title: Stem cell mobilization by hyperbaric oxygen.
abstract: We hypothesized that exposure to hyperbaric oxygen (HBO(2)) would mobilize stem/progenitor cells from the bone marrow by a nitric oxide (*NO) -dependent mechanism. The population of CD34(+) cells in the peripheral circulation of humans doubled in response to a single exposure to 2.0 atmospheres absolute (ATA) O(2) for 2 h. Over a course of 20 treatments, circulating CD34(+) cells increased eightfold, although the overall circulating white cell count was not significantly increased. The number of colony-forming cells (CFCs) increased from 16 +/- 2 to 26 +/- 3 CFCs/100,000 monocytes plated. Elevations in CFCs were entirely due to the CD34(+) subpopulation, but increased cell growth only occurred in samples obtained immediately posttreatment. A high proportion of progeny cells express receptors for vascular endothelial growth factor-2 and for stromal-derived growth factor. In mice, HBO(2) increased circulating stem cell factor by 50%, increased the number of circulating cells expressing stem cell antigen-1 and CD34 by 3.4-fold, and doubled the number of CFCs. Bone marrow *NO concentration increased by 1,008 +/- 255 nM in association with HBO(2). Stem cell mobilization did not occur in knockout mice lacking genes for endothelial *NO synthase. Moreover, pretreatment of wild-type mice with a *NO synthase inhibitor prevented the HBO(2)-induced elevation in stem cell factor and circulating stem cells. We conclude that HBO(2) mobilizes stem/progenitor cells by stimulating *NO synthesis.
authors.affiliation: Institute for Environmental Medicine, University of Pennsylvania, Philadelphia, PA 19104-6068, USA. sthom@mail.med.upenn.edu
authors.forename: Stephen R
authors.initials: SR
authors.lastname: Thom
authors.forename: Veena M
authors.initials: VM
authors.lastname: Bhopale
authors.forename: Omaida C
authors.initials: OC
authors.lastname: Velazquez
authors.forename: Lee J
authors.initials: LJ
authors.lastname: Goldstein
authors.forename: Lynne H
authors.initials: LH
authors.lastname: Thom
authors.forename: Donald G
authors.initials: DG
authors.lastname: Buerk
mesh_terms: D000818:Animals; D018952:Antigens, CD34 / Q000378:metabolism*; D002465:Cell Movement / Q000502:physiology; D049109:Cell Proliferation; D002478:Cells, Cultured; D005260:Female; D006412:Hematopoietic Stem Cells / Q000166:cytology / Q000502:physiology*; D006801:Humans; D006931:Hyperbaric Oxygenation / Q000379:methods*; D008297:Male; D051379:Mice; D018345:Mice, Knockout; D008875:Middle Aged; D009569:Nitric Oxide / Q000378:metabolism*; D010100:Oxygen / Q000378:metabolism*
chemical_list: D018952:Antigens, CD34; D009569:Nitric Oxide; D010100:Oxygen