Left Ventricular Function In Rats Research Articles

Effects of Cavitation from Extracorporeal Shock Wave Combined with Sulfur Hexafluoride Microbubble on Myocardial Ultrastructure in Rats.

In the present study, the effects of extracorporeal cardiac shock waves combined with different concentrations of sulfur hexafluoride ultrasound microbubbles on myocardial ultrastructure in rats were observed. Thirty-six rats were randomly divided into 6 groups: control group (N), extracorporeal cardiac shock wave group, and combined group, i.e., extracorporeal cardiac shock wave combined with different concentrations of sulfur hexafluoride microbubble (0.225 mL/kg/min, 0.45 mL/kg/min, 0.9 mL/kg/min, 1.8 mL/kg/min). The combination of extracorporeal cardiac shock wave combined with sulfur hexafluoride microbubbles of different concentrations had no significant effect on hemodynamic indexes and left ventricular function in rats. There were significant differences in cardiac troponin I (cTnI) and nitricoxide among different groups. Histopathology showed that inflammatory cells infiltrated in the shock wave+microbubble 0.9 and shock wave+microbubble 1.8 groups. The myocardial ultrastructural injury score of shock wave+microbubble1.8 group was significantly higher than that of the N group, shock wave group, shock wave+microbubble 0.225 group, and shock wave+microbubble 0.45 group. The score of shock wave+microbubble 0.9 group was higher than that of the control group (P=.009). Western blot results showed that the expression of vascular endothelial growth factor and endothelial nitricoxide synthase (eNOS) protein in the rats treated with extracorporeal cardiac shock wave combined with sulfur hexafluoride microbubbles of different concentrations was higher than that in the N group and shock wave group, with shock wave+microbubble 0.45 group having the strongest expression. Myocardial ultrastructure damage occurs when high concentrations of sulfur hexafluoride microbubbles are present, but a proper concentration of sulfur hexafluoride microbubbles could promote the cavitation effect of extracorporeal cardiac shock waves. Thus combination therapy may become a new paradigm in coronary heart disease, especially contributing to the treatment of refractory angina. Combination therapy may change coronary heart disease treatment, especially for refractory angina.

Chronic mitochondrial fusion promotor as a novel pharmacological intervention to alleviate left ventricular dysfunction in rats with chronic myocardial infarction

Abstract Background Decreased cardiac mitochondrial fusion associated with increased mitochondrial dysfunction has been demonstrated in acute myocardial infarction pathology. However, whether this pathophysiologic process is associated with myocardial injury in chronic myocardial infarction (CMI) is still unclear. Recently, a novel pharmacological intervention to promote mitochondrial fusion using mitochondrial fusion promotor-M1 (M1) has been shown to exert cardioprotection against myocardial ischemia and reperfusion injury. However, the roles of M1 in CMI has never been investigated. Purpose We investigated the potential cardioprotective benefits of chronic treatment with mitochondrial fusion promotor-M1 in rats with chronic MI model. Methods Adult male Wistar rats were assigned to the sham group (n=5) and the CMI group (n=15), which was induced by a permanent left anterior descending coronary occlusion. After 1 week of operation, rats in the CMI group were randomly divided into 3 subgroups which was treated with one of the followings: 1) vehicle (3% DMSO/day, ip, CON, n=5), 2) enalapril (10 mg/kg/day, po, ENA, n=5), or 3) mitochondrial fusion promotor-M1 (2 mg/kg/day, ip, M1, n=5) once daily for 4 weeks. In the end, echocardiography for the left ventricular (LV) function was performed, and the heart was removed to determine the mitochondrial function and malondialdehyde (MDA) level for oxidative stress. Results CMI rats that received vehicle showed significantly impaired LV function and cardiac mitochondrial function as evidenced by a 60% reduction in LV ejection fraction (LVEF) along with increased mitochondrial reactive oxygen species (ROS) production, mitochondrial depolarization and mitochondrial swelling, respectively, when compared with the sham rats (Fig. 1A–D). The CMI rats also exhibited a higher cardiac tissue MDA level than those of sham rats, further indicating cardiac oxidative stress (Fig. 1E). Interestingly, chronic treatment with either enalapril or M1 effectively attenuated CMI-induced mitochondrial dysfunction and oxidative stress upregulation, thus increasing LVEF (27% improvement for both ENA and M1), when compared with the vehicle group (Fig. 1A). Conclusion Long-term promotion of mitochondrial fusion mitigated cardiac mitochondrial dysfunction and oxidative stress, eventually culminating in improved LV function in rats with CMI. These findings suggest that chronic modulation of mitochondrial fusion could be a promising pharmacological intervention to improve LV function in CMI. Funding Acknowledgement Type of funding sources: Public grant(s) – National budget only. Main funding source(s): 1. The National Science and Technology Development Agency Thailand2. The Thailand Research Fund (RGJ)

Inhibition of microRNA-346 inhibits myocardial inflammation and apoptosis after myocardial infarction via targeting NFIB.

