Parkinson's Disease

Coding Dimension ID: 
313
Coding Dimension path name: 
Neurological Disorders / Parkinson's Disease

Molecular and Cellular Transitions from ES Cells to Mature Functioning Human Neurons

Funding Type: 
Comprehensive Grant
Grant Number: 
RC1-00115
ICOC Funds Committed: 
$2 879 210
Disease Focus: 
Amyotrophic Lateral Sclerosis
Neurological Disorders
Parkinson's Disease
Genetic Disorder
Neurological Disorders
Stem Cell Use: 
Embryonic Stem Cell
oldStatus: 
Closed
Public Abstract: 
Human embryonic stem cells (hESCs) are pluripotent entities, capable of generating a whole-body spectrum of distinct cell types. We have developmental procedures for inducing hESCs to develop into pure populations of human neural stem cells (hNS), a step required for generating authentic mature human neurons. Several protocols have currently been developed to differentiate hESCs to what appear to be differentiated dopaminergic neurons (important in Parkinson’s disease (PD) and cholinergic motor neurons (important in Amyolateral Sclerosis (ALS) in culture dishes. We have developed methods to stably insert new genes in hESC and we have demonstrated that these transgenic cells can become mature neurons in culture dishes. We plan to over express alpha synuclein and other genes associated with PD and superoxide dismutase (a gene mutated in ALS) into hESCs and then differentiate these cells to neurons, and more specifically to dopaminergic neurons and cholinergic neurons using existing protocols. These transgenic cells can be used not only for the discovery of cellular and molecular causes for dopaminergic or cholinergic cell damage and death in these devastating diseases, but also can be used as assays to screen chemical libraries to find novels drugs that may protect against the degenerative process. Until recently the investigation of the differentiation of these human cells has only been observed in culture dishes or during tumor formation. Our recent results show that hESC implanted in the brains of mice can survive and become active functional human neurons that successfully integrate into the adult mouse forebrain. This method of transplantation to generate models of human disease will permit the study of human neural development in a living environment, paving the way for the generation of new models of human neurodegenerative and psychiatric diseases. It also has the potential to speed up the screening process for therapeutic drugs.
Statement of Benefit to California: 
We plan to develop procedures to induce human ES cells into mature functioning neurons that carry genes that cause the debilitating human neurological diseases, Parkinson’s disease and Amyolateral Sclerosis (ALS). We will use the cells to reveal the genes and molecular pathways inside the cells that are responsible for how the mutant genes cause damage to specific types of brain cells. We also will make the cells available to other researchers as well as biotech companies so that other investigators can use these cells to screen small molecule and chemical libraries to discover new drugs that can interfere with the pathology caused by these mutant cells that mimic human disease, in hopes of accelerating the pace of discovery.
Progress Report: 
  • Our research is focused on studying two debilitating diseases of the nervous system: Parkinson’s disease (PD) and Amyotrophic Lateral Sclerosis (ALS) also known as Lou Gehrig’s disease. While the causes and symptoms of these two conditions are very different, they share one aspect in common: patients gradually lose specific types of nerve cells, namely the so-called dopaminergic neurons in PD, and motor neurons in ALS. If we can find ways to protect the neurons from dying, we might be able to slow or even halt disease progression in ALS and PD patients. In the past two years, our lab has developed robust procedures to generate these two classes of neurons from human embryonic stem cells and we have been studying the molecular changes that govern their specialization. Since last year, we have been using neurons to elucidate the molecular mechanisms that underlie the demise of these cells.
