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Monitoring Stem Cell Research 
regeneration of gastrointestinal epithelia in human patients.®® A 
recent study in mice has indicated that bone marrow stem cells can 
also participate in cutaneous healing, contributing to repair of skin 
after wounding.®^ 
PERIPHERAL BLOOD STEM CELLS 
There is abundant evidence that bone marrow stem cells can 
leave the marrow and enter the circulation, and specific mobilization 
of bone marrow stem cells is used to harvest stem cells more easily 
for various bone marrow stem cell treatments.®® Therefore, it is not 
surprising that adult stem cells have been isolated from peripheral 
blood. Mobihzed stem cells in peripheral blood have been 
administered intravenously in a rat model of stroke, ameliorating 
some of the behavioral deficits associated with the damaged neural 
tissue®®, leading to a proposal that stem cell mobilization in patients 
might be used as a treatment for stroke in humans. Mobilized stem 
cells have also been used in cardiac regeneration in mice^^. Two 
recent studies have found that human peripheral blood stem cells 
exhibiting pluripotent properties can be isolated from unmobilized 
human blood. One study showed that the isolated cells were 
adherent, similar to marrow mesenchymal cells, and could be 
induced to differentiate into cells from all three primary germ layers, 
including macrophages, T lymphocytes, epithelial cells, neuronal 
cells, and liver cells. The other study showed induction of the 
peripheral blood stem cells could produce hematopoietic, neuronal, 
or cardiac cells in culture.®^ In the latter study, undifferentiated stem 
cells were negative for both major histocompatability antigens 
(MHC) I and II, expressed high levels of the Oct-4 gene (usually 
associated with pluripotent capacity in other stem cells), and could 
form embryoid body structures in culture. 
NEURONAL STEM CELLS 
One extremely interesting finding of the past few years has 
been the discovery of neuronal stem cells, indicating that cell 
replenishment was possible within the brain (something previously 
considered impossible.) Neuronal stem cells have been isolated from 
various regions of the brain including the more-accessible olfactory 
bulb®® as well as the spinal cord®^, and can even be recovered from 
cadavers soon after death.®® Evidence now exists that neuronal stem 
cells can produce not only neuronal cells but also other tissues, 
including blood and muscle.®®'®^'®®’®®’^®®’^®^ Animal studies have shown 
that adult neural stem cells can participate in repair of damage after 
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