Abnormal Lipid Metabolism Suppresses Adult Neural Stem Cell Proliferation in an Animal Model of Alzheimer’s Disease


The brain is deeply dependent on lipid (fatty molecule) metabolism for proper development and function. Could abnormal lipid metabolism affect the brain’s stem cell population? Oh yes.

Karl J.L. Fernandez and his coworkers from the Research Center of the University of Montreal Hospital in Montreal, Canada and other collaborators has shown that neural stem cell populations in the brain can be compromised by abnormal lipid metabolism and that such abnormalities are characteristic of Alzheimer’s disease.

3xTg-AD mice form plaques in their brains that are similar to those in the brains of Alzheimer’s disease patients. Fernandez and his colleagues discovered that 3xTg-AD mice accumulate lipids within ependymal cells, which line the ventricles of the brain and serve as the main support cell of the forebrain Neural Stem Cells (NSCs). Interestingly, brains from Alzheimer’s disease patients, when examined after death also showed the accumulation of lipids within the same cell population.

Fernandes_graphicalabstact

When these lipids were examined further, it was clear that they were oleic acid-enriched fats (oleic acid is found in olive oil). In fact, injecting oleic acid into this area of the brain could recapitulate this pathology. When Fernandez and others inhibited oleic acid synthesis, they were able to fix the stem cell issues in the 3xTg-AD mice.

This fascinating study shows that the pathology in Alzheimer’s disease might be caused by perturbation of fatty acid metabolism in the stem cell niche that suppresses the regenerative functions of NSCs. Preventing accumulation of these fats in the cells surrounding the NSC population can potentially fix the stem cell abnormalities in patients with Alzheimer’s disease.

This study was published in the journal Cell Stem Cell.

How Neural Stem Cells Become Neurons and Glia


How do neural stem cells differentiate into neurons or glia? A new paper from researchers at the University of California, Los Angeles (UCLA) seeks to explain this very phenomenon.

Neurons serve as the conductive cells of the nervous system. They transmit electrochemical signals from one neuron to another and provide signals to muscles, glands, and so on. They are responsible for consciousness, thought, learning and memory, and personality.

Despite their immense utility, neurons are not the only cells in the nervous system. Glial cells or just glia support neurons, hold them in place, and supply neurons with oxygen and nutrients and protect them from pathogens.

Glial Cells

When mouse neural stem cells were grown in culture, Wange Lu, associate professor of biochemistry and molecular biology at the Keck School of Medicine, and his colleagues came upon a protein called SMEK1 that promotes the differentiation of neural stem and progenitor cells. SMEK1 also keeps neural stem cells in check by preventing them from dividing uncontrollably.

When Lu and others took a more detailed look at the role of SMEK1, they discovered that it does not work alone, but in concert with a protein called Protein Phosphatase 4 (PP4) to suppress the function of a third protein called PAR3. PAR3 discourages the birth of new neurons (neurogenesis), and PAR3 inhibition leads to the differentiation of neural stem progenitor cells into neurons and glia.

“These studies reveal the mechanisms of how the brain keeps the balance of stem cells and neurons when the brain is formed,” said Wange. “If this process goes wrong, it leads to cancer, or mental retardation or other neurological diseases.”

Neural stem and progenitor cells offer tremendous promise as a future treatment for neurodegenerative disorders, and understanding their differentiation is the first step towards co-opting the therapeutic potential of these cells. This could offer new treatments for patients who suffer from Alzheimer’s, Parkinson’s and many other currently incurable diseases.

This work is interesting. It was published in Cell Reports 5, 593–600, November 14, 2013. My only criticism of some of the thinking in this paper is that neural stem cell lines are usually made from aborted fetuses. I realize that some of these neural stem cell lines come from medical abortions in which the baby had already died, but many of them come from aborted babies. If we are going to use neural stem cells for therapeutic purposes, then we should make them from induced pluripotent stem cells and take them from aborted babies.

Stem Cell-Conventional Treatment Combo Offers New Hope in Fighting Deadly Brain Cancer


A new type of treatment that combines neural stem cells with conventional cancer fighting therapies shows promise in animal studies for the most common and deadliest form of adult brain cancer — glioblastoma multiforme (GBM). The details are revealed in a groundbreaking study led by Maciej Lesniak, M.D., that appeared in the journal STEM CELLS Translational Medicine.

