Defining the hematopoietic stem cell niche: the chicken and the egg conundrum
Understanding the in vivo regulation of hematopoietic stem cells (HSCs) will be critical to identifying key factors involved in the regulation of HSC self-renewal and differentiation. The niche (microenvironment) in which HSCs reside has recently regained attention accompanied by a dramatic increase in the understanding of the cellular constituents of the bone marrow HSC niche. The use of sophisti