Producing dopamine-making neurons from stem cells for transplantation into Parkinson’s disease patients remains challenging. Differentiating stem cells into dopaminergic neurons is not as efficient a process as we would like it to be. While several laboratories have managed to make pretty good batches of dopaminergic neurons, reliably producing large and pure batches of dopamine-making neurons from pluripotent stem cells is still somewhat problematic. Secondly, transplanting dopamine-making neurons into either the midbrain or the striatum of the brain represents another patch of problems because the production of too much dopamine can cause unwanted, uncontrollable movements. Preclinical assessments of stem cell-derived dopamine neurons in laboratory animals have produced positive, but highly varied results, even though the transplanted cells are very similar at the time of transplantation.
“This has been frustrating and puzzling, and has significantly delayed the establishment of clinical cell production protocols,” said Malin Parmar, who led the study at Lund University.
To address this issue, Parmar and his colleagues used modern global gene expression studies to gain a better understand the molecular changes that drive the differentiation of stem cells into dopamine-making neurons. Parmar conducted these experiments in collaboration with a team of scientists at Karolinska Institute. In their paper, which appeared in the journal Cell Stem Cell, Parmar and his colleagues used single-cell RNA seq to construct the neuronal development of dopaminergic neurons.
These neurons are characterized by the expression of a gene called LMX1a. However, it turns out that LMX1a-expressing neurons includes not only midbrain dopaminergic neurons (see below at the substantia nigra), but also subthalamic nuclear neurons.
These findings reveal that markers used to identify midbrain dopaminergic neurons do not specifically isolate midbrain dopaminergic neurons, but isolate a mixture of cells. Is there a way to separate these two populations?
Indeed, there is. Parmar and his colleagues in the laboratory of Thomas Perlmann showed that although dopaminergic neurons from the midbrain and subthalamic nuclear neurons are related, they do express a distinct profile of genes that are specific to the two cell types. The authors argue that the application of these distinct marker genes can help optimize those protocols that differentiate dopaminergic neurons from pluripotent stem cells.
See Nigel Kee and others, “Single-Cell Analysis Reveals a Close Relationship between Differentiating Dopamine and Subthalamic Nucleus Neuronal Lineages,” Cell Stem Cell, 2016; DOI: 10.1016/j.stem.2016.10.003.
The Australian government has recently given its approval for a clinical trial of what is almost certainly a medical first. The Carlsbad-based stem cell company, International Stem Cell Corp. (ISCO), a publicly traded biotechnology company, has developed a unique stem cell technology to address particular conditions.
The clinical trial that has been approved will examine the use the ISCO’s unique stem cell products in the treatment of Parkinson’s disease. Twelve Parkinson’s patients will receive implantations of these cells sometime in the first quarter of 2016, according to Russell Kern, ISCO’s chief scientific officer. The implanted cells will be neural precursor cells, which are slightly immature neurons that will complete their maturation in the brain, hopefully into dopamingergic neurons, which are the precise kind of neurons that die off in patients with Parkinson’s disease.
Parkinson’s disease (PD) is a progressive disorder of the nervous system that affects voluntary movement. PD develops gradually and sometimes begins with a slight tremor in only one hand, but PD may also cause stiffness or slowing of movement. PD worsens over time.
PD patients suffer from tremor, or shaking of the limbs, particularly when it is relaxed and at rest. Over time, PD reduces the ability to move and slows movement (bradykinesis) which makes simple tasks difficult and time-consuming. Muscle stiffness may occur and this limits the range of motion and causes pain. PD patients also suffer from stooping posture and balance problems and a decreased ability to perform unconscious movements. For example, they have trouble swinging their arms while they walk, blinking, or smiling. They might also experience speech problems that can range from slurring of the speech to monotone speech devoid of inflexions, or softer speech with hesitations before speaking. Writing might also become problematic.
PD is caused by the gradual death of neurons in the midbrain that produce a chemical messenger called dopamine. The drop in dopamine levels in the system of the brain that controls voluntary movement leading to the signs and symptoms of Parkinson’s disease.
Several different animal experiments with a variety different cell types have established that transplantation to dopamine-making neuronal precursors into the midbrains of laboratory animals with artificially-induced PD can reverse the symptoms of PD. Dopaminergic neurons can be derived from embryonic stem cells (ESCs), mesenchymal stem cells (MSCs), umbilical cord blood hematopoietic stem cells (HSCs), induced pluripotent stem cells (iPSCs), and NSCs (see Petit G. H., Olsson T. T., Brundin P. Neuropathology and Applied Neurobiology. 2014;40(1):60–67). Also, since the 1980s, various cell sources have been tested, including autografts of adrenal medulla, sympathetic ganglion, carotid body-derived cells, xenografts of fetal porcine ventral mesencephalon, and allografts of human fetal ventral mesencephalon (fVM) tissues have been implanted into the midbrains of PD patients (Buttery PC, Barker RA. J Comp Neurol. 2014 Aug 15;522(12):2802-16). While the results of these trials were varied and not terribly reproducible, these studies did show that the signs and symptoms of PD could be reversed, in some people, by implanting dopamine-making neurons into the midbrains of PD patients.
ISCO has derived neural precursor cells from a completely new source. ISCO scientists have taken unfertilized eggs from human egg donors and artificially activated them so that they self-fertilize, and then begin dividing until they form a blastocyst-stage embryo from which stem cells are derived. This new class of stem cells, which were pioneered by ISCO, human parthenogenetic stem cells (hpSCs) have the best characteristics of each of the other classes of stem cells. Since these stem cells are created by chemically stimulating the oocytes (eggs) to begin division, the oocytes are not fertilized and no viable embryo is created or destroyed. This process is called parthenogenesis and parthenogenetic stem cells derived from the parthenogenetically-activated oocytes, are produced from unfertilized human egg cells.
Why did ISCO decide to do this trial in Australia? According to Kern, ISCO chose to conduct their clinical trial in Australia because its clinical trial system is more “interactive,” which allows for better collaboration with Australia’s Therapeutic Goods Administration on trial design. This clinical trial, in fact, is the first stem cell trial for PD according to the clinical trial tracking site clinicaltrials.gov. The test will be conducted by ISCO’s Australian subsidiary, Cyto Therapeutics.
The approach pioneered in this clinical trial might cure or even provide an extended period of relief from the symptoms of PD. If this clinical trial succeeds, the stem cell clinical trial dam might very well break and we will see proposed clinical trials that test stem cell-based treatments for other neurodegenerative diseases such as Huntington’s disease, Lou Gehrig’s disease (ALS), frontotemporal dementia, or even Alzheimer’s disease.