Acute myocardial infarction (AMI) is a sudden cardiovascular event that endangers human life. MicroRNA is considered to be an important participant in the pathophysiology of myocardial infarction (MI). This article aim was to study the function and mechanisms of microRNA-346 (miR-346) on myocardium after MI. To study the role of miR-346 in MI, we established H2O2-induced H9c2 cell injury model and rat MI model. Real-time polymerase chain reaction (RT-PCR) was used to detect miR-346 expression. Western blot was utilized to measure the expression of Bcl-2, Bax, TNF-α, IL-6 and NFIB. Apoptosis of H9c2 cells was detected by TUNEL staining and flow cytometry. Enzyme-linked immunosorbent assay (ELISA) assay was utilized to measure the levels of TNF-α and IL-6 in supernatant. Assessment of left ventricular function in rats was performed using echocardiography. MiR-346 was significantly upregulated in H2O2-treated H9c2 cells and ischemic myocardium. In the H9c2 cell injury model, the expressions of Bax, TNF-α, and IL-6 were greatly increased while Bcl-2 expression was decreased, and the number of TUNEL-positive cells and apoptosis rate were also significantly increased. At the same time, the levels of TNF-α and IL-6 in the cell supernatant were markedly increased. However, after miR-346 expression was suppressed, these results were reversed. The expression of Bcl-2 increased, while the expression of Bax, TNF-α, and IL-6 decreased. The contents of TNF-α and IL-6 in the cell supernatant also decreased significantly. Both the number of TUNEL-positive cells and the apoptosis rate were markedly reduced. After injecting antagomir-346 into the myocardium of rats to silence miR-346, the cardiac function of MI rats was remarkably improved, and the LDH content in the serum of rats also decreased significantly. Using computational predictions tools, Western blotting and Luciferase activity assay, we found that nuclear factor I/B (NFIB) was targeted by miR-346. The expression of miR-346 was increased in H9c2 cells and ischemic myocardium of MI rats. Silencing miR-346 can significantly inhibit the inflammatory response and the apoptosis of cardiomyocytes by targeting NFIB.

Atorvastatin combined with routine therapy on HIF-1, VEGF concentration and cardiac function in rats with acute myocardial infarction

Effect of atorvastatin combined with routine therapy on the expression of hypoxia inducible factor (HIF-1) and vascular endothelial growth factor (VEGF) in rats with acute myocardial infarction (AMI) and its therapeutic effect were investigated. The rat models of acute myocardial infarction were established and divided into routine therapy, study, model, single drug and control group according to the treatment plan, with 10 cases in each group. Enzyme-linked immunosorbent assay (ELISA) was used to detect the concentration of HIF-1 and VEGF in serum of rats before treatment (T0), and 3 days (T1), 5 days (T2) and 7 days (T3) after treatment, and the cardiac function was measured at the same time. The concentrations of HIF-1 and VEGF in serum of the study group and the routine therapy group after treatment were significantly higher than those before treatment. The concentrations of HIF-1 and VEGF in serum of model group at T0 were significantly lower than those at T3 (P<0.05). After treatment, the concentrations of HIF-1 and VEGF in serum of the study group were significantly higher than those of the routine therapy, the model and the control group (P<0.05). One week after administration, there were significant differences in the left ventricular function among the five groups (P<0.001). The left ventricular function in the study group was better than that in the routine therapy, model and control group. The levels of HIF-1 and VEGF in the serum of rats with myocardial infarction were negatively correlated with LVIDs and LVIDd, and positively correlated with LVEF% and LVFS%. In conclusion, atorvastatin combined with routine therapy can better reduce serum HIF-1 and VEGF levels and improve the left ventricular function in rats than routine therapy.

YQWY Decoction Improves Myocardial Remodeling via Activating the IL-10/Stat3 Signaling Pathway.

