The Homing of Hematopoietic Stem Cells to the Bone Marrow

In this article, the author discusses some of the most notable aspects of the work of Mehdi Tavassoli and others on the homing of intravenously transplanted hematopoietic stem cells to the marrow. It is well-recognized that homing of stem cells is a highly selective process, perhaps similar to the homing of lymphocytes to lymphoid tissues. The nature of the selectivity of stem cell homing is unclear, however, and may be mediated through a specific homing receptor or through a method of selective capture, retainment, or survival advantage afforded by the marrow. In this article, the focus is on current research in the identification of a specific homing receptor, the potential regulation of such a receptor by cytokines, the homing phenomenon as a multi-step process, and secondary adhesive interactions mediated by known adhesive molecules. These interactions may serve to strengthen the initial recognition and engraftment of stem cells within the hematopoietic compartment of the marrow.