ISCO has spent many years developing their parthenogenetic technology with meager financing. However the company’s total market value amounts to something close to $11.1 million, presently.
hpSCs are pluripotent like embryonic stem cells. Because they are being used in the brain, they will not be exposed to the immune system. Therefore an exact tissue type match is not necessary for this type of transplantation. In their publications, ISCO scientists have found their cells to be quite stable, but other research groups who have worked with stem cells derived from parthenogenetically-activated embryos have found such cells to be less stable than other types of pluripotent stem cells. The stability of the ISCO hpSCs remains an open question. The lack of a paternal genome might pose a safety challenge for the use of hpSCs.
Rita Vassena and her colleagues in the laboratory of Juan Carlos Izpisua Belmonte at the Salk Institute for Biological Studies in La Jolla, CA examined the gene expression patterns of mesenchymal stem cells derived from hpSCs and found that the overall gene expression patterns were similar to MSCs made from embryonic stem cells or induced pluripotent stem cells. However, upon further differentiation and manipulation, the gene expression patterns of the cells began to show more variability and further depart from normal gene expression patterns (Vassena R, et al Human Molecular Genetics 2012; 21(15): 3366-3373). Therefore, the derivatives of hpSCs might not be as stable as cellular derivatives from other types of stem cells. The good news about hpSCs established from parthenogenetic ESCs were reported to be morphologically indistinguishable from embryonic stem cells derived from fertilized embryos, and seem to show normal gene expression or even correct genomic imprinting in chimeras, when pESCs were used in tissue contribution (T.Horii, et al Stem Cells, vol. 26, no. 1, pp. 79–88, 2008).
For those of us who view the early embryo as the youngest members of the human community who have the right not to be harmed, hpSCs made by ISCO remove this objection, since their derivation does not involve the death of any embryos.
The ISCO approach to Parkinson’s is similar to that of a San Diego group called Summit for Stem Cell, which is going to use induced pluripotent stem cell derivatives. This nonprofit organization is presently raising money for a clinical trial to test the efficacy of their treatment.
Both groups intend to transplant the cells while they are still slightly immature, so that they can complete their development in the brain. Animal studies suggest that implanting immature precursors are better than transplanting mature dopaminergic neurons into the midbrain. The precursors then differentiate into dopamine-making neurons, and other cells differentiate into supportive glial cells, which support the dopamine-making neurons.
“It’s a dual action,” Kern said. “Also, neural stem cells reduce inflammation, and inflammation is huge in Parkinson’s.”
Summit 4 Stem Cell will also take a similar approach, according to stem cell scientist Jeanne Loring, a leader of the Summit 4 Stem Cell project. The cells make proper connections with the brain better when they are still maturing, said Loring, who’s also head of the regenerative medicine program at The Scripps Research Institute in La Jolla. This is all provided that Summit 4 Stem Cell can raise the millions of dollars required for the clinical trial and secure the required approvals from the U.S. Food and Drug Administration.
Loring said she views ISCO as a partner in fighting Parkinson’s. One of her former students is working for the company, she said. “The whole idea is to treat patients by whatever means possible,” Loring said.
ISCO’s choice of Australia for its streamlined regulatory process makes sense, Loring said. Her team, with U.S.-based academics and medical professionals, doesn’t have the same flexibility as ISCO in looking for clinical trial locations, she said.
For the first time, German stem cell scientists from the University of Bielefeld and Dresden University of Technology have used adult human stem cells to “cure” rats with Parkinson’s disease.
Parkinson’s disease results from the death of dopamine-using neurons in the midbrain, and the death of these midbrain-based, dopamine-using neurons causes a loss of control of voluntary motion. Presently, no cure exists for Parkinson disease.
In this study, which was published in STEM CELLS Translational Medicine, the German team produced mature dopamine-using neurons from inferior turbinate stem cells (ITSCs). ITSCs are stem cells taken from tissues that are normally discarded after an adult patient undergoes sinus surgery. The German team tested how ITSCs would behave when transplanted into a group of rats with a chemically-induced form of Parkinson’s disease. Prior to transplantation, the animals showed severe motor and behavioral abnormalities. However, 12 weeks after transplantation of the ITSCs, the cells had not only migrated into the animals’ brains, but their functional ability was fully restored and significant behavioral recovery was also observed. Additionally, none of the treated animals shows any signs of tumors after the transplantations, something that also has been a concern in stem cell therapy.
“Due to their easy accessibility and the resulting possibility of an autologous transplantation approach, ITSCs represent a promising cell source for regenerative medicine,” said UB’s Barbara Kaltschmidt, Ph.D., who led the study along with Alexander Storch, M.D., and Christiana Ossig, M.D., both of Dresden University. “The lack of ethical concerns associated with human embryonic stem cells is a plus, too.”
“In contrast to fighting the symptoms of Parkinson’s disease with medications and devices, this research is focused on restoring the dopamine-producing brain cells that are lost during the disease,” said Anthony Atala, M.D., Editor-in-Chief of STEM CELLS Translational Medicine and director of the Wake Forest Institute for Regenerative Medicine. These cells are easy to access and isolate from nasal tissue, even in older patients, which adds to their attraction as a potential therapeutic tool.”
This is certainly a very exciting animal study, but treating chemically-induced Parkinson’s disease in rodents and treating Parkinson’s disease in aged human patients is two very different things. Thus while this study is important, work in human wild require more testing and studies in larger animals.
Living Cell Technologies (LCT) is a Australasian biotechnology company with offices in Australia and New Zealand. One of the products pioneered by LCT is NTCELL; a capsule coated with alginate (a porous compound extracted from seaweed) that contains clusters of choroid plexus cells from newborn pigs. NTCELL transplantation allows them to function as a biological factory that produces growth factors and other small molecules that promote new central nervous system growth and repair disease induced by nerve degeneration.
The choroid plexus is the structure in the brain that produces cerebrospinal fluid. These cells also filter wastes from the brain and keeps the brain free of debris and other potentially deleterious material. Choroid plexus cells not only produce cerebrospinal fluid, but also a range of neurotrophins (nerve growth factors) that have been shown to protect against neuron (nerve) cell death in animal models of disease.
Several papers have reported on the use of implanted NTCELL capsules in animal model systems. Luo and others used NTCELLs in nonhuman primates that suffered from chemically induced Parkinson’s disease. This paper reported that the transplanted encapsulated choroid plexus clusters significantly improved neurological functions in these monkeys with Parkinson’s disease (J Parkinsons Dis. 2013 Jan 1;3(3):275-91). An earlier paper also showed that implanted improved the neurological function of rodents with a chemically induced form of Huntington’s disease (Borlongan CV and others, Cell Transplant. 2008;16(10):987-92).
