Principles of stem cell biology and cancer: future applications and therapeutics. Edited by T. Regad, T. J. Sayers and R. C. Rees. John Wiley & Sons (2015)
Part I. Stem Cells
Certain tissues, such as skin, gut and, as discussed here, the haematopoietic system, have a high turnover of cells and need to be regenerated continuously. To accomplish this, the bone marrow contains cells called HSCs that are capable of regenerating all the components of the haematopoietic system. The essential property of HSCs (and other stem cells) is the ability to choose between self-renewal and differentiation into one of several lineages. Self-renewal, according to the strictest definition, means that cells have the ability to remain present as productive stem cells indefinitely. While indefinite renewal is difficult to establish experimentally, HSCs are present and function for the lifetime of an organism. Progenitor cells, on the other hand, may retain the potential for significant expansion, and may have the ability to choose from one of several cell fates, but are unable to remain present as productive cells for very long; that is, they can’t self-renew. The essential cellular component in haematopoietic cell transplantation in the form of bone marrow, mobilized peripheral blood or UCB transplantation is HSCs, as they alone have the potential to engraft and produce all the haematopoietic cells needed for life. While other cells in the graft can play important roles, only HSCs can produce all of the cells needed to allow the haematopoietic system to function long-term.