Simultaneous administration of insulin-like growth factor-1 and darbepoetin alfa protects the rat myocardium against myocardial infarction and enhances angiogenesis

The effects of IGF-1 and IGFBP-2 treatments on the atherosclerosis in the aorta and the coronary arteries of the high cholesterol diet-fed rabbits

Several studies have demonstrated suppression of aortic atherosclerosis by insulin like growth factor-1 (IGF-1) in hypercholesterolemic rabbits. Though a recent study has reported that IGF-1 exerts anti-atherogenic effects in coronary arteries, the mechanisms of IGF-1 in coronary arteries need to be further verified. Studies about insulin like growth factor binding protein-2 (IGFBP-2) in atherosclerosis are rarely. The objective of this study is to examine the effects of IGF-1 and IGFBP-2 on the atherosclerosis development in the aorta and coronary arteries of the high-cholesterol diet (HCD)-fed rabbits. New Zealand white rabbits were fed either normal chow (n = 5) or a diet containing 1.0 % cholesterol (n = 18) for 12 weeks. Cholesterol-fed rabbits were given IGF-1 or IGFBP-2 or saline intravenously (each n = 6) for 10 weeks. The results revealed that IGF-1 decreased total cholesterol (TC) and low-density lipoprotein (LDL) levels (p < 0.05), whereas IGFBP-2 did not. IGF-1 significantly attenuated atherosclerotic lesions and reduced accumulated macrophages within the coronary artery plaques, whereas IGFBP-2 deteriorated these changes. Moreover, IGF-1 reduced serum platelet-activating factor acetylhydrolase levels, C reactive protein (CRP), and inhibited the protein expression levels of tumor necrosis factor alpha (TNF-α) and interleukin 6 (IL-6). IGFBP-2 elevated serum 8-hydroxy-2'-deoxyguanosine levels, CRP, and promoted the protein expression levels of TNF-α and IL-6. In conclusion, IGF-1 can substantially suppress plaque formation in coronary arteries with a marked inhibition of macrophage accumulation likely via its anti-inflammatory properties, whereas IGFBP-2 plays an opposite effect on atherosclerosis. The present study highlighted a theoretical basis for pharmacological treatment of atherosclerosis.

The Exosomal lncRNA KLF3-AS1 From Ischemic Cardiomyocytes Mediates IGF-1 Secretion by MSCs to Rescue Myocardial Ischemia-Reperfusion Injury

The purpose of the study was to explore the mechanism by which myocardial ischemia-reperfusion (I/R) injury-induced exosomes modulate mesenchymal stem cells (MSCs) to regulate myocardial injury. In this study, we established an I/R injury model in vivo and a hypoxia-reoxygenation (H/R) model in vitro. Then, exosomes isolated from H/R-exposed H9c2 cells were characterized using transmission electron microscopy (TEM), nanoparticle tracking analysis (NTA), and Western blot analysis. CCK-8 assays and flow cytometry were performed to assess cell injury. ELISA was applied to determine the level of insulin-like growth factor 1 (IGF-1). Echocardiography was used to assess cardiac function in vivo. HE staining and TUNEL assays were conducted to analyze myocardial injury in vivo. In the present study, H/R-exposed H9c2 cells induced IGF-1 secretion from MSCs to inhibit cell myocardial injury. Moreover, exosomes derived from H/R-exposed H9c2 cells were introduced to MSCs to increase IGF-1 levels. The lncRNA KLF3-AS1 was dramatically upregulated in exosomes derived from H/R-treated H9c2 cells. Functional experiments showed that the exosomal lncRNA KLF3-AS1 promoted IGF-1 secretion from MSCs and increased H9c2 cell viability. In addition, miR-23c contains potential binding sites for both KLF3-AS1 and STAT5B, and miR-23c directly bound to the 3'-UTRs of KLF3-AS1 and STAT5B. Furthermore, the lncRNA KLF3-AS1 promoted IGF-1 secretion from MSCs and rescued myocardial cell injury in vivo and in vitro by upregulating STAT5B expression. The lncRNA KLF3-AS1 may serve as a new direction for the treatment of myocardial I/R injury.

