Posts tagged iPSCs
Articles and news from the latest research reports.
'Disease in a dish' approach could aid Huntington's disease discovery efforts
Creating induced pluripotent stem cells or iPS cells allows researchers to establish “disease in a dish” models of conditions ranging from Alzheimer’s disease to diabetes. Scientists at Yerkes National Primate Research Center, Emory University have now applied the technology to a model of Huntington’s disease (HD) in transgenic nonhuman primates, allowing them to conveniently assess the efficacy of potential therapies on neuronal cells in the laboratory.
(Image caption: Neural progenitor cells derived from transgenic rhesus macaque iPS cells show features of Huntington’s disease pathology, making them a useful tool for therapeutic discovery.)
The results were published this week in Stem Cell Reports.
"A highlight of our model is that our progenitor cells and neurons developed cellular features of HD such as intranuclear inclusions of mutant Huntingtin protein, which most of the currently available cell models do not present," says senior author Anthony Chan, PhD, DVM, associate professor of human genetics at Emory University School of Medicine and Yerkes National Primate Research Center. "We could use these features as a readout for therapy using drugs or a genetic manipulation."
Chan and his colleagues were the first in the world to establish a transgenic nonhuman primate model of HD. HD is an inherited neurodegenerative disorder that leads to the appearance of uncontrolled movements and cognitive impairments, usually in adulthood. It is caused by a mutation that introduces an expanded region where one amino acid (glutamine) is repeated dozens of times in the huntingtin protein.
The non-human primate model has extra copies of the huntingtin gene that contains the expanded glutamine repeats. In the non-human primate model, motor and cognitive deficits appear more quickly than in most cases of Huntington’s disease in humans, becoming noticeable within the first two years of the monkeys’ development.
First author Richard Carter, PhD, a graduate of Emory’s Genetics and Molecular Biology doctoral program, and his colleagues created iPS cells from the transgenic monkeys by reprogramming cells derived from the skin or dental pulp. This technique uses retroviruses to introduce reprogramming factors into somatic cells and induces a fraction of them to become pluripotent stem cells. Pluripotent stem cells are able to differentiate into any type of cell in the body, under the right conditions.
Carter and colleagues induced the iPS cells to become neural progenitor cells and then differentiated neurons. The iPS-derived neural cells developed intracellular and intranuclear aggregates of the mutant huntingtin protein, a classic sign of Huntington’s pathology, as well as an increased sensitivity to oxidative stress.
The sensitivity to oxidative stress was a useful indicator; it could be ameliorated in cell culture, either by a RNA-based gene knockdown approach, or the drug memantine, which is currently being investigated for Huntington’s disease in a human clinical trial.
"We tested two known experimental interventions, but our findings are a proof of principle that this system could be a valuable tool for the discovery and evaluation of other therapies," Chan says.
(Source: news.emory.edu)
'Support cells' in brain play important role in Down syndrome
Researchers from UC Davis School of Medicine and Shriners Hospitals for Children – Northern California have identified a group of cells in the brain that they say plays an important role in the abnormal neuron development in Down syndrome. After developing a new model for studying the syndrome using patient-derived stem cells, the scientists also found that applying an inexpensive antibiotic to the cells appears to correct many abnormalities in the interaction between the cells and developing neurons.
The findings, which focused on support cells in the brain called astroglial cells, appear online today in Nature Communications.
“We have developed a human cellular model for studying brain development in Down syndrome that allows us to carry out detailed physiological studies and screen possible new therapies,” said Wenbin Deng, associate professor of biochemistry and molecular medicine and principal investigator of the study. “This model is more realistic than traditional animal models because it is derived from a patient’s own cells.”
Down syndrome is the most common chromosomal cause of mild to moderate intellectual disabilities in the United States, where it occurs in one in every 691 live births. It develops when a person has three copies of the 21st chromosome instead of the normal two. While mouse models have traditionally been used in studying the genetic disorder, Deng said the animal model is inadequate because the human brain is more complicated, and much of that complexity arises from astroglia cells, the star-shaped cells that play an important role in the physical structure of the brain as well as in the transmission of nerve impulses.