Heart failure (HF) has been known as a global health problem, and cardiac remodeling plays an essential role in the development of HF. We hypothesized that YQWY decoction might exert a cardioprotective effect against myocardium inflammation, fibrosis, and apoptosis via activating the interleukin-10 (IL-10)/Stat3 signaling pathway. To test this hypothesis, the HF model in rats was established by pressure overload through the minimally invasive transverse aortic constriction (MTAC). Echocardiography was performed to assess the left ventricular function of rats. Myocardial fibrosis in rats was observed by Masson and Picrosirius red staining, and the degree of myocardial apoptosis was detected via TUNEL staining. In addition, expression levels of IL-10, tumor necrosis factor-α (TNF-α), Stat3 (P-Stat3), P65 (P-P65), CD68, collagen I, TGF-β, CTGF, Bax, Bcl-2, cleaved caspase-3, and PARP in rat serum and myocardium samples were examined by ELISA, western blot, and immunohistochemistry, respectively. YQWY decoction treatment significantly improved left ventricular function in HF rats, especially in those of the high-dose group (LVEF%: 51.29 ± 5.876 vs. 66.02 ± 1.264, P < 0.01;, LVFS%: 27.75 ± 3.757 vs. 37.76 ± 1.137, P < 0.01). Furthermore, YQWY decoction markedly inhibited MTAC-induced myocardial fibrosis as evidenced by downregulated collagen I, TGF-β, and CTGF in myocardium and alleviated apoptosis (downregulated caspase-3 and PARP and increased Bcl-2/Bax ratio in cardiomyocytes). In addition, YQWY decoction decreased the level of the proinflammatory cytokine TNF-α in both circulating blood and myocardium and attenuated infiltration of inflammatory cells in heart tissue from HF rats. Most importantly, YQWY decoction suppressed MTAC-induced NF-κB activation and phosphorylated Stat3 by upregulating IL-10 in rat heart tissues. Our study showed that YQWY decoction could attenuate MTAC-induced myocardial inflammation, fibrosis, apoptosis, and reverse the impairment of cardiac function in rats by activating the IL-10/Stat3 signaling pathway and improving myocardium remodeling. Our findings suggested a therapeutic potential of YQWY decoction in HF.

Comparison of renal impairment post-myocardial infarction with reduced and preserved left ventricular function in rats with normal renal function

This study aimed to compare the renal impairments in post-myocardial infarction (MI) rats with normal renal biochemical parameters at baseline with versus without cardiac dysfunction and explore the potential mechanisms involved in these differences. Sprague–Dawley rats with permanent ligation of coronary artery were used as MI models. Renal function, histological and molecular changes were compared between the reduced ejection fraction (EF) (EF < 40%) group and the preserved EF (EF ≥ 40%) group 3 or 9 weeks post-MI. The results revealed that blood cystatin C increased significantly at 9 but not 3 weeks, but it was not associated with cardiac dysfunction. Renal fibrosis and inflammatory cell infiltrations increased significantly in the reduced EF group than in the preserved EF group at 3 and 9 weeks. Glomerular podocyte injury, identified by increased immunostaining for desmin and decreased immunostaining for Wilms’ tumor-1, was more significant in the reduced EF group than in the preserved EF group at 9, but not 3 weeks. The number of p16ink4a-positive and 8-hydroxy-2′-deoxyguanosine-positive podocytes was greater in the reduced EF group than in the preserved EF group at both time points. These changes were associated with increased expression of angiotensin II type 1/2 receptors at both time points. In conclusion, our study demonstrated that cardiac dysfunction accounted for substantially severity in renal parenchymal impairment in a partially time-dependent manner, and local activation of angiotensin II receptors, increased cell senescence and oxidative stress, and enhanced inflammatory reaction may be potential modulators participated in the deterioration of renal parenchymal injury.

Sodium tanshinone IIA sulfonate attenuates cardiac dysfunction and improves survival of rats with cecal ligation and puncture-induced sepsis

