Circ J 2009; 73: 411 -418 arious vasodilators, including nitric oxide (NO), prostacyclin, and endothelium-derived hyperpolarizing factor (EDHF), as well as vasoconstrictors, are released from the endothelium. 1,2 NO plays an important role in the regulation of vascular tone, inhibition of platelet aggregation, and suppression of vascular smooth muscle cell proliferation. 3,4 Impaired endothelium-dependent vasodilation has been found in the forearm, coronary, and renal vasculature of patients with hypertension, 5-11 dyslipidemia, 12,13 diabetes mellitus, [14][15][16] and coronary artery diseases. [17][18][19][20][21] Endothelial dysfunction is an early feature of both atherosclerosis and vascular diseases in humans. 22 Improvement or augmentation of endothelial function will prevent the development of atherosclerosis, resulting in a reduction in cardiac events.There are several possible mechanisms for impaired endothelial function in patients with cardiovascular diseases. Decreased NO bioavailability (decreased NO production and/or increased NO inactivation) induces endothelial dysfunction. A balance of endothelium-derived vasodilators, especially NO, and reactive oxygen species (ROS) modulates endothelial function. Therefore, an imbalance of NO and ROS, so-called oxidative stress, is involved in endothelial dysfunction through the inactivation of NO. Oxidative Stress in Cardiovascular DiseasesROS are produced by various oxidase enzymes, including nicotinamide-adenine dinucleotide phosphate (NADPH) oxidase, xanthine oxidase, uncoupled endothelial NO synthase (eNOS), cyclooxygenase, glucose oxidase, and lipooxygenase, and mitochondrial electron transport (Figure 1). ROS include superoxide anion (O2 -), hydrogen peroxide (H2O2), hydroxyl radical (OH), hypochlorous acid (HOCl), NO, and peroxynitrite (ONOO -). O2 -, OH, and NO are classified as free radicals that have unpaired electrons and potent oxidation ability. H2O2, HOCl, and ONOO -are classified as non-free radicals that also have oxidation ability. The sources of ROS are a variety of cell types, including vascular smooth muscle cells (VSMCs), endothelial cells and mononuclear cells. The antioxidant enzyme superoxide dismutase (SOD) has been identified as 3 enzymatic types: Cu/Zn SOD, Mn SOD, and extracellular SOD. SOD rapidly dismutates O2 -to H2O2, then H2O2 is eliminated by glutathione peroxidase (GPx) and catalase to water.Several lines of evidence demonstrate that oxidative stress plays an important role in the pathogenesis and development of cardiovascular diseases, including hypertension, dyslipidemia, diabetes mellitus, atherosclerosis, myocardial infraction, angina pectoris, and heart failure. [23][24][25][26] The susceptibility of vascular cells to oxidative stress is a function of the overall balance between the degree of oxidative stress and the antioxidant defense capability. Protective antioxidant mechanisms are complex and multifactorial. Antioxidant defense systems, such as SOD, GPx and catalase, scavenge ROS in the vasculature, resulting i...

Background-Aerobic exercise enhances endothelium-dependent vasodilation in hypertensive patients, patients with chronic heart failure, and healthy individuals. However, it is unclear how the intensity of exercise affects endothelial function in humans. The purpose of the present study was to determine the effects of different intensities of exercise on endothelium-dependent vasodilation in humans. Methods and Results-We evaluated the forearm blood flow responses to acetylcholine, an endothelium-dependent vasodilator, and isosorbide dinitrate, an endothelium-independent vasodilator, before and after different intensities of exercise (mild, 25% V O 2 max; moderate, 50% V O 2 max; and high, 75% V O 2 max; bicycle ergometers, 30 minutes, 5 to 7 times per week for 12 weeks) in 26 healthy young men. Forearm blood flow was measured using a mercury-filled Silastic strain-gauge plethysmograph. Twelve weeks of moderate-intensity exercise, but not mild-or high-intensity exercise, significantly augmented acetylcholine-induced vasodilation (7.5Ϯ2.4 to 11.4Ϯ5.8 mL/min per 100 mL tissue; PϽ0.05). No intensity of aerobic exercise altered isosorbide dinitrate-induced vasodilation. The administration of N G -monomethyl-L-arginine, a nitric oxide synthase inhibitor, abolished the moderate-intensity exercise-induced augmentation of the forearm blood flow response to acetylcholine. High-intensity exercise increases plasma concentrations of 8-hydroxy-2Ј-deoxyguanosine (from 6.7Ϯ1.1 to 9.2Ϯ2.3 ng/mL; PϽ0.05) and serum concentrations of malondialdehyde-modified low-density lipoprotein (from 69.0Ϯ19.5 to 82.4Ϯ21.5 U/L; PϽ0.05), whereas moderate exercise tended to decrease both indices of oxidative stress. Conclusions-These findings suggest that moderate-intensity aerobic exercise augments endothelium-dependent vasodilation in humans through the increased production of nitric oxide and that high-intensity exercise possibly increases oxidative stress. (Circulation. 2003;108:530-535.)