“Although neurons are regarded as our ‘thinking cells,’ the astroglia have an extremely important supportive role,” said Deng. “Astroglial function is increasingly recognized as a critical factor in neuronal dysfunction in the brain, and this is the first study to show its importance in Down syndrome.”
Creating a unique human cellular model
To investigate the role of astroglia in Down syndrome, the research team took skin cells from individuals with Down syndrome and transformed them into stem cells, which are known as induced pluripotent stem cells (iPSC). The cells possess the same genetic make-up as the donor and an ability to grow into different cell types. Deng and his colleagues next induced the stem cells to develop into separate pure populations of astroglial cells and neurons. This allowed them to systematically analyze factors expressed by the astroglia and then study their effects on neuron development.
They found that a certain protein, known as S100B, is markedly increased in astroglial cells from patients with Down syndrome compared with those from healthy controls. S100B released by astroglial cells promotes harmful astroglial activation (astrogliosis) and adversely affects neurons, causing them to die at increased rates or develop in multiple dysfunctional ways.
The investigators obtained further evidence of the critical role of astroglial cells in Down syndrome by implanting the skin-cell derived astroglial cells from Down syndrome patients into mice. Those mice then developed the neuropathological phenotypes of Down syndrome, while mice implanted with Down syndrome neurons did not.
Neuroprotective effects of antibiotics
The research team also screened candidate drugs using a ‘disease-in-a-dish’ model. When they administered minocycline — a tetracycline antibiotic with anti-inflammatory properties commonly used to treat bacterial infections, acne and arthritis — many of the abnormalities in the astroglial cells were corrected and there were more healthy interactions between the astroglia and neurons compared to the control cells without the defect.
“The advent of induced pluripotent stem cell technology has created exciting new approaches to model neurodevelopmental and neurodegenerative diseases for the study of pathogenesis and for drug screening,” said David Pleasure, professor of neurology and pediatrics and a co-author of the study. “Using this technology, the study is the first to discover the critical role of astroglial cells in Down syndrome as well as identify a promising pathway for exploring how a drug such as minocycline may offer an effective way to help treat it.”
Pleasure, who is research director at Shriner’s Hospital for Children Northern California and also directs the Institute for Pediatric Regenerative Medicine, noted that considerable research interest has arisen about the use of minocycline for diseases of the central nervous system because of the increasing evidence about its neuroprotective effects. Unlike many drugs, minocycline can cross from the bloodstream into the brain so that it can act on the astroglial cells. The drug has never been tested as a treatment for Down syndrome, and both Pleasure and Deng cautioned that its safety and efficacy will require clinical trials in people with Down syndrome.
Currently, Deng’s laboratory is conducting additional preclinical studies using the human-derived stem cells from Down syndrome patients and mouse models to determine whether cellular and behavioral abnormalities can be improved with minocycline therapy and other candidate drugs.
“The abnormalities we identified occur in the early stages of Down syndrome,” said Deng. “While much more research is needed, it is exciting to consider that pharmacological intervention in these cellular processes might help slow or even prevent disease progression.”
(Image: iStockphoto)
Researchers Use Human Stem Cells to Create Light-Sensitive Retina in a Dish
Using a type of human stem cell, Johns Hopkins researchers say they have created a three-dimensional complement of human retinal tissue in the laboratory, which notably includes functioning photoreceptor cells capable of responding to light, the first step in the process of converting it into visual images.
(Image caption: Rod photoreceptors (in green) within a “mini retina” derived from human iPS cells in the lab. Image courtesy of Johns Hopkins Medicine)
“We have basically created a miniature human retina in a dish that not only has the architectural organization of the retina but also has the ability to sense light,” says study leader M. Valeria Canto-Soler, Ph.D., an assistant professor of ophthalmology at the Johns Hopkins University School of Medicine. She says the work, reported online June 10 in the journal Nature Communications, “advances opportunities for vision-saving research and may ultimately lead to technologies that restore vision in people with retinal diseases.”
Like many processes in the body, vision depends on many different types of cells working in concert, in this case to turn light into something that can be recognized by the brain as an image. Canto-Soler cautions that photoreceptors are only part of the story in the complex eye-brain process of vision, and her lab hasn’t yet recreated all of the functions of the human eye and its links to the visual cortex of the brain. “Is our lab retina capable of producing a visual signal that the brain can interpret into an image? Probably not, but this is a good start,” she says.