Cardiac dysfunction, a common consequence of sepsis, is the major contribution to morbidity and mortality in patients. Sodium tanshinone IIA sulfonate (STS) is a water-soluble derivative of Tanshinone IIA (TA), a main active component of Salvia miltiorrhiza Bunge, which has been widely used in China for the treatment of cardiovascular and cerebral system diseases. In the present study, the effect of STS on sepsis-induced cardiac dysfunction was investigated and its effect on survival rate of rats with sepsis was also evaluated. STS treatment could significantly decrease the serum levels of C-reactive protein (CRP), procalcitonin (PCT), cardiac troponin I (cTn-I), cardiac troponin T (cTn-T), and brain natriuretic peptide (BNP) in cecal ligation and puncture (CLP)-induced) septic rats and improve left ventricular function, particularly at 48 and 72 h after CLP. As the pathogenesis of septic myocardial dysfunction is attributable to dysregulated systemic inflammatory responses, several key cytokines, including tumor necrosis factor-α (TNF-α), interleukin-1β (IL-1β), interleukin-6 (IL-6), interleukin-10 (IL-10) and high mobility group protein B1 (HMGB1), were detected to reveal the possible mechanism of attenuation of septic myocardial dysfunction after being treated by STS. Our study showed that STS, especially at a high dose (15 mg·kg–1), could efficiently suppress inflammatory responses in myocardium and reduce myocardial necrosis through markedly reducing production of myocardial TNF-α, IL-6 and HMGB1. STS significantly improved the 18-day survival rate of rats with sepsis from 0% to 30% (P < 0.05). Therefore, STS could suppress inflammatory responses and improve left ventricular function in rats with sepsis, suggesting that it may be developed for the treatment of sepsis.

Theophylline-Induced Left Ventricular Relaxation Disturbance in Magnesium-Deficient Rats: Improvement by K201, a Novel 1,4-Benzothiazepine Derivative.

Although magnesium deficiency induces left ventricular dysfunction, it is not known whether both systolic and diastolic functions are altered to the same extent. In this study, we investigated the effects of theophylline on left ventricular function in rats fed a normal diet or a magnesium-deficient diet for 1 month, and determined whether K201, a multi-channel blocker, modulated the effects of theophylline. Theophylline was infused at 5 mg/kg/min for 15 min in 6 control rats and 6 magnesium-deficient rats, and hemodynamic measurements were performed. In another 6 magnesium-deficient rats, K201 was infused at 0.1 mg/kg/min for 15 min simultaneously with theophylline. Theophylline induced persistent increases in heart rate, peak positive first derivative of left ventricular pressure (+dP/dt), and a transient increase in left ventricular end-diastolic pressure (LVEDP), but did not affect left ventricular systolic pressure (LVSP) and peak negative first derivative of left ventricular pressure (-dP/dt) in the control rats. In contrast, in the magnesium-deficient rats, there was a persistent decrease in LVSP and a persistent increase in -dP/dt after theophylline infusion, although increases in heart rate, +dP/dt and LVEDP were similar to those in the control rats. When K201 was infused along with theophylline in the magnesium-deficient rats, both the decrease in LVSP and increase in -dP/dt were suppressed. Theophylline impaired left ventricular function in the magnesium-deficient rats, and this was improved by K201. K201 may provide new insights regarding future strategies for heart failure treatment.

The Change of Left Ventricular Function in Rats with Subclinical Hypothyroid and the Effects of Thyroxine Replacement.

Objective The main purpose of this study was to explore the relationships between serca2a, Ryr2, adipokines, and the left ventricular function in the subclinical hypothyroidism with different TSH levels and to determine the impact of L-T4 treatment on these indexes. Methods Sixty-five male Wistar rats were randomly divided into five groups: control group; sHT A, B, and C group; and sHT + T4 group. The sHT rats were induced by methimazole (MMI), and the sHT + T4 rats were administered with L-T4 treatment after 8 weeks of MMI administration. Serum TT4, TSH, APN, chemerin, and TNF-α were detected by radioimmunoassay kits and ELISA kits; left ventricular function was measured by PowerLab system via subclavian artery catheter. The expression of Serca2a, Ryr2, APN, chemerin, and TNF-α were detected by RT-PCR, Western blot, and immunohistochemistry. Results The sHT groups had significantly higher TSH, chemerin, and TNF-α and lower Serca2a, Ryr2, and APN. The left ventricular pressure and heart rate in sHT groups were significantly lower in control and sHT + T4 group. Histopathological examination revealed the pathological changes in the sHT rats' heart. L-T4 administration reduced TSH level and improved left ventricular function. Conclusions TSH can impair left ventricular function by regulating several factors, and L-T4 treatment ameliorates it in sHT rats.

