On the Cover: Isolated fibrocytes produce a second wave of connective tissue growth factor (CTGF) in AngII-induced myocardial fibrosis.Purified fibrocytes isolated from the myocardium of AngII-exposed mice demonstrate immunofluorescent staining for the mesenchymal marker COL1 (green) and the hematopoietic marker CD45 (red), with nuclei counterstained with Hoescht stain (blue).
Treatment with erythropoietin (EPO) was reported to accelerate reendothelialization, accompanying endothelial progenitor cell (EPC) induction, to result in suppression of neointimal hyperplasia in the carotid artery after balloon injury. We injured the right carotid artery of male SD rats (200 to 250 g) with an oversized balloon. Treatment with recombinant human EPO (1000 IU/kg/day) or asialoerythropoietin (AEPO, 1000 IU/kg/day), a nonerythrogenic derivative of EPO, was started at 1 week after injury when neointimal proliferates and continued for 3 days. The rats were examined 2 weeks after the surgery. The hemoglobin level was significantly increased in the EPO-treated rats but was unchanged in the saline control and AEPO-treated groups. FACS analysis revealed significantly increased circulating EPCs in the EPO-treated group but not in the AEPO-treated group. Reendothelialization was accelerated in both EPO- and AEPO-treated groups. However, the area of neointima was significantly greater in both treatment groups compared with the control group and accordingly the area of neointimal to medial area ratio (%) was significantly greater in the EPO- (150+/−26%) and AEPO-treated (157+/−15%) groups compared with the control group (132+/−7%). Alpha-smooth muscle actin-positive cell population was also greater in both treatment groups. The incidence of proliferating cells labeled with Ki-67 antigen was significantly greater not only in the endothelium but also in the neointima of the EPO- and AEPO-treated groups compared with the control group. In conclusion, EPO receptor signaling can proliferate not only endothelial cells but also intimal smooth muscle-like cells independently of EPC induction, which might have aggravated neointimal hyperplasia when EPO receptor was stimulated at the phase of intimal proliferation after injury. These findings caution an easy use of EPO in patients after vascular intervention.
We previously reported that cardiomyocyte autophagy is an innate mechanism that protects against progression of postinfarction cardiac remodeling. In the present study, we examined effect of caloric restriction (CR), a potent inducer of autophagy, on post infarction cardiac remodeling. Myocardial infarction (MI) was induced in mice by ligating the left coronary artery. After one week of MI, mice were randomly divided into the following four groups. The control group was fed ad libitum (100%). Others were fed restricted diet: 80%, 60%, and 40% of the total calorie which was taken by control mice. The water was provided ad libitum. Three weeks later, we performed echocardiography and catheter to evaluate the left ventricular (LV) function. There was no mouse that died through the period. The body weight was decreased in CR groups (post/pre ratio: 1.08±0.01 in control, 0.83±0.01 in 80% CR, 0.76±0.01 in 60% CR, 0.70±0.01 in 40% CR, p<0.001). However, there was no difference in heart/body weight ratio. The dilatation and hypofunction of the LV were apparent in the control group: left ventricular diastolic dimension (LVDd) = 4.9±0.1 mm; left ventricular ejection fraction (LVEF) = 27±3.3%; and dP/dT = 4677±277 mmHg/s. However, both dilatation and hypofunction were significantly mitigated in groups undergoing CR: in 80%, 60%, and 40% CR, respectively, LVDd = 4.0±0.1 mm, 3.4±0.2 mm and 4.0±0.1 mm; LVEF = 36±2.8%, 51±4.3% and 43±1.5%; and dP/dT = 6849±221 mmHg/s, 7758±638 mmHg/s and 6923±553 mmHg/s, among which the 60% CR group showed the strongest therapeutic effect on postinfarction cardiac remodeling (control vs. 60% CR: p<0.001). Cardiomyocyte autophagy was markedly activated in CR groups as evidenced by the overexpressed microtubule-associated protein 1 light chain 3-II (LC3-II) and specific ultrastructural findings including autophagosome formation. In conclusion, caloric restriction enhances cardiomyocyte autophagy and mitigates postinfarction cardiac remodeling and dysfunction; the optimal caloric restriction is suggested to be 60%. These findings suggest an important clinical implication that a dietary protocol can be a preventive strategy against progression of postinfarction left ventricular remodeling and heart failure.
Anemia may accelerate angiogenesis in ischemic organs through its ability to augment tissue hypoxia-induced generation of several known angiogenic factors and to increase erythropoietin levels, which are also potently angiogenic. We examined the effect of controlled phlebotomy (bloodletting) on blood flow in a mouse ischemic leg model. We ligated the right femoral artery of BALB/c mice. In the phlebotomy group, 200 microl of blood were drawn from the tail vein once a week. After 4 wk, blood flow in the ischemic leg was significantly better in the phlebotomy group (flow ratio of the ischemic to nonischemic leg, 0.87 + or - 0.04) than the control group (0.59 + or - 0.05, P < 0.05), and capillary density was significantly higher. Repeated phlebotomy increased serum erythropoietin levels as well as the expression of hypoxia-inducible transcription factor-1alpha and vascular endothelial growth factor and both the expression and activity of Akt and endothelial nitric oxide synthase (eNOS) in ischemic legs. Treatment with wortmannin or N(omega)-nitro-l-arginine methyl ester significantly attenuated the phlebotomy-induced improvement of blood flow. In addition, fluorescence-activated cell sorting analysis revealed an increase in circulating peripheral endothelial progenitor cells in the phlebotomy group, and treatment with AMD3100, a specific inhibitor of the chemokine receptor CXCR4, blocked the beneficial effect of phlebotomy. These findings suggest that repeated phlebotomy improves blood flow in ischemic legs through an angiogenic action that involves the Akt/eNOS pathway, endothelial progenitor cell mobilization, and their complicated cross talk. An adequately controlled phlebotomy might be one method by which to induce therapeutic angiogenesis.
Active autophagy has recently been reported in doxorubicin-induced cardiotoxicity, of which pathophysiological role we here investigated. Acute cardiotoxicity was induced in green fluorescent prote...
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