Bone marrow homing: the players, the playfield, and their evolving roles

Although homing of hematopoietic cells to the bone marrow was described as a functional concept several decades ago, the analysis of its components and the molecular pathways involved remains an ongoing challenge. Because of the biologic and clinical significance of homing, a resurgence of studies delving into the mechanistic and molecular aspects of homing is appearing. These recent studies, highlighted in this brief review, emphasize newly appreciated roles of some known regulators and their interacting partners in homing, although some novel regulators also seem to enter the scene. The homing field still has disparities in experimental design and evaluation of data; however, the ever-expanding search for new information, together with the application of novel technologies, especially when combinations of approaches are used, will certainly bring our understanding of homing to a new level.