We hypothesized that a small molecule CXCR4 antagonist, AMD3100 (AMD), could augment the mobilization of bone marrow (BM)-derived endothelial progenitor cells (EPCs), thereby enhancing neovascularization and functional recovery after myocardial infarction. Single-dose AMD injection administered after the onset of myocardial infarction increased circulating EPC counts and myocardial vascularity, reduced fibrosis, and improved cardiac function and survival. In mice transplanted with traceable BM cells, AMD increased BM-derived cell incorporation in the ischemic border zone. In contrast, continuous infusion of AMD, although increasing EPCs in the circulation, worsened outcome by blocking EPC incorporation. In addition to its effects as a CXCR4 antagonist, AMD also up-regulated VEGF and matrix metalloproteinase 9 (MMP-9) expression, and the benefits of AMD were not observed in the absence of MMP-9 expression in the BM. These findings suggest that AMD3100 preserves cardiac function after myocardial infarction by enhancing BM-EPC-mediated neovascularization, and that these benefits require MMP-9 expression in the BM, but not in the ischemic region. Our results indicate that AMD3100 could be a potentially useful therapy for the treatment of myocardial infarction.angiogenesis | stem cell | vasculogenesis

ObjectiveSodium-glucose cotransporter 1 (SGLT1) is thought to be expressed in the heart as the dominant isoform of cardiac SGLT, although more information is required to delineate the subtypes of SGLTs in human hearts. Moreover, the functional role of SGLTs in the heart remains to be fully elucidated. We herein investigated whether SGLT1 is expressed in human hearts and whether SGLTs significantly contribute to cardiac energy metabolism during ischemia-reperfusion injury (IRI) via enhanced glucose utilization in mice.Methods and ResultsWe determined that SGLT1 was highly expressed in both human autopsied hearts and murine perfused hearts, as assessed by immunostaining and immunoblotting with membrane fractionation. To test the functional significance of the substantial expression of SGLTs in the heart, we studied the effects of a non-selective SGLT inhibitor, phlorizin, on the baseline cardiac function and its response to ischemia-reperfusion using the murine Langendorff model. Although phlorizin perfusion did not affect baseline cardiac function, its administration during IRI significantly impaired the recovery in left ventricular contractions and rate pressure product, associated with an increased infarct size, as demonstrated by triphenyltetrazolium chloride staining and creatine phosphokinase activity released into the perfusate. The onset of ischemic contracture, which indicates the initiation of ATP depletion in myocardium, was earlier with phlorizin. Consistent with this finding, there was a significant decrease in the tissue ATP content associated with reductions in glucose uptake, as well as lactate output (indicating glycolytic flux), during ischemia-reperfusion in the phlorizin-perfused hearts.ConclusionsCardiac SGLTs, possibly SGLT1 in particular, appear to provide an important protective mechanism against IRI by replenishing ATP stores in ischemic cardiac tissues via enhancing availability of glucose. The present findings provide new insight into the significant role of SGLTs in optimizing cardiac energy metabolism, at least during the acute phase of IRI.

In addition to the various effects of natriuretic peptides (NPs) on cardiovascular systems, increasing attention is being paid to the possibility that NPs induce adipose tissue browning and activate thermogenic program. We herein established a direct intracellular temperature measurement system using a fluorescent thermoprobe and investigated the thermogenic effects of A-type NP (ANP) on brown adipocytes. The thermoprobe was successfully introduced into rat brown adipocytes, and the temperature dependent change in fluorescence intensity ratio was measured using a fluorescence microscope. After one-hour incubation with ANP, the degree of the change in fluorescence intensity ratio was significantly higher in ANP-treated (P < 0.01) adipocytes compared to untreated controls. The ANP treatment increased uncoupling protein-1 (UCP1) mRNA levels, which is one of the markers of thermogenesis in adipocytes, while the intracellular ATP content was not changed, indicating mitochondrial uncoupled respiration. Intriguingly, these thermogenic actions of ANP were more prominent when brown adipocytes were incubated at 35 °C than at 37 °C. Moreover, the increase in the intracellular temperature and the expression of UCP1 induced by ANP were cancelled by p38MAPK inhibition. Taken together, this study directly demonstrated the thermogenic actions of ANP in brown adipocytes through the use of a novel method of intracellular temperature measurement.