On the strength of these successful animal studies, LCT launched human clinical trials in patients with Parkinson’s disease. On December 15th of last year, LCT announced that the final patient had been successfully implanted in its Phase I/IIa clinical trial of regenerative cell therapy NTCELL for Parkinsons disease. These implantations required a minor surgical procedure, which took place at Auckland City Hospital
This Phase I/IIa clinical trial is being led by Dr. Barry Snow, and is an open-label investigation of the safety and clinical effects of NTCELL in Parkinson’s patients who no longer respond to current therapy. Dr. Snow is the leader of the Auckland Movement Disorders Clinic at the Auckland District Health Board but is also an internationally recognized clinician and researcher in Parkinson’s disease.
These patients will be carefully tracked for improvements in the control of movement and balance. LCT hopes to present the results on this clinical trial, which will last 29 weeks) at the 19th International Congress of Parkinson’s Disease and Movement Disorders in San Diego in June 2015.
Dr Ken Taylor, chief executive, notes that the success of the implant procedure means that the time scale for the LCT clinical program remains intact.
“The treatment phase of the trial has been completed on schedule. We believe NTCELL has the potential to be the first disease-modifying treatment for patients who are failing the current conventional treatment for Parkinson’s disease,” said Dr Taylor.
Even though this Phase I/IIa clinical trial is meant to test the efficacy of NTCELL in Parkinson disease patients, NTCELL also has the potential to be used in a number of other central nervous system indications such as Huntington’s, Alzheimer’s and other types of diseases that affect motor neurons.
Let me emphasize that the huge number of posters and talks at the SfN conference made it impossible to attend all of them, so my recollections here are some of the high points that I was able to take in. There is a lot of terrific science going on out there and these conferences are windows into it.
One poster described a feeding study in rats. One group of rats received a diet rich in omega-3 fatty acids, which are found in fish oils and soy. Another group was fed a standard laboratory diet that tends to skim on the omega-3 fatty acids. In the brains of the omega-3-fed rats, the expression off the gene that encodes Brain Derived Neurotropic Factor or BDNF increased significantly.
This is significant because BDNF promotes the survival of nerve cells (neurons) by playing a role in the growth, maturation (differentiation), and maintenance of these cells. In the brain, BDNF protein is active at the connections between nerve cells (synapses), where cell-to-cell communication occurs. The synapses can change and adapt over time in response to experience, a characteristic called synaptic plasticity, and BDNF regulates synaptic plasticity, which is important for learning and memory.
When these researchers examined why the BDNF gene was unregulated in rats fed the omega-3-rich diet, they discovered that the starting point of the gene, which is called the promoter was nice and clear. In the standard diet rats, the promoter of the BDNF gene was chemically modified with methyl (-CH3) groups. In the absence of the methyl groups, the transcription factor CTCF was able to bind and increase the rate of transcription. If the promoter was chemically modified with methyl groups, then a protein called MeCP2 bound to the promoter and prevented expression of BDNF.
This group looked further and discovered that the omega-3-rich diet seemed to influence the expression of BDNF by means of the balance of reduced and oxidized versions of electron carriers in cells, in particular, the ratio of NAD+ to NADH. NAD is a major electron carrier in cells and the ratio of NAD+, the oxidized version of this molecule, to the reduced version of this molecule, NADH, is a measure of the energy charge of the cell and how well-fed the individual is. More importantly, NAD is a substrate for another regulator of gene expression called Sirtuins.
Sirtuins are protein deacetylases, but they are unusual deacetylases since many of them they do not simply hydrolyze acetyl-lysine residues. Instead they couple lysine deacetylation to NAD hydrolysis. This hydrolysis produces O-acetyl-ADP-ribose, which is the deacetylated substrate and nicotinamide, which is an inhibitor of sirtuin activity. The dependence of sirtuins on NAD links their enzymatic activity directly to the energy status of the cell via the cellular NAD:NADH ratio.
The fact that a diet high in omega-3 fatty acids affects the NAD/NADH ratio is significant for Alzheimer’s disease because the sirtuin, SIRT1, deacetylates and coactivates the promoter for the gene that encodes the retinoic acid receptor beta gene, which subsequently upregulates the expression of alpha-secretase (ADAM10). Alpha-secretase is able to suppress beta-amyloid production. ADAM10 activation by SIRT1 also induces the Notch signaling pathway, which is known to repair neuronal damage in the brain. All of this begins with a dietary factor that actually protects the brain from Alzheimer’s disease by profound changes in gene expression.
Another poster from an Italian group used the 5XFAD mouse model of Alzheimer’s disease to test a growth factor called “painless Nerve Growth Factor” on mice with protein plaque formation in their brains. The growth factor was given by placing droplets of the growth factor in the noses of the mice while they were anesthetized. The results were stunning. Normally, 5XFAD mice get plaques quickly in their brains and lots of them. However, the growth factor was able to rescue the onset of behavioral deficits and reduces, although not eliminate, plaque formation. Other brain-specific pathologies found in these mice were reduced, such as astrocytosis. The wandering white cells in the brain known as microglia did a better job of gobbling up protein aggregates and clearing them from the brain, and the markers of inflammation were significantly reduced. I asked the investigator if there were plans to try to move this to clinical trials, and she said that she was unable to do so because of a lack of funding. Maybe someone will collaborate with this dear lady to make it so?
In another poster, the overexpression of an enzyme called heparanase in the brain decreased the burden of protein aggregates in the brains of mice with Alzheimer’s disease. I was not able to get into the details of this poster because of time.
In another poster, a very energetic young man told me about his very interesting work with a Parkinson’s disease model in rodents. If mice are administered a drug called MPTP (short for 1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine), the dopamine-using neurons in the brain will specifically take up this drug in high concentrations and it will kill them. Therefore, this drug is an excellent model system to study Parkinson’s disease in mice.
Prokineticin-2 is a gene that is expressed in high quantities in the surviving dopamine-using neurons that came from the brains of Parkinson’s disease patients after their deaths. When Prokineticin-2 was overexpressed in cultured dopaminergic neurons, they unregulated a protein called Bcl-2. Bcl-2 is one of the group of proteins can protect cells from dying. Therefore, Prokineticin-2 is a prosurvival protein.