Effects of neuregulin GGF2 (cimaglermin alfa) dose and treatment frequency on left ventricular function in rats following myocardial infarction

Neuregulins are important growth factors involved in cardiac development and response to stress. Certain isoforms and fragments of neuregulin have been found to be cardioprotective. The effects of a full-length neuregulin-1β isoform, glial growth factor 2 (GGF2; USAN/INN; also called cimaglermin) were investigated in vitro. Various dosing regimens were then evaluated for their effects on left ventricular (LV) function in rats with surgically-induced myocardial infarction. In vitro, GGF2 bound with high affinity to erythroblastic leukemia viral oncogene (ErbB) 4 receptors, potently promoted Akt phosphorylation, as well as reduced cell death following doxorubicin exposure in HL1 cells. Daily GGF2 treatment beginning 7–14 days after left anterior descending coronary artery ligation produced improvements in LV ejection fraction and other measures of LV function and morphology. The improvements in LV function (e.g. 10% point increase in absolute LV ejection fraction) with GGF2 were dose-dependent. LV performance was substantially improved when GGF2 treatment was delivered infrequently, despite a serum half-life of less than 2h and could be maintained for more than 10 months with treatment once weekly or once every 2 weeks. These studies confirm previous findings that GGF2 may improve contractile performance in the failing rat heart and that infrequent exposure to GGF2 may improve LV function and impact remodeling in the failing myocardium. GGF2 is now being developed for the treatment of heart failure in humans.

Induced Pluripotent Stem Cell Derived Cardiomyocyte Scaffold Improves Electro-Mechanical Coupling and Left Ventricular Function in Rats With Heart Failure

Induced Pluripotent Stem Cell Derived Cardiomyocyte Scaffold Improves Electro-Mechanical Coupling and Left Ventricular Function in Rats With Heart Failure

Abstract 425: Induced Pluripotent Stem Cell Derived Cardiomyocyte Tissue Engineered Scaffold Improves Left Ventricular Function and Electro-Mechanical Coupling in Rats with Heart Failure

Background: Chronic Heart Failure (CHF) is the leading cause of hospital readmissions in the United States. It may result from systolic or diastolic dysfunction, which often coexists. Here we report the effects of delivering human induced pluripotent stem cells derived cardiomyocytes (hiPSC-CMs) via a bioengineered patch on left ventricular function in rats with CHF. Methods: Adult male Sprague-Dawley rats underwent left coronary artery ligation and were randomized to Sham, CHF, and hiPSC-CM patch. High purity human hiPSC-CMs were obtained from Cellular Dynamics International, seeded and co-cultured onto a vicryl matrix embedded with human dermal fibroblasts. Echocardiography was performed at 3 and 6 weeks post-randomization. Hemodynamic pressure measurements were performed at 6 weeks post-ligation with Millar solid state micromanometer catheters. Open chest Electrophysiologic (EP) mapping was performed at 6 weeks post ligation. Results: Patches constructed with hiPSC-CMs displayed synchronized and spontaneous contractions within 48hrs of culture which developed in robustness over time. At maximal robustness, contractions were visualized across the full thickness of the construct. Contractions were recorded at 36+5 beats BPM. Three weeks after implantation, the hiPSC-CM patch decreased LV EDP (45%), Tau (29%), E/e’ (23%) and increased, EF (14%), e’ (20%), and e’/a’ (36%) versus CHF. EP studies show electro-mechanical coupling between the patch and the native myocardium with normal activation through the patch and increases (P&lt;0.05) voltage amplitude in CHF versus hiPSC-CM patch treated rats (1±0.5 mV vs 6±1.5mV). Conclusion: Cardiac patch implantation with human iPSC derived cardiomyocytes is an effective and feasible method of treating CHF with improvements in systolic function, diastolic function, and electro-mechanical coupling in rats with CHF.

MicroRNA-29b Mediates the Antifibrotic Effect of Tanshinone IIA in Postinfarct Cardiac Remodeling.

Tanshinone IIA (TSN) is one of the main components isolated from Danshen, which is widely used for the treatment of cardiovascular diseases. The transforming growth factor beta (TGF-β) signaling pathway and microRNA (miR)-29b play important roles in the progression of cardiac fibrosis and the modulation of cardiac fibroblast (CF) function. Our study investigated the role of miR-29b in the cardioprotective effects of TSN in postinfarct cardiac remodeling. Echocardiography demonstrated that medium-dose TSN (TSN-M) and high-dose TSN (TSN-H) significantly inhibited postinfarct cardiac fibrosis and improved the impaired left ventricular function in rats subjected to acute myocardial infarction. Moreover, quantitative real-time polymerase chain reaction and Western blot demonstrated that TSN-M and TSN-H downregulated the expression of TGF-β1, Col1a1, Col3a1, and α-SMA but upregulated the expression of miR-29b. CFs treated with TSN showed inhibited TGF-β signaling pathway, downregulated expression of Col1a1, Col3a1, and α-SMA, and upregulated miR-29b expression in vitro. Furthermore, treatment with a miR-29b inhibitor dramatically inhibited these TSN-induced antifibrotic effects, suggesting that miR-29b may be responsible for the antifibrotic effects of TSN. In addition, treatment with Smad3 siRNA significantly inhibited miR-29b expression in CFs, which implies that Smad3 signaling promotes miR-29b expression on CFs. TSN exerts antifibrotic effects in postinfarct cardiac fibrosis by upregulating the expression of miR-29b, which is mediated by the TGF-β-Smad3 signaling pathway.

