Infarction In Mice Research Articles

Soluble epoxide hydrolase inhibitors, t-AUCB, regulated microRNA-1 and its target genes in myocardial infarction mice.

PurposeSoluble epoxide hydrolase inhibitors (sEHIs) had been demonstrated to produce cardioprotective effects against ischemia-induced lethal arrhythmias, but the exact mechanisms remain unknown. The present study was designed to investigate whether the beneficial effects of sEHIs are related to regulation of microRNA-1, which was a proarrhythmic factor in the ischemic heart.MethodsA mousemyocardial infarction (MI) model was established by ligating the coronary artery. sEHI t-AUCB (0.2, 1, 5 mg/L in drinking-water) was administered daily seven days before MI. The incidence of arrhythmias was assessed by in vivo electrophysiologic studies. miR-1, KCNJ2 (encoding the K+ channel subunit Kir2.1), and GJA1 (encoding connexin 43 [Cx43]) mRNA were measured by real-time PCR; Kir2.1 and Cx43 protein were assessed by western blotting and immunohistochemistry.ResultsWe demonstrated that sEHIs reduced the myocardium infarct size and incidence of inducible arrhythmias in MI mice. Up-regulation of miR-1 and down-regulation of KCNJ2/Kir2.1 and GJA1/Cx43 mRNA/protein were observed in ischemic myocaridum, whereas administration of sEHIs produced an opposite effect. In addition, miR-1 overexpression inhibited expression of the target mRNA and their corresponding proteins, whereas t-AUCB reversed the effects. Our results further revealed that PI3K/Akt signaling pathway might participate in the negatively regulation of miR-1 by sEHi.ConclusionsWe conclude that sEHIs can repress miR-1, thus stimulate expression of KCNJ2/Kir2.1 and GJA1/Cx43 mRNA/protein in MI mice, suggesting a possible mechanism for its potential therapeutic application in ischemic arrhythmias.

Erratum: Interval and continuous aerobic exercise training similarly increase cardiac function and autonomic modulation in infarcted mice.

[This corrects the article on p. 257 in vol. 13, PMID: 28702435.].

In Vivo Functional Selection Identifies Cardiotrophin-1 as a Cardiac Engraftment Factor for Mesenchymal Stromal Cells.

Transplantation of cells into the infarcted heart has significant potential to improve myocardial recovery; however, low efficacy of cell engraftment still limits therapeutic benefit. Here, we describe a method for the unbiased, in vivo selection of cytokines that improve mesenchymal stromal cell engraftment into the heart both in normal conditions and after myocardial infarction. An arrayed library of 80 secreted factors, including most of the currently known interleukins and chemokines, were individually cloned into adeno-associated viral vectors. Pools from this library were then used for the batch transduction of bone marrow-derived mesenchymal stromal cells ex vivo, followed by intramyocardial cell administration in normal and infarcted mice. Three weeks after injection, vector genomes were recovered from the few persisting cells and identified by sequencing DNA barcodes uniquely labeling each of the tested cytokines. The most effective molecule identified by this competitive engraftment screening was cardiotrophin-1, a member of the interleukin-6 family. Intracardiac injection of mesenchymal stromal cells transiently preconditioned with cardiotrophin-1 preserved cardiac function and reduced infarct size, parallel to the persistence of the transplanted cells in the healing hearts for at least 2 months after injection. Engraftment of cardiotrophin-1-treated mesenchymal stromal cells was consequent to signal transducer and activator of transcription 3-mediated activation of the focal adhesion kinase and its associated focal adhesion complex and the consequent acquisition of adhesive properties by the cells. These results support the feasibility of selecting molecules in vivo for their functional properties with adeno-associated viral vector libraries and identify cardiotrophin-1 as a powerful cytokine promoting cell engraftment and thus improving cell therapy of the infarcted myocardium.

Hesperetin protects against inflammatory response and cardiac fibrosis in postmyocardial infarction mice by inhibiting nuclear factor κB signaling pathway.