“In this work, we describe a highly innovative gene therapy approach, which is being developed along with the NIH and the FDA. Specifically, our group has developed an allogeneic neural stem cell line that is a carrier for a virus that can selectively infect and break down cancer cells,” explained Dr. Lesniak, the University of Chicago’s director of neurosurgical oncology and neuro-oncology research at the Brain Tumor Center.

The stem cell line used is a neural stem cell line called HB1.F3 NSC. The US Food and Drug Administration has recently approved this cell line for use in a phase I human clinical trial.

Glioblastoma multiforme remains fatal despite intensive treatment with surgery, radiation and chemotherapy. Cancer-killing viruses have been used in clinical trials to treat those tumors that resist treatment with other therapies and infiltrate throughout the brain. Unfortunately, according to Lesniak, this therapy was subject to some “major drawbacks.”

“When you inject a virus into a tumor alone (without a carrier, like NSC), the virus stays at the site of the injection, and does not spread. Moreover, our immune system clears it. By using NSCs, we can achieve a widespread distribution of the virus throughout the tumor mass, since the NSC travel. Also, they act like a stealth fighter, hiding the virus from the immune system.” Lesniak and his co-workers used NSCs loaded with a novel oncolytic adenovirus. This virus selectively targets glioblastoma multiforme in combination with chemo-radiotherapy. Using this strategy, Lesniak’s team was able to overcome the limitations associated with anticancer viral therapies.

Using mice that had glioblastoma multiforme, the research team showed that their neural stem cell line, which is derived from human fetal cells, significantly increased the median survival time of the mice beyond conventional treatments alone. The addition of chemo-radiotherapy further enhanced the benefits of this novel stem cell-based gene therapy approach.

“Our study argues in favor of using stem cells for delivery of oncolytic viruses along with multimodal chemo-radiotherapy for the treatment of patients with glioblastoma multiforme, and this is something that we believe warrants further clinical investigation,” Dr. Lesniak concluded.

Lesniak’s team is completing final FDA-directed studies. He expects to start a human clinical trial, in which a novel oncolytic virus will be delivered via NSCs to patients with newly diagnosed glioblastoma multiforme, early in 2014.

Treatment of glioblastoma multiforme depends on novel therapies,” said Anthony Atala, M.D., Editor of STEM CELLS Translational Medicine and director of the Wake Forest Institute for Regenerative Medicine. “This study establishes that a combination of conventional and gene therapies may be most effective and suggests a protocol for a future clinical investigation.”

How Neural Stem Cells Create New and Varied Neurons


A new study in fruit flies has elucidated a mechanism in neural stem cells by which these types of stem cells generate the wide range of neurons that they form.

Chris Doe, a professor of biology from the Institute of Neuroscience at the University of Oregon, and his co-authors have used the common fruit fly Drosophila melanogaster to investigate the cellular mechanism by which neural stem cells make their distinctive progeny.

As Doe put it, “The question we confronted was ‘How does a single kind of stem cell, like a neural stem cell, make all kinds of neurons?”

Researchers have known for some period of time that stem cells have the capacity to produce new cells, but the study by Doe’s group shows how a select group of stem cells can create progenitor cells that can generate numerous subtypes of cells.

Doe’s study builds on previous studies in which Doe and his colleagues identified the specific set of stem cells that generated neural precursors. These so-called “intermediate neural progenitors” or INPs can expand to form several different new cell types. However, this study did not account for the diversity of the cells generated even if it did account for the number of cells generated (see Boone JQ, Doe CQ, Dev Neurobiol. 2008 Aug;68(9):1185-95).

“While it’s been known that individual neural stem cells or progenitors could change over time to make different types of neurons and other types of cells in the nervous system, the full extent of this temporal patterning had not been described for large neural stem cell lineages, which contain several different kinds of neural progenitors,” according to this study’s first author Omar Bayraktar.

The cell types discovered in this study have analogs in the developing human brain and the research has potential applications for human biologists who want to know how neurons form in the human brain.

The paper from Doe’s lab was published along another study on the generation of diverse neurons by a group from New York University. These two papers provide new insight into the means by which neural stem cells generate the wide range of neurons found in the brains of fruit flies and humans.