Rationale: The mobilization of bone marrow (BM) progenitor cells (PCs) is largely governed by interactionsbetween stromal cell-derived factor (SDF)-1 and CXC chemokine receptor (CXCR)4. Ischemic injury disrupts the SDF-1-CXCR4 interaction and releases BM PCs into the peripheral circulation, where the mobilized cells are recruited to the injured tissue and contribute to vessel growth. BM PCs can also be mobilized by the pharmacological CXCR4 antagonist AMD3100, but the other components of the SDF-1-CXCR4 signaling pathway are largely unknown. c-kit, a membrane-bound tyrosine kinase and the receptor for stem cell factor, has also been shown to play a critical role in BM PC mobilization and ischemic tissue repair.Objective: To investigate the functional interaction between SDF-1-CXCR4 signaling and c-kit activity in BM PC mobilization. Key Words: CXCR4 Ⅲ c-kit Ⅲ stem cells Ⅲ bone marrow Ⅲ mobilization T he mobilization or release of progenitor cells (PCs) from the bone marrow (BM) to the peripheral blood (PB) is highly regulated and occurs both under normal conditions and in response to stress. 1,2 PB PCs have an essential role in blood cell formation and homeostasis 3 and in the response of various tissues to noxious insults. Thus, therapies that enhance PC mobilization are being investigated as novel strategies for promoting tissue repair. 4,5 Ample evidence suggests that PCs are retained in the BM by interactions between the CXC chemokine stromal cell-derived factor (SDF)-1 and CXC chemokine receptor (CXCR)4. 6 -10 CXCR4 is expressed by BM mononuclear cells (MNCs), and SDF-1 is expressed by osteoblasts, endothelial cells, and a subset of reticular cells scattered throughout the BM. 7 Ischemic injury disrupts the SDF-1-CXCR4 interaction and releases BM PCs into the peripheral circulation; then, the mobilized cells are recruited to Original received March 25, 2010; revision received August 25, 2010; accepted August 27, 2010. In August 2010, the average time from submission to first decision for all original research papers submitted to Circulation Research was 13.2 days. Methods and ResultsFrom the injured tissue and contribute to vessel growth. 11,12 BM PCs can also be mobilized by the pharmacological CXCR4 antagonist AMD3100, 13-15 but the downstream components of the SDF-1-CXCR4 signaling pathway are largely unknown. Like CXCR4, c-kit is expressed predominantly in BM PCs, and the ligand for c-kit, stem cell factor (SCF), is constitutively produced by BM endothelial cells and fibroblasts. 16 c-kit is a class III receptor tyrosine kinase, and administration of a c-kit-neutralizing antibody (ACK2) to wild-type (WT) mice released BM cells to the peripheral circulation and enhanced the engraftment of intravenously injected BM cells. 17 On the other hand, PC mobilization is markedly blunted in c-kit W/W-V mutant mice, which are defective in c-kit kinase activity but have normal levels of c-kit expression and SCF binding at the cell surface. 18 -21 Furthermore, the kinetics of BM PC mobilization induced by the c-kit...

Background CXC-chemokine receptor 4 (CXCR4) regulates the retention of stem/progenitor cells in the bone marrow (BM), and the CXCR4 antagonist AMD3100 improves recovery from coronary-ligation injury by mobilizing stem/progenitor cells from the BM to the peripheral blood. Thus, we investigated whether AMD3100 also improves recovery from ischemia-reperfusion (IR) injury, which more closely mimics myocardial infarction in patients, because blood flow is only temporarily obstructed. Methods and Results Mice were treated with single subcutaneous injections of AMD3100 (5 mg/kg) or saline after IR injury. Three days later, histological measurements of the infarct-area/area-at-risk ratio were smaller in AMD3100-treated mice than in mice administered saline, and echocardiographic measurements of left-ventricular function were greater in the AMD3100-treated mice at week 4. CXCR4+ cells were mobilized for just 1 day in both groups, but the mobilization of sca1+/flk1+ cells endured for 7days in AMD3100-treated mice compared to just 1 day in the saline-treated mice. AMD3100 upregulated BM levels of endothelial nitric oxide synthase (eNOS) and two targets of eNOS signaling, matrix-metalloproteinase 9 and soluble Kit ligand. Furthermore, the loss of BM eNOS expression abolished the benefit of AMD3100 on sca1+/flk1+ cell mobilization without altering the mobilization of CXCR4+ cells, and the cardioprotective effects of AMD3100 were retained in eNOS-knockout mice that had been transplanted with BM from wild-type mice, but not in wild-type mice with eNOS-knockout BM. Conclusions AMD3100 prolongs BM progenitor mobilization and improves recovery from IR injury, and these benefits appear to occur through a previously unidentified link between AMD3100 and BM eNOS expression.

