The course of various pathological conditions relies on the mobilization of stem cells and partially differentiated progenitor cells. Bone marrow transplantation studies have demonstrated that medullary hematopoietic and endothelial progenitors can undergo mobilization and trafficking. While the ability of the bone marrow to boost its resources in fighting disease or repairing injury declines with age, other organs have surfaced as reservoirs of various progenitor cell populations. This chapter discusses our current understanding of non-bone marrow-derived progenitor pools, focusing on mesenchymal stem cells. The evidence for the extramedullary progenitor mobilization, with a specific emphasis on white adipose tissue, is presented.