High-sodium intake aggravates myocardial injuries induced by aldosterone via oxidative stress in Sprague-Dawley rats

To evaluate the effects of aldosterone with or without high sodium intake on blood pressure, myocardial structure and left ventricular function in rats, and to investigate the mechanisms underlying the effects. Eight-week-old male Sprague-Dawley rats were randomly divided into 3 groups: (1) control (CON) group fed a normal sodium diet, (2) aldosterone (ALD) group receiving aldosterone infusion and a normal sodium diet, and (3) high sodium plus aldosterone (HS-ALD) group receiving 1% NaCl diet in conjunction with aldosterone infusion. Aldosterone was administered through continuously subcutaneous infusion with osmotic minipump at the rate of 0.75 μg/h for 8 weeks. The myocardium structure was observed using transthoracic echocardiography and transmission electron microscopy. The collagen deposition in left ventricle was evaluated with Masson's trichrome staining. The expression of IL-18, p22phox, and p47phox proteins was examined using Western blot analysis. The systolic blood pressure in the ALD and HS-ALD groups was significantly higher than that in the CON group after 2-week treatment. But the blood pressure showed no significant difference between the HS-ALD and ALD groups. The left ventricular hypertrophy, myocardial collagen deposition and oxidative stress were predominantly found in the HS-ALD and ALD group. Furthermore, the breakdown of myocardial structure and oxidative stress were more apparent in the HS-ALD group as compared with those in the ALD group. Long-term infusion of aldosterone results in hypertension and profibrotic cardiovascular responses in rats fed a normal sodium diet, which were mediated by oxidative stress. High-sodium intake could aggravate myocardial injuries induced by aldosterone.

Abstract P020: A Bioengineered Neonatal Cardiomyocyte Scaffold Promotes Cell Survival and Improves Left Ventricular Function in Rats with Heart Failure

Background: Cell-based regenerative therapies hold promise as a new treatment for heart failure. Tissue engineered scaffolds used for cell delivery enhance potential improvements in cardiac function by providing the structural and nutrient support for transplanted cell survival, integration, and re-population of injured tissues. Previously, our laboratory reported improvements in left ventricular (LV) function in rats with chronic heart failure (CHF) after placement of a neonatal cardiomyocyte (NCM) seeded 3-dimensional fibroblast construct (3DFC). In brief, 3 weeks after implantation of the NCM-3DFC, LV function improves by increasing (p&lt;0.05) ejection fraction 26% and cardiac index 33%, while decreasing (p&lt;0.05) LV end diastolic pressure 38%. The current report focuses on NCM survival and LV improvements out to 7 weeks post NCM-3DFC implantation. Methods and Results: Cardiomyocytes were isolated from neonatal rat hearts and seeded onto a 3DFC. We evaluated NCM-3DFC in vitro for cellular organization and the presence of functional gap junctions, which demonstrated extensive cell-to-cell connectivity. At 5 days in culture, the seeded patch contracted spontaneously in a rhythmic and directional fashion, beating at 43±3 beats/min with a mean displacement of 1.3±0.3 mm and contraction velocity of 0.8±0.2 mm/sec. The seeded patch could be electrically paced at near physiological rates (270±30 beats/min) while maintaining coordinated, directional contractions. For in vivo evaluation, rats underwent coronary artery ligation and allowed to recover for 3 weeks to establish CHF. NCM-3DFC were implanted 3 weeks after ligation and evaluated 3 and 7 weeks later (6 and 10 weeks after ligation respectively). Live cell tracking of implanted NCM using Q-Dots revealed ∼9% survival of transplanted cells 3 weeks after implantation. In addition, improvements in LV function continued at 7 weeks after implantation of the NCM-3DFC by increasing (p&lt;0.05) ejection fraction 37%. Conclusion: A multicellular, electromechanically organized, cardiomyocyte scaffold, engineered in vitro can improve LV function when implanted directly on the hearts of rats with CHF; the transplanted cells survive and improve LV function chronically.

