Reactive oxygen species regulate the quiescence of CD34-positive cells derived from human embryonic stem cells.

AIMS: Reactive oxygen species (ROS) are involved in a wide range of cellular processes. However, few studies have examined the generation and function of ROS in human embryonic vascular development. In this study, the sources of ROS and their roles in the vascular differentiation of human embryonic stem cells (hESCs) were investigated. METHODS AND RESULTS: During vascular differentiation of hESCs, CD34(+) cells had quiescence-related gene expression profiles and a large fraction of these cells were in G0 phase. In addition, levels of ROS, which were primarily generated through NOX4, were substantially higher in hESC-derived CD34(+) cells than in hESC-derived CD34(-) cells. To determine whether excess levels of ROS induce quiescence of hESC-derived CD34(+) cells, ROS levels were moderately reduced using selenium to enhance antioxidant activities of thioredoxin reductase and glutathione peroxidase. In comparison to untreated CD34(+) cells, selenium-treated CD34(+) cells exhibited changes in gene expression that favoured cell cycle progression, and had a greater proliferation and a smaller fraction of cells in G0 phase. Thus, selenium treatment increased the number of hESC-derived CD34(+) cells, thereby enhancing the efficiency with which hESCs differentiated into vascular endothelial and smooth muscle cells. CONCLUSION: This study reveals that NOX4 produces ROS in CD34(+) cells during vascular differentiation of hESCs, and shows that modulation of ROS levels using antioxidants such as selenium may be a novel approach to increase the vascular differentiation efficiency of hESCs.

Activation of vasculogenic progenitor cells by ent-16α,17-dihydroxy-kauran-19-oic acid.

Vasculogenic progenitor cells (VPCs) circulate in the blood and have the ability to differentiate into endothelial cells that make up the lining of blood vessels. Therefore, VPC transplantation is a new strategy for the treatment of ischemic diseases. Because priming/preconditioning of VPCs before transplantation enhances their regenerative potential, the present study investigated whether ent-16α,17-dihydroxy-kauran-19-oic acid (DHK) isolated from Siegesbeckia pubescens could stimulate/activate VPCs in vitro. Therefore, the effect of DHK (1-100 µM concentration) on the proliferation, migration, and tube forming of VPCs was examined in various systems, and related signaling pathways were identified. DHK treatment significantly increased the proliferation, migration, and tube formation of VPCs in a dose-dependent manner. Phosphorylation of extracellular signal-regulated kinase (ERK)1/2 and Akt was significantly increased by DHK, but chemical inhibitors against ERK1/2 (U0126) and Akt (LY294002) significantly attenuated DHK-enhanced proliferation, migration, and tube formation of VPCs. Collectively, these results indicated that DHK shows promise as a novel VPC primer/activator.