Stem Cells Ease Parkinson Symptoms in Monkeys
Tracy Hampton, PhD
JAMA. 2007;298:165.
Brain implants of human neural stem cells can ease the Parkinson symptoms in primates with a chemically induced form of the disease, according to new research (Redmond DE et al. Proc Natl Acad Sci USA. doi: 10.1073/pnas.0704091104; published online ahead of print June 11, 2007).
Prior to implantation, African green monkeys with Parkinson disease had difficulty walking, moving, and eating, and they experienced head and limb tremors. But 2 months after receiving injections of neural stem cells from a human fetal cadaver, the animals improved progressively compared with sham-injected controls.
To understand the basis for this functional recovery, brain sections from the treated monkeys were analyzed to assess the fate of donor and host cells. The investigators found that some of the implanted human stem cells developed into dopamine-producing neurons, but many more formed supportive astrocytes that help regulate the chemical environment around nerve cells and respond to injury.
The researchers also noted the appearance of many dopamine-producing neurons that were not derived from the implanted stem cells. This finding suggests that stem cells may coax other cells in the brain to take part in the healing process. The authors proposed that multiple modes of reciprocal interaction between the implanted stem cells and the brain may be involved.
Long-term studies will be needed to verify the study's results and to assess the potential adverse effects, such as dyskinesia and immunorejection of stem cells, before attempting human studies, the authors wrote. But they are hopeful that their strategy will have clinical applications. Some patients have benefited from grafts of fetal dopaminergic neurons and from systemic administration of dopamine precursors and dopamine agonists, but such therapies have been limited.
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