Imaging in Stem Cell Transplant and Cell-based Therapy

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4.2 Mesenchymal Stem Cells: Unique Attributes

As stated above, mesenchymal stem cells are pluripotent cells found in various
organs including bone marrow, adipocytes, placenta, amniotic fluid and umbilical
cord blood. Certain specific criteria as defined by the Mesenchymal and Tissue
Stem Cell Committee of the International Society for Cellular Therapy are required
for stem cells from these various sources to be considered standard stem cells and
equivalent to each other [ 1 ]. These include spindle cell morphology, adherence to
plastic, ability to differentiate into adipocytic, chondrogenic and osteogenic cell
lines and expression of certain specific cell markers (CD73+ CD90+ CD105+
CD34− CD45−CD11b− CD14− CD19−CD79a− HLA-DR−).
Mesenchymal stem cells have certain unique attributes that make them suitable
for usage in multiple organ systems. These are summarized in Table 4.3.
In addition to their ability to divide infinitely and differentiate into several meso-
dermal cell lines such as adipocytes, chondrocytes and osteocytes, mesenchymal
stem cells in several in vitro models have also known to have the capacity to dif-
ferentiate into non-mesodermal cell lines and thus have found applications in organ
systems such as liver, brain and heart. Although several in  vivo models of injury
have shown engraftment and differentiation of mesenchymal cells into various other
cell lines such as hepatocytes, neural cells and cardiomyocytes, it is unknown if
these effects are solely due to trans differentiation or due to other effects such as
paracrine effects as well [ 2 , 3 ].
Mesenchymal cells also exert immuno suppressive and anti inflammatory prop-
erties, predominantly by suppressing T lymphocyte and natural killer cell prolifera-
tion, B cell function and cytokine production. Several products such as transforming
growth factor-beta, hepatocyte growth factor assist in the anti inflammatory proper-
ties of these cells [ 4 ].
Mesenchymal cells are also known to selectively migrate to sites of active inflam-
mation in the body, mainly due to interaction with specific receptors such as chemo-
kine receptor 4, stromal cell derived factor receptor, vascular endothelial growth
factor receptor and platelet derived growth factor receptor [ 5 ]. Injured tissues
express higher proportion of these receptors and thus facilitate homing of mesen-
chymal cells selectively.
Due to the above mentioned attributes and the ease with which they can be isolated
as well as their low immunogenicity and high tolerance in tissues, mesenchymal stem

Table 4.3 Unique attributes
of stem cells

1. Ability to differentiate into both
   mesodermal and non mesodermal
   lineages


2. Immune modulation


3. Migratory capacity and homing in


4. Paracrine effects


5. Easy isolation and ex vivo
   expansion

4 Clinical Applications of Stem Cell Transplant in Treating Non-Hematologic...