Taohong Siwu Decoction Exerts a Beneficial Effect on Cardiac Function by Possibly Improving the Microenvironment and Decreasing Mitochondrial Fission after Myocardial Infarction

Cardiovascular disease has been established as a major cause of morbidity and mortality worldwide, resulting in a huge burden to patients, families, and society. Traditional Chinese Medicine (TCM) presents several advantages for the prevention and treatment of cardiovascular diseases including multitargets, multi-ingredients, fewer side effects, and low cost. In this study, a rat model of myocardial infarction (MI) was established by ligating the anterior descending branch of the left coronary artery, and the effect of the Taohong Siwu decoction (THSWD) on cardiac function was evaluated in MI rats. Following the intragastric administration of THSWD, the cardiac function was examined using echocardiography. The infarct size and collagen deposition in the infarct area were measured using Masson's trichrome staining, and the number of CD31- and α-SMA-positive blood vessels in the peri-infarct and infarct area was evaluated by immunofluorescent staining. The mRNA expression of bFGF, IGF-1, and HGF was detected using RT-PCR assay. Cell apoptosis in the infarcted area was assessed by TUNEL staining, and the p-Akt level was detected using the western blot assay. The mitochondrial ROS production was measured using MitoSOX staining, and mitochondrial dynamics and mitophagy were evaluated with western blotting 7 days after THSWD treatment. THSWD increased the ejection fraction (EF) and fractional shortening (FS) values in the rat hearts; however, no statistical difference was found between the THSWD and MI groups 4 weeks after treatment. Furthermore, THSWD significantly decreased the value of the left ventricular end-systolic volume (LVESV). Compared with the model group, THSWD significantly increased the expression of IGF-1 and bFGF, reduced collagen deposition, promoted angiogenesis, reduced cell apoptosis, and activated the PI3K/Akt signaling pathway. Notably, THSWD significantly decreased mitochondrial ROS production and Fis1 expression. No statistical differences were observed in the expression of mitochondrial LC3B and Mfn1 between the THSWD and control groups. In summary, THSWD may possess a beneficial effect on cardiac function by improving the local ischemic microenvironment and by decreasing mitochondrial fission after MI. Hence, this may present a promising auxiliary strategy in the treatment of ischemic cardiomyopathy such as MI.

Effect of olprinone on ischemia-reperfusion induced myocardial injury in rats

AIMS

This study investigated the effect of olprinone on ischemia-reperfusion (I/R) induced cardiac injury, and the underlying mechanism.

MAIN METHODS

Male Sprague-Dawley rats were subjected to a 30-min coronary arterial occlusion followed by 24 h reperfusion. After the start of reperfusion, rats were respectively treated with olprinone in three different dosages (0.2, 0.6, 2 mg/kg, intraperitoneal injection, i.p./12 h). Twenty-four hours later, a mean arterial pressure (MAP) heart function analysis system was used to monitor hemodynamic parameters; TTC staining method was used to detect the myocardial infarct size; 24-hour mortality of rats was recorded; western blot was used to detect the protein expressions of Caspase-3, Bax, Bcl-2, Beclin-1 and LC3-II/LC3-I.

RESULTS

Cardiac function in I/R group was lower than that in sham group (dp/dt max: 1348.29 ± 266.01 vs. 3333.73 ± 1258.03, -dp/dt max: 1163.23 ± 588.18 vs. 3198.93 ± 1416.00, P <  0.05), which was significantly improved by treatment with high dosage of olprinone (dp/dt max: 1348.29±266.01 vs. 2022.43±493.39, -dp/dt max: 1163.23±588.18 vs. 1784.50±418.92, P <  0.05). The percentage of myocardial infarct size in medium and high dosages of olprinone group was lower than that in I/R group (42.67 ± 2.94, 22.33 ± 3.63 vs. 63.67 ± 5.86, P <  0.05). There was no significant difference in mortality among each group within 24 h. Compared with sham group, the expression of Caspase-3 was significantly up-regulated in I/R group (3.44±0.47-fold of sham, P <  0.05), which was inhibited by medium dosage of olprinone treatment (2.00±0.52-fold of sham, P <  0.05 vs. I/R group); also, expression of Bax was increased compared with sham group (4.06±0.25-fold of sham, P <  0.05), which was markedly inhibited by all dosages of olprinone treatment (low: 2.16±0.61-fold, medium: 2.74±0.66-fold, high 1.65±0.55-fold, P <  0.05 vs. I/R group). Expression of Bcl-2 was increased after I/R (1.17±0.06-fold, P < 0.05), which was further elevated in all dosages of olprinone treatment (low: 1.62 ± 0.13-fold, medium: 1.46 ± 0.13-fold, high: 1.82 ± 0.39-fold, P <  0.05 vs. I/R group). In addition, compared with sham group, the expression of Beclin-1 was up-regulated to 1.44±0.05-fold of sham in I/R group (P <  0.05), which was further increased in low and medium dosages of olprinone group (low: 2.46±0.44-fold, medium: 2.80±0.75-fold, P <  0.05 vs. I/R group). Moreover, expression of LC3-II was elevated in low dosage of olprinone treated group (low: 4.50±0.47-fold, P <  0.05 vs. I/R group).

