Stem Cell Technology Enables New Disease in a dish

I like the brain in a dish comment, with that I would hope it makes it easier to determine what works and what doesn't for stroke rehab. I know this is for schizophrenia but the concept should work to determine behavior of brain cells trying to integrate into a damaged brain. Way above my pay grade but I can at least ask the questions. Ask your researcher about this possibility.
http://dana.org/uploadedFiles/News_and_Publications/BrainWork/bw_summer2011.pdf
The Neuroscience Newsletter BRAINWORK
THE DANA FOUNDATION’S
Vol. 19, No. 3 | Fall 2010 http://www.dana.org/
BrainWork / Fall 2010 / 1
For some brain diseases,laboratory models makes it hard for
researchers to understand disease-causes and develop
therapies. New stem cell technology offers a powerful solution.
By Jim Schnabe l
Stem cell therapies for disease are still mostly over the horizon. But stem
cell technology is already boosting scientists’ abilities to study diseases and
test drugs against them. The technology is proving particularly useful for brain disorders
that are hard to model in animals. Using an “induced pluripotent stem
cell” (iPS) technique first reported for human cells only in 2007, scientists now
can take skin cells from patients, convert them to iPS cells and then neurons in a lab
dish, and study the patient-derived neurons to gain insights into disease mechanisms
and therapies. Two recent reports show the power of the “brain-in-a-dish”
technique.
“We’re going to see a lot of these papers coming out,” says Clive Svendsen,
director of the Regenerative Medicine Institute at Cedars-Sinai Medical Center in
Los Angeles.

Modeling Schizophrenia
Schizophrenia features abnormalities in some of our more evolutionarily advanced
neural circuitry, including weak connectivity among the prefrontal and temporal
cortices and the hippocampus. The causes of schizophrenia are not well understood:
Although it is largely genetic, its known genetic risk factors are varied, and mostly
subtle. The disease is often described as being caused by “many rare mutations”
that somehow feed into a final common pathway of vulnerability. There is no good
animal model. In a study published online in Nature
on April 13, researchers led by senior investigator Fred H. Gage at the Salk
Institute took skin cells from four different people with schizophrenia. Using the
iPS technique, they reprogrammed the patients’ skin cells to act like fetal stem
cells—then used a biochemical recipe to “differentiate” these into neural progenitor
cells, which proliferated and produced mature neurons.
The technique produced a large supply of neurons per patient, and as newborn
neurons will, they spontaneously formed clusters that connected to each other.
Gage’s team thus was able study in detail how these schizophrenia-patient-derived
neurons were different from neurons that had been derived from healthy people
using the same iPS technique.
Comparing gene expression patterns, for example, they found in the schizophrenia
neurons 596 genes that, on average, were expressed at least 30 percent more
than normal or 30 percent less than normal. “When we looked at the categories
of functions for these genes, we found certain pathways that stood out quite
strongly, which gives us new leads about what may be going on in schizophrenia,”
says Gage, who also is a member of the Dana Alliance for Brain Initiatives. The
pathways disturbed in the schizophrenia neurons included those controlling
neuronal growth and the maintenance of synapses—the interfaces at which
neurons communicate. In one-quarter of cases, the gene expression changes in the
schizophrenia neurons confirmed changes known from previous research.
Gage’s team also was able to quantify how connected the neurons were to one
another. On average, the schizophrenia neurons had only about half the connectivity
of normal neurons, a difference that corresponded to some of the changes
seen in gene expression. When the researchers treated the
cells for 20 days each with five standard schizophrenia drugs, they found that each
drug improved connectivity and gene expression patterns—moving them in the
direction of normality—for at least some patients’ iPS-derived neurons. One drug,
loxapine, significantly boosted connectivity for all four sets of neurons. “And these
were all different and quote-unquote sporadic cases of schizophrenia,” Gage notes.
“The fact that one of the compounds could generally increase the connectivity
was quite impressive to us.”
Only three earlier studies of humaniPS-derived models have been published,
Stem Cell Technology Enables New ‘Disease in a Dish’ Models of Brain Disorders
Summer 2011
(Continued on page 2)
Summer 2011/ 1
BrainWork / Summer 2009 / 2
and each involved relatively simple comparisons of survival/degeneration
between patient-derived and control neurons. Gage’s group’s techniques had to
be more sophisticated to detect the more subtle neuronal disturbances at the heart
of schizophrenia. One such technique permitted the tracing of connections among
neurons using a modified rabies virus. Rabies viruses evolved to “swim” upstream
along nerve fibers and across synapses, hopping from neuron to neuron until they
get to the brain. In this case, Gage’s group, using a method developed elsewhere at
the Salk Institute, created a rabies virus that lacks a key protein, forcing it to stop
after a single hop. Because the modified rabies viruses expressed a fluorescent
tracer protein, their movements—and thus the neurons’ connections—could be
tracked.