Next, this chap switched from a culture system to a “in a living animal” system or an in vivo system. By using genetically engineered viruses that overexpressed Prokineticin-2 in the brains of mice, he discovered that this viruses did not adversely affect the mice and he did in fact achieve high levels of Prokineticin-2 in the brains of mice with this recombinant viruses. The overexpression did not affect the mice in the least. When he did the same experiment with MPTP-treated mice – oh, just to be clear, he overexpressed Prokineticin-2 first and then administered the MPTP because it takes about 30 days for the viruses to properly upregulate Prokineticin-2 – he saw decreased inflammation in the brain, and increase in Bcl-2 and Pink1 expression in the brain (both of these genes are pro-survival genes), and the behavioral problems of the mice never emerged with the severity of the MPTP mice. When he examined TH – an enzyme that makes the neurotransmitter dopamine, he saw that levels of this enzyme were up too. This means that the dopamine-using neurons were surviving. Is this cool stuff or what?
According to the Japan Times, Kyoto University’s Jun Takahashi and his team have plans to launch a clinical study for Parkinson’ disease patients that will utilize cells derived from induced pluripotent stem cells made from the patient’s own cells.
In an interview with Takahashi, the Japan Times reported on Wednesday of this week that he hopes to develop the induced Pluripotent Stem Cell (iPSCs) treatment as soon as possible so that Kyoto University Hospital can provide this treatment by fiscal year 2018 as a designated advanced medical technique that can be used in combination with other conventional treatments and medicines already covered by various insurance policies. Takahashi also expressed his hope that by fiscal year 2023, public health insurance will pay for his treatment.
For this clinical study, Parkinson’s disease patients whose conditions have progressed to the point where their medications are no longer effective will be the primary targeted group. “It will take a long time” to establish an effective treatment for the progressive disorder, which is incurable at present, Takahashi said, stressing the importance of maintaining a positive attitude toward development and not losing hope.
Parkinson’s disease causes the nerve cells in the brain that utilize the neurotransmitter dopamine to die off. The death of these dopaminergic neurons adversely affects voluntary muscle movement.
The design of this clinical study will include the production of iPSCs from adult cells collected from participating patients. These stem cells will be differentiated into neural stem cells that make dopaminergic neurons. These dopaminergic neuron precursor cells will be transplanted back into the midbrains of the donors before they develop into nerve cells, according to Takahashi. This way, all injected cells will still have the capacity to divide and migrate once implanted into the brain, but they will still have the capacity to form dopaminergic neurons.
Takahashi’s team will also seek to develop a method for producing a nerve cell drug created from cells taken out of healthy people, to ease the financial burden on patients, he said, since the derivation of iPSCs remains prohibitively expensive.
Takahashi also said he aims to being clinical trials by March 2019.
Induced pluripotent stem cells (iPSCs) are made from mature adult cells by means of genetic engineering and cell culture techniques. These cells have embryonic stem cell-like capacities and can, potentially differentiate into any adult cell type. Because neurons made from iPSCs have sometimes not shown instability, the ability of neurons derived from iPSCs to stably integrate into brain has been questioned.
Schwamborn and Hemmer showed that six months after implantation, their iPSCs-derived neurons had become fully functionally integrated into the brain. This successful integration of iPSC-derived neurons into lastingly stable implants raises hope for future therapies that will replace sick neurons with healthy ones in the brains of patients with Parkinson’s disease, Alzheimer’s disease and Huntington’s chorea, for example. This work was published in the current issue of Stem Cell Reports.
The LCSB research group hopes to bring cell replacement therapy to maturity as a treatment for neurodegenerative diseases. The replacement of sick and/or dead neurons in the brain could one day cure disorders such as Parkinson’s disease. However, devising a successful therapy in human is a long, arduous process, and for good reasons. “Successes in human therapy are still a long way off, but I am sure successful cell replacement therapies will exist in future. Our research results have taken us a step further in this direction,” declared Schwamborn.
In their latest tests, the LCSB research group, in collaboration with colleagues from the Max Planck Institute and the University Hospital Münster and the University of Bielefeld, made stable neuronal implants in the brain from neurons that were derived from reprogrammed skin cells. They used a newer technique in which the neurons were produced from neural stem cells (NSCs). These NSCs or induced neural stem cells (iNSCs) had, in turn been made from iPSCs that were made from the host animal’s own skin cells, which considerably improves the compatibility of the implanted cells. Mice who received the neuronal implants showed no adverse side effects even six months after implantation. The new neurons were implanted into the hippocampus and cortex regions of the brain. Implanted neurons were fully integrated into the complex network of the brain and they exhibited normal activity and were connected to the original brain cells via newly formed connections known as synapses, which are the contact points between nerve cells.
These tests demonstrate that stem cells researchers are continuing to get a better handle on how to use cells derived from something other than human embryos in order to successfully replace damaged or dead tissue. “Building upon the current insights, we will now be looking specifically at the type of neurons that die off in the brain of Parkinson’s patients – namely the dopamine-producing neurons,” Schwamborn reports.
In future experiments, implanted neurons could provide the neurotransmitter dopamine (which is lacking in patients with Parkinson’s disease) directly into the patient’s brain and transport it to the appropriate sites. Such a result would herald an actual cure for the disease rather than a short-term fix. The first trials in mice are in progress at the LCSB laboratories on the university campus Belval.
Stem cell treatments for curing Parkinson’s disease have been one of the dreams of stem cell scientists ever since the first embryonic stem cells were derived from mouse embryos in 1981. Unfortunately, this proved to be one of the harder therapeutic nuts to crack. Several experiments have shown that while feasible, getting the recipe right has required a fair amount of tweaking.
Parkinson’s disease (PD) results from the progressive death of neurons in the midbrain that release a neurotransmitter called dopamine, To review briefly, the brain consists of the forebrain, midbrain and hindbrain. The forebrain consists of the two large cerebral hemispheres that occupy the vast majority of the space within your skull. In addition to the left and right cerebral hemispheres is the diencephalon that consists of the thalamus, subthalamus, hypothalamus, and epithalamus. The thalamus serves as a relay station for a whole variety of nerve fiber tracts, the hypothalamus regulates visceral activities by way of other brain regions and the autonomic nervous system. and the epithalamus connects the limbic system to the rest of the brain. The midbrain, which lies below the diencephalon, is part of the brain stem and dopamine produced in two regions of the midbrain, the substantia nigra and ventral tegmental area play roles in motivation and habituation, and refinement of the control of voluntary movement, The hindbrain consists of the metencephalon and the myelencephalon, both of which contain mutiple fiber tracts and nuclei for vital functions.