CONCLUSIONS

Olprinone improves the cardiac function in response to myocardial I/R injury by regulation of anti-apoptotic, pro-apoptotic. In addition, autophagic signal pathways may also play a role in olprinone's therapeutic effect.

Therapeutic effects of a mesenchymal stem cell‑based insulin‑like growth factor‑1/enhanced green fluorescent protein dual gene sorting system in a myocardial infarction rat model

The present study was conducted in order to improve gene expression efficiency of insulin‑like growth factor‑1 (IGF‑1)‑transfected mesenchymal stem cells (MSCs) using a non‑viral carrier and a simplified method of dual gene selection. The therapeutic efficacy of this MSC‑based IGF‑1/enhanced green fluorescent protein (EGFP) dual gene sorting system was evaluated in a rat myocardial infarction (MI) model. IGF‑1 and EGFP genes were expressed in MSCs in vitro. The purity of dual gene‑expressing MSCs was 95.1% by fluorescence‑activated cell sorting. Transfected MSCs injected into rats were identified based on green fluorescence, with an increased signal intensity observed in rats injected with sorted cells, compared with unsorted cells. IGF‑1 expression levels were additionally increased in the sorted group, and decreases in infarct size, fibrotic area and fraction of apoptotic cells were observed. These results demonstrated that IGF‑1 overexpression protects against fibrosis and apoptosis in the myocardium and reduces infarct size following MI. Additionally, the present vector sorting system may potentially be applied to other types of stem cell‑based gene therapy.

Periostin alters transcriptional profile in a rat model of isoproterenol-induced cardiotoxicity

Periostin is an extracellular matrix protein from the fasciclin family that guides cellular trafficking and extracellular matrix organization. Periostin stimulates mature cardiomyocytes to reenter the cell cycle. The molecular mechanism behind such stimulation remains to be explored. A DNA microarray technology constituting 30,429 gene-level probe sets was utilized to investigate effects of recombinant murine periostin peptide on the gene expression pattern in a rat model of isoproterenol (ISO)-induced myocardial injury. The experiment was performed on 84 adult male Sprague-Dawley rats in four groups ( n = 21): (1) control group, (2) only periostin applied group, (3) ISO cardiotoxicity group, and (4) ISO + periostin group. The experiment was continued for 28 days, and rats were killed on days 1, 7, and 28 ( n = 7). Microarray analyses revealed that periostin significantly altered the expression of at least ±2-fold of 2474 genes in the ISO + periostin group compared to the ISO cardiotoxicity group of which 521 genes altered out of 30,429 gene-level probe sets. Ingenuity pathway analysis indicated that multiple pathway networks were affected by periostin, with predominant changes occurring in the expression of genes involved in oxidative phosphorylation, oxidative stress, fatty acid metabolism, and TNF-α NF-κB signaling pathways. These findings indicate that periostin alters gene expression profile in the ISO-induced myocardial injury and modulates local myocardial inflammation, possibly mitigating inflammation through TNF-α NF-κB signaling pathway along with a decreased Casp7 activity and apoptotic cell death.

Insulin-like growth factor 1 prevents diastolic and systolic dysfunction associated with cardiomyopathy and preserves adrenergic sensitivity

AIMS

Insulin-like growth factor 1 (IGF-1)-dependent signalling promotes exercise-induced physiological cardiac hypertrophy. However, the in vivo therapeutic potential of IGF-1 for heart disease is not well established. Here, we test the potential therapeutic benefits of IGF-1 on cardiac function using an in vivo model of chronic catecholamine-induced cardiomyopathy.

