The human blood system--in particular the hematopoietic stem cell (HSC) or blood stem cell--has been extensively studied; however, the exact mechanics behind how an HSC undergoes self-renewal remains unclear. Self-renewal is the process by which an HSC grows and divides to create an exact replica of itself, as well as cells different from itself (i.e. one or more specific types of blood cells that cannot renew).

"It's important that we understand the mechanics behind self-renewal because it's responsible for the life-long maintenance of the human blood system," explains OCI study-lead Dr. Norman Iscove.

His recent study findings identified a new population of HSCs, known as 'intermediate term' cells that persisted for a period of 6-8 months before becoming extinct or losing their ability to self-renew. The team used a mouse model and genetic approach to their investigations that have provided important information towards our understanding of stem cells.

"It is important for investigators to be able to distinguish between the different types of cells in the blood system," explains Dr. Iscove. "We need to be able to separate short-, intermediate- and long-term cells from one another so that HSC studies examine those cells capable of maintaining the blood system which is critically important for stem cell transplantation."

Patricia Benveniste, Catherine Frelin, Salima Janmohamed, Mary Barbara, Robert Herrington, Deborah Hyam, Norman N. Iscove. Cell Stem Cell 8 January 2010; 6(1):48-58 [epub ahead]. [Pubmed abstract]. Research supported by the Terry Fox Foundation, the Canadian Institutes of Health Research, the Stem Cell Network, the National Institutes of Health, and the McEwen Centre for Regenerative Medicine.