Cardiac inflammation and cardiac fibrosis are important parts of cardiac remodeling following myocardial infarction (MI), which may be the basic mechanisms of the development of chronic heart failure. The nuclear factor (NF)-κB signaling pathway promotes cardiac inflammation and fibrosis. It has reported that hesperetin inhibits cardiac remodeling induced by pressure overload in mice. However, it has remained elusive whether and how hesperetin has a role in cardiac fibrosis post-MI. Therefore, a mouse model of MI was established by left anterior descending coronary artery ligation. Mice received hesperetin (30 mg/kg/day) or vehicle after surgery. After 8 weeks, all mice underwent echocardiography to evaluate cardiac function. Gene expression of cardiac fibrosis markers such as connective tissue growth factor (CTGF) as well as collagen I and III, and histological analysis were applied to determine the level of cardiac fibrosis. The expression of inflammatory markers such as tumor necrosis factor (TNF)-α, interleukin (IL)-1β and IL-6 were assessed by reverse-transcription quantitative PCR and ELISA, and activation of the NF-κB signaling pathway was detected by western blot analysis. It was found that hesperetin reduced the expression levels of TNF-α, IL-1β, IL-6 and CTGF as well as collagen I and III. The level of collagen deposition in post-MI myocardium was attenuated with the treatment of hesperetin. In additionally, administration of hesperetin inhibited the activation of the NF-κB signaling pathway. These findings indicated that hesperetin may inhibit cardiac inflammation post-MI through blocking the NF-κB signaling pathway, which may be a key mechanism via which hesperetin attenuates cardiac fibrosis.

Interval and continuous aerobic exercise training similarly increase cardiac function and autonomic modulation in infarcted mice.

The present study aimed to compare the effects of moderate-intensity continuous and high-intensity interval exercise training (ET) on exercise tolerance, cardiac morphometry and function, hemodynamic, and cardiac autonomic modulation in myocardial infarcted mice. Wild-type mice (WT) were divided into four groups: sedentary WT (S); WT myocardium infarction sedentary (IS); WT myocardium infarction underwent to moderate-intensity continuous ET (MICT), and WT myocardium infarction underwent to high-intensity interval ET (MIIT). After 60 days of descending coronary artery ligation, moderate-intensity continuous ET consisted of running at 60% of maximum, while the high-intensity interval training consisted of eight sprints of 4 min at 80% of maximum and a 4-min recovery at 40% of maximum. Both exercises were performed 1 hr a day, 5 days a week, during 8 weeks. Results demonstrated that IS showed elevated exercise tolerance, as well as decreased hemodynamic and heart function, and autonomic control. On the other hand, both programs of ET were equally effective to increase all parameters, without further differences between the groups. In conclusion, the results of the present study showed that myocardial infarction leads to damage in both investigated strains and the two types of physical exercise attenuated the major impairments provoked by myocardial infarction in exercise tolerance, cardiac structure, cardiac function, hemodynamic and cardiac autonomic modulation.

Activation of cannabinoid receptor type II by AM1241 protects adipose-derived mesenchymal stem cells from oxidative damage and enhances their therapeutic efficacy in myocardial infarction mice via Stat3 activation.

The poor survival of cells in ischemic sites diminishes the therapeutic efficacy of stem cell therapy. Previously we and others have reported that Cannabinoid receptor type II (CB2) is protective during heart ischemic injury for its anti-oxidative activity. However, whether CB2 activation could improve the survival and therapeutic efficacy of stem cells in ischemic myocardium and the underlying mechanisms remain elusive. Here, we showed evidence that CB2 agonist AM1241 treatment could improve the functional survival of adipose-derived mesenchymal stem cells (AD-MSCs) in vitro as well as in vivo. Moreover, AD-MSCs adjuvant with AM1241 improved cardiac function, and inhibited cardiac oxidative stress, apoptosis and fibrosis. To unveil possible mechanisms, AD-MSCs were exposed to hydrogen peroxide/serum deprivation to simulate the ischemic environment in myocardium. Results delineated that AM1241 blocked the apoptosis, oxidative damage and promoted the paracrine effects of AD-MSCs. Mechanistically, AM1241 activated signal transducers and activators of transcription 3 (Stat3) through the phosphorylation of Akt and ERK1/2. Moreover, the administration of AM630, LY294002, U0126 and AG490 (inhibitors for CB2, Akt, ERK1/2 and Stat3, respectively) could abolish the beneficial actions of AM1241. Our result support the promise of CB2 activation as an effective strategy to optimize stem cell-based therapy possibly through Stat3 activation.