METHODS

Rats were perfused with isoproterenol via osmotic pump (1 mg kg(-1) per day) and treated with 2 mg kg(-1) IGF-1 (2 mg kg(-1) per day, 6 days a week) for 2 or 4 weeks. Echocardiography, ECG, and blood pressure were assessed. In vivo pressure-volume loop studies were conducted at 4 weeks. Heart sections were analysed for fibrosis and apoptosis, and relevant biochemical signalling cascades were assessed.

RESULTS

After 4 weeks, diastolic function (EDPVR, EDP, tau, E/A ratio), systolic function (PRSW, ESPVR, dP/dtmax) and structural remodelling (LV chamber diameter, wall thickness) were all adversely affected in isoproterenol-treated rats. All these detrimental effects were attenuated in rats treated with Iso+IGF-1. Isoproterenol-dependent effects on BP were attenuated by IGF-1 treatment. Adrenergic sensitivity was blunted in isoproterenol-treated rats but was preserved by IGF-1 treatment. Immunoblots indicate that cardioprotective p110α signalling and activated Akt are selectively upregulated in Iso+IGF-1-treated hearts. Expression of iNOS was significantly increased in both the Iso and Iso+IGF-1 groups; however, tetrahydrobiopterin (BH4) levels were decreased in the Iso group and maintained by IGF-1 treatment.

CONCLUSION

IGF-1 treatment attenuates diastolic and systolic dysfunction associated with chronic catecholamine-induced cardiomyopathy while preserving adrenergic sensitivity and promoting BH4 production. These data support the potential use of IGF-1 therapy for clinical applications for cardiomyopathies.

Myocardial Ablation of G Protein-Coupled Receptor Kinase 2 (GRK2) Decreases Ischemia/Reperfusion Injury through an Anti-Intrinsic Apoptotic Pathway

Studies from our lab have shown that decreasing myocardial G protein–coupled receptor kinase 2 (GRK2) activity and expression can prevent heart failure progression after myocardial infarction. Since GRK2 appears to also act as a pro-death kinase in myocytes, we investigated the effect of cardiomyocyte-specific GRK2 ablation on the acute response to cardiac ischemia/reperfusion (I/R) injury. To do this we utilized two independent lines of GRK2 knockout (KO) mice where the GRK2 gene was deleted in only cardiomyocytes either constitutively at birth or in an inducible manner that occurred in adult mice prior to I/R. These GRK2 KO mice and appropriate control mice were subjected to a sham procedure or 30 min of myocardial ischemia via coronary artery ligation followed by 24 hrs reperfusion. Echocardiography and hemodynamic measurements showed significantly improved post-I/R cardiac function in both GRK2 KO lines, which correlated with smaller infarct sizes in GRK2 KO mice compared to controls. Moreover, there was significantly less TUNEL positive myocytes, less caspase-3, and -9 but not caspase-8 activities in GRK2 KO mice compared to control mice after I/R injury. Of note, we found that lowering cardiac GRK2 expression was associated with significantly lower cytosolic cytochrome C levels in both lines of GRK2 KO mice after I/R compared to corresponding control animals. Mechanistically, the anti-apoptotic effects of lowering GRK2 expression were accompanied by increased levels of Bcl-2, Bcl-xl, and increased activation of Akt after I/R injury. These findings were reproduced in vitro in cultured cardiomyocytes and GRK2 mRNA silencing. Therefore, lowering GRK2 expression in cardiomyocytes limits I/R-induced injury and improves post-ischemia recovery by decreasing myocyte apoptosis at least partially via Akt/Bcl-2 mediated mitochondrial protection and implicates mitochondrial-dependent actions, solidifying GRK2 as a pro-death kinase in the heart.

A novel and efficient model of coronary artery ligation in the mouse

Coronary artery ligation to induce myocardial infarction (MI) and ischemia/reperfusion (I/R) injury in mice is typically performed by an invasive and time-consuming approach that requires ventilation and a full thoracotomy (classical method), often resulting in extensive tissue damage and high mortality. Here, we describe a novel and rapid surgical method to induce MI that does not require ventilation. This method is much more efficient and safer than the classical method of MI and I/R injury.