  • ALS is one of the most common neuromuscular diseases, afflicting more than 30,000 Americans. Patients rapidly lose their motor neurons – the nerve cells that extend from the brain through the spinal cord to the muscles, thereby controlling their movement. Therapy options are extremely limited and people with ALS usually succumb to respiratory failure or pneumonia within three to five years from the onset of symptoms. Most ALS patients have no family history of ALS and carry no known genetic defects that may help explain why they develop the disease. However, a small number of ALS patients have mutations in the superoxide dismutase 1 (SOD1) gene, which encodes an enzyme that scavenges so-called free radicals – aggressive oxidizing molecules that are by-products of the cells’ normal metabolism. Researchers therefore believe that accumulation of these free radicals may damage motor neurons in ALS and contribute to their death.
  • To test this idea, we introduced the mutated form of the SOD1 gene into astrocytes – cells that provide metabolic and structural support to neurons – and cultured our stem cell-derived motor neurons along with these SOD1-mutant astrocytes. Indeed, while motor neurons grown on ‘normal’ astrocytes were fully viable, we saw widespread death of motor neurons in cocultures with ‘mutant’ astrocytes, along with elevated levels of free radicals. We think that this is due to our mutant astrocytes being causing inflammation, and so our future efforts are focused on understanding the role of the immune system, specifically the function of microglia – the resident immune cells of the brain and spinal cord – in our co-cultures with human motor neurons. We are very excited about these results because they show that our cocultures may be a very useful tool to screen drugs that may counteract the neurotoxicity caused by inflammation and free radicals. We have already begun testing several known antioxidants, and found some of them to be very effective in improving motor neuron survival in the culture dish. Such compounds may ultimately improve the condition of ALS patients.
  • PD is the second most common neurodegenerative disease and develops when neurons in the brain, and in particular, in a part of the brain known as the substantia nigra die. These neurons are called dopaminergic because they produce dopamine, a molecule that is necessary for coordinated body movement. Many dopaminergic neurons are already lost when patients develop PD symptoms, which include trembling, stiffness, and slow movement. Around one million Americans are currently suffering from PD, and 60,000 new cases are diagnosed each year. While several surgical and pharmacological treatment options exist, they cannot slow or halt disease progression and are instead aimed at treating the symptoms. The exact causes for neuron death in PD are unknown but among others inflammation in the affected brain area may play a role in disease progression.
  • In a joint effort with the laboratories of Christopher Glass and Michael Rosenfeld at the University of California, San Diego, we showed using animal experiments that a protein called Nurr1 is crucial for the development and survival of dopaminergic neurons. We found that the Nurr1 gene is turned on by inflammatory signals and suppresses genes that encode neurotoxic factors. Microglia are the major initiators of the neurotoxic response to inflammatory stimuli, which is then amplified by astrocytes. Thus our findings reveal an important role for Nurr1 in microglia and astrocytes to protect dopaminergic neurons from exaggerated production of inflammation-induced neurotoxic mediators. We are now using human embryonic stem cell-derived dopaminergic neurons, cultured along with human atrocytes and microglia to test whether we can demonstrate this positive role of Nurr1 in a culture dish as well.
  • We are investigating the molecular mechanisms underlying two major neurological diseases: Parkinson’s disease (PD) and Amyotrophic Lateral Sclerosis (ALS), also known as Lou Gehrig’s disease. In the past year, we have taken our previously developed human embryonic stem cell (hESC)-based cell culture model for PD and ALS another step further: we have begun building an assay system that may eventually allow both the identification of biomarkers for early diagnosis and the screening of drug candidates for ALS and PD. By transplanting hESC-derived neurons into live animals and brain slices, we have also made first inroads into recapitulating the disease processes in animal model systems.