Cardiac fibroblast participates as an immune modulator in IL-17A-driven post-injury cardiac inflammation and remodeling

Abstract Heart diseases are the leading causes of mortality and morbidity worldwide. The post-injury cardiac inflammation and remodeling process determined the severity of cardiac damage and the likelihood of developing heart failure. We have adapted both experimental autoimmune myocarditis (EAM) and myocardial infarction (MI) mouse model to investigate the mechanism behind cardiac inflammation and remodeling. We showed that Interleukin 17 (IL-17A) signaling is required for adverse cardiac remodeling and fibrosis in both EAM and MI models. IL-17A induces cardiac fibroblast (CF) to produce granulocyte-macrophage colony stimulating factor (GM-CSF). GM-CSF in turn drives the development of adverse cardiac remodeling and fibrosis. Despite the heterogeneity of CF population, we successfully identified a specific subset of cardiac fibroblast to be the main recipient of IL-17A signal to produce GM-CSF, CCL2 and other cytokines/chemokines. The same CF subset was detected in heart failure patient biopsies from various etiologies including myocarditis, ischemia patients, etc. Further investigation also revealed that this subset is plastic in cytokine production. Lastly, both complete knockout of IL-17A receptor (R) and specific ablation of IL-17RA in this subset significantly reduced ventricular dilation and infarct scar size. Our findings provide an excellent opportunity to develop specific treatment for post-injury cardiac remodeling and fibrosis through specific targeting the IL-17A signaling to this CF subset or the downstream cytokine production by these cells.

Cartilage Intermediate Layer Protein 1 Suppresses TGF-β Signaling in Cardiac Fibroblasts

Since transforming growth factor (TGF)-β1-induced cardiac fibrosis following myocardial infarction (MI) leads to heart failure and poor clinical prognosis, we aimed to identify a novel and unknown target for cardiac fibrosis related to the TGF-β signaling. We performed and investigated RNA-Seq using infarcted mouse hearts, culminating in cartilage intermediate layer protein 1 (CILP1). Interestingly, Cilp1 expression was increased along with TGF-β1 expression in infarcted hearts, and was also upregulated after TGF-β1 stimulation in cardiac fibroblasts in vitro. Histological analysis revealed that Cilp1 was localized at the fibrotic regions of infarcted hearts. Full length CILP1 (F-CILP1) was cleaved into both N-terminal CILP1 (N-CILP1) and C-terminal CILP1 at the furin cleavage site, and both F-CILP1 and N-CILP1 were extracellularly secreted. We further found that CILP1 bound to TGF-β1 via thrombospondin type 1 domain, and suppressed both smad3 phosphorylation and fibroblasts differentiation to myofibroblasts induced by TGF-β1. We identified CILP1 as a potential regulator of cardiac fibrosis by inhibiting TGF-β signaling, and these results suggest the promise of CILP1 as a novel therapeutic target for preventing cardiac fibrosis and heart failure in MI patients.

Natriuretic Peptide Receptor B modulates the proliferation of the cardiac cells expressing the Stem Cell Antigen-1

Brain Natriuretic Peptide (BNP) injections in adult “healthy” or infarcted mice led to increased number of non-myocyte cells (NMCs) expressing the nuclear transcription factor Nkx2.5. The aim of this study was to identify the nature of the cells able to respond to BNP as well as the signaling pathway involved. BNP treatment of neonatal mouse NMCs stimulated Sca-1+ cell proliferation. The Sca-1+ cells were characterized as being a mixed cell population involving fibroblasts and multipotent precursor cells. Thus, BNP treatment led also to increased number of Sca-1+ cells expressing Nkx2.5, in Sca-1+ cell cultures in vitro and in vivo, in the hearts of neonatal and adult infarcted mice. Whereas BNP induced Sca-1+ cell proliferation via NPR-B receptor and protein kinase G activation, CNP stimulated Sca-1+ cell proliferation via NPR-B and a PKG-independent mechanism. We highlighted here a new role for the natriuretic peptide receptor B which was identified as a target able to modulate the proliferation of the Sca-1+ cells. The involvement of NPR-B signaling in heart regeneration has, however, to be further investigated.