In their study, Bayraktar and Doe specifically examined stem cells in fruit fly brains known as type II neuroblasts, which generate INPs. However, in this study, the type II neuroblasts were shown to generate INPs, which then go on to form distinct neural subtypes. Even though previous work showed that INPs went on to form about 100 new neurons, in this paper, the INPs were shown to make about 400-500 new neurons.

Another interesting finding was that the gene expression patterns of INPs, which began with three different transcription factors (Dichaete, Grainy Head, and Eyeless). These transcription factors lay the groundwork for INP differentiation, but once INP formation occurs, a new transcriptional program is extended that extends the types of neurons that INPs can form. Such nested transcriptional programs are also common during the specification of neural stem cell progeny in humans brains, with many of the same transcription factors playing a central role in neuron specification.

“If human biologists understand how the different types of neurons are made, if we can tell them ‘This is the pathway by which x, y, and Z neurons are made,’ then they may be able to reprogram and redirect stem cells to make these precise neurons,” Doe said.

However, the mechanism described in this paper has its limits. Eventually the process of generation new cells stops. One of the next questions to answer will be what makes the mechanism turn off, according to Doe.

“This vital research will no doubt capture the attention of human biologists,” said Kimberly Andrews Espy, who is vice-president for research and innovation and the dean of the UP graduate school. “Researchers at the University of Oregon continue to further our understanding of the processes that undergird development to improve the health and well-being of people throughout the world.”

See Bayraktar OA, Doe CQ. Combinatorial temporal patterning in progenitors expands neural diversity. Nature. 2013 Jun 27;498(7455):449-55. doi: 10.1038/nature12266.

Human Neural Stem Cell Line Heals Spinal Cord-Injured Rats


Spinal cord injuries represent one of the most intractable problems for regenerative medicine. When the spinal cord is injured, a tissue that is normally isolated from the bloodstream, now comes into contact with a variety of inflammatory factors and cells that increase the destruction of the original lesion. The spinal responds with a glial scar that plugs the lesion and prevents further exposure of the spinal cord to damaging inflammation, but the scar is also filled with molecules that repel neuronal axon growth cones. This spells curtains for neuronal regeneration, and finding a cell type that can negotiate around the glial scar and find the original muscle is a genuine tour de force.

Given this to be the case, there have been many experiments in rodents to examine the efficacy of various stem cell populations to as treatments for spinal cord injuries. A recent paper in Stem Cell Research and Therapy (van Gorp et al., 2013, 4:57) has examined human fetal spinal cord-derived neural stem cells (HSSCs) and their ability to restore motor function in rats with spinal cord injuries to the lower back. Because this group examined movement and spinal cord tissue samples, this paper contributes something significant to our knowledge of HSSC-mediate healing of spinal cord injuries.

The HSSC line used in this paper is neural stem cell line NSI566RSC, which was extracted from the spinal cord of an 8-week old “fetus.” I have placed fetus in quotes because at eight weeks, the fetus is actually a very old embryo, since the end of the eighth week is end of embryonic development. I realize that these types of age calculations have room for error, and therefore, the baby might very well have been at the early fetal stage. However, the baby’s mother terminated her pregnancy (yes it was an abortion and no I am not cool with that) and donated the dead baby’s tissue to UC San Diego for research purposes.

Sprague-Daley rats were subjected to spinal cord injuries at the level of the third lumbar vertebra. Three days later, half of the rats were given saline injections into their spinal cord and the other half were given HSSC injections into their spinal cords. The animals were evaluated for two months after the treatments on a daily basis. After two months, the rats were sacrificed (put down) and the spinal cord tissue was extensively analyzed.

Of the 35 animals employed in this study, 3 were excluded because of paw injuries or drug toxicity. Eight weeks after the cells were implanted, the rats were tested with a CatWalk apparatus to determine their gait. The rats injected with HSSCs showed a much more normal gait than those injected with saline. To give you some idea of the improvement, the rats that were not injured had a RCHPP or rostro-caudal hind paw positioning score of 0+/- 1.7mm, and the saline injected animals had an average RCHPP of -18 +/- 3.1 mm, and those injected with HSSCs had an RCHPP of -9.0 +/- 1.9 mm.

Despite these improvements, there were no significant differences in ladder climbing, stride length, overall coordination, or single-frame motion.