Abstract P345: The Neuregulin Glial Growth Factor 2 (GGF2) Produces Sustained Improvement in Left Ventricular Function in Rats with Both Early and Established Heart Failure

Neuregulin-1β is essential for fetal cardiac development and adult cardiac function. Previous reports indicate that neuregulins improve left ventricular function in heart failure models, however the duration of the functional improvements with early or late initiation of neuregulin treatment has not been characterized. The present studies examine the effects of early and delayed initiation of intravenous GGF2 treatment on left ventricular (LV) function in rats with myocardial infarction (MI). Rats underwent surgically-induced MI by left anterior coronary artery ligation. Treatment with vehicle or GGF2 (2.6 mg/kg) was initiated at 2 or 16 w post-MI and continued once or twice weekly or once every two weeks for the in-life duration of the study (approximately 40 weeks). LV function was assessed echocardiographically up to once weekly for the duration of the study. Early and delayed initiation of GGF2 treatment caused sustained and significant improvement (p &lt; 0.05) in both ejection fraction (EF) and fractional shortening (FS) in all regimens tested. The greatest improvements were seen with the once weekly dosing paradigm after early initiation (average EF (%) at 40 weeks post initiation of dosing: vehicle = 44.4 ± 6.0, n = 8 rats, vs. GGF2 = 64.7±6.1. n = 9 rats) and twice weekly dosing paradigm after delayed initiation (average EF (%) at 4 weeks post initiation of dosing: vehicle = 34.18±1.6, n = 7 rats, vs. GGF2 = 50.69±4.68, n = 7 rats). In addition, LV function improved when rats were re-challenged with GGF2 following an extended wash out period. This observation indicates potential efficacy for treatment paradigms that utilize intermittent dosing. These findings suggest that GGF2 produces sustained improvement in LV function after early or delayed initiation of treatment following MI in rats.

Scaffold Delivery of Neonatal Cardiomyocyte Results in Prolonged Cellular Survival and Improvements in Left Ventricular Function in Rats with Chronic Heart Failure

Tissue engineered scaffolds used for cell delivery enhance improvements in cardiac function by providing structural and nutrient support for transplanted cell survival, integration, and re-population of injured tissues. Previously, our laboratory reported improvements in left ventricular (LV) function in rats with chronic heart failure (CHF) after placement of a neonatal cardiomyocyte seeded 3-dimensional fibroblast construct (NCM-3DFC). The current report focuses on NCM survival and LV improvements out to 7 weeks post NCM-3DFC implantation. Implantation of a neonatal cardiomyocyte scaffold promotes transplanted cell survival and prolongs improvements in left ventricular function in rats with chronic heart failure. Cardiomyocytes were isolated from neonatal rat hearts. Briefly, hearts were excised, atria removed and ventricles minced, and digested in a pancreatin/collagenase solution. Cardiomyocytes were collected and re-suspended in DMEM with 10% FBS. The NCM-3DFC were cultured in 10% FBS in DMEM-LG, maintained under standard culture conditions. We evaluated NCM-3DFC in vitro for cellular organization and the presence of functional gap junctions, which demonstrated extensive cell-to-cell connectivity. At 5 days in culture, the seeded patch contracted spontaneously in a rhythmic and directional fashion, beating at 43±3 beats/min with a mean displacement of 1.3±0.3 mm and contraction velocity of 0.8±0.2 mm/sec. The seeded patch could be electrically paced at 270±30 beats/min while maintaining coordinated, directional contractions. For in vivo evaluation, NCM-3DFC were implanted 3 weeks after ligation and evaluated 3 and 7 weeks later (6 and 10 weeks after ligation respectively). Live cell tracking of implanted NCM revealed ∼9% survival of transplanted cells 3 weeks after implantation and improved LV function by increasing (p<0.05) ejection fraction 26% and cardiac index 33%, while decreasing (p<0.05) LV end diastolic pressure 38%. Improvements in LV function continued at 7 weeks after implantation of the NCM-3DFC by increasing (p<0.05) ejection fraction 37%. A multicellular, electromechanically organized, cardiomyocyte scaffold, engineered in vitro can improve LV function when implanted directly on the hearts of rats with CHF; the transplanted cells survive and improve LV function chronically.