The death of dopamine-producing neurons in the pars compacta region of the substantia nigra region of the midbrain causes PD. The par compacta sends nerve fibers to the cerebral hemispheres, in particular to cluster of neurons called the basal ganglia. The basal ganglia do not initiate movement, but they refine movement and stabilize the limbs and other body parts while moving. Thus the basal ganglia normally exert a constant inhibitory influence on a wide range of movements. preventing movement at inappropriate times. When someone decides to move, this inhibition is reduced for the required motor system, thereby releasing it for activation. Dopamine releases this inhibition, and therefore high levels of dopamine tend to promote movement and low levels of dopamine demand greater exertion to generate any given movement. Thus the net effect of dopamine depletion is to produce hypokinesia, or less overall movement.
Now that we have some knowledge of PD and what causes it, we can examine how to cure it. Since the death of dopamine-secreting neurons causes PD, replacing death or moribund neurons should be possible. Several preclinical studies in laboratory animals and clinical studies with human patients has shown that this is possible.
Rodents can contract a synthetic form of PD if they are treated with a drug called 6-hydroxydopamine. This drug kills off their dopamine-secreting neurons and creates a PD-like disease. Embryonic stem cells can be differentiated in the laboratory into dopamine-secreting neurons, which can then be transplanted into the midbrain. In PD rats, this strategy has reversed the symptoms of PD, but tumor growth has been a nagging problem. The biggest problem is that isolating fully differentiated dopamine-secreting cells has proven difficult because of a lack of good, solid indicators that say to the scientists, “This one is a dopamine-secreting neuron and this one is not.” Thus, isolating nice, clean cultures of only dopamine-secreting cells has been kind of tough to do.
Fortunately, Doi and others in the Takahashi lab at the University of Kyoto showed that prolonged maturation culture system (42 days long) can eliminate most of the tumor-making cells. However, this culture system is laboriously long. Now, Takahashi and Doi and others have struck again in a paper published in Stem Cell Reports in which they used induced pluripotent stem cells to derive dopamine-secreting neurons to treat PD rats. Because induced pluripotent stem cells are made from a patient’s own adult cells and are converted into embryonic-like stem cells by means of a combination of genetic engineering and cell culture techniques, they are patient-specific and do not require the dismembering of human embryos.
The novelty of this paper is that Doi and others used a protein that acts as an earmark for dopamine-secreting midbrain neurons and this protein is called CORIN. CORIN is a protease, which simply means that it clips other proteins into small pieces. Nevertheless, by using the CORIN protein, Takahashi, Doi and others successfully and efficiently isolated dopamine-secreting midbrain neurons from other cells in their cultures. Additionally, Doi and the gang were able to differentiate the induced pluripotent stem cells into dopamine-secreting progenitor cells. This means that the cells were poised to differentiate into dopamine-secreting neurons, but were not quite there yet. This way, the cells would grow in culture, but upon transplantation, they would differentiate into dopamine-secreting neurons rather than form tumors. High numbers of cells are required for clinical purposes and this technique allows the for production of large number of cells.
The technique used in this paper also produced the cells under conditions that were safe, scalable and potentially usable for clinical use. These high-quality cells never produced any tumors and produced definitive behavioral improvements in the implanted laboratory animals. The problems that remain are one of scale. The grafts of dopamine-secreting cells that survived in the midbrains of these mice were relatively small (about 1 square millimeter in size or the thickness of a dime). This is probably due to the fact that the cells differentiate when transplanted rather than growing. Therefore, this technique will need to be adapted to somehow increase the size of the graphs of dopamine-secreting neurons. In some PD patients such small graphs will probably work just fine, but in others, probably not. The other issue is that these implanted cells might be subjected to the same bad intracerebral environment as the original cells and die off quickly, thus abrogating any positive clinical effect they might have. This is another issue that will need to be examined.
The work goes on, without the need to destroy any embryos.
See Daisuke Doi at al., Isolation of Human Induced Pluripotent Stem Cell-Derived Dopaminergic Progenitors by Cell Sorting for Successful Transplantation. Stem Cell Reports 2014, 2: 337-350.
Using stem cells to model neurodegenerative diseases shows terrific promise, but because the stem cells tend to produce young cells, they often fail to accurately model disorders that show late-onset. To solve this problem, a research group has published a paper in the December 5th edition of the journal Cell Stem Cell that describes an ingenious new method that converts induced pluripotent stem cells (iPSCs) into nerve cells that recapitulate features associated with aging as well as Parkinson’s disease. This simple approach, which involves exposing iPSC-derived cells to a protein associated with premature aging called “progerin,” could provide a way for scientists to use stem cells to model a range of late-onset disorders. This technique could potentially open new avenues for preventing and treating these devastating diseases.
“With current techniques, we would typically have to grow pluripotent stem cell-derived cells for 60 or more years in order to model a late-onset disease,” says senior study author Lorenz Studer of the Sloan-Kettering Institute for Cancer Research. “Now, with progerin-induced aging, we can accelerate this process down to a period of a few days or weeks. This should greatly simplify the study of many late-onset diseases that are of such great burden to our aging society.”
Induced pluripotent stem cells allow scientists to model a specific patient’s disease in a culture dish. By extracting a small sample of skin cells and genetically engineering them with pluripotency factors, the cells are reprogrammed into embryonic-like stem cells that have the ability to differentiate into other disease-relevant cell types like neurons or blood cells. However, iPSC-derived cells are immature and they can take months to become functional. Consequently, their slow maturation process causes iPSC-derived cells to be too young to effectively model diseases that emerge later in life.
To overcome this hurdle, Studer’s team exposed iPSC-derived skin cells and neurons that originated from both young and old donors, to a protein called “progerin.” Progerin is a mutant form of the nuclear lamin proteins that provide structure to the nuclear membrane. Mutations in these proteins cause premature aging and an early death from old age. Short-term exposure of these iPSC-derived cells to progerin caused them to manifest age-associated markers that are normally present in older cells.
Then Studer and others used iPSC technology to reprogram skin cells taken from patients with Parkinson’s disease and differentiated them into dopaminergic neurons; the type of neuron that is defective in these patients. After exposure to progerin, these cultured neurons recapitulated disease-related features, including neuronal degeneration and cell death as well as mitochondrial defects.
“We could observe novel disease-related phenotypes that could not be modeled in previous efforts of studying Parkinson’s disease in a dish,” says first author Justine Miller of the Sloan-Kettering Institute for Cancer Research. “We hope that the strategy will enable mechanistic studies that could explain why a disease is late-onset. We also think that it could enable a more relevant screening platform to develop new drugs that treat late-onset diseases and prevent degeneration.”