Gage says the set of techniques used in this study could be applied to other
brain diseases in which researchers suspect abnormal connectivity. But he also
wants to refine the techniques to glean more insights about schizophrenia. “We’re
developing protocols to differentiate these cells specifically into hippocampal
neurons versus cortical neurons, so we can apply the same basic analysis using
more specific neuronal types,” he says. With these more sophisticated techniques
and a more diverse set of patient-derived neurons, he hopes the deep biology of
schizophrenia will eventually become much clearer. “We’re looking for a core
program that underlies the disease,” he says. “Perhaps not 596 gene expression
alterations, but some subset. This is not a single-gene disease.”
Modeling Spinal Muscular Atrophy One of the first clinical successes
enabled by the iPS-modeling technology could be for spinal muscular atrophy
(SMA). An iPS-derived model of SMA was reported in 2009 by Svendsen’s lab and
the lab of stem cell researcher James Thomson.
SMA is a childhood recessive genetic disease in which both parental genes
for the protein SMN are defective. The deficiency of SMN—for reasons that
haven’t been understood—causes spinal muscle-controlling neurons to degenerate.
In severe cases, SMA can proceed from the first symptoms at the age of about
six months to fatal paralysis a year and a half later. “It’s horrific for parents,” says
Svendsen. “There’s nothing they can do; there’s no cure for it.”
Svendsen’s and Thomson’s labs converted fibroblasts from a single SMA
patient into motor neurons like those affected in the disease, and were able to
show that the neurons underwent an SMA like process of degeneration, compared
with neurons generated from fibroblasts taken from the patient’s healthy mother.
“In effect we were able to replay the disease,”
says Svendsen. “The motor neurons were born and they were fine for a few
weeks, and then they underwent degeneration, so we actually watched them die.”
Since that initial demonstration, Svendsen and Thomson have developed
and studied neuronal lines from other SMA patients, and Svendsen says they
have found changes in the neurons that may account for their degeneration when
deprived of SMN. He and Thomson are about to submit their findings for publication.
“We’re also getting closer to thinking about rational drug design based on the
mechanism of these motor neuron deaths in the kids,” he says.
Tomorrow’s Must-Have Lab Tech Svendsen expects a flood of iPS-model
papers to be published in the next few years, particularly for the strongly genetic,
early-onset diseases like SMA that seem best suited to the technique. The iPS
induction process resets cells to something like a newborn state, and seems to erase
many of the cellular changes that occur with aging and environmental stresses. “I
always look at iPS models as developmental models essentially,” he says. “Because
you’re taking the cell back in time and then making it undergo development again.”
For this reason, he was surprised that Gage’s group found such clear connectivity
deficits in iPS-derived neurons from patients with schizophrenia—a disease
that normally doesn’t manifest until late childhood. “But if that [result] reproduces
in more neuron lines, it’ll be a very nice way of looking at the mechanism of cell
connections in schizophrenia,” he says. Later-onset diseases such as
Parkinson’s, Alzheimer’s, and Huntington’s could be more difficult to model in neurons generated by the iPS technique. But researchers might still generate useful
models for these disorders if they can find a way to artificially age or otherwise stress the cells, to see whether disease-derived neurons are more vulnerable than control neurons. “Many groups are looking at the possibility of adding toxins to the cell cultures, for example,” Svendsen says. He is mindful that these are only labdish models. “We’re not going to do away with whole-animal models,” he says. But
the technology is potentially valuable enough that he expects it to spread widely
in academic and commercial labs, replacing older cell-based disease modeling
techniques. “Eventually I think if you’re going to study a human disease or look
at a related pathway or a system, you’ll be expected to grab an iPS line from that disease
model if it’s available,” says Svendsen. Jim Schnabel is a science journalist and
author based in Florida.
Summer 2011
(stem cell tech, continued from page 1)
“I always look at iPS models as developmental models essentially, because you’re taking the cell back in time and then making it undergo development again.”
--Clive Svendsen, Regenerative Medicine Institute