Regulation of hematopoiesis through adhesion receptors.

Normal steady-state hematopoiesis takes place in the bone marrow microenvironment. Soluble factors as well as contact interactions between the hematopoietic cells and the marrow microenvironment dictate the fate of hematopoietic stem cells and progenitors. Over the last decade it has become clear that cell-cell and cell-extracellular matrix interactions through adhesion receptors play a major role in the hematopoietic process. They are required for the residence of stem cells and progenitors in the marrow, as well as for homing of stem and progenitor cells to the marrow in the setting of stem cell transplantation. Furthermore, adhesion receptors play an important role in regulation of cell behavior, either through direct activation of signal pathways important for cell survival, cell growth, and cell fate decision-making processes, or by modulating responses to growth factors. Insights in the abnormalities seen in these interactions in diseases of the hematopoietic system will help to develop better therapeutic strategies based on the pathogenesis of these diseases.