DEPARTAMENTO DE CIÊNCIAS DA VIDA ... - Estudo Geral

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There are many advantages in using UCM as an alternative source of human MSCs
when comparing to BM and other adult tissues. Because the umbilical cord (UC)
physiologically supports development of the embryo only throughout fetal life until
birth, it is normally discarded at birth, being a tremendous waste, since the procedure
of collection is painless, non-invasive and harmless either to the mother or the
newborn. This procedure can increase the potential donors of MSCs (Weiss and Troyer
2006) and diminish the ethical and clinical issues (Malgieri et al., 2010). Moreover,
those are not the only positive aspects, there is also the fact that MSCs isolated from
the UC seem to be more primitive, have greater expansion capacity in vitro and shorter
doubling time than MSCs isolated from adult tissues (Park et al.,2006). Despite not
being as immature as embryonic stem cells (ESCs), UCM- and UCB-MSCs have a big
differentiation potential, being able to differentiate into cell types with characteristics
of the three germ layers and with very low chances to develop tumors when
transplanted (Lee et al., 2004).
When comparing the efficiency of MSCs isolation from the UC tissues (blood
and matrix), the blood is the one with lower efficiency (about 30%) (Bieback et
al.,2004) and this is a disadvantage when compared with the matrix that has been
consistently reported as having an efficiency of 100% (Secco et al.,2008; Zeddou et
al.,2010; Taghizadeh et al.,2011).
I.1.2 - In vitro characterization of MSCs
For many years the search for the identity of mesenchymal stem cell was mainly
dependent on three culture systems: the CFU-F assay, the isolation and analysis of
bone marrow stroma, and the cultivation of mesenchymal stem cell lines. The isolation
and culture conditions used to expand these cells rely mostly on the ability of MSCs to
adhere to plastic surfaces. MSCs populations in culture are typically composed by cells
that comprise some heterogeneity, in terms of differentiation potential and expression
of secondary MSC markers. Whether the culture conditions selectively favor the
expansion of different bone marrow precursors or induce similar cell populations to
acquire different phenotypes is not clear (Nardi and da Silva Meirelles, 2006).