Endothelial Progenitor Cells Are Rapidly Recruited to Myocardium and Mediate Protective Effect of Ischemic Preconditioning via “Imported” Nitric Oxide Synthase Activity

Abstract

Background-The function of bone marrow-derived endothelial progenitor cells (EPCs) in repair of ischemic tissue has been the subject of intense scrutiny, and the capacity of these cells to contribute significantly to new blood vessels remains controversial. The possibility that EPCs could act as reservoirs of cytokines has been implied by several observations; however, a specific role for cytokine delivery has not been identified. Methods and Results-We performed a series of experiments that revealed the rapid recruitment of EPCs to the myocardium by very short periods of ischemia, so-called ischemic preconditioning. The recruited EPCs express an array of potentially cardioprotective cytokines including nitric oxide synthase isoforms. Bone marrow transplantation studies, using donor marrow null for nitric oxide synthase isoforms, revealed that both endothelial and inducible nitric oxide synthase derived from bone marrow cells play essential roles in the cardioprotective effect that normally occurs after ischemic preconditioning. Conclusions-These findings provide novel insights about the role of bone marrow-derived cells in ischemic preconditioning and also reveal that distinct mechanisms regulate recovery after ischemia-reperfusion and chronic ischemic injury.

Tumor Necrosis Factor-α Receptor p75 Is Required in Ischemia-Induced Neovascularization

“…Furthermore, animal studies have shown that transplanted BM cells or BM-derived EPCs contribute to the processes of neovascularization 41,44 and the development of collateral vessels that contribute to more rapid recovery of blood flow in the ischemic areas. 13,23,[41][42][43] Our BM transplantation data showing that transplantation of young WT but not p75KO BM MNCs into old p75KO mice rescued ischemic limbs from autoamputation suggest that ischemia-induced neovascularization and mobilization of EPCs from BM are mediated, at least in part, by TNFR2/p75 signaling.…”

Synergistic effect of adipose-derived stem cell therapy and bone marrow progenitor recruitment in ischemic heart

“…MI was induced by ligating a left anterior descending (LAD) coronary artery as described previously. 19,20 Briefly, after the fourth to fifth intercostals space was opened, the heart was exteriorized, and the pericardium was incised. Thereafter, the heart was held with forceps, and MI was induced by ligating the LAD coronary artery at just the proximal site of the bifurcation of diagonal branch with a 7-0 (for mice)/6-0 (for rats) nylon suture.…”

“…The tissues were embedded in OCT compound (Sakura FineTek, Japan) and sectioned at 1 mm for rats and 0.5 mm for mice just below the LAD ligation level at 5-mm thickness as described previously. 19 To measure fibrosis area, Masson's Trichrome staining was performed, and the fibrosis area (blue) was measured and calculated as the percent of the area of fibrosis to entire cross-sectional area of LV by using the NIH Image J 1.42 software and Adobe Photoshop CS4 (Adobe Systems, San Jose, CA, USA) software.…”

“…The procedure of BMT was performed as described previously with some modifications. 19 Briefly, The background/recipient mice were lethally irradiated for BM ablation with 9.0 Gy and received 5 million of donor BM mononuclear cells. At 4-6 weeks after BMT, by which time the BM of the recipient mice was reconstituted, MI surgery with hMADSCs (1 Â 10 5 /20 ml PBS) or PBS (20 ml) injection was performed.…”

“…19 Briefly, hMADSCs (5 Â 10 4 cells per well) were seeded onto upper chambers in 24-well culture plates and lower chambers were filled with DMEM with 20% FBS followed by incubation for 6 h at 371C in 1, 5, and 20% O 2 /5% CO 2 . Migrated cells were stained with DAPI and counted in randomly selected four HPFs ( Â 200, 0.15 mm 2 per HPF) per chamber under a fluorescent microscope and averaged.…”