Constituent components of the hematopoietic stem cell niche

Stem cell fate is influenced by specialized microenvironments that remain poorly defined in mammals. Hematopoietic stem cells reside in a specialized niche that regulates their abundance and fate. Components of the niche have generally been defined in terms of cells and signaling pathways. Osteoblastic cells represent a regulatory cellular component of the hematopoietic stem cell niche that influences stem cell function through Notch activation. We define a role for a matrix glycoprotein, osteopontin (OPN), as a non-cellular constraining factor on hematopoietic stem cells within the bone marrow microenvironment.…