Growing Brain Cells Drugs that trigger the birth of
neurons could provide the next generation of treatments for
neurodegenerative diseases such as Parkinson’s
SOURCE: “Dopamine D3 Receptor Agonist Delivery to a Model of Parkinson’s Disease Restores the Nigrostriatal Pathway and Improves Locomotor Behavior” J. M. Van Kampenand C. B. Eckman Journal of Neuroscience 26(27): 7272-7280
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Results: Scientists
at the Mayo Clinic in Jacksonville, FL, found that a drug similar to
ones used to treat Parkinson’s disease can spur growth of new neurons
in the substantia nigra, the brain area damaged in the disease. In a
study of rodents genetically engineered to model Parkinson’s disease,
twice as much neurogenesis, or birth of new neurons, was seen in
animals treated with the drug as in control animals. Many of the newly
generated cells appeared to develop into dopamine-producing
neurons–the kind that are lost in Parkinson’s. In addition, treated
animals showed an 80 percent improvement in motor ability.
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Why it matters: Current
treatments for Parkinson’s disease replace or mimic dopamine, an
important signaling molecule in the brain. But those treatments lose
their effectiveness over time; boosting the brain’s ability to make
more of the dopamine-producing cells could provide a more effective
strategy.
Methods: Scientists treated rodents
with a compound that triggers a dopamine receptor, delivering it
directly to their brains for up to eight weeks. They then tracked the
birth and development of new neurons and monitored the rodents’
performance in motor tasks.
Next steps: The
team is now testing drugs currently used to treat Parkinson’s disease
to see if they also trigger neurogenesis and, if so, how best to
deliver these compounds to maximize effectiveness. Ultimately, they
hope to find compounds that will help replace cells lost in a range of
neurodegenerative diseases, such as Alzheimer’s and Huntington’s.
Stem Cell Mix Helps Paralyzed Rats Walk Rodents regained mobility after receiving a combination of drugs and stem cells that rewired their nervous systems
SOURCE: “Recovery from Paralysis in Adult Rats Using Embryonic Stem Cells” D. M. Deshpande et al. Annals of Neurology 60(1): 32-44
Results:
Scientists from Johns Hopkins University found that a complex
combination of treatments, including stem cells and growth factors, can
heal damaged neural circuits, allowing partially paralyzed rats to
walk. According to the findings, 11 out of 15 rats with spinal-cord
injuries regained some motor function after receiving the full battery
of treatments.
Why it matters: Previous studies
on paralyzed rats demonstrated the possibility of boosting the function
of the nervous system and improving motor skills. But this is the first
study to show that newly grown nerve fibers can emerge from the spinal
cord, extend all the way to muscles in the rats’ haunches and limbs,
and form functional connections with them. These findings represent a
significant step forward in regenerative medicine, providing new
treatment possibilities for some types of spinal-cord injury and for
diseases in which motor neurons are damaged, such as amyotrophic
lateral sclerosis (ALS).
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Methods: The
researchers transplanted motor neurons, derived from embryonic stem
cells, into the spinal cord. Then they added a mix of growth factors to
help the new cells survive and grow, as well as two chemicals known to
block the signals that normally keep nerve fibers from growing out of
the spinal cord.
In order to get the newly sprouted fibers to
span the wide gap between the spinal cord and the muscles, the
researchers injected neural stem cells into the target muscles. These
cells produced a nerve growth stimulator that drew growing motor
neurons to the muscle and allowed them to make functional neuromuscular
connections.
Next steps: The team is now
planning tests in pigs. Studies in larger animals are necessary to make
sure that the new neurons can grow to great enough lengths that the
treatment will work in humans. If those experiments are successful, the
scientists say, human clinical trials could begin within five years.