Next, Marsala and colleagues showed that the muscle spasms associated with spinal cord injury were slightly decreased by the implantation of HSSCs and not by injection of saline. To measure spasticity, the ankle or front paw is rotated and the electromyograph of the muscle is measured. The electromyograph or EMG measures the electrical activity of the muscle showed modest improvements in the HSSC-injected animals

Sensory sensitivity was improved in the HSSC-injected animals, and this improvement was progressive. When the rats were prodded below the level of the injury, where they should have no feeling, the HSSC-injected rats showed better response to the stimulation. This was the case with mechanical stimulation and thermal stimulation.

Post-mortem analysis also showed something interesting. When the fluid-filled cavity of the damaged spine was examined, the HSSC-injected animals had a significantly small cavity. Because the injected cells had been labeled with green fluorescent protein, they glowed under UV light and any neuronal cells derived from the injected HSSCs glowed green too. The lesioned areas in the HSSC-injected mice were repopulated with cells. Motorneurons, interneurons and glial cells were detected.

What to make of this study? The repopulation of the spinal cord and the growth of spinal nerve elements within the fluid-filled cavity is remarkable, but the lack of better motor function is disappointing. The recovery of sensory ability is significant, especially, since it is pretty clearly not due to spinal hypersensitivity.

There are two possibilities for the low motor recovery. First, there is a possibility that the these experiments were not conducted for as long a time period as they needed to be. Since the sensory ability improvement was progressive, maybe the motor recovery was too, perhaps? Secondly, maybe the grow and connection of motor neurons had trouble with the glial scar. Why the sensory nerves did not have such a problem and the motor neurons would is inexplicable at this time. However, another possibility is that the muscular targets of motor neurons are not as obvious in adult animals as they are in a developing animal. Finding ways to “paint” the muscles might be a way to increase motor neuron innervation in the future.

Thus, this cell line, NSI-566 RSC is certainly a potential treatment for spinal cord patients. A phase I trial is in the works.

StemCells, Inc. Human Neural Stem Cells Restore Memory in Models of Alzheimer’s Disease


StemCells, Inc., a Newark, California-based company has announced preclinical data that demonstrates that its proprietary human neural stem cell line restored memory and enhanced synaptic function in two animal models that are relevant to Alzheimer’s disease (AD). They presented these data at the Alzheimer’s Association International Conference 2012 in Vancouver, Canada.

In this study, neuroscientists from University of California, Irvine transplanted a neural stem cell line called HuCNS-SC, a proprietary stem cell line made by StemCells and is a purified human neural stem cell line, into a specific region of the brain, the hippocampus in laboratory animals. These injections improved the memories of two different types of laboratory animal that act as AD-significant models. The hippocampus is a portion of the brain that is critically important to the control of memory, and unfortunately, it is severely affected by AD. Specifically, hippocampal synaptic density is reduced in AD and these reductions in synaptic connections are highly correlated with memory loss. After injections of HuCNS-SCs, the animals showed increased synaptic density and improved memory after the cells had been transplanted. Importantly, these results did not require reduction in beta amyloid or tau that accumulate in the brains of patients with AD and account for the pathological hallmarks of the disease.

This research study resulted from collaboration between Frank LaFerla, Ph.D., who is the Director of the University of California, Irvine (UCI) Institute for Memory Impairments and Neurological Disorders (UCI MIND), and Chancellor’s Professor, Neurobiology and Behavior in the School of Biological Sciences at UCI, and Matthew Blurton-Jones, Ph.D., Assistant Professor, Neurobiology and Behavior at UCI.

“This is the first time human neural stem cells have been shown to have a significant effect on memory,” said Dr. LaFerla. “While AD is a diffuse disorder, the data suggest that transplanting these cells into the hippocampus might well benefit patients with Alzheimer’s. We believe the outcomes in these two animal models provide strong rationale to study this approach in the clinic and we wish to thank the California Institute of Regenerative Medicine for the support it has given this promising research.”

Stephen Huhn, M.D., FACS, FAAP, Vice President and Head of the CNS Program at StemCells Inc, added, “While reducing beta amyloid and tau burden is a major focus in AD research, our data is intriguing because we obtained improved memory without a reduction in either of these pathologies. AD is a complex and challenging disorder. The field would benefit from the pursuit of a diverse range of treatment approaches and our neural stem cells now appear to offer a unique and viable contribution in the battle against this devastating disease.”