  • While the causes and symptoms of ALS and PD are very different, they share one aspect in common: in both, patients gradually lose specific types of nerve cells, namely, the so-called dopaminergic neurons in PD, and motor neurons in ALS; it this neuron death that causes both diseases. Previously, we showed with our hESC-based cell culture system that an inflammatory response in astrocytes (the brain cells that provide metabolic and structural support to neurons) is involved in loss of motor neurons. Similarly, we demonstrated that microglia (the brain’s immune cells) and astrocytes together protect dopaminergic neurons from exaggerated production of inflammation-induced neurotoxic mediators. This function of astrocytes and microglia was dependent on a protein called Nurr1: we found that the Nurr1 gene is turned on by inflammatory signals and suppresses genes that encode neurotoxic factors.
  • We have now begun to characterize in depth the specific signaling molecules that communicate the inflammation cue from the glial cells to neurons. To do this, we cultured astrocytes and microglia in the petri dish, induced inflammation and collected cell culture supernatants from the ‘inflamed’ and normal cells. We then measured the levels of specific so-called cytokines, the inflammatory signaling molecules secreted by the glial cells. Once we have obtained a characteristic cytokine ‘signature’ of disease-associated glial cells, we can begin to unravel the molecular pathways that lead to inflammation. Thus our research may lead to the discovery of early diagnostic markers and enable drug screening for compounds that suppress or prevent these neurotoxic inflammatory processes.
  • Our cell culture assays have provided a great deal of insight into the signaling cascades that eventually lead to neuron death. However, they probably cannot fully recapitulate the complex interplay between the neurons and the cellular environment in which they reside within the brain. We have therefore begun to transplant hESC-derived neurons into the brains of mice. Our results indicate that the neurons rapidly extended processes and developed dendritic branches and axons that integrated into the existing neuronal network. In the coming year, we plan to build on these results, using our hESC-derived neuronal models of PD and ALS to better understand mechanisms of dysregulation. Specifically, we will examine alterations in synapse formation, cell survival, and neuron maturation. We will also devise strategies for functional recovery and rescue in the context of the living animal.
  • We are investigating the molecular mechanisms underlying two major neurological diseases: Parkinson’s disease (PD) and Amyotrophic Lateral Sclerosis (ALS), also known as Lou Gehrig’s disease. In the past year, we took our human embryonic stem cell (hESC)-based neural cell culture model for PD and ALS another step further and built sensitive and quantitative assays that can allow for the screening of drug candidates for ALS and PD. We have also consistently improved our transplanting techniques and are now able to detect functional, electrophysiologically active, hESC-derived neurons in live animals. This experiment was crucial to show that, under our culture conditions, human neurons derived from embryonic stem cells were able to integrate and form meaningful connections with other neurons in a given adult brain environment.
  • Moreover, we are now performing an in-depth characterization of the specific signaling molecules that communicate the inflammation cues from the glial cells to neurons in the presence of ALS-causing mutations (SOD1G37R) and PD-causing mutations (recombinant alfa-synuclein). In this report we have explored another functional assay to measure glial function and inflammatory response using astrocytes that express ALS-causing mutations. In addition, we report here that adding PD-causing mutagens to mixed cultures of human neurons and astrocytes results in the death of dopaminergic neurons, the type of neurons affected in PD. We are currently testing new compounds that can decrease the neuronal toxicity observed.
  • Our research may not only lead to the discovery of early diagnostic markers but also enable drug screening for compounds that suppress or prevent these neurotoxic inflammatory processes.

