Background-Recent studies have suggested that endogenous erythropoietin (Epo) plays an important role in the mobilization of bone marrow-derived endothelial progenitor cells (EPCs). However, it remains to be elucidated whether the Epo system exerts protective effects on pulmonary hypertension (PH), a fatal disorder encountered in cardiovascular medicine. Methods and Results-A mouse model of hypoxia-induced PH was used for study. We evaluated right ventricular systolic pressure, right ventricular hypertrophy, and pulmonary vascular remodeling in mice lacking the Epo receptor (EpoR) in nonerythroid lineages (EpoR Ϫ/Ϫ rescued mice) after 3 weeks of exposure to hypoxia. Those mice lack EpoR in the cardiovascular system but not in the hematopoietic system. The development of PH and pulmonary vascular remodeling were accelerated in EpoR Ϫ/Ϫ rescued mice compared with wild-type mice. The mobilization of EPCs and their recruitment to the pulmonary endothelium were significantly impaired in EpoR Ϫ/Ϫ rescued mice. By contrast, reconstitution of the bone marrow with wild-type bone marrow cells ameliorated PH in the EpoR Ϫ/Ϫ rescued mice. Hypoxia enhanced the expression of EpoR on pulmonary endothelial cells in wild-type but not EpoR Ϫ/Ϫ rescued mice. Finally, hypoxia activated endothelial nitric oxide synthase in the lungs in wild-type mice but not in EpoR Ϫ/Ϫ rescued mice. Conclusions-These results indicate that the endogenous Epo/EpoR system plays an important role in the recruitment of EPCs and prevents the development of PH during chronic hypoxia in mice in vivo, suggesting the therapeutic importance of the system for the treatment of PH.

Abstract-We have recently demonstrated that endogenous erythropoietin (Epo)/Epo receptor (EpoR) system plays an important protective role in hypoxia-induced pulmonary hypertension. However, it remains to be examined whether vascular EpoR system contributes to angiogenesis in response to ischemia. We examined angiogenesis in EpoR Ϫ/Ϫ -rescued mice that lack EpoR in most organs including cardiovascular system except erythroid-lineage cells. Two weeks after femoral artery ligation, blood flow recovery, activation of VEGF/VEGF receptor system, and mobilization of endothelial progenitor cells were all impaired in EpoR Ϫ/Ϫ -rescued mice as compared with wild-type (WT) mice. Bone marrow (BM) transplantation with WT-BM cells in EpoR Ϫ/Ϫ -rescued mice partially but significantly improved blood flow recovery after hindlimb ischemia. The extent of VEGF upregulation and the number of BM-derived cells in ischemic tissue were significantly less in EpoR Ϫ/Ϫ -rescued mice compared with WT mice even after BM reconstitution with WT-BM cells. Similarly, the recovery of blood flow was significantly impaired in recipient EpoR Ϫ/Ϫ -rescued mice that had been transplanted with WT-BM or EpoR Ϫ/Ϫ -rescued-BM as compared with recipient WT mice. Furthermore, the Matrigel implantation assay and aortic ring assay showed that microvessel growth in vitro was significantly reduced in EpoR Ϫ/Ϫ -rescued mice as compared with WT mice. These results indicate that vascular EpoR system also plays an important role in angiogenesis in response to hindlimb ischemia through upregulation of VEGF/VEGF receptor system, both directly by enhancing neovascularization and indirectly by recruiting endothelial progenitor cells and BM-derived proangiogenic cells. Key Words: angiogenesis Ⅲ ischemia Ⅲ progenitor cells Ⅲ VEGF Ⅲ erythropoietin P rognosis of patients with severe peripheral artery disease (PAD) still remains poor when there is no indications of revascularization therapies such as bypass surgery or percutaneous transluminal angioplasty. 1 Angiogenesis is a promising new therapeutic strategy for severe PAD, however, the effects of angiogenic therapies to improve ischemia are not durable or stable. 2-4 Hypoxia inducible factor-1 (HIF-1) is one of the important factors to induce angiogenesis, 5,6 which upregulates both erythropoietin (Epo) and VEGF. 7,8 These angiogenic cytokines play an important role in recruitment of bone marrow (BM)-derived cells to ischemic tissue, enhancing endothelial cell proliferation and migration, synthesis of extracellular matrix and resultant angiogenesis. 9 -11 Epo is a hypoxia-induced hormone that exclusively stimulates proliferation and differentiation of erythroid progenitor cells and endothelial cells. 12-15 Furthermore, systemic administration of Epo mobilizes endothelial progenitor cells (EPCs) and recruits them to ischemic tissue, 16,17 where EPCs produce abundant cytokines including VEGF and promote postnatal vasculogenesis. 18,19 Although Epo receptor (EpoR) is known to be expressed abundantly not only in BM but al...

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Circulation Journal Official Journal of the Japanese Circulation Society http://www. j-circ.or.jp he number of patients with severe angina pectoris without indications for coronary artery bypass grafting (CABG) or percutaneous coronary intervention (PCI) is rapidly increasing worldwide and their prognosis still remains poor. 1,2 Thus, it is crucial to develop new therapeutic strategies for these patients. We have previously demonstrated that extracorporeal cardiac shock wave (SW) therapy with low-energy SW (≈10% of the energy density used for urolithiasis) ameliorates myocardial ischemia and dysfunction in a porcine model of chronic myocardial ischemia in vivo. 3, 4 We subsequently demonstrated in an open trial that our SW therapy effectively improved chest pain symptoms and exercise tolerance without any adverse effects in 9 patients with severe angina pectoris. 3,5 In the present study, to further confirm the effectiveness and safety of our SW therapy, we performed a double-blind placebo-controlled trial in patients with severe angina pectoris. MethodsWe enrolled 8 consecutive patients with severe angina pectoris who already had undergone CABG or PCI, but who no longer had further indications for these therapies even though they still suffered from stable effort angina under intensive medication (M/F, 5/3; age, 70±3 years) (Table).The patients were treated with one series of placebo and the SW therapy in a double-blind and cross-over manner with an interval of 3 months. One series of therapy comprised 3 sessions per week. Throughout the study, the patient and the doctor in charge were not informed of the type of therapy. We performed the SW therapy (200 shoots/spot at 0.09 mJ/mm 2 for 40-60 spots per session; Modulith SLC, Storz Medical, Kreuzlingen, Switzerland) as described previously. 3,5 As placebo, the patients underwent the procedure of SW therapy but without irradiation. The patients were followed-up for 3 months after completion of the therapy. We evaluated symptoms using the Canadian Cardiovascular Society (CCS) class score, the patient's requirement for nitroglycerin, 5 exercise tolerance in a 6-min walk, and a cardiopulmonary exercise test, and cardiac function assessed by MRI (Achieva 1.5 T, Philips, Eindhoven, Netherlands). The left ventricular ejection fraction (LVEF) was measured using contiguous short-axis slices obtained by cine MRI; end-diastolic and end-systolic endocardial traces were used to determine end-diastolic and end-systolic left ventricular (LV) volumes, respectively. We also evaluated the number of circulating progenitor cells in peripheral blood by FACS analysis 2 days before the 1 st session and 1 h after the 3 rd session in 7 of the 8 patients Background: Low-energy shock wave (SW) therapy has improved myocardial ischemia in both a porcine model and in patients with severe angina pectoris.