Maintenance of Adult Stem Cells: Role of the Stem Cell Niche

Self-renewing stem cells are maintained in functionally specific microenvironments that are termed niches. Optimum combination of intrinsic programs and extrinsic stimuli from niches is essential for maintaining stem cell quiescence and for proper mobilization and differentiation. The most advanced imaging technologies allow the clearer real-time visualization of the behavior of hematopoietic stem cells in living animal. Functions of niche factors, such as adhesion molecules and cytokines, are well studied. Concentration levels of local oxygen and reactive oxygen species also affect the fate of stem cells in their niches. Analysis of niche regulation will lead to a better understanding of stem cell behavior. Moreover, altering the cancer stem cell fate through modification of the niche regulation may be one of the candidates for new therapeutic strategies for diseases such as chemoresistant leukemia.