Modeling Parkinson's Disease Using Human Embryonic Stem Cells

Funding Type: 
SEED Grant
Grant Number: 
RS1-00331
ICOC Funds Committed: 
$758 999
Disease Focus: 
Parkinson's Disease
Neurological Disorders
Stem Cell Use: 
Embryonic Stem Cell
Cell Line Generation: 
Embryonic Stem Cell
oldStatus: 
Closed
Public Abstract: 
Parkinson’s disease (PD) is the most frequent neurodegenerative movement disorder caused by damage of dopamine-producing nerve cells (DA neuron) in patient brain. The main symptoms of PD are age-dependent tremors (shakiness). There is no cure for PD despite administration of levodopa can help to control symptoms. Most of PD cases are sporadic in the general population. However, about 10-15% of PD cases show familial history. Genetic studies of familial cases resulted in identification of PD-linked gene changes, namely mutations, in six different genes, including α-synuclein, LRRK2, uchL1, parkin, PINK1, and DJ-1. Nevertheless, it is not known how abnormality in these genes cause PD. Our long-term research goal is to understand PD pathogenesis at cellular and molecular levels via studying functions of these PD-linked genes and dysfunction of their disease-associated genetic variants. A proper experimental model plays critical roles in defining pathogenic mechanisms of diseases and for developing therapy. A number of cellular and animal models have been developed for PD research. Nevertheless, a model closely resembling generation processes of human DA nerve cells is not available because human neurons are unable to continuously propagate in culture. Nevertheless, human embryonic stem cells (hESCs) provide an opportunity to fulfill the task. hESCs can grow and be programmed to generate DA nerve cells. In this study, we propose to create a PD model using hESCs. The strategy is to express PD pathogenic mutants of α-synuclein or LRRK2 genes in hESCs. Mutations in α-synuclein or LRRK2 genes cause both familial and sporadic PD. α-Synuclein is a major component of Lewy body, aggregates found in the PD brain. The model will allow us to determine molecular action of PD pathogenic α-synuclein and LRRK2 mutants during generation of human DA neuron and interactions of PD related genes and environmental toxins in DA neurons derived from hESCs. Our working hypothesis is that PD associated genes function in hESCs-derived DA neurons as in human brain DA neurons. Pathogenic mutations in combination with environmental factors (i.e. aging and oxidative stress) impair hESCs-derived DA function resulting in eventual selective neuronal death. In this study, we will firstly generate PD cellular models via expressing two PD-pathogenic genes, α-synuclein and LRRK2 in hESCs. We will next determine effects of α-synuclein and LRRK2 on hESCs and neurons derived from these cells. Finally, we will determine whether PD-causing toxins (i.e. MPP+, paraquat, and rotenone) selectively target to DA neurons derived from hESCs. Successful completion of this study will allow us to study the pathological mechanism of PD and to design strategies to treat the disease.
Statement of Benefit to California: 
Parkinson’s disease (PD) is the second leading neurodegenerative disease with no cure currently available. Compared to other states, California is among one of the states with the highest incidence of this particular disease. First, California growers use approximately 250 million pounds of pesticides annually, about a quarter of all pesticides used in the US (Cal Pesticide use reporting system). A commonly used herbicide, paraquat, has been shown to induce parkinsonism in both animals and human. Other pesticides are also proposed as potential causative agents for PD. Studies have shown increased PD-caused mortality is agricultural pesticide-use counties in comparison to those non-use counties in California. Second, California has the largest Hispanic population. Studies suggest that incidence of PD is the highest among Hispanics (Van Den Eeden et al, American Journal of Epidemiology, Vol. 157, pages 1015-1022, 2003). Thus, finding effective treatments of PD will significantly benefit citizen in California.
Progress Report: 
  • Parkinson’s disease (PD) is the most frequent neurodegenerative movement disorder caused by damage of dopamine-producing nerve cells (DA neuron) in patient brain. The main symptoms of PD are age-dependent tremors (shakiness). There is no cure for PD despite administration of levodopa can help to control symptoms.

  • Most of PD cases are sporadic in the general population. However, about 10-15% of PD cases show familial history. Genetic studies of familial cases resulted in identification of PD-linked gene changes, namely mutations, in six different genes, including α-synuclein, LRRK2, uchL1, parkin, PINK1, and DJ-1. Nevertheless, it is not known how abnormality in these genes cause PD. Our long-term research goal is to understand PD pathogenesis at cellular and molecular levels via studying functions of these PD-linked genes and dysfunction of their disease-associated genetic variants.

  • A proper experimental model plays critical roles in defining pathogenic mechanisms of diseases and for developing therapy. A number of cellular and animal models have been developed for PD research. Nevertheless, a model closely resembling generation processes of human DA nerve cells is not available because human neurons are unable to continuously propagate in culture. Nevertheless, human embryonic stem cells (hESCs) provide an opportunity to fulfill the task. hESCs can grow and be programmed to generate DA nerve cells. In this study, we propose to create a PD model using hESCs.

  • During the funding period, we have generated a number of human ES cell lines overexpressing α-synuclein and two disease-associated α-synuclein mutants. These cells are being used to determine the cellular and molecular effects of the disease genes on human ES cells and the PD affected dopaminergic neurons made from these cells. We have found that normal and disease α-synucleins have little effect on hESC growth and differentiation. We will continue to investigate roles of this protein in modulating PD affected dopaminergic neurons. Completion of this study will allow us to study the pathological mechanism of PD and to design strategies to treat the disease.