MR Assessment of Acute Pathologic Process after Myocardial Infarction in a Permanent Ligation Mouse Model: Role of Magnetic Nanoparticle-Contrasted MRI.

We evaluated the relationship between myocardial infarct size and inflammatory response using cardiac magnetic resonance imaging (CMR) in an acute myocardial infarction (AMI) mouse model. Myocardial infarction (MI) was induced in 14 mice by permanent ligation of the left anterior descending artery. Late gadolinium enhancement (LGE), manganese-enhanced MRI (MEMRI), and magnetofluorescent nanoparticle MRI (MNP-MRI) were performed 1, 2, and 3 days after MI, respectively. The size of the enhanced lesion was quantitatively determined using Otsu's thresholding method in area-based and sector-based approaches and was compared statistically. Linear correlation between the enhanced lesion sizes was evaluated by Pearson's correlation coefficients. Differences were compared using Bland-Altman analysis. The size of the inflammatory area determined by MNP-MRI (57.1 ± 10.1%) was significantly larger than that of the infarct area measured by LGE (40.8 ± 11.7%, P < 0.0001) and MEMRI (44.1 ± 14.9%, P < 0.0001). There were significant correlations between the sizes of the infarct and inflammatory lesions (MNP-MRI versus LGE: r = 0.3418, P = 0.0099; MNP-MRI versus MEMRI: r = 0.4764, P = 0.0002). MNP-MRI provides information about inflammatory responses in a mouse model of AMI. Thus, MNP-MRI associated with LGE and MEMRI may play an important role in monitoring the disease progression in MI.

In Vivo Quantification of Myocardial Infarction in Mice Using Micro-CT and a Novel Blood Pool Agent.

We herein developed a micro-CT method using the innovative contrast agent ExiTron™ MyoC 8000 to longitudinally monitor cardiac processes in vivo in small animals. Experiments were performed on healthy mice and mice with myocardial infarction inflicted by ligation of the left anterior descending artery. Time-dependent signal enhancement in different tissues of healthy mice was measured and various contrast agent doses were investigated so as to determine the minimum required dose for imaging of the myocardium. Due to its ability to be taken up by healthy myocardium but not by infarct tissue, ExiTron MyoC 8000 enables detection of myocardial infarction even at a very low dose. The signal enhancement in the myocardium of infarcted mice after contrast agent injection was exploited for quantification of infarct size. The values of infarct size obtained from the imaging method were compared with those obtained from histology and showed a significant correlation (R2 = 0.98). Thus, the developed micro-CT method allows for monitoring of a variety of processes such as cardiac remodeling in longitudinal studies.

Abstract 13106: Over Expression of Glyoxalase 1 Prevents Chronic Hyperglycemia Induced Explant Derived Cardiac Stem Cell Dysfunction

