Biomedical Engineering Reference
In-Depth Information
Thus, in the only reported clinical trial in persons with stroke affected basal ganglia,
received implants of neurons generated from the human NT-2 teratocarcinoma cell
line into the infracted area. The introduction of a proliferation step as free-floating
cell spheres cuts the total time needed to obtain high yields of purified NT-2 neurons
to about 24-28 days [
8
]. The cells obtained show neuronal morphology and migrate
to form ganglion-like cell conglomerates. Differentiated cells express neuronal
polarity markers such as the cytoskeleton-associated proteins MAP2 and Tau.
Moreover, the generation of neurons in sphere cultures induced immunoreactivity to
the ELAV-like neuronal RNA-binding proteins HuC/D, which have been implicated
in mechanisms of nerve cell differentiation [
8
]. However, there is no substantial new
neuron formation in the cerebral cortex after stroke. Whether the new neurons
formed after stroke are functional is unknown.
Recent findings in rodents suggest an alternative approach to cell therapy in stroke
based upon self-repair [
9
]. Stem cells taken from adult human bone marrow have
been manipulated by scientists at the Maxine Dunitz Neurosurgical Institute at
Cedars-Sinai Medical Center to generate aggregates of cells called spheres that are
similar to those derived from neural stem cells of the brain [
10
]. In addition, the bone
marrow-derived adult stem cells, which could be differentiated into neurons and
other cells making up the CNS, spread far and wide and behaved like neural stem
cells when transplanted into the brain tissue of chicken embryos [
10
] . Results of the
experiments, described in the February 2007 of the Journal of Neuroscience Research,
support the concept of using adult bone marrow-derived stem cells to create thera-
pies to treat brain tumors, strokes, and neurodegenerative diseases [
10
] . Similar study
using bone marrow-derived stem cells of rats appeared as the cover article of the
December 2002 issue of
Experimental Neurology
[
11-
14
] . These fi ndings reinforce
the data that came from the study of rat (adult) bone marrow-derived stem cells.
Using two methods, scientists showed evidence for the bone marrow derived stem
cells being neural cells, and demonstrated that it is feasible to grow the cells in large
numbers. They also documented that these cells function electrophysiologically as
neurons, using similar voltage-regulating mechanisms [
11
] .
Progressing from the rat study to experiments with human cells and transplanta-
tion into mammal brain tissue, the international research team continues to build a
foundation for translating laboratory research into human clinical trials. Based on
some studies to date, a patient's own bone marrow appears to offer a viable and
renewable source of neural stem cells, allowing us to avoid many of the issues
related to other types of stem cells [
15-
17
]. The replacement of damaged brain
cells with healthy cells cultured from stem cells is considered to potentially be a
promising therapy for the treatment of stroke, neurodegenerative disorders, and
even brain tumors, but finding a reliable source for generating neural cells for
transplantation has been a challenge. The use of embryonic and fetal tissue has
raised ethical questions among some and brings with it the possibility of immune
rejection. And while neural stem cells can be taken from brain tissue, the removal
of healthy tissue from a patient's brain introduces a new set of safety, practicality,
and ethical issues.