Stem cell scientists from the University of Wisconsin at Madison have transplanted neural cells that were made from a monkey’s skin cells into the brain of that same monkey. The transplanted cells formed variety of new brain cells that were entirely normal after six months.
This experiment is a proof-of-principle investigation that shows that personalized medicine in which regenerative treatments are designed for specific individuals is possible. These neural cells were derived from the monkey’s skin cells and were, therefore, no foreign. Therefore, there is no risk of them being rejected by the host immune system.
Su-Chun Zhang, professor of neuroscience at the University of Wisconsin-Madison, said: “When you look at the brain, you cannot tell that it is a graft. Structurally the host brain looks like a normal brain; the graft can only be seen under the fluorescent microscope.”
Marina Emborg, associate professor of medical physics at UW-Madison and one of the lead co-authors of the study, said: “This is the first time I saw, in a nonhuman primate, that the transplanted cells were so well-integrated, with such a minimal reaction. And after six months, to see no scar, that was the best part.”
The skin-derived neural cells were implanted into the monkey brain by means of a state-of-the-art surgical procedure whereby the surgeon was guided by a live MRI. The three rhesus monkeys used in the study at the Wisconsin National Primate Research Center had brain lesions that caused Parkinson’s disease. Up to one million Americans suffer from Parkinson’s disease, and some 60,000 new patients are diagnosed with it each year. Parkinson’s disease results from the death of midbrain neurons that manufacture the neurotransmitter dopamine.
The cells that were transplanted into the brain were derived from induced pluripotent stem cells (iPSCs), which, like embryonic stem cells, can develop into virtually any cell in the adult human body.
Once the iPSC lines were established, Zhang and his colleagues differentiated them into neural progenitor cells (NPCs), which have the ability to form a wide variety of brain-specific cells. Zhang was the first scientist to ever successfully differentiate iPSCs into NPCs, and therefore, this paper utilized his unique expertise.
According to Zhang, “We differentiate the stem cells only into neural cells. It would not work to transplant a cell population contaminated by non-neural cells. By taking cells from the animal and returning them in a new form to the same animal, this is a first step toward personalized medicine. Now we want to more ahead and see if this leads to a real treatment for this awful disease.”
Another positive sign was the absence of any signs of cancer, which is a troubling but potential outcome of stem cell transplants. Zhang jubilantly but guardedly announced that the appearance of the cells is “normal, and we also used antibodies that mark cells that are dividing rapidly, as cancer cells are, and we do not see that. And when you look at what the cells have become, the become neurons with long axons, as we’d expect. The also build oligodendrocytes that are helping build insulating sheaths for neurons, as they should. That means they have matured correctly, and are not cancerous.”
Zhang and his colleagues at the Waisman Center on the UW-Madison campus designed this experiment as a proof of principle investigation, but because they did not transplant enough dopamine-making cells into the brain, the animal’s behavior did not improve. Thus, although this transplant technique is certainly very promising, it is some ways from the clinic.
As noted by Emborg: “Unfortunately, this technique cannot be used to help patients until a number of questions are answered: Can this technique improve the symptoms? Is it safe? Six months is not long enough.” Emborg continued, “And what are the side effects? You may improve some symptoms, but if that leads to something else, then you have not solved the problem.”
Regardless of these shortcomings, this study still represents a genuine breakthrough. “By taking cells from the animal and returning them in a new form to the same animal, this is a first step toward personalized medicine,” said Emborg.
When we hear the word cholesterol we often have very negative thoughts of clogged arteries, heart attacks and strokes. However, cholesterol serves several vital roles in our bodies. It regulates the fluidity of the membranes of our cells, serves as a precursor for the synthesis of steroid hormones (such as estrogen, testosterone, cortisol and others), and is an important signaling molecule for several biological processes. Therefore. cholesterol is not all bad. Cholesterol when we get too much of it and our bodies handle the excess cholesterol poorly. Then wandering cells called macrophages have to mop up the excess cholesterol, but it makes them sick, and they get lost underneath the inner layers of blood vessels. That, however, is for another blog post.
In the present study, scientist from Karolinska Institutet in Sweden have identified two molecules, both of which are derivatives of cholesterol, that can help turn brain cells into the kind of cells that die during Parkinson’s disease. This finding might be useful for producing large quantities of neurons in the laboratory for therapeutic purposes.
As I have blogged before Parkinson’s disease results from the death of midbrain neurons that use the neurotransmitter dopamine. Because these midbrain neurons project to, in part, regions of the brain involved in voluntary movement, the death of the dopamine-using neurons in the midbain produces pronounced defects in voluntary movement and resting stability. Several experiment in humans and laboratory animals have definitively shown that cell transplantation experiments can improve the symptoms of patients with Parkinson’s disease. Therefore, cultivating and growing dopamine-using neurons in the laboratory is of cardinal importance in the treatment of this devastating disease.
Workers in the laboratory of Ernest Arenas investigated molecules known to play a role in the differentiation of midbrain neurons. They discovered that a group of receptors collectively known as “liver X receptors” or LXRs are necessary for making ventral midbrain neurons from neural stem cells. However, they were unsure what molecules bound to the LXRs in order to activate them.
Enter cholesterol stage right. By subjecting LXRs to a cocktail of molecules from living organisms and analyzing by means of mass spectrometry, they discovered that two molecules, cholic acid (a bile salt), and 24,25-EC, both of which are derivatives of cholesterol, bind to LXR and activate it.
Cholic acid binds to LXR and stimulates the neural stem cells to form a group of midbrain cells known as the “red nucleus.” The red nucleus receives signals from several different parts of the brain to coordinate the movements of several different parts of the body. The other molecule, 24,25-EC binds to LXR and induces the formation of dopamine-using midbrain neurons – the ones that die off during Parkinson’s disease.
These data could open the possibility that cholesterol derivatives can be used to produce dopamine-using neurons from neural stem cells to treat Parkinson’s disease.
Ernest Arenas, professor of stem cell neurobiology in the department of biochemistry and biophysics, who led this study said: “We are familiar with the idea of cholesterol as a fuel for cells, and we know that it is harmful for humans to consume too much cholesterol. What we have shown now is that cholesterol has several functions, and that it is involved in extremely important decisions for neurons. Derivatives of cholesterol control the production of new neurons in the developing brain. When such a decision has been taken, cholesterol aids in the construction of these new cells, and in their survival. Thus cholesterol is extremely important for the body, and in particular for the development and function of the brain.”