Diabetes increases the risk of heart disease and worsens clinical outcomes after myocardial infarction. Given that hyperglycemia promotes the generation of toxic methylglyoxal, the influence of the key detoxification enzyme glyoxalase 1 (Glo1) on chronic hyperglycemia induced explant-derived cardiac stem cell (EDC) dysfunction was investigated. Methods/Results: Sixteen-week old wild type (WT, n=22) or constitutive Glo1 overexpressing (Glo1TG, n=12) mice were studied 2 months after treatment with streptozotocin or vehicle (2.0±0.1 fold increase in glycated hemoglobin, p=0.001 vs vehicle treated mice). Hyperglycemia reduced overall culture yields (86±3% fewer EDCs cultured, p=0.0009) and prolonged population doubling time (30±4% slower growth, p=0.04) while increasing the cellular content of reactive dicarbonyls (27±3% more reactive oxygen species, p=0.0006) within EDCs cultured from WT mice. These intrinsic cell changes reduced the angiogenic potential (74±2% less total endothelial tubule formation, p=0.001) and production of pro-healing exosomes (43±6% fewer exosomes secreted, p=0.04) by hyperglycemic EDCs while promoting EDC senescence (98±28% more senescent EDCs, p=0.03). As compared to transplant of normoglycemic WT EDCs, hyperglycemia reduced the EDC-mediated increases in echocardiographic ejection fraction and dP/dTmax in infarcted normoglycemic WT mice 3 weeks after intra-myocardial injection by 37±8% (p=0.0001) and 25±1% (p=0.001), respectively. In contrast to EDCs cultured from WT hyperglycemic donors, EDCs cultured from Glo1TG mice: 1) decreased the reactive oxygen species content by 46±2% (p=0.0001), 2) increased cell culture yields by 2.2±0.2 fold (p=0.0004) and 3) boosted echocardiographic left ventricular ejection fraction by 27±7% (p=0.0001) while increasing dP/dTmax by 21±4% (p=0.007). Conclusions: Chronic hyperglycemia decreases the regenerative performance of EDCs. Over-expression of Glo1 reduces dicarbonyl stress and prevents chronic hyperglycemia-induced EDC dysfunction.

Abstract 028: Effects of N-acetyl-seryl-aspartyl-lysyl-proline on Inflammatory Cells During the Acute Stage of Myocardial Infarction

Background: The natural peptide N-Acetyl-Seryl-Aspartyl-Lysyl-Proline (Ac-SDKP) decreases inflammation in chronic diseases such as hypertension and heart failure. The effects of Ac-SDKP on acute inflammatory responses during myocardial infarction (MI) are unknown. During the first 72 hours post-MI, neutrophils, M1 macrophages (pro-inflammatory), and M2 macrophages (pro-resolution) and the release of myeloperoxidase (MPO) and matrix metalloproteinases (MMP) play a role in the development of cardiac rupture which is an uncommon, but fatal complication. We hypothesize that in the acute stage of MI, Ac-SDKP decreases the incidence of cardiac rupture and mortality by preventing the infiltration of immune cells and by decreasing the activation of MPO and MMP. Methods: MI was induced by the ligation of the left descending coronary artery in C57 mice. Vehicle or Ac-SDKP (1.6 mg/kg/d) was infused via osmotic minipump. Cardiac immune cell infiltration was assessed by flow cytometry, cardiac MPO and MMP activities were measured at 24-48 hrs post-MI. The incidence of cardiac rupture and mortality was determined at 7 days post-MI. Neutrophil migration was studied in vitro by chemotaxis transwell assay. Results: In infarcted mice, Ac-SDKP decreased the incidence of cardiac rupture from 51.0% (26 of 51 animals) to 27.3% (12/44; p=0.015) and mortality from 56.9% (29/51) to 31.8% (14/44; p=0.019). Ac-SDKP also reduced the cardiac infiltration by the M1 macrophages (veh: 1,495±236 vs Ac-SKDP: 765±69 cells/heart, p=0.027), without affecting M2 macrophages. Ac-SDKP did not affect neutrophil and MPO activity in vivo and neither affected neutrophil chemotaxis in vitro . However, Ac-SDKP prevented the activation of MMP-9 (veh: 3,686±508 vs Ac-SDKP: 1,696±512 optical density units, p=0.029) in infarcted hearts. Conclusion: Ac-SDKP prevents cardiac rupture and mortality in acute MI. These protective effects of Ac-SDKP are associated with a decrease in pro-inflammatory M1 macrophage infiltration and MMP-9 activation. Perspective: Cardiac rupture is an uncommon, but fatal complication of MI that could be prevented by the administration of Ac-SDKP or a peptidase resistant analog.

