Hematopoietic stem cell niches

The graphic depicts endosteal and perivascular niches for hematopoietic stem cells (HSCs); it is not known whether HSCs migrate between these niches. The niches regulate HSC quiescence, self-renewal, mobilization, and differentiation. Cell-cell contact, secreted cytokines, and extracellular matrix (ECM) factors all play roles. Some of the secreted factors are shown. ECM factors include fibronectin, hyaluronic acid, collagen, laminin, glycosaminoglycans, heparan sulfate, and chondroitin sulfate.