Objective: In this study the ability of unrestricted somatic stem cells (USSC) and mononuclear cord blood cells (MN-CBC) was tested to improve heart function and left ventricular (LV) remodeling after myocardial infarction (MI). Methods: The cells were delivered by i.v. or intramyocardial injections in rat models of MI by permanent coronary artery occlusion and by ischemia/reperfusion (I/R) injury. Heart function and remodeling was followed by recurrent echocardiography over 8 or 12 weeks after which catheterization was performed. Results: Although injected labeled cells could be observed within the myocardium for up to 6 d, there was no sign of cardiac regeneration 8 or 12 weeks after MI. However, the mRNA expression of components of the extracellular matrix was attenuated in the infarct scar 12 weeks after MI and cell injection. Additionally, the expression of interleukin (IL)-6 but not of IL-1β increased at the site of injury and the adjacent border-zone 12 weeks after I/R and USSC-injection. However, these effects did not translate into improved heart function or attenuated LV dilatation. Conclusion: These data indicate that cord blood cell implantation after MI acts through paracrine mechanisms to modify remodeling rather than myocyte regeneration. The role of myofibroblasts and the optimal conditions of cell application need to be determined to translate these mechanisms into functional improvement.

The purpose of the present study was to analyze the changes in blood pressure, left ventricular (LV) wall thickness and LV systolic function of aged spontaneously hypertensive rats (SHRs) either with or without antihypertensive therapy. Twenty-one SHRs aged 60.5±0.25 weeks were investigated over 22 weeks. They were divided into the following three groups (7 per group): untreated controls (CTRL), treatment with captopril (CAP, 60 mg kg(-1) daily) and treatment with captopril plus nifedipine (CAP+NIF, 60+10 mg kg(-1) daily). Systolic blood pressure (SBP) was regularly measured using the tail cuff method, and an echocardiogram was repeatedly obtained to examine the LV systolic and diastolic area, LV systolic fractional area change, cardiac output and LV myocardial wall thickness. Finally, heart catheterization was performed. While SBP remained stable in the CTRL animals over the experimental period, both of the antihypertensive treatments significantly reduced SBP by 20% in the treated animals (P<0.001). Echocardiography demonstrated that both the systolic and the diastolic LV function of the untreated SHRs deteriorated over time, whereas both types of antihypertensive treatments attenuated and delayed but did not completely prevent the decline in LV systolic function. Cardiac output, as determined by pulsed wave Doppler echocardiography, remained significantly higher in the treated animals than in CTRLs until week 20, but it then decreased. Heart catheterization showed a significant decrease in LV function, as reflected by the LV systolic pressure and contractility, in the CTRLs but not in treated animals. These findings clearly indicate that late-onset antihypertensive treatment with CAP or CAP+NIF is beneficial with respect to blood pressure reduction, LV hypertrophy attenuation and LV systolic function preservation.

Background: Matrix metalloproteinases (MMPs) play an important role in myocardial remodeling. Their activity is regulated by the tissue inhibitors of metalloproteinases (TIMPs). The present study analyzed the contribution of changes in functional and molecular parameters to early cardiac remodeling in mice hearts. The role that TIMPs might play in this process was specially acknowledged. Methods: The remodeling was induced by norepinephrine (NE) given sc in balb/c mice. Varying concentrations, time and the addition of a neutralizing TIMP-1 antibody were evaluated. Results: High dose NE led to insufficiency of the left ventricle (LV) as evidenced by reduced NE-induced elevation of LV systolic pressure, contractility and relaxation. Further, signs of lung congestion were seen. NE induced a concentration-dependent increase of LV weight/body weight (LVW/BW) ratio and elevated mRNA expression of atrial natriuretic peptide (ANP). This was accompanied by induction of collagen type I and III, as well as TIMP-1 expression. Conclusions: The NE-induced increase of TIMP-1 expression may induce the elevation of the antihypertrophic cardiac factor ANP since NE-induced increase of ANP expression was abolished by neutralizing TIMP-1 antibody. Thus, TIMP-1 may mediate ANP-induced attenuation of NE-induced hypertrophy in the mouse heart.

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Objective: In this study the effect of ribose on heart function and infarct-size was analyzed 6 h after myocardial infarction (MI) in rats. Methods: Continuous i.v.-infusion of NaCl or ribose (200 mg/kg/h) was started one day prior to induction of MI in female Sprague-Dawley rats which was done by ligation of the left coronary artery. Six hours after MI heart function was measured with 3F tip catheter, cardiac output by thermodilution method. Thereafter the ischemic area was delineated by Evans Blue infusion, and the infarct area was visualized by triphenyltetrazolium chloride staining. The mRNA expression of interleukin (IL)-1β, IL-6, matrix-metalloproteinase (MMP)-8, and -9 was measured by ribonuclease protection assay. Results: Heart function was severely depressed 6 hours after coronary artery occlusion, but recovered significantly under the influence of ribose. Left ventricular (LV) systolic pressure (LVSP) and contractility (LVdP/dt_max) were restored to the normal levels of sham-operated animals, while parameters of LV relaxation (LVdP/dt_min and time constant of relaxation τ) were impaired compared to sham-operated animals, but significantly improved by ribose treatment compared to sham-treated MI-rats. Moreover, the infarct size was significantly smaller in the ribose treated animals despite a comparable ischemic area at risk in all MI-rats. The cytokine mRNA expression after MI was significantly reduced after ribose treatment, while there were no differences regarding MMP expression. Conclusion: MI size was significantly reduced and LV function significantly improved by ribose treatment at 6 h after MI. This seemed to be based on slowing the velocity of the necrotic wave front across the LV wall after MI resulting in smaller infarcts.