A research group from Kobe, Japan at the RIKEN Center for Molecular Imaging Science and collaborators from Osaka, Kyoto, and Tokyo have successfully differentiated bone marrow mesenchymal stem cells (MSCs) into dopamine-making neurons (the kind that die off during Parkinson’s disease), and transplanted them into macaques (a type of monkey shown below) that have Parkinson’s disease. The implanted cells relieved the motor symptoms of Parkinson’s disease. This is a remarkable proof-of-priniciple publication.
Parkinson’s disease causes a variety of motor (motor simply means associated with voluntary movement) problems. Parkinson’s disease patients have tremors, rigidity, slowness of movement, and difficulty walking. These symptoms result from the death of neurons in the midbrain that make a neurotransmitter called dopamine. Dopamine-making neurons in the midbrain are connected to regions in the cerebral cortex that help coordinate voluntary movement. Without these dopamine-making neurons, voluntary movement suffers and the characteristic symptoms of Parkinson’s disease ensue.
Several experiments have shown that replacing the dead dopamine-making neurons with manufactured neurons is feasible, but finding the right stem cell to do this has been laborious. In this new publication, a collaborative research team from Japan, led by Takuya Hayashi at the RIKEN center for Molecular Imaging Science in Kobe used a very versatile stem cell from bone marrow called the mesenchymal stem cell (also known as a stromal stem cell) for this experiment. MSCs, particularly those from bone marrow, have been used in many different regenerative medical experiments and clinical trials. However, the ability of MSCs to form neurons remains rather controversial. Even though researchers could get MSCs to form cells that looked like neurons in culture, several labs have presented observations that challenge this notion. Nevertheless, several groups have used genetic engineering techniques to place specific genes into MSCs, and these introduced genes do push MSCs to become not only neurons, but dopamine-making neurons (for papers, see Dezawa M, et al. J Clin Invest. 2004 113(12):1701–10, and Nagane K, et al., Tissue Eng Part A. 2009;15(7):1655–65).
Once it was confirmed that Hayashi and his co-workers had indeed made dopamine-making neurons from the MSCs, they were surgically transplanted into the brains of macaques that had been given a drug-induced form of Parkinson’s disease. Those animals that received the dopamine-making neurons made from bone marrow MSCs showed significant improvement in motor defects.
Did the cells integrate into the brain? Clearly they did. PET scans of the animal’s brains showed that the implanted cells were metabolically active and making dopamine. Further postmortem examination of the macaque brains confirmed that the implanted cells were still in the brains after seven months. Also, the PET scans and postmortem examination also confirmed that none of the implanted animals had any tumors or showed changes in blood chemistry. Thus the implanted cells improved symptoms, integrated into the brain. and did not produce any significant side effects or tumors.
This paper nicely illustrates that it is entirely possible to treat a patient’s Parkinson’s disease with cells from their own bone marrow in a manner that is safe and relatively effective.
Parkinson’s disease (PD) is a neurodegenerative disease that is a global problem and the incidence of PD increases as the population lives longer and longer. PD results from the loss of dopamine-making neurons in the midbrain. The main treatment for PD is a drug called L-DOPA, which can cross the blood-brain barrier, but this drug decreases in effectiveness as time progresses because the neurons become less sensitive to the drug and L-DOPA does not prevent dopamine-making neurons in the midbrain from dying.
Experimental stem cell treatments of PD have used embryonic stem cells and induced pluripotent stem cells that were differentiated into dopamine-making neurons and transplanted into the midbrain of rodents that suffered from drug-induced PD. Unfortunately, even though symptom relief was observed, tumors were formed in many of these animals in these experiments. Until a more sure-fire way is discovered to identify and isolated dopamine-secreting neurons from other cells types, this approach will always seem too dangerous for clinical trials. References: Embryonic stem cells – Brederlau, et al., Stem Cells 2006 24:1433-40; Sonntag KC, et al. (2007) Stem Cells 25:411–418. and Roy, et al., Nature Medicine 2006 12:1259-68. Induced Pluripotent Stem Cells – Chang, et al., Cell Transplant 2012 21:313-32.
A paper that used induced pluripotent stem cells and differentiated them into dopamine-producing neurons which were transplanted into the brains of PD rodents did not produce tumors (see Hargus, et al., Proceedings of the National Academy of Sciences USA 2010 107:15921-6). It is likely that the stringent isolation procedures employed in this paper decreased tumor incidence (48 different cell lines were generated in this paper and none of them produced detectable tumors).
These experiments show that stem cell-based treatments for PD are feasible. The key is to find the right cell. Well, an old bromide says that “your nose knows.” Maybe this is true in the case of PD treatments. In the nose resides a tissue known as the “olfactory epithelium,” (OE) which is a source of stem cells that can form neurons. OEs can be harvested with minimally invasive nasal surgery (see Winstead W, et al., American Journal of Rhinology 2005 19:83-90). In fact, more than 150 different patient-specific cell lines of “human olfactory neural progenitor” (hONPs) cells have been established from cultures of adult olfactory epithelial cells taken from cadavers (see Roisen FJ, et al., Brain Research 2001 890:11-22).
Human ONPs can also be differentiated into dopamine-making neurons in culture (Zhang X., et al., Stem Cells 2006 24:434-442). Therefore, these cells should be candidate stem cells for making treatments for PD.
Fred Roisen and his cohorts from the University of Louisville, Kentucky, has used hONPs to treat rats with drug-induced PD. In their paper, Roisen and others used cultures of hONPs and then proceeded to differentiate them into dopamine-making neurons. Then they transplanted these cells into the midbrains of rats that had been treated with 6-hydroxydopamine, which is a drug that kills off dopamine-making neurons in the midbrain and induces PD. However, it is important to understand that the dopamine-producing neurons were only destroyed on the right side of the brain, thus leaving the left side intact. When they stem cells were injected into the midbrains of these rats, they were only injected into the right side, the side that had been damaged by the drugs. Therefore, the right side of the midbrain served as a control throughout these experiments.
The behavioral tests on these PD rats determined if the transplanted hONPs helped decrease the effects of PD. In all three behavioral tests, the hONP-injected rats showed significant improvements over the untreated rats. Were these improvements due to the formation of new dopamine-making neurons? The answer is a clear yes, since postmortem analyses of the brains of these rats showed that the hONP-injected rats not only showed the presence of dopamine-making neurons on the injected side, but the levels of dopamine production in the right side of the brain as compared to the left side of the brain were higher in the hONP-injected animals, even though they were three times lower than those dopamine levels found in the left side of the midbrain.