Background-Several nonpharmacological interventions, including exercise, are recommended in primary prevention of hypertension and other cardiovascular diseases in which the pathogenetic role of endothelial dysfunction has been suggested. We studied the effects of long-term aerobic exercise on endothelial function in patients with essential hypertension. Methods and Results-The forearm blood flow was measured by strain-gauge plethysmography. The responses of forearm vasculature to acetylcholine were smaller in the hypertensive patients than in the normotensive subjects. There was no significant difference in forearm vascular responses to isosorbide dinitrate in the normotensive and hypertensive subjects. We evaluated the effects of physical exercise for 12 weeks on forearm hemodynamics in untreated patients with mild essential hypertension who were divided randomly into an exercise group (nϭ10) and a control group (nϭ7). After 12 weeks, the forearm blood flow response to acetylcholine increased significantly, from 25.8Ϯ9.8 to 32.3Ϯ11.2 mL ⅐ min Ϫ1 ⅐ 100 mL tissue Ϫ1 (PϽ0.05), in the exercise group but not in the control group. The increase in the forearm blood flow after isosorbide dinitrate was similar before and after 12 weeks of follow-up in both groups. The infusion of N G -monomethyl-L-arginine abolished the exercise-induced enhancement of forearm vasorelaxation evoked by acetylcholine in the exercising group. In normotensive subjects also, long-term aerobic exercise augmented acetylcholine-stimulated nitric oxide release. Conclusions-These findings suggest that long-term physical exercise improves endothelium-dependent vasorelaxation through an increase in the release of nitric oxide in normotensive as well as hypertensive subjects. (Circulation. 1999;100:1194-1202.)

Paracrine signaling by bone-marrow-derived mesenchymal stem cells (MSCs) plays a major role in tissue repair. Although the production of regulatory cytokines by MSC transplantation is a critical modulator of tissue regeneration, we focused on exosomes, which are extracellular vesicles that contain proteins and nucleic acids, as a novel additional modulator of cell-to-cell communication and tissue regeneration. To address this, we used radiologic imaging, histological examination, and immunohistochemical analysis to evaluate the role of exosomes isolated from MSC-conditioned medium (CM) in the healing process in a femur fracture model of CD9 2/2 mice, a strain that is known to produce reduced levels of exosomes. We found that the bone union rate in CD9 2/2 mice was significantly lower than wild-type mice because of the retardation of callus formation. The retardation of fracture healing in CD9 2/2 mice was rescued by the injection of exosomes, but this was not the case after the injection of exosomes-free conditioned medium (CM-Exo). The levels of the bone repairrelated cytokines, monocyte chemotactic protein-1 (MCP-1), MCP-3, and stromal cell-derived factor-1 in exosomes were low compared with levels in CM and CM-Exo, suggesting that bone repair may be in part mediated by other exosome components, such as microRNAs. These results suggest that exosomes in CM facilitate the acceleration of fracture healing, and we conclude that exosomes are a novel factor of MSC paracrine signaling with an important role in the tissue repair process. STEM CELLS TRANSLATIONAL MEDICINE 2016;5:1620-1630 SIGNIFICANCEThis work focuses on exosomes, which are extracellular vesicles, as a novel additional modulator of cell-to-cell communication. This study evaluated the role of exosomes isolated from mesenchymal stem cell (MSC)-conditioned medium (MSC-CM) in the fracture-healing process of CD9 2/2 mice, a strain that is known to produce reduced levels of exosomes. Retardation of fracture healing in CD9 2/2 mice was rescued by the injection of MSC exosomes, but this was not the case after the injection of exosome-free CM. This study finds that MSC exosomes are a novel factor of MSC paracrine signaling, with an important role in the tissue repair process.

