Biomedical Engineering Reference
In-Depth Information
more than 50 % of the time in unrelated bone marrow transplants (BMT) [
3
] led
researchers to investigate alternate sources of stem cells for treatment of blood,
immune, and metabolic disorders. Research in the early 1980s revealed that the
blood in the umbilical cord and placenta after the birth of a child was comparable
to bone marrow in stem cell transplantation [
4
-
11
], and offered a number of
advantages over bone marrow, including a lower incidence of GVHD and less
strict HLA-matching requirements [
12
,
13
]. In the past 20 years, more than 25,000
transplants have been performed worldwide [
14
].
Stem cell transplantation for hematological malignancies and genetic disorders
is an uncommon occurrence. However, research performed by several independent
laboratories [
15
-
20
] demonstrated that cord blood also contains a mixture of
pluripotent stem cells capable of giving rise to cells derived from the endodermal,
mesodermal, and ectodermal lineages. In addition, mesenchymal stem cells can be
isolated from CT and preserved for later use. Thus, CB and CT are readily
available for use in tissue engineering and regenerative medicine applications,
which are hypothesized to be more frequent events. It is estimated that almost 1 in
3 individuals in the United States, or 128 million people, could benefit over their
lifetime from regenerative medicine, including therapies for cardiovascular, neu-
rological, and orthopedic diseases [
21
]. Diseases such as myocardial infarction,
stroke, and spinal cord injury might possibly be treated with greater efficacy using
cell-therapy based approaches than current treatment options. Translation of these
potential therapies from the laboratory to the clinic requires that the stem cells are
medically and economically available. Political and ethical controversy surrounds
the use of embryonic stem cells, and significant biological and regulatory concerns
limit their clinical use. However, cord blood is non-controversial and if preserved
at birth, will provide a source of autologous stem cells for an individual's use in
regenerative medicine. Furthermore, cord tissue also exhibits the potential to
replace embryonic stem cell sources in the regenerative medicine arena.
In vitro and in vivo research has shown that CB stem cells have the ability to
regenerate numerous tissue types, and when transplanted into animals and humans,
have produced measurable functional improvements [
19
,
22
]. Clinical trials have
begun using cord blood stem cells to treat cerebral palsy and peripheral vascular
disease among others [
22
,
23
]. In addition, recent efforts have focused on the
isolation, characterization, and utilization of mesenchymal stem cells (MSC)
isolated from CT. In fact, CT stem cells have also now made their way into clinical
trials. In this paper we will review the latest developments in the use of cord blood
and cord tissue stem cells for regenerative medicine.
In terms of clinically available stem cell sources, CB and CT represent an
almost limitless supply of stem cells for various clinical uses. In the US there are
more than 4 million babies born annually from whom such stem cells may be
collected. Stem cells are present in large numbers that may be collected and
processed economically, for less than $2,000 and can either be used immediately
or banked for future applications [
24
]. The vast majority of CB collections are red
blood cell (RBC)-depleted prior to cryopreservation. Several methods are in use to
accomplish
this
goal
including
Hespan
sedimentation
to
obtain
a
modified
