Biomedical Engineering Reference
In-Depth Information
It has been demonstrated that many adhesion molecules are expressed by HSCs
Based on their structures and manner of adhesion, the adhesion molecules
expressed by HSCs are divided into at least i ve families: cadherin family, integrin
family, immunoglobulin superfamily, CD44 family and sialomucin family. In this
section, we show representative adhesion molecules on HSCs.
Fig. 1C
Regulation of self-renewal and dif erentiation of HSCs in their niche: Interaction
between HSCs and niche cells through cell surface molecules. h e maintenance of stemness, self-
renewal and dif erentiation of HSCs are controlled by the interaction with niche cells.
N-cadherin is expressed by both HSCs and the niche cells. Homophilic binding
of the molecules induces the adhesion, stretching and migration of HSCs, because
the intracellular domain of N-cadherin is associated with β catenin connecting
with the actin cytoskeleton. Although many functions of N-cadherin have been
proposed, the main function of this molecule might be to physically associate
HSCs with niche cells at the proper position.
Integrins (VLA-4, VLA-5 and LFA-1) can interact with cell adhesion molecules
belonging to the immunoglobulin superfamily (VCAM-1 and ICAM-1) expressed
by vascular endothelial cells and niche cells. h e trai cking of HSCs from the
blood to the bone marrow cavity and their subsequent adhesion to niche cells (this
process is designated as homing) can thus be induced. Integrins can also interact
with extracellular matrix components (e.g., collagen, laminin and i bronectin).
Such interactions between integrins and their ligands are important for the
trai cking and homing of HSCs during embryogenesis and adult hematopoiesis,
since HSCs obtained from integrin-dei cient fetal or adult mice have a normal
dif erentiation capacity, but cannot seed fetal or adult hematopoietic tissues
(Potocnik
et al.
2000).
CD34 (a member of the sialomucin family, mucosialin, HCPA-1) is a well-
known HSC/HPC-marker and has been used for HSC/HPC-purii cation in mice
and humans, although the biological signii cance of the molecule remains to be