Myocardial infarction: cardioprotection by erythropoietin

Extensive research during the last decade demonstrated that a single systemic administration of -erythropoietin (EPO) lead to significant attenuation of myocardial infarction (MI) induced in animals, mostly small rodents, either by a myocardial ischemia followed by reperfusion or by a permanent ligation of a coronary artery. Both methods are critically reviewed with the aim of helping the reader in appreciating key issues in the translation of experimental results to the clinic. Results of several clinical trials in patients with acute MI completed to date failed to demonstrate beneficial effects of EPO, and thus put into question the validity of results obtained in animal models. Comprehensive review of design and results of animal experiments and clinical trials presented here allowed authors to postulate that therapeutic window for EPO during developing MI is very narrow and was possibly missed in negative clinical trials. This point was illustrated by the negative outcome of experiment in the rat model of MI in which timing of EPO administration was similar to that in clinical trials. The design of future clinical trials should allow for a narrow therapeutic window of EPO. Given current standards for onset-to-door and door-to-balloon time the optimal time for EPO administration should be just prior to PCI.

Long-term cerebral cortex protection and behavioral stabilization by gonadal steroid hormones after transient focal hypoxia

Sex steroids are neuroprotective following traumatic brain injury or during neurodegenerative processes. In a recent short-term study, we have shown that 17β-estradiol (E) and progesterone (P) applied directly after ischemia reduced the infarct volume by more than 70%. This protection might primarily result from the anti-inflammatory effects of steroids. Here, we focus on the long-term neuroprotection by both steroids with respect to the infarct volume, functional recovery, and vessel density in the penumbra. The application of E/P during the first 48h after stroke (transient middle cerebral artery occlusion, tMCAO) revealed neuroprotection after two weeks. The infarct area was reduced by 70% and motor activity was preserved compared to placebo-treated animals. Blood vessel density in the penumbra using immunohistochemistry for von Willebrand factor showed increased vessel density after tMCAO which was not affected by hormones. Expression of vascular endothelial growth factor (VEGF) and its receptor (R1) was increased at 24h after tMCAO and up-regulated by E/P but not changed 14 days after stroke. These findings suggest that the neuroprotective potency of both steroids is sustained and persists for at least two weeks. Besides anti-inflammatory and anti-apoptotic actions, angiogenesis in the damaged area appears to be initially affected early after ischemia and is manifested up to two weeks. This article is part of a Special Issue entitled 'Neurosteroids'.

Low serum IGF-1 is a risk factor for cardiac allograft vasculopathy in cardiac transplant recipients

BACKGROUND

Cardiac allograft vasculopathy (CAV) has an incidence of 43% at 8 years after heart transplantation with extremely limited treatment options and unclear pathogenesis. CAV constitutes a significant complication that limits the long-term survival of heart recipients. Insulin-like growth factor-1 (IGF-1) is associated with different cardiovascular diseases; however, its role in CAV pathogenesis remains unknown.

METHODS

Serum samples of 10 matched recipients with CAV and 10 with no-CAV were initially screened with a protein array. Subsequently, IGF-1- and IGF-binding protein-3 (IGFBP-3) were analyzed using enzyme-linked immunosorbent assay in 44 randomly selected CAV and 50 no-CAV patients at two time points.

RESULTS

The initial screening showed that IGF-1 and IGFBP-3 are differentially expressed in CAV compared with no-CAV patients (P=0.037 and P<0.0001, respectively). Subsequent enzyme-linked immunosorbent assay analyses indicated that serum IGF-1 protein concentrations were significantly lower in CAV patients (159.7±114 ng/mL) as compared with no-CAV patients (234.1±136 ng/mL; P=0.02). Serum IGFBP-3 protein concentrations were significantly lower in CAV (0.46±0.37 mg/L) as compared with no-CAV patients (1.03±0.73 mg/L; P=0.04). Multivariate logistic regression analyses showed that IGF-1 (odds ratio, 0.89; P=0.04) and IGFBP-3 (odds ratio, 0.09; P=0.03) are independent risk factors for CAV.

CONCLUSION

Low IGF-1 and IGFPB-3 serum concentrations are associated with CAV. The assessment of serum IGF-1 and IGFPB-3 might be beneficial in identifying cardiac allograft recipients who are prone to develop CAV. Moreover, IGF-1 might be a useful therapy that could protect cardiac allografts against CAV.

