Hematopoietic stem cell trafficking: regulated adhesion and attraction to bone marrow microenvironment.

Hematopoiesis takes place preferentially within bone cavities, suggesting that bone-derived factors contribute to blood formation. Hematopoietic stem and progenitor cells (HSPCs) can be mobilized from the bone marrow parenchyma to the circulation by various agonists whose common downstream action leads to alteration in the expression or function of the chemokine CXCL12 and adhesion molecules mediating migration. Granulocyte colony-stimulating factor (G-CSF), the most prevalent drug used to mobilize HSPCs, dramatically suppresses osteoblast function. Recent studies suggest that G-CSF-mediated suppression requires signals from the sympathetic nervous system (SNS). This review summarizes emerging concepts thought to contribute to stem cell migration.