Objectives To compare the effectiveness of Sonic hedgehog (Shh) gene transfer, AMD3100-induced progenitor-cell mobilization, and Shh-AMD3100 combination therapy for treatment of surgically induced myocardial infarction (MI) in mice. Background Shh gene transfer improves myocardial recovery by upregulating angiogenic genes and enhancing the incorporation of bone-marrow–derived progenitor cells (BMPCs) in infarcted myocardium. Here, we investigated whether the effectiveness of Shh gene therapy could be improved with AMD3100-induced progenitor-cell mobilization. Methods Gene expression and cell function were evaluated in cells cultured with medium collected from fibroblasts transfected with plasmids encoding human Shh (phShh). MI was induced in wild-type mice, in matrix metalloproteinase 9 (MMP-9)–knockout mice, and in mice transplanted with bone marrow that expressed green-fluorescent protein. Mice were treated with 100 μg phShh (administered intramyocardially), 5 mg/kg AMD3100 (administered subcutaneously), or both; cardiac function was evaluated echocardiographically, and fibrosis, capillary density, and BMPC incorporation were evaluated immunohistochemically. Results phShh increased vascular-endothelial growth factor and stromal-cell–derived factor 1 expression in fibroblasts; the medium from phShh-transfected fibroblasts increased endothelial-cell migration and the migration, proliferation, and tube formation of BMPCs. Combination therapy enhanced cardiac functional recovery (i.e., left-ventricular ejection fraction) in wild-type mice, but not in MMP-9–knockout mice, and was associated with less fibrosis, with greater capillary density and smooth-muscle–containing vessel density, and with enhanced BMPC incorporation. Conclusions Combination therapy consisting of intramyocardial Shh gene transfer and AMD3100-induced progenitor-cell mobilization improves cardiac functional recovery after MI and is superior to either individual treatment for promoting therapeutic neovascularization.

Increasing evidence suggests natriuretic peptides (NPs) coordinate inter-organ metabolic crosstalk with adipose tissues and play a critical role in energy metabolism. We recently reported A-type NP (ANP) raises intracellular temperature in cultured adipocytes in a low-temperature-sensitive manner. We herein investigated whether exogenous ANP-treatment exerts a significant impact on adipose tissues in vivo. Mice fed a high-fat-diet (HFD) or normal-fat-diet (NFD) for 13 weeks were treated with or without ANP infusion subcutaneously for another 3 weeks. ANP-treatment significantly ameliorated HFD-induced insulin resistance. HFD increased brown adipose tissue (BAT) cell size with the accumulation of lipid droplets (whitening), which was suppressed by ANP-treatment (re-browning). Furthermore, HFD induced enlarged lipid droplets in inguinal white adipose tissue (iWAT), crown-like structures in epididymal WAT, and hepatic steatosis, all of which were substantially attenuated by ANP-treatment. Likewise, ANP-treatment markedly increased UCP1 expression, a specific marker of BAT, in iWAT (browning). ANP also further increased UCP1 expression in BAT with NFD. Accordingly, cold tolerance test demonstrated ANP-treated mice were tolerant to cold exposure. In summary, exogenous ANP administration ameliorates HFD-induced insulin resistance by attenuating hepatic steatosis and by inducing adipose tissue browning (activation of the adipose tissue thermogenic program), leading to in vivo thermogenesis during cold exposure.

BackgroundManagement of renal cell carcinoma (RCC) with tumor thrombus extending to the renal vein and inferior vena cava (IVC) is challenging. The aim of this study was to evaluate the benefit of surgical management in such patients.MethodsFrom February 1995 to February 2013, 520 patients were treated for RCC at Hirosaki University Hospital, Hirosaki, Japan. The RCC patients with tumor thrombus extending to the renal vein (n = 42) and IVC (n = 43) were included in this study. The records of these 85 patients were retrospectively reviewed to assess the relevant clinical and pathological variables and survival. Prognostic factors were identified by multivariate analysis. The benefit of surgical management was evaluated using propensity score matching to compare overall survival between patients who received surgical management and those who did not.ResultsRCC was confirmed by pathological examination of surgical or biopsy specimens in 74 of the 85 patients (87%). Sixty-five patients (76%) received surgical management (radical nephrectomy with thrombectomy). Distant metastasis was identified in 45 patients (53%). The proportion of patients with tumor thrombus level 0 (renal vein only), I, II, III, and IV was 49%, 13%, 18%, 14%, and 5%, respectively. The estimated 5-year overall survival rate was 70% in patients with thrombus extending to the renal vein and 23% in patients with thrombus extending to the IVC. Multivariate analysis identified thrombus extending to the IVC, presence of distant metastasis, surgical management, serum albumin concentration, serum choline esterase concentration, neutrophil-lymphocyte ratio, and Carlson comorbidity index as independent prognostic factors. In propensity score-matched patients, overall survival was significantly longer in those who received surgical management than those who did not.ConclusionsSurgical management may improve the prognosis of RCC patients with thrombus extending to the renal vein and IVC.