The achievement emerged from experiments with human induced pluripotent stem cells (iPS) and could, eventually, enable genetically engineered retinal cell transplants that halt or even reverse a patient’s march toward blindness, the researchers say.
The iPS cells are adult cells that have been genetically reprogrammed to their most primitive state. Under the right circumstances, they can develop into most or all of the 200 cell types in the human body. In this case, the Johns Hopkins team turned them into retinal progenitor cells destined to form light-sensitive retinal tissue that lines the back of the eye.
Using a simple, straightforward technique they developed to foster the growth of the retinal progenitors, Canto-Soler and her team saw retinal cells and then tissue grow in their petri dishes, says Xiufeng Zhong, Ph.D., a postdoctoral researcher in Canto-Soler’s lab. The growth, she says, corresponded in timing and duration to retinal development in a human fetus in the womb. Moreover, the photoreceptors were mature enough to develop outer segments, a structure essential for photoreceptors to function.
Retinal tissue is complex, comprising seven major cell types, including six kinds of neurons, which are all organized into specific cell layers that absorb and process light, “see,” and transmit those visual signals to the brain for interpretation. The lab-grown retinas recreate the three-dimensional architecture of the human retina. “We knew that a 3-D cellular structure was necessary if we wanted to reproduce functional characteristics of the retina,” says Canto-Soler, “but when we began this work, we didn’t think stem cells would be able to build up a retina almost on their own. In our system, somehow the cells knew what to do.”
When the retinal tissue was at a stage equivalent to 28 weeks of development in the womb, with fairly mature photoreceptors, the researchers tested these mini-retinas to see if the photoreceptors could in fact sense and transform light into visual signals.
They did so by placing an electrode into a single photoreceptor cell and then giving a pulse of light to the cell, which reacted in a biochemical pattern similar to the behavior of photoreceptors in people exposed to light.
Specifically, she says, the lab-grown photoreceptors responded to light the way retinal rods do. Human retinas contain two major photoreceptor cell types called rods and cones. The vast majority of photoreceptors in humans are rods, which enable vision in low light. The retinas grown by the Johns Hopkins team were also dominated by rods.
Canto-Soler says that the newly developed system gives them the ability to generate hundreds of mini-retinas at a time directly from a person affected by a particular retinal disease such as retinitis pigmentosa. This provides a unique biological system to study the cause of retinal diseases directly in human tissue, instead of relying on animal models.
The system, she says, also opens an array of possibilities for personalized medicine such as testing drugs to treat these diseases in a patient-specific way. In the long term, the potential is also there to replace diseased or dead retinal tissue with lab-grown material to restore vision.
(Source: hopkinsmedicine.org)
In a cloning first, scientists create stem cells from adults
Scientists have moved a step closer to the goal of creating stem cells perfectly matched to a patient’s DNA in order to treat diseases, they announced on Thursday, creating patient-specific cell lines out of the skin cells of two adult men.
The advance, described online in the journal Cell Stem Cell, is the first time researchers have achieved “therapeutic cloning” of adults. Technically called somatic-cell nuclear transfer, therapeutic cloning means producing embryonic cells genetically identical to a donor, usually for the purpose of using those cells to treat disease.
First stem cell study of bipolar disorder yields promising results
Stem cell model shows nerve cells develop, behave and respond to lithium differently – opening doors to potential new treatments
What makes a person bipolar, prone to manic highs and deep, depressed lows? Why does bipolar disorder run so strongly in families, even though no single gene is to blame? And why is it so hard to find new treatments for a condition that affects 200 million people worldwide?
New stem cell research published by scientists from the University of Michigan Medical School, and fueled by the Heinz C. Prechter Bipolar Research Fund, may help scientists find answers to these questions.
The team used skin from people with bipolar disorder to derive the first-ever stem cell lines specific to the condition. In a new paper in Translational Psychiatry, they report how they transformed the stem cells into neurons, similar to those found in the brain – and compared them to cells derived from people without bipolar disorder.
The comparison revealed very specific differences in how these neurons behave and communicate with each other, and identified striking differences in how the neurons respond to lithium, the most common treatment for bipolar disorder.