N-acetylcysteine offers cardioprotection by decreasing cardiac lipid hydroperoxides and 8-isoprostane level in isoproterenol-induced cardiotoxicity in rats

This study investigated the cardioprotective effect of N-acetylcysteine (NAC) on isoproterenol (ISO)-induced cardiotoxicity in rats. Male Sprague-Dawley rats were divided into control, NAC alone (100 mg/kg BW orally for 14 days), ISO-control (85 mg/kg BW), and ISO with NAC (for 14 days). Serum creatine kinase-MB and Lactate dehydrogenase were measured. From the heart homogenate lipid hydroperoxides (LPO), superoxide dismutase (SOD), total glutathione (GSH), and 8-isoprostane (IP) were measured. Histopathological examination of the heart was also carried out. There was a significant increase (P < 0.05) in LPO and IP levels in ISO-control group and NAC treatment reduced these changes. Antioxidant enzyme, SOD and GSH, level decreased significantly (P < 0.05) in ISO-control group, and treatment with NAC was able to reverse these changes significantly (P < 0.05). Histopathologically, ISO-control group showed morphological changes suggestive of cardiotoxicity with large areas of coagulative necrosis, with diffused interstitial edema. NAC treatment successfully reduced these histopathological changes. In conclusion, the study proves that NAC has a strong cardioprotective effect against isoproterenol-induced cardiac changes. NAC decreases isoproterenol-induced LPO and IP levels in the heart tissue and prevented free radicals-induced damage to the myocardium.

Insulin like growth factor-1 (IGF-1) causes overproduction of IL-8, an angiogenic cytokine and stimulates neovascularization in isoproterenol-induced myocardial infarction in rats

Angiogenesis factors are produced in response to hypoxic or ischemic insult at the site of pathology, which will cause neovascularization. Insulin like growth factor-1 (IGF-1) exerts potent proliferative, angiogenic and anti-apoptotic effects in target tissues. The present study was aimed to evaluate the effects of IGF-1 on circulating level of angiogenic cytokine interleukin-8 (IL-8), in experimentally-induced myocardial ischemia in rats. Male Sprague-Dawley rats were divided into control, IGF-1 treated (2 μg/kg/day subcutaneously, for 5 and 10 days), isoproterenol (ISO) treated (85 mg/kg, subcutaneously for two days) and ISO with IGF-1 treated (for 5 and 10 days). Heart weight, serum IGF-1, IL-8 and cardiac marker enzymes (CK-MB and LDH) were recorded after 5 and 10 days of treatment. Histopathological analyses of the myocardium were also done. There was a significant increase in serum cardiac markers with ISO treatment indicating myocardial infarction in rats. IGF-1 level increased significantly in ISO treated groups and the level of IGF-1 was significantly higher after 10 days of treatment. IL-8 level increased significantly after ISO treatment after 5 and 10 days and IGF-1 concurrent treatment to ISO rats had significantly increased IL-8 levels. Histopathologically, myocyte necrosis and nuclear pyknosis were reduced significantly in IGF-1 treated group and there were numerous areas of capillary sprouting suggestive of neovascularization in the myocardium. Thus, IGF-1 protects the ischemic myocardium with increased production of circulating angiogenic cytokine, IL-8 and increased angiogenesis.

Effects of combination of proliferative agents and erythropoietin on left ventricular remodeling post-myocardial infarction

Erythropoietin (EPO) has the potential to improve ischemic tissue by mobilizing endothelial progenitor cells and enhancing neovascularization. We hypothesized that combining EPO with human chorionic gonadotrophin (hCG) would improve post-myocardial infarction (MI) effects synergistically.

METHODS

After MI, five to seven animals were randomly assigned to each of the following treatments: control; hCG; EPO; hCG + EPO, and prolactin (PRL) + EPO. Follow-up echocardiograms were performed to assess cardiac structure and function. Apoptosis was determined by terminal deoxynucleotidyl transferase-mediated dUTP nick end-labeling (TUNEL) assay and western blot analysis for apoptosis-related proteins, and cell proliferation by immunostaining for Ki67 and c-kit cells.

RESULTS

The MI-mediated increased chamber systolic dimension (p < 0.05 in controls) was attenuated by hCG, EPO, and hCG + EPO (p < 0.05 vs. control) but not PRL + EPO. Similarly all treatment groups, except PRL + EPO, reduced MI-induced increases (p < 0.05 vs. control) in ejection fraction (EF). The functional improvement in the EPO-treated groups was accompanied by increased capillary density. Apoptosis was markedly reduced in all treated groups. Significantly more cardiac c-kit(+) cells were found in the hCG + EPO group.