Abstract P196: Effects of the Physiological Increase in Angiotensin-converting Enzyme in Acute Myocardial Infarction

The angiotensin converting enzyme (ACE) act in the production of ANG II and degradation of bradykinin. It is believed that higher levels of ACE could modulate susceptibility to coronary occlusion. To investigate this possibility we used adult males mice genetically modified to express different concentrations of ACE similar to that found in humans. Animals (1, 2 or three copies of ACE gene; n = 6 each group) were subjected to acute myocardial infarction (AMI) and evaluated 7 days after. Systolic, diastolic, and mean blood pressure (BP), heart rate, heart rate variability (HRV) were evaluated as well as cardiac function by echocardiography. Regarding hemodynamic data, AMI induced no difference in systolic, diastolic and mean BP of diferente gene copies mice (ACE1: 74.02 ± 3.0; ACE2: 108.65 ± 2.8; ACE3: 102.07 ± 4.1mmHg). Regarding heart rate it was observed a reduction in 3 copies group (ACE1: 654.51 ± 26.34; ACE2: 668.22 ± 10; ACE3: 534.11 ± 33.4 BPM). The heart rate variability evaluated by SDNN (ACE1: 5.16 ± 0.93; ACE2: 5.84 ± 1:32; ACE3: 7.69 ± 1.4 ms), RMSSD (ACE1: 5.91 ± 0.69; ACE2: 5.7 ± 1:14; ACE3: 6.78 ± 1.2ms), and the total variance (ACE1: 30 ± 12.4; ACE2: 37 ± 13.8; ACE3: 69.9 ± 25.6 ms) was higher in the ACE 3 infarcted group. Regarding the spectral analysis of HRV a higher sympathetic modulation (ACE1: 5.14 ± 3; ACE2: 7.2 ± 2.8; ACE3: 12.9 ± 4.1ms 2 ) and a lower parasympathetic modulation (ACE1: 7 ± 2; ACE2: 8.6 ± 3.2; ACE3: 5.5 ± 2.8 ms 2 ) were observed in ACE 3 infarcted mice. The variability of the BP (ACE1: 18.7 ± 6.2; ACE2: 14.85 ± 1.6; ACE3: 13.76 ± 4.2 mmHg 2 ) and the sympathetic modulation component of the vessels were reduced in the ACE 3 AMI group (ACE1: 60.5 ± 6.2; ACE2: 54.6 ± 1.7; ACE3: 53 ± 3.3 mmHg 2 ). Echocardiographic data showed diastolic dysfunction expressed by E / A ratio (ACE1: 3.40 ± 0.67; ACE2: 3:02 ± 1:36; ACE3: 2.0 ± 0.75) and increase in FAC - Fractional Area Change (ACE1: 27.9 ± 4.5; ACE2: 26.4 ± 5.7; ACE3: 33.5 ± 1.3) in the ACE 3 group after AMI. Our data suggest that increasing the number of ACE gene copies may promote autonomic imbalance evidenced by increased sympathetic modulation and the reduction of parasympathetic modulation of the cardiovascular system as well as the impairment of the diastolic function.

Mesp1 Marked Cardiac Progenitor Cells Repair Infarcted Mouse Hearts.

Mesp1 directs multipotential cardiovascular cell fates, even though it’s transiently induced prior to the appearance of the cardiac progenitor program. Tracing Mesp1-expressing cells and their progeny allows isolation and characterization of the earliest cardiovascular progenitor cells. Studying the biology of Mesp1-CPCs in cell culture and ischemic disease models is an important initial step toward using them for heart disease treatment. Because of Mesp1’s transitory nature, Mesp1-CPC lineages were traced by following EYFP expression in murine Mesp1Cre/+; Rosa26EYFP/+ ES cells. We captured EYFP+ cells that strongly expressed cardiac mesoderm markers and cardiac transcription factors, but not pluripotent or nascent mesoderm markers. BMP2/4 treatment led to the expansion of EYFP+ cells, while Wnt3a and Activin were marginally effective. BMP2/4 exposure readily led EYFP+ cells to endothelial and smooth muscle cells, but inhibition of the canonical Wnt signaling was required to enter the cardiomyocyte fate. Injected mouse pre-contractile Mesp1-EYFP+ CPCs improved the survivability of injured mice and restored the functional performance of infarcted hearts for at least 3 months. Mesp1-EYFP+ cells are bona fide CPCs and they integrated well in infarcted hearts and emerged de novo into terminally differentiated cardiac myocytes, smooth muscle and vascular endothelial cells.

