Critical Roles of Reactive Oxygen Species in Age-Related Impairment in Ischemia-Induced Neovascularization by Regulating Stem and Progenitor Cell Function

Table 2

Summary of distinctive features of stem and progenitor cells.

Cell type	Features and functions
Hematopoietic stem cells (HSCs)
Lin−/CD34+/AnV−	Lineage depleted, viable (annexin negative), undifferentiated, and primitive multipotential hematopoietic stem cells
	ROS: self-renewal, ↑telomerase
	ROS: limited self-renewal, ↑p16Ink4a, ↑p38/MAPK
Lin−/CD34+/CD38−	Lineage depleted, undifferentiated, and primitive multipotential hematopoietic stem cells
	ROS sensitive; Serial transplantation of Lin−/CD34+/CD38− leads to DNA damage and premature senescence
Lin−/CD34+/CD38+	Lineage depleted, primitive hematopoietic/lymphoid stem cells; Less sensitive to ROS elevation and resistant to oxidative DNA damage
Scal+/c-kit+/Lin−	Primitive stem cells; Mobilized into circulation via increasing ROS in response to ischemia
Embryonic stem cells (ES)
	Active in proliferation and differentiation
	Require low levels of H2O2 to trigger cardiomyogenesis
	↑Nox1, ↑Nox2, and ↑Nox4
	↓Antioxidative and stress resistance genes
Progenitor cells
Endothelial progenitor cells (EPCs)	Ex vivo cultured for 4 days; ↑MnSOD, ↑catalase, and ↑glutathione peroxides; Stable intracellular ROS levels; Resistance to ROS-induced apoptosis
Late-outgrowth endothelial cells (OECs)	Ex vivo cultured for 2-3 weeks; ↑MnSOD; Similar levels of CuZnSOD and catalase compared to mature endothelial cells