CONCLUSION

Our findings revealed that EPO, hCG, or their combination ameliorate cardiac remodeling post-MI. Whereas EPO stimulates neovascularization only and hCG + EPO stimulates c-kit+ cell proliferation. These data suggest that combining mobilizing and proliferative agents adds to the durability and sustainability of cytokine-based therapies for remodeling post-MI.

The combined administration of multiple soluble factors in the repair of chronically infarcted rat myocardium

The purpose of this study was to investigate a potential benefit of simultaneous administration of multiple soluble factors (SFs) in the repair of chronically infarcted rat myocardium. Rats subjected to a permanent coronary artery occlusion (myocardial infarction) received a cocktail of SF or a phosphate buffer. Four SFs, fibroblast growth factor-2 (2 μg), insulin-like growth factor-1 (1 μg), hepatocyte growth factor (2 μg), and stromal cell-derived factor-1α (0.6 μg) were injected directly into the ischemic myocardium at the onset of occlusion and subsequently at 3, 7, 14, and 21 days of surgery (intraperitoneally). Cardiac contractile function, infarct size and remodeling, and blood vessel density were studied at 4 weeks postsurgery. Infarct size, left ventricular circumference and cavity volume, thinning ratio, and expansion index were not statistically different between groups. Treatment of SF did not alter ejection fraction, compared with control. No statistical difference in total blood vessel density in the infarct zone was observed in SF versus control. In conclusion, our results that there were no enhancements in cardiac function, reductions in infarct size, improvements in remodeling, or increases in vasculature density in SF versus control do not support the study hypothesis that the combined use of multiple SF benefits the hearts with myocardial infarct.

Myocardial injury after ischemia-reperfusion in mice deficient in Akt2 is associated with increased cardiac macrophage density

Akt2 protein kinase has been shown to promote cell migration and actin polymerization in several cell types, including macrophages. Because migrating macrophages constitute an important inflammatory response after myocardial ischemia, we determined cardiac macrophage expression after ischemia-reperfusion (I/R) injury and cryo-injury in mice lacking Akt2 (Akt2-KO). At 7 days post-I/R, Akt2-KO cardiac tissues showed an increase in immunohistochemical staining for macrophage markers (Galectin 3 and F4/80) compared with wild-type (WT) mice, indicating macrophage density was increased in the injured Akt2-KO myocardium. This change was time dependent because macrophage density was similar between WT and Akt2-KO myocardium at 3 days post-I/R, but by 7 and 14 days post-I/R, macrophage density was significantly increased in Akt2-KO myocardium. Concomitantly, infarct size was larger and cardiac function was reduced in Akt2-KO mice subjected to I/R. However, when cryo-infarction produced similar infarct sizes in the anterior wall in both WT and Akt2-KO mice, macrophage density remained higher in Akt2-KO mouse myocardium, suggesting Akt2 regulates myocardial macrophage density independent of infarct size. Consistently, bone marrow from Akt2-KO mice enhanced myocardial macrophage density in both C57/B6 WT and Akt2-KO recipient mice. Finally, reciprocal ex-vivo coculturing of macrophages and cardiac myocytes showed that activated Akt2-KO peritoneal macrophages had reduced mobility and adhesion when compared with WT littermate controls. Thus, although Akt-2 KO mice did not affect the initial inflammation response after injury and Akt2 deficiency has been shown to impair cell migration or motility in macrophages, our data suggested a novel mechanism in which increasing retention of Akt2-KO macrophages resulted in increasing cardiac Akt2-KO macrophage density in the myocardial space.

Insulin-Like Growth Factor-1 (IGF-1) Reduces ischemic changes and increases circulating angiogenic factors in experimentally - induced myocardial infarction in rats

Background

Coronary artery disease is a global health concern in the present day with limited therapies. Extensive efforts have been devoted to find molecular therapies to enhance perfusion and function of the ischemic myocardium. Aim of the present study was to look into the effects of insulin like growth factor -1 (IGF-1) on circulating angiogenic factors after myocardial ischemia in rats.

Methods

Adult male Sprague-Dawley rats were randomly divided into 10-days control, myocardial infarction, IGF-1 alone (2 μg/rat/day) and ISO+IGF-1 groups. Isoproterenol (ISO), a synthetic catecholamine was used to induce myocardial infarction. Serum transforming growth factor-β (TGF-β) and vascular endothelial growth factor (VEGF) levels were checked after 10-days of IGF-1 administration.