Intramyocardial transplantation of human adipose-derived stromal cell and endothelial progenitor cell mixture was not superior to individual cell type transplantation in improving left ventricular function in rats with myocardial infarction

BackgroundBoth adipose-derived stromal cells (ASCs) and endothelial progenitor cells (EPCs) have high potential for promoting tissue revascularization and functional recovery in acute myocardial infarction (AMI) models. We investigated the functional effects of intramyocardial transplantation of a human ASC and EPC mixture in immunodeficient rats after MI. MethodsMI was induced by ligating left anterior descending coronary artery. Survived rats were randomly assigned to 1 of 4 different groups: the control group (n=10, saline in 100μL), the ASC group (n=10, 106 ASCs), the EPC group (n=10, 106 EPCs), or the ASC+EPC group (n=10, 2×105 ASCs+8×105 EPCs). Left ventricular (LV) function was compared using echocardiography during the 28-day follow-up. GAP43+ nerve sprouting and smooth muscle α-actin+angiogenesis were also compared. ResultsSerial changes in LV ejection fraction (EF) and fractional shortening revealed significant increases in the ASC, EPC, and ASC+EPC groups when compared to the control group during the follow-up (49±3%, 49±4%, 47±4%, 39±2%, P<0.001, respectively for LVEF) (33±4%, 32±2%, 31±2%, 23±2%, P=0.002, respectively for fractional shortening). The number of α-actin+arterioles and GAP43+ nerve area was significantly greater in the ASC, EPC, and ASC+EPC groups when compared to the control group in the peri-infarct area (34.4±1.0/mm2, 35.9±1.1/mm2, 35.3±0.9/mm2, 17.4±0.7/mm2, P<0.001, respectively for angiogenesis) (346.2±10.7μm2/mm2, 357.2±12.8μm2/mm2, 368.0±9.7μm2/mm2, 174.6±7.9μm2/mm2, P<0.001, respectively for nerve sprouting). ConlusionsIntramyocardial injections of ASCs, EPCs, or ASCs+EPCs are effective modalities for the treatment of myocardial damage in rats and may expand the potential clinical application of ASC or EPC therapy in patients with ischemic heart disease.

Medroxyprogesterone Acetate Aggravates Oxidative Stress and Left Ventricular Dysfunction in Rats with Chronic Myocardial Infarction

The role of estrogens during myocardial ischemia has been extensively studied. However, effects of a standard hormone replacement therapy including 17β-estradiol (E2) combined with medroxyprogesterone acetate (MPA) have not been assessed, and this combination could have contributed to the negative outcomes of the clinical studies on hormone replacement. We hypothesized that adding MPA to an E2 treatment would aggravate chronic heart failure after experimental myocardial infarction (MI). To address this issue, we evaluated clinical signs of heart failure as well as left ventricular (LV) dysfunction and remodeling in ovariectomized rats subjected to chronic MI receiving E2 or E2 plus MPA. After eight weeks MI E2 showed no effects. Adding MPA to E2 aggravated LV remodeling and dysfunction as judged by increased heart weight, elevated myocyte cross-sectional areas, increased elevated left ventricle end diastolic pressure, and decreased LV fractional shortening. Impaired LV function in rats receiving MPA plus E2 was associated with increased cardiac reactive oxygen species generation and myocardial expression levels of NADPH oxidase subunits. These results support the interpretation that adding MPA to an E2 treatment complicates cardiovascular injury damage post-MI and therefore contributes to explain the adverse outcome of prospective clinical studies.

A new hydrodynamic approach by infusion of drag-reducing polymers to improve left ventricular function in rats with myocardial infarction

Recent studies have shown that drag-reducing polymers (DRPs) prolonged survival time in rats with acute myocardial infarction (MI), but their effect on cardiac function post MI remains unknown. This study sought to test the hypothesis that intravenous infusion of DRPs may improve left ventricular (LV) function in rats following surgically induced MI. MI was induced by ligation of the left anterior descending coronary artery in 36 Sprague-Dawley rats, and sham operations were performed in 12 animals. DRPs were then administered to 18 of the MI rats. Echocardiograpy was used to evaluate the changes of impaired LV function and global wall motion. Besides, the hydrodynamic effect of DRPs on microcirculation was also assessed. The survival rate at 24h following MI was significantly different among the sham, MI and DRP groups (p = 0.023). DRP-treated animals had marked smaller left ventricular end-systolic diameter and better anterior systolic wall thickness comparison with untreated rats. Significant improvement of fractional shortening and ejection fraction were detected in MI rats with DRP. Wall motion score index and contrast score index were both significantly reduced by DRP treatment. DRPs were shown to have beneficial effects on microvascular variables including red blood cell velocity, diameter, blood flow and calculated wall shear stress in third-order arteriole. Acute administration of DRPs improved LV function in a rat model of MI possibly by improving microvascular blood flow due to their unique hydrodynamic properties. DRPs may offer a new approach to the treatment of coronary artery ischemic diseases.