Excessive dietary phosphorus may increase cardiovascular risk in healthy individuals as well as in patients with chronic kidney disease, but the mechanisms underlying this risk are not completely understood. To determine whether postprandial hyperphosphatemia may promote endothelial dysfunction, we investigated the acute effect of phosphorus loading on endothelial function in vitro and in vivo. Exposing bovine aortic endothelial cells to a phosphorus load increased production of reactive oxygen species, which depended on phosphorus influx via sodium-dependent phosphate transporters, and decreased nitric oxide production via inhibitory phosphorylation of endothelial nitric oxide synthase. Phosphorus loading inhibited endothelium-dependent vasodilation of rat aortic rings. In 11 healthy men, we alternately served meals containing 400 mg or 1200 mg of phosphorus in a double-blind crossover study and measured flow-mediated dilation of the brachial artery before and 2 h after the meals. The high dietary phosphorus load increased serum phosphorus at 2 h and significantly decreased flow-mediated dilation. Flow-mediated dilation correlated inversely with serum phosphorus. Taken together, these findings suggest that endothelial dysfunction mediated by acute postprandial hyperphosphatemia may contribute to the relationship between serum phosphorus level and the risk for cardiovascular morbidity and mortality.

a b s t r a c tMesenchymal stem cell (MSC) transplantation is used for treatment of many diseases. The paracrine role of MSCs in tissue regeneration is attracting particular attention. We investigate the role of MSC exosomes in skeletal muscle regeneration. MSC exosomes promote myogenesis and angiogenesis in vitro, and muscle regeneration in an in vivo model of muscle injury. Although MSC exosomes had low concentrations of muscle-repair-related cytokines, a number of repair-related miRNAs were identified. This study suggests that the MSC-derived exosomes promote muscle regeneration by enhancing myogenesis and angiogenesis, which is at least in part mediated by miRNAs such as miR-494.

These findings suggest that excessive oxidative stress is involved, at least in part, in impaired endothelium-dependent vasodilatation in patients with renovascular hypertension.

Recently, mesenchymal stem cells (MSCs) were reported to migrate to tumor stroma as well as injured tissue. We examined the role of human MSCs in tumor stroma using an orthotopic nude mice model of KM12SM colon cancer. In in vivo experiments, systemically injected MSCs migrated to the stroma of orthotopic colon tumors and metastatic liver tumors. Orthotopic transplantation of KM12SM cells mixed with MSCs resulted in greater tumor weight than did transplantation of KM12SM cells alone. The survival rate was significantly lower in the mixed-cell group, and liver metastasis was seen only in this group. Moreover, tumors resulting from transplantation of mixed cells had a significantly higher proliferating cell nuclear antigen labeling index, significantly greater microvessel area and significantly lower apoptotic index. Splenic injection of KM12SM cells mixed with MSCs, in comparison to splenic injection of KM12SM cells alone, resulted in a significantly greater number of liver metastases. MSCs incorporated into the stroma of primary and metastatic tumors expressed a-smooth muscle actin and platelet-derived growth factor receptor-b as carcinoma-associated fibroblast (CAF) markers. In in vitro experiments, KM12SM cells recruited MSCs, and MSCs stimulated migration and invasion of tumor cells through the release of soluble factors. Collectively, MSCs migrate and differentiate into CAFs in tumor stroma, and they promote growth and metastasis of colon cancer by enhancing angiogenesis, migration and invasion and by inhibiting apoptosis of tumor cells.Mesenchymal stem cells (MSCs) are characterized by their ability to self-renew and differentiate into tissues of mesodermal origin, including bone, cartilage and adipose and connective tissues. Thus, they contribute to tissue regeneration.