It’s the first time scientists have directly measured differences in brain cell formation and function between people with bipolar disorder and those without.
The researchers are from the Medical School’s Department of Cell & Developmental Biology and Department of Psychiatry, and U-M’s Depression Center.
Stem cells as a window on bipolar disorder
The team used a type of stem cell called induced pluripotent stem cells, or iPSCs. By taking small samples of skin cells and exposing them to carefully controlled conditions, the team coaxed them to turn into stem cells that held the potential to become any type of cell. With further coaxing, the cells became neurons.
“This gives us a model that we can use to examine how cells behave as they develop into neurons. Already, we see that cells from people with bipolar disorder are different in how often they express certain genes, how they differentiate into neurons, how they communicate, and how they respond to lithium,” says Sue O’Shea, Ph.D., the experienced U-M stem cell specialist who co-led the work.
“We’re very excited about these findings. But we’re only just beginning to understand what we can do with these cells to help answer the many unanswered questions in bipolar disorder’s origins and treatment,” says Melvin McInnis, M.D., principal investigator of the Prechter Bipolar Research Fund and its programs.
“For instance, we can now envision being able to test new drug candidates in these cells, to screen possible medications proactively instead of having to discover them fortuitously.”
The research was supported by donations from the Heinz C. Prechter Bipolar Research Fund, the Steven M. Schwartzberg Memorial Fund, and the Joshua Judson Stern Foundation. The A. Alfred Taubman Medical Research Institute at the U-M Medical School also supported the work, which was reviewed and approved by the U-M Human Pluripotent Stem Cell Research Oversight committee and Institutional Review Board.
O’Shea, a professor in the Department of Cell & Developmental Biology and director of the U-M Pluripotent Stem Cell Research Lab, and McInnis, the Upjohn Woodworth Professor of Bipolar Disorder and Depression in the Department of Psychiatry, are co-senior authors of the new paper.
McInnis, who sees firsthand the impact that bipolar disorder has on patients and the frustration they and their families feel about the lack of treatment options, says the new research could take treatment of bipolar disorder into the era of personalized medicine.
Not only could stem cell research help find new treatments, it may also lead to a way to target treatment to each patient based on their specific profile – and avoid the trial-and-error approach to treatment that leaves many patients with uncontrolled symptoms.
More about the findings:
The skin samples were used to derive the 42 iPSC lines. When the team measured gene expression first in the stem cells, and then re-evaluated the cells once they had become neurons, very specific differences emerged between the cells derived from bipolar disorder patients and those without the condition.
Specifically, the bipolar neurons expressed more genes for membrane receptors and ion channels than non-bipolar cells, particularly those receptors and channels involved in the sending and receiving of calcium signals between cells.
Calcium signals are already known to be crucial to neuron development and function. So, the new findings support the idea that genetic differences expressed early during brain development may have a lot to do with the development of bipolar disorder symptoms – and other mental health conditions that arise later in life, especially in the teen and young adult years.
Meanwhile, the cells’ signaling patterns changed in different ways when the researchers introduced lithium, which many bipolar patients take to regulate their moods, but which causes side effects. In general, lithium alters the way calcium signals are sent and received – and the new cell lines will make it possible to study this effect specifically in bipolar disorder-specific cells.
Like misdirected letters and packages at the post office, the neurons made from bipolar disorder patients also differed in how they were ‘addressed’ during development for delivery to certain areas of the brain. This may have an impact on brain development, too.
The researchers also found differences in microRNA expression in bipolar cells – tiny fragments of RNA that play key roles in the “reading” of genes. This supports the emerging concept that bipolar disorder arises from a combination of genetic vulnerabilities.
The researchers are already developing stem cell lines from other trial participants with bipolar disorder, though it takes months to derive each line and obtain mature neurons that can be studied. They will share their cell lines with other researchers via the Prechter Repository at U-M. They also hope to develop a way to use the cells to screen drugs rapidly, called an assay.