Identifying small molecules that stimulate the differentiation of hESCs into dopamine-producing neurons

Funding Type: 
SEED Grant
Grant Number: 
RS1-00215
ICOC Funds Committed: 
$564 309
Disease Focus: 
Parkinson's Disease
Neurological Disorders
Stem Cell Use: 
Embryonic Stem Cell
oldStatus: 
Closed
Public Abstract: 
In this application, we propose to identify small molecule compounds that can stimulate human embryonic stem cells to become dopamine-producing neurons. These neurons degenerate in Parkinson’s disease, and currently have very limited availability, thus hindering the cell replacement therapy for treating Parkinson’s disease. Our proposed research, if successful, will lead to the identification of small molecule compounds that can not only stimulate cultured human embryonic stem cells to become DA neurons, but may also stimulate endogenous brain stem cells to regenerate, since the small molecule compounds can be made readily available to the brain due to their ability to cross the blood-brain barrier. In addition, these small molecule compounds may serve as important research tools, which can tell us the fundamental biology of the human embryonic stem cells.
Statement of Benefit to California: 
The proposed research will potentially lead to a cure for the devastating neurodegenerative, movement disorder, Parkinson’s disease. The proposed research will potentially provide important research tools to better understand hESCs. Such improved understanding of hESCs may lead to better treatments for a variety of diseases, in which a stem-cell based therapy could make a difference.
Progress Report: 
  • Parkinson’s disease is the most common movement disorder due to the degeneration of brain dopaminergic neurons. One strategy to combat the disease is to replenish these neurons in the patients, either through transplantation of stem cell-derived dopaminergic neurons, or through promoting endogenous dopaminergic neuronal production or survival. We have carried out a small molecule based screen to identify compounds that can affect the development and survival of dopaminergic neurons from pluripotent stem cells. The small molecules that we have identified will not only serve as important research tools for understanding dopaminergic neuron development and survival, but potentially could also lead to therapeutics in the induction of dopaminergic neurons for treating Parkinson’s disease.

