ABSTRACT
BACKGROUND: Disruption of ATP-sensitive potassium (K(ATP)) channel activity results in the development of dilated cardiomyopathy in response to different forms of stress, likely due to the underlying metabolic defects. To further understand the role of Kir6.2-containing channels in the development of cardiac disease, we analysed the left ventricular (LV) wall oxygenation and the physiologic responses induced by acute stress in non-dilated Kir6.2(-/-) hearts. METHODS: Control (C57BL6) and Kir6.2(-/-) mouse hearts were perfused in constant flow Langendorff mode with Krebs-Henseleit buffer. Myocardial oxygenation was evaluated using a newly developed technique, near infrared spectroscopic imaging (NIRSI) of the myoglobin (Mb) oxygen saturation parameter (OSP, ratio of oxy- to total Mb). RESULTS: 2,4-dinitrophenol (DNP, 50-µM) and isoproterenol (0.1-µM) failed to produce a transient vasodilatory response and caused a significant diastolic pressure increase in Kir6.2(-/-) hearts. DNP strongly suppressed contractile function in both groups and induced severe mean OSP decreases in Kir6.2(-/-) hearts. Isoproterenol-induced decreases in OSP were similar despite the lack of contractile function stimulation in the Kir6.2(-/-) group. The index of OSP spatial heterogeneity (relative dispersion, RD) was lower by 15% in the Kir6.2(-/-) group at the baseline conditions. Recovery after stress caused reduction of RD values by 20% (DNP) and 8% (isoproterenol) in controls; however, these values did not change in the Kir6.2(-/-) group. CONCLUSIONS: 1) NIRSI can be used to analyse 2-D dynamics of LV oxygenation in rodent models of cardiomyopathy; 2) Kir6.2-containing K(ATP) channels play an important role in maintaining myocardial oxygenation balance under acute stress conditions and in post-stress recovery.
Subject(s)
Cardiomyopathy, Dilated/metabolism , Myocardium/metabolism , Myoglobin/metabolism , Oxygen/metabolism , Potassium Channels, Inwardly Rectifying/metabolism , Stress, Physiological/physiology , 2,4-Dinitrophenol/pharmacology , Acute Disease , Animals , Cardiomyopathy, Dilated/genetics , Cardiotonic Agents/pharmacology , Female , In Vitro Techniques , Isoproterenol/pharmacology , Male , Mice , Mice, Inbred C57BL , Mice, Knockout , Models, Biological , Potassium Channels, Inwardly Rectifying/genetics , Spectroscopy, Near-Infrared/methods , Stress, Physiological/drug effects , Uncoupling Agents/pharmacology , Vasodilation/drug effectsABSTRACT
This study assessed the potential therapeutic efficacy of adipose-derived stem cells (ASCs) on infarcted hearts. Myocardial infarction was induced in rat hearts by occlusion of the left anterior descending artery (LAD). One week after LAD occlusion, the rats were divided into three groups and subjected to transplantation of ASCs or transplantation of cell culture medium (CCM) or remained untreated. During a 1-mo recovery period, magnetic resonance imaging showed that the ASC-treated hearts had a significantly greater left ventricular (LV) ejection fraction and LV wall thickening than did the CCM-treated and untreated hearts. The capillary density in infarct border zone was significantly higher in the ASC-treated hearts than in the CCM-treated and untreated hearts. However, only 0.5% of the ASCs recovered from the ASC-treated hearts were stained positive for cardiac-specific fibril proteins. It was also found that ASCs under a normal culture condition secreted three cardiac protective growth factors: vascular endothelial growth factor, hepatocyte growth factor, and insulin-like growth factor-1. Results of this study suggest that ASCs were able to improve cardiac function of infarcted rat hearts. Paracrine effect may be the mechanism underlying the improved cardiac function and increased capillary density.
Subject(s)
Heart Failure/therapy , Magnetic Resonance Imaging , Myocytes, Cardiac/cytology , Stem Cell Transplantation/methods , Stem Cells/cytology , Subcutaneous Fat/cytology , Animals , Biomarkers/metabolism , Capillaries/physiology , Cell Differentiation , Coronary Circulation/physiology , Disease Models, Animal , Female , Heart Failure/pathology , Heart Failure/prevention & control , Hepatocyte Growth Factor/genetics , Insulin-Like Growth Factor I/genetics , Membrane Proteins/metabolism , Myocardial Infarction/pathology , Myocardial Infarction/therapy , Myocytes, Cardiac/metabolism , RNA, Messenger/metabolism , Rats , Rats, Inbred Lew , Stem Cells/metabolism , Vascular Endothelial Growth Factor A/genetics , Ventricular Function, Left , Ventricular Remodeling/physiologyABSTRACT
The objectives of this study were (1) to determine whether superparamagnetic iron oxide (SPIO) affects viability, transdifferentiation potential and cell-factor secretion of adipose-derived stem cells (ASCs); and (2) to determine whether SPIO-enhanced magnetic resonance (MR) imaging highlights living stem cells. Rat ASCs were incubated in SPIO-containing cell culture medium for 2 days. The SPIO-treated ASCs were then subjected to adipogenic, osteogenic and myogenic transdifferentiation. Expression of vascular endothelial growth factor, hepatocyte growth factor and insulin-like growth factor 1 by the SPIO-treated ASCs was measured using reverse transcription polymerase chain reaction. Cell viability was assessed using trypan blue stain. For in vivo experiments, SPIO-labeled ASCs were injected into 10 rat hearts. The hearts were monitored using MRI. We found that survival rate of the ASCs cultured in the SPIO-containing medium was very high (97-99%). The SPIO-treated ASCs continued to express specific markers for the three types of transdifferentiation. Expression of the cell factors by the ASCs was not affected by SPIO. Signal voids on MR images were associated with the living SPIO-labeled ASCs in the rat hearts. We conclude that SPIO does not affect viability, transdifferentiation potential or cell-factor secretion of ASCs. MRI mainly highlights living SPIO-labeled stem cells.
