which are involved in systemic regulation. These niches act as stem cells shelters
where they maintain quiescence and self-renewal (Ema 2012).
12.3 Components of Stem Cell Niche
12.3.1 Extra-Cellular Matrix (ECM)
ECM is the essential component of the stem cell niche and plays an important role in
regulating the stem cell fate (Frantz et al. 2010; Xie and Li 2007). ECM provides
space and physical support to stem cells to anchor and orient (Kerever et al. 2007).
Understanding and analyzing the structure and composition of ECM is important to
mimic its function to make the products for synthetic cell culture. One approach to
study the ECM structure and its organization is through tissue decellularization
process. Decellularization eliminates the cellular components from the tissue leaving
the ECM intact which can be further studied microscopically (Badylak et al. 2011;
Baptista et al. 2011; Batchelder et al. 2015; Moorman et al. 2003; Sabetkish et al.
2014).
12.3.2 Surface Receptors Proteins
Anchorage dependent cells interact with their ECM by means of cell surface
receptors proteins, namely integrins, selectins, and cadherins. Integrins are
heterodimeric transmembrane molecules (α and β subunits) involved in cell adhesion, migration, differentiation, and even in apoptosis (Le Gall et al. 1998). The
commonly expressed subunits in most human cells are β1, α5, and αV. Integrin are
expressed ubiquitously in almost all the stem cells. Integrins have the ability to bind
directly to the ECM proteins such as laminin, collagen, vitronectin, and fibronectin.
(Assoian 1997).
Cadherins, the second type of surface receptor proteins, are regulate cell–cell
interactions (Chen et al. 2013). The subunit E (epithelial) cadherin (CDH1) is best
studied and is involved in adhesion of stem cell niche. Maintenance of the selfrenewal potential of stem cells and retention of nondifferentiated cells in the niche
are mediated via interaction with E-cadherin (Moore and Lemischka 2006).
N (neural)-cadherin (CDH2) which is another subtype of cadherins is expressed
during the neuronal plate development. In the HSC niche, both HSCs and osteoblasts
express N-cadherin. N-cadherin in multiple studies has also been reported to affect
the self-renewal potential of HSCs in the niche (Moore and Lemischka 2006).
However, few studies are emerging which counter indicate this by showing that
the expression of N-cadherin in HSCs is not necessary for niche function (Kiel et al.
2009).
The satellite stem cells in the skeletal muscle niche express a third subtype of
cadherin molecule M (myotubule)-cadherin (CDH15). Which is expressed at the site
facing the muscle fibers (Moore and Lemischka 2006).
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A. Kumar et al.
where they maintain quiescence and self-renewal (Ema 2012).
12.3 Components of Stem Cell Niche
12.3.1 Extra-Cellular Matrix (ECM)
ECM is the essential component of the stem cell niche and plays an important role in
regulating the stem cell fate (Frantz et al. 2010; Xie and Li 2007). ECM provides
space and physical support to stem cells to anchor and orient (Kerever et al. 2007).
Understanding and analyzing the structure and composition of ECM is important to
mimic its function to make the products for synthetic cell culture. One approach to
study the ECM structure and its organization is through tissue decellularization
process. Decellularization eliminates the cellular components from the tissue leaving
the ECM intact which can be further studied microscopically (Badylak et al. 2011;
Baptista et al. 2011; Batchelder et al. 2015; Moorman et al. 2003; Sabetkish et al.
2014).
12.3.2 Surface Receptors Proteins
Anchorage dependent cells interact with their ECM by means of cell surface
receptors proteins, namely integrins, selectins, and cadherins. Integrins are
heterodimeric transmembrane molecules (α and β subunits) involved in cell adhesion, migration, differentiation, and even in apoptosis (Le Gall et al. 1998). The
commonly expressed subunits in most human cells are β1, α5, and αV. Integrin are
expressed ubiquitously in almost all the stem cells. Integrins have the ability to bind
directly to the ECM proteins such as laminin, collagen, vitronectin, and fibronectin.
(Assoian 1997).
Cadherins, the second type of surface receptor proteins, are regulate cell–cell
interactions (Chen et al. 2013). The subunit E (epithelial) cadherin (CDH1) is best
studied and is involved in adhesion of stem cell niche. Maintenance of the selfrenewal potential of stem cells and retention of nondifferentiated cells in the niche
are mediated via interaction with E-cadherin (Moore and Lemischka 2006).
N (neural)-cadherin (CDH2) which is another subtype of cadherins is expressed
during the neuronal plate development. In the HSC niche, both HSCs and osteoblasts
express N-cadherin. N-cadherin in multiple studies has also been reported to affect
the self-renewal potential of HSCs in the niche (Moore and Lemischka 2006).
However, few studies are emerging which counter indicate this by showing that
the expression of N-cadherin in HSCs is not necessary for niche function (Kiel et al.
2009).
The satellite stem cells in the skeletal muscle niche express a third subtype of
cadherin molecule M (myotubule)-cadherin (CDH15). Which is expressed at the site
facing the muscle fibers (Moore and Lemischka 2006).
254
A. Kumar et al.