Identification and characterization of human ES-derived DA neuronal subtypes

Funding Type: 
Basic Biology I
Grant Number: 
RB1-01358
ICOC Funds Committed: 
$1 407 076
Disease Focus: 
Parkinson's Disease
Neurological Disorders
Stem Cell Use: 
Embryonic Stem Cell
oldStatus: 
Closed
Public Abstract: 
Parkinson’s disease (PD) is a neurodegenerative movement disorder that affects 1 in 100 people over the age of 60, one million people in the US and six million worldwide. Patients show a resting tremor, slowness of movement (bradykinesia), postural instability and rigidity. Parkinson's disease results primarily from the loss of neurons deep in the middle part of the brain (the midbrain), in particular neurons that produce dopamine (referred to as “dopaminergic”). There are actually two groups of midbrain dopaminergic (DA) neurons, and only one, those in the substantia nigra (SN) are highly susceptible to degeneration in Parkinson’s patients. There is a relative sparing of the second group and these are called ventral tegmental area (VTA) dopaminergic neurons. These two groups of neurons reside in different regions of the adult ventral midbrain and importantly, they deliver dopamine to their downstream neuronal targets in different ways. SN neurons deliver dopamine in small rapid squirts, like a sprinkler, whereas VTA neurons have a tap that provides a continuous stream of dopamine. A major therapeutic strategy for Parkinsons’ patients is to produce DA neurons from human embryonic stem cells for use in transplantation therapy. However early human trials were disappointing, since a number of patients with grafts of human fetal neurons developed additional, highly undesirable motor dyskinesias. Why this occurred is not known, but one possibility is that the transplant mixture, which contained both SN and VTA DA neurons, provided too much or unregulated amounts of DA (from the VTA neurons), overloading or confusing the target region in the brain that usually receives dopamine from SN neurons in small, regular quantities. Future human trials will likely utilize DA neurons that have been made from human embryonic stem cells (hES). Since stem cells have the potential to develop into any type of cell in the body, these considerations suggest that we should devise a way to specifically produce SN neurons and not VTA neurons from stem cells for use in transplantation. However, although we can produce dopaminergic neurons from hES cells, to date the scientific community cannot distinguish SN from VTA neurons outside of their normal brain environment and therefore has no ability to produce one selectively and not the other. We do know, however, that these two populations of neurons normally form connections with different regions in the brain, and we propose to use this fact to identify molecular markers that distinguish SN from VTA neurons and to determine optimal conditions for the differentiation of hES to SN DA neurons, at the expense of VTA DA neurons. Our studies have the potential to significantly impact transplantation therapy by enabling the production of SN over VTA neurons from hES cells, and to generate hypotheses about molecules that might be useful for coaxing SN DA neurons to form appropriate connections within the transplanted brain.
Statement of Benefit to California: 
The goal of our work is to further optimize our ability to turn undifferentiated human stem cells into differentiated neurons that the brain can use as replacement for neurons damaged by disease. We focus on Parkinson’s disease, a neurodegenerative disease that afflicts 4-6 million people worldwide in all geographical locations, but which is more common in rural farm communities compared to urban areas, a criteria important for California's large farming population. In Parkinson’s patients, a small, well-defined subset of neurons, the midbrain dopaminergic neurons have died, and one therapeutic strategy is to transplant healthy replacement neurons to the patient. Our work will further our understanding of the biology of these neurons in normal animals. This will allow us to refine the process of turning human embryonic stem cells onto biologically active dopaminergic neurons that can be used in transplantation therapy. Our work will be of benefit to all Parkinson's patients including afflicted Californians. Further, this project will utilize California goods and services whenever possible.
Progress Report: 
  • Parkinson's disease results primarily from the loss of neurons deep in the middle part of the brain (the midbrain), in particular neurons that produce dopamine (referred to as “dopaminergic”). In this region of the midbrain there are actually two different groups of dopaminergic (DA) neurons, and only one of them, the neurons of the substantia nigra (SN) are highly susceptible to degeneration in patients with PD. There is a relative sparing of the second group of midbrain dopaminergic neurons, called the ventral tegmental area (VTA) dopaminergic neurons. These two groups of neurons reside close to each other in the brain and both make dopamine. They are virtually indistinguishable except for one major functional difference—they release dopamine, the transmitter that is lost in Parkinson’s patients, to their downstream neuronal targets in different ways. SN neurons deliver dopamine in small rapid squirts, like a sprinkler, whereas VTA neurons have a tap that provides a continuous stream of dopamine.
  • A major therapeutic strategy for patients with PD is to make new DA neurons from human embryonic stem cells (hES). As stem cells have the potential to develop into any type of cell in the body, these considerations suggest that we should devise a way to produce SN neurons in the absence of VTA neurons from stem cells for use in transplantation. At present although we can produce dopaminergic neurons from hES cells, the scientific community cannot distinguish SN from VTA neurons in vitro due to lack of molecular markers or a bioassay, and we are therefore unable to identify culture conditions that favor the production of one over the other,
