving a catecholamine-sensitive mechanism.