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Reactive oxygen species (ROS) and pro-inflammatory cytokines are crucial in ventricular remodelling, such as inflammation-associated myocarditis. We previously reported that tumour necrosis factor-α (TNF-α)-induced ROS in human aortic smooth muscle cells is mediated by NADPH oxidase subunit Nox4. In this study, we investigated whether TNF-α-induced ventricular remodelling was mediated by Nox2 and/or Nox4. An intravenous injection of murine TNF-α was administered to a group of mice and saline injection was administered to controls. Echocardiography was performed on days 1, 7 and 28 post-injection. Ventricular tissue was used to determine gene and protein expression of Nox2, Nox4, ANP, interleukin (IL)-1β, IL-2, IL-6, TNF-α and to measure ROS. Nox2 and Nox4 siRNA were used to determine whether or not Nox2 and Nox4 mediated TNF-α-induced ROS and upregulation of IL-1β and IL-6 in adult human cardiomyocytes. Echocardiography showed a significant increase in left ventricular end-diastolic and left ventricular end-systolic diameters, and a significant decrease in the ejection fraction and fractional shortening in mice 7 and 28 days after TNF-α injection. These two groups of mice showed a significant increase in ventricular ROS, ANP, IL-1β, IL-2, IL-6 and TNF-α proteins. Nox2 and Nox4 mRNA and protein levels were also sequentially increased. ROS was significantly decreased by inhibitors of NADPH oxidase, but not by inhibitors of other ROS production systems. Nox2 and Nox4 siRNA significantly attenuated TNF-α-induced ROS and upregulation of IL-1β and IL-6 in cardiomyocytes. Our study highlights a novel TNF-α-induced chronic ventricular remodelling mechanism mediated by sequential regulation of Nox2 and Nox4 subunits.

Tissue-engineered scaffolds may improve experimental outcomes in cardiac cell therapy by targeted delivery of stem cells and mechanically support an infarcted left ventricular (LV) wall. We transplanted cardiomyocyte-like cells (5×10(5)) with scaffolding via epicardial patching (cell patch, n=17) or a low-dose intramyocardial hydrogel (LD hydrogel, n=18), a high-dose (5×10(6)) intramyocardial hydrogel (HD hydrogel, n=18) or transplanting a serum-free medium control (control, n=13), a blank patch (n=14), and a blank gel (n=16) for targeted cardiomyoplasty in a myocardial infarcted rat model. LV real-time hemodynamics were assessed using a 1.9-F pressure-volume catheter 7 weeks after stem cell transplantation. All mode of scaffold transplantation protected diastolic function by preserving LV wall integrity that resulted in a lower end diastolic pressure-volume relationship (EDPVR) as compared to a control medium-injected group. Moreover, epicardial patching, but not hydrogel injection, reduced ventricular wall stress with a significantly better LV end diastolic pressure (EDP: 5.3±2.4 mmHg vs. 9.6±6.9 mmHg, p<0.05) as compared to control. Furthermore, epicardial patching additionally preserved systolic function by modulating negative remodeling through restricting dilatation of the LV chamber. In comparison to control, an improved ejection fraction in the cell patch group (80.1%±5.9% vs. 67.9%±3.2%, p<0.01) was corroborated by load-independent enhancement of the end systolic pressure-volume relationship (ESPVR: 0.88±0.61 mmHg/uL vs. 0.29±0.19 mmHg/uL, p<0.05) and preload recruitable stroke work (PRSW: 68.7±26.4 mmHg vs. 15.6±16.2 mmHg, p<0.05) in systolic function. Moreover, the cell patch group (14.2±1.7 cells/high-power field vs. 7.4±1.6 cells/high power field, p<0.05) was significantly better in myocardial retention of transplanted stem cells as compared to the LD hydrogel group. Collectively, myocardial transplantation of compliant scaffolding materials alone may physically improve wall mechanics, largely independent of stem cells. However, epicardially grafted cell patch conferred added systolic contractility by improving stem cell retention and cellular alignment leading to improved LV remodeling and geometric preservation postinfarction.

Background. Speckle tracking echocardiography (STE) using dedicated high-resolution ultrasound is a relatively new technique that is useful in assessing myocardial deformation in 3 myocardial layers in small animals. However, comparative studies of STE parameters acquired from murine are limited. Methods. A high-resolution rodent ultrasound machine (VSI Vevo 2100) and a clinically validated ultrasound machine (GE Vivid 7) were used to consecutively acquire echocardiography images from standardized parasternal long axis and short axis at midpapillary muscle level from 13 BALB/c mice. Speckle tracking strain (longitudinal, circumferential, and radial) from endocardial, myocardial, and epicardial layers was analyzed using vendor-specific offline analysis software. Results. Intersystem differences were not statistically significant in the global peak longitudinal strain (−16.8 ± 1.7% versus −18.7 ± 3.1%) and radial strain (46.8 ± 14.2% versus 41.0 ± 9.5%), except in the global peak circumferential strain (−16.9 ± 3.1% versus 27.0 ± 5.2%, P < 0.05). This was corroborated by Bland Altman analysis that revealed a weak agreement in circumferential strain (mean bias ± 1.96 SD of −10.12 ± 6.06%) between endocardium and midmyocardium. However, a good agreement was observed in longitudinal strain between midmyocardium/endocardium (mean bias ± 1.96 SD of −1.88 ± 3.93%) and between midmyocardium/epicardium (mean bias ± 1.96 SD of 3.63 ± 3.91%). Radial strain (mean bias ± 1.96 SD of −5.84 ± 17.70%) had wide limits of agreement between the two systems that indicated an increased variability. Conclusions. Our study shows that there is good reproducibility and agreement in longitudinal deformation of the 3 myocardial layers between the two ultrasound systems. Directional deformation gradients at endocardium, myocardium, and epicardium observed in mice were consistent to those reported in human subjects, thus attesting the clinical relevance of STE findings in murine cardiovascular disease models.

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