ABSTRACT
Recently, there has been great progress in the isolation of tissue-specifi c stem cells. Hematopoietic stem cells (HSCs) have been most extensively studied, and highly purifi ed HSCs can now be obtained. Th e niche of the HSCs is also well elucidated. Th e HSCs are known to express adhesion molecules of cadherin family (N-cadherin), integrin family (VLA-4 and VLA-5, etc.), immunoglobulin superfamily (ICAM-1 and VCAM-1, etc.), CD44 family and sialomucin family (CD34), by which the HSCs interact with the niche cells. Mesenchymal stem cells (MSCs) have the capacity to diff erentiate into mesodermal, endodermal and ectodermal lineage cells. Th e cells can proliferate extensively in vitro and have the important ability to suppress the proliferation of lymphocytes. Th e approach by which MSCs are used for the treatment of graft -versus-host diseases is now gaining support. It is known that MSCs express the immunoglobulin superfamily (ICAM-1, ICAM-3, VCAM-1 and ALCAM), CD44 and P-selectin. Th e purifi cation of neural stem cells (NSCs), hepatic stem cells (HpSCs) and hair follicle stem cells (HFSCs) remains inadequate despite having been extensively studied. Cadherin and integrin molecules are expressed by NSCs, HpSCs and HFSCs and contribute to the maintenance of stemness, the proliferation and the migration of these stem cells. Th e fi nal goal of regenerative medicine is to isolate stem cells from their niche, expand them in vitro and implant them into patients. For this purpose, it is necessary to understand the mechanism by which the stem cells localize in their niche and how their self-renewal and diff erentiation are regulated. Th us, the characterization of adhesion molecules on stem cells will provide insights for a wide range of clinical applications.