Scientists use latest stem cell and gene-editing techniques to generate neurons in a dish, and reveal new clues behind deadly diseases of the brain
There is no easy way to study diseases of the brain. Extracting neurons from a living patient is both difficult and risky, while examining a patient’s brain post-mortem usually only reveals the disease’s final stages. And animal models, while incredibly informative, have frequently fallen short during the crucial drug-development stage of research. The result: we are woefully unprepared to fight—and win—the war against this class of diseases.
But scientists at the Gladstone Institutes and the University of California, San Francisco (UCSF) are taking a potentially more powerful approach: an advanced stem-cell technique that creates a human model of degenerative disease in a dish.
Using this model, the team uncovered a molecular process that causes neurons to degenerate, a hallmark sign of conditions such as Alzheimer’s disease and frontotemporal dementia (FTD). The results, published in the latest issue of Stem Cell Reports, offer fresh ammunition in the continued battle against these and other deadly neurodegenerative disorders.
The research team, led by Gladstone Investigator Yadong Huang, MD, PhD, identified an important mechanism behind tauopathies. A group of disorders that includes both Alzheimer’s and FTD, tauopathies are characterized by the abnormal accumulation of the protein Tau in neurons. This buildup is thought to contribute to the degeneration of these neurons over time, leading to debilitating symptoms such as dementia and memory loss. But while this notion has been around for a long time, the underlying processes have largely remained unclear.
“So much about the mechanisms that cause tauopathies is a mystery, in part because traditional approaches—such as post-mortem brain analysis and animal models—give an incomplete picture,” explained Dr. Huang. “But by using the latest stem-cell technology, we generated human neurons in a dish that exhibited the same pattern of cell degeneration and death that occurs inside a patient’s brain. Studying these models allowed us to see for the first time how a specific genetic mutation may kick start the tauopathy process.”
Other scientists recently discovered that the Tau mutation in question could increase a person’s risk of developing different tauopathies, including Alzheimer’s or FTD. So the research team, in collaboration with Bruce Miller, MD, who directs the UCSF Memory and Aging Center and who provided skin cells from a patient with this mutation, transformed these cells into induced pluripotent stem cells, or iPS cells. This technique, pioneered by Gladstone Investigator and 2012 Nobel Laureate Shinya Yamanaka, MD, PhD, allows scientists to reprogram adult skin cells into cells that are virtually identical to stem cells. These stem cells can then develop into almost any cell in the body.
The team combined this method with a cutting-edge gene-editing technique that essentially eliminated the Tau mutation in some of the iPS cells. The result was a system that allowed the team to compare neurons that had the mutation to those that did not.
“Our approach allowed us to grow human neurons in a dish that contained the exact same mutation as the neurons in the brain of the patient,” explained first author Helen Fong, PhD, who is also a California Institute for Regenerative Medicine postdoctoral scholar. “By comparing these diseased neurons with the ‘genetically corrected’ healthy neurons, we could see—cell by cell—how the Tau mutation leads to the abnormal build up of Tau and, over time, neuronal degeneration and death.”
“Tau’s main functions include keeping the skeletal structure of individual neurons intact and regulating neuronal activity,” said Dr. Huang. “But our research showed that the Tau produced by neurons from people with the Tau mutation is different; so it is red-flagged by the cell and targeted for destruction. However, instead of being flushed out, Tau gets chopped into pieces. These potentially toxic fragments accumulate over time and may in fact cause the neuron to degenerate and die.”
But by correcting the Tau mutation, the team effectively removed Tau’s red flag. The protein remained in one piece, the abnormal buildup ceased and the neurons remained healthy. Ongoing studies aim to determine whether the abnormal fragmentation and buildup of mutant tau is really the main cause of the neuronal death and, if so, how to block it.
Finding a way to block this toxic buildup of tau fragments has been a key focus of drug development—but has thus far been unsuccessful. But Dr. Huang and his colleagues are optimistic that their approach could be exactly what researchers need to fight back against deadly tauopathies.
“These findings not only offer a glimpse into how these powerful new models can shed light on mechanisms of disease” said Dr. Miller, “They may also prove invaluable for screening potential drugs that could be developed into better treatments for Alzheimer’s disease, FTD and related conditions.”
Stanford/Yale study gives insight into subtle genomic differences among our own cells
Stanford University School of Medicine scientists have demonstrated, in a study conducted jointly with researchers at Yale University, that induced-pluripotent stem cells — the embryonic-stem-cell lookalikes whose discovery a few years ago won this year’s Nobel Prize in medicine — are not as genetically unstable as was thought.
