Abstract
We hypothesized that oxidative stress from hyperbaric oxygen (HBO
2
, 2.8 ATA for 90 min daily) exerts a trophic effect on vasculogenic stem cells. In a mouse model, circulating stem/progenitor cell (SPC) recruitment and differentiation in subcutaneous Matrigel were stimulated by HBO
2
and by a physiological oxidative stressor, lactate. In combination, HBO
2
and lactate had additive effects. Vascular channels lined by CD34
+
SPCs were identified. HBO
2
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 were abrogated by
N
-acetyl cysteine, dithioerythritol, oxamate, apocynin, U-0126, neutralizing anti-vascular endothelial growth factor, or anti-stromal cell-derived factor-1 antibodies, and small inhibitory RNA to Trx reductase, lactate dehydrogenase, gp91
phox
, HIF-1 or -2, and in mice conditionally null for HIF-1 in myeloid cells. By causing an oxidative stress, HBO
2
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.