Intravenous delivery of adeno-associated virus 9-encoded IGF-1Ea propeptide improves post-infarct cardiac remodelling.

The insulin-like growth factor Ea propeptide (IGF-1Ea) is a powerful enhancer of cardiac muscle growth and regeneration, also blocking age-related atrophy and beneficial in multiple skeletal muscle diseases. The therapeutic potential of IGF-1Ea compared with mature IGF-1 derives from its local action in the area of synthesis. We have developed an adeno-associated virus (AAV) vector for IGF-1Ea delivery to the heart to treat mice after myocardial infarction and examine the reparative effects of local IGF-1Ea production on left ventricular remodelling. A cardiotropic AAV9 vector carrying a cardiomyocyte-specific IGF-1Ea-luciferase bi-cistronic gene expression cassette (AAV9.IGF-1Ea) was administered intravenously to infarcted mice, 5 h after ischemia followed by reperfusion (I/R), as a model of myocardial infarction. Virally encoded IGF-1Ea in the heart improved global left ventricular function and remodelling, as measured by wall motion and thickness, 28 days after delivery, with higher viral titers yielding better improvement. The present study demonstrates that single intravenous AAV9-mediated IGF-1Ea Gene Therapy represents a tissue-targeted therapeutic approach to prevent the adverse remodelling after myocardial infarct.

Effects of vitamin A deficiency in the postnatal mouse heart: role of hepatic retinoid stores.

To determine whether hepatic depletion of vitamin A (VA) stores has an effect on the postnatal heart, studies were carried out with mice lacking liver retinyl ester stores fed either a VA-sufficient (LRVAS) or VA-deficient (LRVAD) diet (to deplete circulating retinol and extrahepatic stores of retinyl esters). There were no observable differences in the weights or gross morphology of hearts from LRVAS or LRVAD mice relative to sex-matched, age-matched, and genetically matched wild-type (WT) controls fed the VAS diet (WTVAS), but changes in the transcription of functionally relevant genes were consistent with a state of VAD in LRVAS and LRVAD ventricles. In silico analysis revealed that 58/67 differentially expressed transcripts identified in a microarray screen are products of genes that have DNA retinoic acid response elements. Flow cytometric analysis revealed a significant and cell-specific increase in the number of proliferating Sca-1 cardiac progenitor cells in LRVAS animals relative to WTVAS controls. Before myocardial infarction, LRVAS and WTVAS mice had similar cardiac systolic function and structure, as measured by echocardiography, but, unexpectedly, repeat echocardiography demonstrated that LRVAS mice had less adverse remodeling by 1 wk after myocardial infarction. Overall, the results demonstrate that the adult heart is responsive to retinoids, and, most notably, reducing hepatic VA stores (while maintaining circulating levels of VA) impacts ventricular gene expression profiles, progenitor cell numbers, and response to injury.

0542 : Vascular smooth muscle mineralocorticoid receptor contributes to coronary and left ventricular dysfunction after myocardial infarction

