Biomedical Engineering Reference
In-Depth Information
Recently, there has been great progress in the isolation of tissue-specii c stem
cells. Hematopoietic stem cells (HSCs) have been most extensively studied, and
highly purii ed HSCs can now be obtained. h e niche of the HSCs is also well
elucidated. h 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 dif erentiate into mesodermal, endodermal and
ectodermal lineage cells. h e cells can proliferate extensively
in vitro
and have
the important ability to suppress the proliferation of lymphocytes. h e approach
by which MSCs are used for the treatment of grat -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. h e purii 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.
h e i 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 dif erentiation are regulated. h us, the
characterization of adhesion molecules on stem cells will provide insights for a
wide range of clinical applications.
INTRODUCTION
Pluripotent stem cells are dei ned as cells that have the ability to self-renew
(generating new pluripotent stem cells) and to dif erentiate into multilineage cells.
Pluripotent stem cells can be found in special areas in tissues and organs, where
their stemness is maintained and controlled. Such areas are called niches. h e stem
cells need a niche as a scaf old for their self-renewal and dif erentiation. In the
niche, stem cells receive signals through their interaction with niche cells: adhesion
molecules, cytokines produced by the niche cells and cell matrix molecules (such
as collagen, laminin and teneicin). Several molecules (e.g., Notch-Jagged system
and Tie2/angiopoietin system) play an important role in stem cell dormancy.
In recent decades, many tissue-specii c stem cells have been purii ed and
identii ed in adult humans and animals, including hematopoietic stem cells
(HSCs), mesenchymal stem cells (MSCs), neural stem cells (NSCs), hepatic stem
cells (HpSCs), and hair follicle stem cells (HFSCs). Many other tissue-specii c
stem cells have also been identii ed and characterized. However, the problem
of insui cient analysis of adhesion molecules remains in the case of some stem
cells. In this chapter, we provide an overview and a description of our current
