Give Me Air: Hematopoietic Stem Cells in Hypoxic Niches

Tokyo, Japan -

It is generally known that early, non-proliferative stem cell reserves are sequestered in hypoxic niches.

In a recent paper (Kubota et al. Bone marrow long label-retaining cells reside in the sinusoidal hypoxic niche. Biochem Biophys Res Commun. 2007 Nov 26) histological assessment was performed of cells in hypoxic niches of the bone marrow. The investigators analyzed BrdU label retaining cells, which essentially are cells in the bone marrow that proliferate very slowly. It was found that these cells preferentially are localized in the sinusoidal areas that are known to be hypoxic, and distal from the normoxic "vascular niche".

Interestingly, myeloablation by 5-FU causes the BrdU retaining cells to upregulate c-kit expression and to enter cell cycle.

These data suggest that bone marrow stem cells are found in hypoxic areas which can be activated to proliferate when needed. These concepts will be interesting to assess in other systems, such as in the CNS, where some evidence exists that hypoxia is associated with self-renewal or differentiation.