Mineralocorticoid receptor (MR) antagonists slow down the progression of heart failure after myocardial infarction (MI), but the cell-specific role of MR in these benefits is unclear. In the present study, the role of MR expressed in vascular smooth muscle cells (VSMC) was investigated. Two months after coronary artery ligation causing MI, mice with VSMC-specific MR deletion (MI-MRSMKO) and mice treated with the MR antagonist finerenone (MIfine) had improved left ventricular (LV) compliance and elastance when compared to infarcted control mice (MI-CTL), as well as reduced interstitial fibrosis. Importantly, the coronary reserve assessed by magnetic resonance imaging was preserved (difference in myocardial perfusion before and after induction of vasodilatation, ml/mg/min: MI-CTL: 1.1±0.5, NS; MIMRSMKO: 4.6±1.6, P<0.05; MI-fine: 3.6±0.7, P<0.01). The endothelial function, tested on isolated septal coronary arteries by analyzing the acetylcholineinduced NO-dependent relaxation, was also improved by MR deletion in VSMC or by finerenone treatment (relaxation %: MI-CTL: 36±5, MIMRSMKO: 54±3 and MI-fine: 76±4; P<0.05). Such impairment of the coronary endothelial function upon MI involved an oxidative-stress that was reduced when MR was deleted in VSMC or by finerenone treatment. Moreover, short-term incubation of coronary arteries isolated from non-infarcted animals with low dose angiotensin-II (10-9mol/L) induced oxidative-stress and impaired acetylcholine-induced relaxation in CTL but neither in MRSMKO nor in mice pre-treated with finerenone. In conclusion, deletion of MR in VSMC improved LV dysfunction after MI, likely through maintenance of the coronary reserve and improvement of coronary endothelial function. MR blockage by finerenone had similar effects. The author hereby declares no conflict of interest

Vascular Smooth Muscle Mineralocorticoid Receptor Contributes to Coronary and Left Ventricular Dysfunction After Myocardial Infarction

Mineralocorticoid receptor (MR) antagonists slow down the progression of heart failure after myocardial infarction (MI), but the cell-specific role of MR in these benefits is unclear. In this study, the role of MR expressed in vascular smooth muscle cells (VSMCs) was investigated. Two months after coronary artery ligation causing MI, mice with VSMC-specific MR deletion (MI-MR(SMKO)) and mice treated with the MR antagonist finerenone (MI-fine) had improved left ventricular compliance and elastance when compared with infarcted control mice (MI-CTL), as well as reduced interstitial fibrosis. Importantly, the coronary reserve assessed by magnetic resonance imaging was preserved (difference in myocardial perfusion before and after induction of vasodilatation, mL mg(-1) min(-1): MI-CTL: 1.1 ± 0.5, nonsignificant; MI-MR(SMKO): 4.6 ± 1.6 [P<0.05]; MI-fine: 3.6 ± 0.7 [P<0.01]). The endothelial function, tested on isolated septal coronary arteries by analyzing the acetylcholine-induced nitric oxide-dependent relaxation, was also improved by MR deletion in VSMCs or by finerenone treatment (relaxation %: MI-CTL: 36 ± 5, MI-MR(SMKO): 54 ± 3, and MI-fine: 76 ± 4; P<0.05). Such impairment of the coronary endothelial function on MI involved an oxidative stress that was reduced when MR was deleted in VSMCs or by finerenone treatment. Moreover, short-term incubation of coronary arteries isolated from noninfarcted animals with low-dose angiotensin-II (10(-9) mol/L) induced oxidative stress and impaired acetylcholine-induced relaxation in CTL but neither in MR(SMKO) nor in mice pretreated with finerenone. In conclusion, deletion of MR in VSMCs improved left ventricular dysfunction after MI, likely through maintenance of the coronary reserve and improvement of coronary endothelial function. MR blockage by finerenone had similar effects.

Lineage Reprogramming of Fibroblasts into Proliferative Induced Cardiac Progenitor Cells by Defined Factors

Several studies have reported reprogramming of fibroblasts into induced cardiomyocytes; however, reprogramming into proliferative induced cardiac progenitor cells (iCPCs) remains to be accomplished. Here we report that a combination of 11 or 5 cardiac factors along with canonical Wnt and JAK/STAT signaling reprogrammed adult mouse cardiac, lung, and tail tip fibroblasts into iCPCs. The iCPCs were cardiac mesoderm-restricted progenitors that could be expanded extensively while maintaining multipotency to differentiate into cardiomyocytes, smooth muscle cells, and endothelial cells in vitro. Moreover, iCPCs injected into the cardiac crescent of mouse embryos differentiated into cardiomyocytes. iCPCs transplanted into the post-myocardial infarction mouse heart improved survival and differentiated into cardiomyocytes, smooth muscle cells, and endothelial cells. Lineage reprogramming of adult somatic cells into iCPCs provides a scalable cell source for drug discovery, disease modeling, and cardiac regenerative therapy.