Results

There was a significant increase in heart weight after IGF-1 treatment. A significant increase in cardiac enzyme level (CK-MB and LDH) was seen in isoproterenol treated rats when compared to control group. IGF-1treatment induced a significant increase in serum angiogenic factors, IGF-1, VEGF and TGF beta levels. IGF-1 also reduced the ischemic changes in the myocardium when compared to the isoproterenol alone treated group.

Conclusions

In conclusion, treatment with insulin-like growth factor-1 (IGF-1) in myocardial infarction significantly increased circulating angiogenic growth factors like IGF-1, VEGF and TGF beta thus, protecting against myocardial ischemia.

A novel and efficient model of coronary artery ligation and myocardial infarction in the mouse

RATIONALE

coronary artery ligation to induce myocardial infarction (MI) in mice is typically performed by an invasive and time-consuming approach that requires ventilation and chest opening (classic method), often resulting in extensive tissue damage and high mortality. We developed a novel and rapid surgical method to induce MI that does not require ventilation.

OBJECTIVE

the purpose of this study was to develop and comprehensively describe this method and directly compare it to the classic method.

METHODS AND RESULTS

male C57/B6 mice were grouped into 4 groups: new method MI (MI-N) or sham (S-N) and classic method MI (MI-C) or sham (S-C). In the new method, heart was manually exposed without intubation through a small incision and MI was induced. In the classic method, MI was induced through a ventilated thoracotomy. Similar groups were used in an ischemia/reperfusion injury model. This novel MI procedure is rapid, with an average procedure time of 1.22 ± 0.05 minutes, whereas the classic method requires 23.2 ± 0.6 minutes per procedure. Surgical mortality was 3% in MI-N and 15.9% in MI-C. The rate of arrhythmia was significantly lower in MI-N. The postsurgical levels of tumor necrosis factor-α and myeloperoxidase were lower in new method, indicating less inflammation. Overall, 28-day post-MI survival rate was 68% with MI-N and 48% with MI-C. Importantly, there was no difference in infarct size or post-MI cardiac function between the methods.

CONCLUSIONS

this new rapid method of MI in mice represents a more efficient and less damaging model of myocardial ischemic injury compared with the classic method.

Level of G protein-coupled receptor kinase-2 determines myocardial ischemia/reperfusion injury via pro- and anti-apoptotic mechanisms

RATIONALE

Activation of prosurvival kinases and subsequent nitric oxide (NO) production by certain G protein-coupled receptors (GPCRs) protects myocardium in ischemia/reperfusion injury (I/R) models. GPCR signaling pathways are regulated by GPCR kinases (GRKs), and GRK2 has been shown to be a critical molecule in normal and pathological cardiac function.

OBJECTIVE

A loss of cardiac GRK2 activity is known to arrest progression of heart failure (HF), at least in part by normalization of cardiac β-adrenergic receptor (βAR) signaling. Chronic HF studies have been performed with GRK2 knockout mice, as well as expression of the βARKct, a peptide inhibitor of GRK2 activity. This study was conducted to examine the role of GRK2 and its activity during acute myocardial ischemic injury using an I/R model.

METHODS AND RESULTS

We demonstrate, using cardiac-specific GRK2 and βARKct-expressing transgenic mice, a deleterious effect of GRK2 on in vivo myocardial I/R injury with βARKct imparting cardioprotection. Post-I/R infarct size was greater in GRK2-overexpressing mice (45.0±2.8% versus 31.3±2.3% in controls) and significantly smaller in βARKct mice (16.8±1.3%, P<0.05). Importantly, in vivo apoptosis was found to be consistent with these reciprocal effects on post-I/R myocardial injury when levels of GRK2 activity were altered. Moreover, these results were reflected by higher Akt activation and induction of NO production via βARKct, and these antiapoptotic/survival effects could be recapitulated in vitro. Interestingly, selective antagonism of β(2)ARs abolished βARKct-mediated cardioprotection, suggesting that enhanced GRK2 activity on this GPCR is deleterious to cardiac myocyte survival.

CONCLUSION

The novel effect of reducing acute ischemic myocardial injury via increased Akt activity and NO production adds significantly to the therapeutic potential of GRK2 inhibition with the βARKct not only in chronic HF but also potentially in acute ischemic injury conditions.