Biomedical Engineering Reference
In-Depth Information
et al. (21)], myocardial ischaemia [Leor et al. (22)], and also in inducing angiogen-
esis, only to name a few common clinical conditions.
The most important advantage is the less-strict HLA matching requirement.
This is because cord blood is a much more developmentally immature source of
stem cells as opposed to stem cells derived from adult sources. It has the addi-
tional advantage of easy availability. A source of hematopoietic cells, cord blood
contains potent angiogenesis-stimulating cells. Several phenotypes have been
ascribed to cord blood angiogenic-stimulating cells. In one report, the CD34
+
,
CD11b
+
fraction, which is approximately less than half of the CD34
+
fraction of
cord blood, was demonstrated to possess the ability to differentiate into func-
tional endothelial cells
in vitro
and
in vivo
[Hildbrand et al. (23)]. Mesenchymal
stem cells are another important constituent of cord blood. These are classically
defi ned as adhering to plastic and expressing a non-hematopoietic cell surface
phenotype, consisting of CD34
−
, CD45
−
, HLA - DR
−
, while possessing markers
such as STRO - 1, VCAM, CD13, CD29, CD44, CD90, CD105, SH - 3, and STRO - 1
[De Ugarte et al. (24)]. To date, mesenchymal stem cells have been purifi ed from
the placenta, scalp tissue, bone marrow, adipose tissue and cord blood [Kadivar
et al. (25)]. The transdifferential properties of mesenchymal stem cells into hepa-
tocytes, cardiomyocyte, and neuronal cell line, to name a few, have now been sci-
entifi cally proven. Cord blood mesenchymal stem cells are capable of expansion
to approximately 20 times, whereas adipose derived cells expand to an average of
eight times, and bone marrow derived cells expand fi ve times, [Kern et al. (26)].
Cells with markers and activities resembling embryonic stem cells have also been
found in cord blood. Zhao et al. (27) identifi ed a population of CD34
−
cells
expressing OCT-4, Nanog, SSEA-3 and SSEA-4, which could differentiate into
cells of the mesoderm, ectoderm and endoderm lineage.
A “cocktail” of these three elements may perhaps be used in the future to
treat one of the more than 80 diseases that have responded to stem cell transplan-
tation. Thus, it may have the potential to treat degenerative diseases such as heart
disease, endocrine disorders such as diabetes, and neurodegenerative diseases
such as stroke, Alzheimer's disease, Parkinson's disease and spinal cord injuries,
and so on. However, stem cells constitute only .01% of the nucleated cells (hema-
topoietic stem cells, which is similar to that found in bone marrow: approximately
0.1 - 0.8 CD34
+
cells per 100 nucleated cells) of placental blood. The rest, that is,
99.99% of the placental blood, is discarded as trash. The global wastage of placen-
tal blood with all its potentials amounts to approximately ten billion milliliters
per annum (at the current birth rate of 100 million per year). It should also be
remembered that the so-called placental barrier, which is one of nature's fi nest
biological sieves, screens this blood.
19.5 RATIONALITY FOR THE USE OF CORD BLOOD AS A TRUE
BLOOD SUBSTITUTE
Cord blood is the blood collected aseptically from the placenta after the birth of
a healthy baby. The blood volume of a term fetus is approximately 80-85 ml/kg.
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