Self-renewal and differentiation of hematopoietic stem cells.

Hematopoietic stem cells (HSCs) are characterized by their ability to self-renew and differentiate into all blood lineage cells. The fate decisions of HSCs (self-renewal versus differentiation) are made through the process of cell division and are often compared to "birth" and "death". Stem cells give rise to undifferentiated stem cells (birth) or differentiate into progenitor cells (death). This process is regulated by asymmetric/symmetric divisions of HSCs. It has been proposed that fate determination occurs as a stochastic process and that individual stem cell dynamics are randomly regulated. The behavior of HSCs is known to be regulated by the cell intrinsic factor and extrinsic (microenvironmental) stimuli. Therefore, it is possible that the signals from a specific microenvironment (niche) have the potential to control or modulate stem cell dynamics. This review focuses on the functions of the HSC niche and the application of single cell analysis for understanding the mechanisms underlying the HSC decision-making process.