  • In addition to releasing dopamine differently, SN and VTA neurons have axons that project to different regions of the striatum. It has been shown over the last decade that specific classes of guidance cues guide axons to their particular targets. One approach we have taken has been to investigate whether differences in axon guidance receptor expression and or responses to guidance cues in vitro might provide both markers and a bioassay that will distinguish SN from VTA neurons. Over the last year we have shown that VTA and SN neurons respond differentially to Netrin-1 and express different markers associated with the guidance cue family. We now have a bioassay and markers that distinguish these two populations of neurons in vitro and in the coming year we plan to utilize this information to identify cultures conditions that favor the production of SN over VTA neurons, from hES cells.
  • Parkinson’s disease results primarily from the loss of neurons deep in the middle part of the brain (the midbrain), in particular neurons that produce dopamine (referred to as “dopaminergic”). In this region of the midbrain there are actually two different groups of dopaminergic (DA) neurons, and only one of them, the neurons of the substantia nigra (SN) are highly susceptible to degeneration in patients with PD. There is a relative sparing of the second group of midbrain dopaminergic neurons, called the ventral tegmental area (VTA) dopaminergic neurons. These two groups of neurons reside close to each other in the brain and both make dopamine. They are virtually indistinguishable except for one major functional difference—they release dopamine, the transmitter that is lost in Parkinson’s patients, to their downstream neuronal targets in different ways. SN neurons deliver dopamine in small rapid squirts, like a sprinkler, whereas VTA neurons have a tap that provides a continuous stream of dopamine. 
A major therapeutic strategy for patients with PD is to make new DA neurons from human embryonic stem cells (hES). As stem cells have the potential to develop into any type of cell in the body, these considerations suggest that we should devise a way to produce SN neurons in the absence of VTA neurons from stem cells for use in transplantation. At present although we can produce dopaminergic neurons from hES cells, the scientific community cannot distinguish SN from VTA neurons in vitro due to lack of molecular markers or a bioassay, and we are therefore unable to identify culture conditions that favor the production of one over the other, 
In addition to releasing dopamine differently, SN and VTA neurons have axons that project to different regions of the striatum. It has been shown over the last decade that specific classes of guidance cues guide axons to their particular targets. One approach we have taken has been to investigate whether differences in axon guidance receptor expression and or responses to guidance cues in vitro might provide both markers and a bioassay that will distinguish SN from VTA neurons. We showed previously that VTA and SN neurons respond differentially to Netrin-1 and express different markers associated with the guidance cue family. Also, in this year using backlabeling, laser capture and microarray analysis of SN vs VTA neurons, we have identified a number of genes expressed in on or the other population. We now have a bioassay and markers that distinguish these two populations of neurons in vitro and in the coming year we plan to utilize this information to identify cultures conditions that favor the production of SN over VTA neurons, from hES cells.
  • Parkinson's disease (PD) is a neurodegenerative movement disorder that affects more than six million people worldwide. The main symptoms of the disease result from the loss of neurons from the midbrain that produce dopamine (referred to as "dopaminergic" or DA neurons).Human embryonic stem cells (hESC) offer an exciting opportunity to treat Parkinson’s disease by transplanting hESC-derived DA neurons to replace those that have died. There are actually two groups of midbrain DA neurons in the human brain. Those from the substantia nigra (SN) are highly susceptible to degeneration in Parkinson's patients while those from the ventral tegmental area (VTA) are not. These two types of neurons have similar features but have different functions and it is important to ensure that DA neurons from hESC are the correct SN type before they are used in therapy. The primary goal of this research was to study these two neuronal types in animals and determine if the distinguishing features discovered in mice or rats can be used to more easily recognize and purify SN-type DA neurons made from hESC.
  • One of the discoveries made in this research is that SN and VTA neurons show differences in how they make connections within the brain. We have been able to identify some of the molecules that guide each neuron to connect to it appropriate target and have found that SN and VTA neurons placed in the petri dish can be distinguished from each other by their response to guidance molecules. Work in the final period of this grant has focused on testing guidance response in hESC-derived DA neurons and we have found that many of the neurons produced from hESC do show SN-like responses to guidance molecules. This discovery is being further developed as a screening tool to help guide our ongoing efforts to make increasingly pure populations of DA neurons from hESC.
  • Future human trials will likely utilize such DA neurons but since embryonic stem cells have the potential to develop into any type of cell in the body, it is important to ensure that the production methods used to make a therapeutic product for Parkinson’s disease do indeed specifically produce SN neurons. Prior to the research supported under this CIRM grant, the scientific community was not able to distinguish SN from VTA neurons outside of their normal brain environment and therefore had no ability to confirm whether a method produced one type selectively and not the other. Further refinements of the assay tools developed in our research may provide a practical means of quantifying the purity of a DA neuron preparation. This would have a significant impact transplantation therapy as well as provide useful insights into the molecular mechanisms that underlie proper connectivity and function of SN and VTA DA neurons in humans.

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