Hyperbaric oxygen stimulates vasculogenic stem cell growth and differentiation in vivo

We hypothesized that oxidative stress from hyperbaric oxygen (HBO2, 2.8 ATA for 90 min daily) exerts a trophic effect on vasculogenic stem cells. Ina mouse model, circulating stem/progenitor cell (SPC) recruitment and differentiation in subcutaneous Matrigel were stimulated by HBO2 and by a physiological oxidative stressor, lactate. In combination, HBO2 and lactate had additive effects. Vascular channels lined by CD34 SPCs were identified. HBO2 and lactate accelerated channel development, cell differentiation based on surface marker expression, and cell cycle entry. CD34 SPCs exhibited increases in thioredoxin-1 (Trx1), Trx reductase, hypoxia-inducible factors (HIF)-1, -2, and -3, phosphorylated mitogen-activated protein kinases, vascular endothelial growth factor, and stromal cell-derived factor-1. Cell recruitment to Matrigel and protein synthesis responses wereabrogated by N-acetyl cysteine, dithioerythritol, oxamate, apocynin, U-0126, neutralizing anti-vascular endothelial growth factor, or antistromal cell-derived factor-1 antibodies, and small inhibitory RNA to Trx reductase, lactate dehydrogenase, gp91phox, HIF-1 or -2, and in mice conditionally null for HIF-1 in myeloid cells. By causing an oxidative stress, HBO2 activates a physiological redox-active autocrine loop in SPCs that stimulates vasculogenesis. Thioredoxin system activation leads to elevations in HIF-1 and -2, followed by synthesis of HIF-dependent growth factors. HIF-3 has a negative impact on SPCs.