fig1

Figure 1. The HSC niche. Under normal conditions, HSCs reside near the bone marrow vessels, either endosteal arterioles or sinusoids. Endothelial cells, as well as mesenchymal stem cell populations (Nestin-GFP NG2⁺ cells and CAR cells) promote the maintenance of HSCs. The endosteal niche contributes to the creation of a microenvironment with higher pO₂ levels; the type H vessels constituting the endosteal niche display low permeability and create an environment low in reactive oxygen species (ROS), promoting HSC quiescence. The sinusoidal niche contributes to the creation of a microenvironment with lower pO₂ levels; the L vessels constituting the sinusoidal niche have a high permeability and create a microenvironment high in ROS, promoting HSC proliferation and differentiation. HSC: hematopoietic stem cell