This experiment shows that hONPs should be considered serious players in the treatment of PD. In none of the transplanted animals were tumors found. Therefore, hONPs seem to be safe, they are easily acquired, and they have the capacity to form dopamine-making neurons. The goal should be to jack up the dopamine levels in the transplanted cells.
See Meng Wang, Chengliang Lu, Fred Roisen, “Adult human olfactory epithelial-derived progenitors: A potential autologous source for cell-based treatment for Parkinson’s disease,” Stem Cells Translational Medicine 2012 1:492-502.
A research team led by Virginia Lee, who works as a neurobiologist at the University of Pennsylvania in Philadelphia has provided a mechanism for how misfolded proteins cause Parkinson’s disease. Lee’s group has resurrected an old treatment strategy that was discarded long ago that just might to slow the progression of this neurological disease.
Alpha-synuclein is a strange name for a protein, but it is a specifically found in the nervous system. Alpha-synuclein protein can compose as much as 1% of all the protein in the cytoplasm of a neuron. It is found all over the brain. What this protein actually does is a bit of a mystery, but the latest data suggests that alpha-synuclein helps traffic proteins from membranes to other places in the cell (Cooper et al., (2006). Science 313: 324–328).
In the brains of patients with Parkinson’s disease, neurons accumulate protein aggregates known as Lewy bodies. A major component of Lewy bodies is alpha-synuclein that has folded in an aberrant manner. These aggregations of misfolded alpha-synuclein cause a variety of problems inside cells that culminate in the death of the neuron.
This is the story of Parkinson’s disease so far, but Lee and her colleagues injected a misfolded synthetic version of α-synuclein into the brains of normal mice and saw the key characteristics of Parkinson’s disease develop and progressively worsen. While that is not a surprise, what Lee and co-workers found when they examined the brains of the injected laboratory animals astounded them. This study, which was published in the journal Science, shows that the injected misfolded alpha-synuclein was able to spread from one nerve cell to another. Therefore, the malformed protein did not just take up residence inside neurons, but instead was able to travel from one neuron to another.
Apparently, cells affected by misfolded alpha-synuclein are able to secrete it into the areas that surround them and this secreted protein is taken up by healthy cells. Once taken up, the misfolded alpha-synuclein induces the normal copies of the alpha-synuclein protein snap into the misfolded conformation. This eventually kills off the once-healthy neuron and also turns it into a new factory for the secretion of misfolded alpha-synuclein, which them goes on to damage other neurons.
This finding, however, raises the possibility that an antibody that binds the misfolded α-synuclein could potentially bind the protein and prevent it from passing between nerve cells. “It’s very hard to ask antibodies not only to get inside the brain, but to get inside cells,” says Lee. “But now you have the possibility of stopping the spreading. And if you stop the spreading, perhaps you can slow the progression of the disease.”
The tendency of the pathology of Parkinson’s disease to spread from neuron to neuron by a rogue protein was actually suggested in 2008. Fetal neural tissue transplants were used to treat Parkinson’s patients, but upon post-mortem examination of the transplanted fetal tissue, it was quickly recognized that these transplants has developed the characteristic Lewy bodies associated with Parkinson’s disease. This indicated that the nearby diseased cells were able to infect the transplanted tissue with Parkinson’s disease. Subsequent studies have shown that misfolded alpha-synuclein does spread between neighboring cells and induce cell death (Desplats, P. et al. Proc. Natl Acad. Sci. USA 106, 13010–13015 (2009).). The neurons, apparently, can release vesicles filled with misfolded alpha-synuclein in the same way they release neurotransmitters. This release bathes the nearby cells in misfolded alpha-synuclein, but there are still questions as to whether or not the misfolded alpha-synuclein is responsible for the cascade of brain damage seen in Parkinson’s.
Lee says that her team has now captured the full consequences of runaway α-synuclein in the brain. “We knew this transfer from one cell to another can happen, but whether it could play a significant role in the disease was still open,” says Tim Greenamyre, director of the Pittsburgh Institute for Neurodegenerative Diseases in Pennsylvania, who was not involved in the latest work.
Besides Lewy bodies, the brains of patients with Parkinson’s disease also show a dramatic loss of those neurons that produce the chemical messenger dopamine. When Lee’s team injected the misfolded α-synuclein into a part of the mouse brain rich in dopamine-producing cells, Lewy bodies began to form, followed by the death of dopamine neurons. Nerve cells linked to those near the injection site also developed Lewy bodies, which showed that cell-to-cell transmission was occurring.
Greenamyre says that is possible, but hasn’t yet been proved. “All of the cells affected in this paper were those directly in contact with the injection site,” he says. But, within six months of the injection, coordination of movement, grip strength and balance had all deteriorated in the mice, which is a recapitulation of what occurs in people with Parkinson’s disease.
“It’s really pretty extraordinary,” says Eliezer Masliah, a neuroscientist at the University of California, San Diego. “We have been trying that experiment for a long time in the lab and we have not seen such dramatic effects.” According to Masliah, Lee’s work provides the impetus for that handful of biotechnology companies that are sponsoring clinical trials of alpha-synuclein antibodies for as therapeutic agents for Parkinson’s disease. Masliah hopes that this will also motivate neuroscientists to examine exactly how the protein enters and exits cells.
There is still one mystery that has not been addressed to data: why do the Lewy bodies appear in the first place? “Parkinson’s disease is not a disorder in which somebody injects synuclein into your brain,” notes Ted Dawson, director of the Institute for Cell Engineering at Johns Hopkins University in Baltimore, Maryland. “So what sets it in motion?” Clearly some mutations in the gene that encodes alpha-synuclein increase the tendency for this protein to spontaneously misfold. But this also suggests that there are particular triggers that lead to such events. The nature of these triggers will certainly be the subject of future work.
Oprah had a show dedicated to stem cells. Her guests were Michael J. Fox, who suffers from Parkinson’s Disease and is an enthusiastic advocate for embryonic stem cell research, and Dr. Oz who seems to think that adult stem cells might be able to do all the heavy lifting for regenerative treatments. He actually brought a brain to the show and showed the midbrain to demonstrate the cells that die off during Parkinson’s disease.
Unfortunately, something Dr. Oz does not mention is that cells introduced into the brain tend to be shielded from the immune system and any embryonic stem cell derivatives that were introduced into the brains of patients with Parkinson’s disease are protected from the immune system by the blood-brain barrier. Thus, Dr. Oz’s concern about immunological rejection probably does not apply to the brain, unless the blood-brain barrier is damaged.