The new study, published online Nov. 18 in Nature, showed that what seemed to be changes in iPS cells’ genetic makeup — presumed to be inflicted either in the course of their generation from adult cells or during their propagation and maintenance in laboratory culture dishes — instead are often accurate reflections of existing but previously undetected genetic variations among the cells comprising our bodies.
That’s good news for researchers hoping to use the cells to study disease or, someday, for regenerative medicine. But it raises the question of whether and to what extent we humans are really walking mosaics whose constituent cells differ genetically from one to the next in possibly significant respects, said Alexander Urban, PhD, assistant professor of psychiatry and behavioral sciences. Urban shared senior authorship of the study with bioinformatics professor Mark Gerstein, PhD, and neurobiology professor Flora Vaccarino, MD, both of Yale.
Researchers use stem cells to show connection between neural cell disruption and Parkinson’s disease
A diverse team of biologists has shown using induced pluripotent stem cells (iPSCs) that a gene mutation that causes malformations in the structure of the nuclear envelope of neural cells, is associated with Parkinson’s disease. In their paper published in the journal Nature, they describe how they found iPSC cells taken from Parkinson’s patients over time demonstrated the same cell disruption found in neural cells taken from other deceased patient’s with the disease. They also found that by introducing a compound known to disrupt the gene mutation, that they could reverse the cell malformation.
Parkinson’s disease is a degenerative disorder of the nervous system characterized by shaking, slowness of movement and difficulty walking. Over time most patients succumb to dementia and eventually die. Much research has centered on the disruption and death of dopamine-generating cells as the root cause of the disorder despite evidence that such a disruption would not result in all of the symptoms Parkinson’s patient’s exhibit. For that reason, researchers have looked to other causes.
In this new effort, the researchers looked at possible reasons for disruption to the nuclear envelope, the thin film that separates the nucleus from the cytoplasm in neural cells. Such disruptions have been associated with Parkinson’s but no definitive correlation has been found, until now.
To gain a better understanding of what might be causing such disruptions, the research team obtained samples of induced iPSCs from Parkinson’s patients and allowed them to grow in an external environment. They noted that the same disruptions occurred as the iPSCs grew into neural cells, suggesting a genetic cause. Prior research had indicated that a mutation of the LRRK2 gene was connected to Parkinson’s disease but no clear indication of the mechanism involved had been found. Testing the cells derived from the iPSCs showed the same mutation, implicating it as a possible cause of the disorder. The researchers also induced the mutation in human embryo stem cells and found that they too developed the same disruption as they grew into neural cells as was found with the iPSCs.
Next the researchers generated a line of iPSCs minus the mutation and found that the cells did not develop the disruptions. They followed that up by adding a chemical compound known to disrupt the mutation to already affected cells and discovered that it prevented them from being disrupted as well.
The researchers don’t know why the mutation occurs but believe a new therapy for treating Parkinson’s patients might be on the horizon as a result of their research.
(Source: medicalxpress.com)
Cell reprogramming: much promise, many hurdles
Research in reprogrammed cells, which on Monday earned the 2012 Nobel Prize, has been hailed as a new dawn for regenerative medicine but remains troubled by several clouds.
Britain’s John Gurdon and Japan’s Shinya Yamanaka were honoured with the world’s paramount award in medicine for induced pluripotent stem cells (iPSCs).
They discovered that a mature, adult cell can be turned back to an infant, versatile state called a stem cell.
First theorised in the late 19th century, stem cells are touted as a source of replacement tissue, fixing almost anything from malfunctioning hearts and lungs, damaged spines, Parkinson’s disease or even baldness.
The first human trials were launched only in 2010, and progress has been dogged by the contested use of stem cells taken from early-stage embryos, where the most adaptable, or pluripotent, cells are found.
Created by Yamanaka in 2006, iPSCs ease the moral row as they derive from adult cells and not embryos, said University of Oxford ethics professor Julian Savulescu. Ordinary skin cells can be used as the starting material.
"Many people objected to the creation of embryos for research, describing it as cannabalizing human beings," he said.