Posts tagged medicine
Articles and news from the latest research reports.
Monell scientists identify elusive taste stem cells
Scientists at the Monell Center have identified the location and certain genetic characteristics of taste stem cells on the tongue. The findings will facilitate techniques to grow and manipulate new functional taste cells for both clinical and research purposes.
"Cancer patients who have taste loss following radiation to the head and neck and elderly individuals with diminished taste function are just two populations who could benefit from the ability to activate adult taste stem cells," said Robert Margolskee, M.D., Ph.D., a molecular neurobiologist at Monell who is one of the study’s authors.
Taste cells are located in clusters called taste buds, which in turn are found in papillae, the raised bumps visible on the tongue’s surface.
Two types of taste cells contain chemical receptors that initiate perception of sweet, bitter, umami, salty, and sour taste qualities. A third type appears to serve as a supporting cell.
A remarkable characteristic of these sensory cells is that they regularly regenerate. All three taste cell types undergo frequent turnover, with an average lifespan of 10-16 days. As such, new taste cells must constantly be regenerated to replace cells that have died.
For decades, taste scientists have attempted to identify the stem or progenitor cells that spawn the different taste receptor cells. The elusive challenge also sought to establish whether one or several progenitors are involved and where they are located, whether in or near the taste bud.
Drawing on the strong physiological relationship between oral taste cells and endocrine (hormone producing) cells in the intestine, the Monell team used a marker for intestinal stem cells to probe for stem cells in taste tissue on the tongue.
Stains for the stem cell marker, known as Lgr5 (leucine-rich repeat-containing G-protein-coupled receptor 5), showed two patterns of expression in taste tissue. The first was a strong signal underlying taste papillae at the back of the tongue and the second was a weaker signal immediately underneath taste buds in those papillae.
The Monell scientists hypothesize that the two levels of expression could indicate two different populations of cells. The cells that more strongly express Lgr5 could be true taste stem cells, whereas those with weaker expression could represent those stem cells that have begun the transformation into functional taste cells.
Additional studies revealed that the Lgr5-expressing cells were capable of becoming any one of the three major taste cell types.
The findings are published online in the journal Stem Cells.
"This is just the tip of the iceberg," said senior author Peihua Jiang, Ph.D., also a Monell molecular neurobiologist. "Identification of these cells opens up a whole new area for studying taste cell renewal, and contributes to stem cell biology in general."
Future studies will focus on identifying the factors that program the Lgr5-expressing cells to differentiate into the different taste cell types, and explore how to grow these cells in culture, thus providing a renewable source of taste receptor cells for research and perhaps even clinical use.
(Image: Getty)
Type II diabetes and the Alzheimer’s connection
A research team in Israel has devised a novel approach to identifying the molecular basis for designing a drug that might one day decrease the risk diabetes patients face of developing Alzheimer’s disease. The team will present its work at the 57th Annual Meeting of the Biophysical Society (BPS), held Feb. 2-6, 2013, in Philadelphia, Pa.
A recent study suggests that people who suffer from type 2 diabetes face twice the risk of developing Alzheimer’s disease later in life compared to those who do not have diabetes. The link these diseases share relates to the formation of two types of peptide deposits that aggregate, or clump together. Peptides are chains of amino acids; longer chains form proteins. One type of peptide, called amyloid beta, is found in Alzheimer plaques in neurons of the brain. The other type, amylin, is found in the pancreas and the brain. Two years ago, researchers found both molecules in the pancreas of diabetic patients, and in both diseases their presence has been linked to the progression of the disease state.
To explore the hypothesis that interactions between the two molecules might play a critical role in the self-assembly of peptides that leads to protein aggregation, Yifat Miller, assistant professor from Ben-Gurion University of the Negev, Beer-Sheva, Israel, characterized the way the two protein molecules interact with each other through an examination of their structure. It was the first analysis of its kind.
"By identifying the specific ‘hot regions’ of these peptides that strongly interact with each other, our study may provide insight into the link between type 2 diabetes and Alzheimer’s disease," Miller says. "We believe that preventing these interactions by developing a drug will decrease the risk that type 2 diabetes patients face of developing Alzheimer’s disease later life."
(Source: eurekalert.org)
Joslin scientists report the first generation of human induced pluripotent stem cells from patients with an uncommon form of diabetes, maturity onset diabetes of the young (MODY). These cells offer a powerful resource for studying the role of genetic factors in the development of MODY and testing potential treatments. The findings appear in the Journal of Biological Chemistry.
Human induced pluripotent stem cells (hiPSCs) are adult cells that have been genetically reprogrammed to exhibit the characteristics of embryonic stem cells, including the ability to differentiate into specialized cell types. The generation of hiPSCs, which was first reported in 2006, was a major scientific breakthrough with the potential to increase understanding of many diseases and aid in drug development.
Maturity onset diabetes of the young (MODY) is a form of diabetes that mainly affects individuals age 25 or younger and accounts for about 1 to 5 percent of all diabetes cases in the United States. Unlike type 1 and type 2 diabetes, which are polygenic and result from alterations in genetic and environmental factors, MODY is a monogenic disease that results from mutations in a single gene. To date, eight types of MODY and eleven MODY genes have been identified. Some types of MODY produce only mild symptoms and are often treated solely with oral diabetic medications.
Joslin Diabetes Center is one of a limited number of research institutes with the capability to generate hiPSCs from patients with diabetes. The cells used to produce the hiPSCs were obtained from patients with five different types of MODY at Joslin Diabetes Center and Haukeland University Hospital, Bergen, Norway. The MODY-hiPSCs are morphologically, molecularly and functionally indistinguishable from human pluripotent stem cells (hPSCs).
As a monogenic disease, MODY provides “a valuable opportunity to directly study in more detail the genetic mechanisms underlying the disease and not be influenced by other factors, such as insulin resistance,” says senior author Rohit N. Kulkarni, M.D., Ph.D., a Principal Investigator in the Section on Islet Cell and Regenerative Biology at Joslin and Associate Professor of Medicine at Harvard Medical School.
The scientists will first induce the MODY-hiPSCs to differentiate towards beta cells and in the process learn more about the potential blocks in their ability to differentiate. Using the iPSC-derived beta cells, they plan to study how MODY genes regulate the insulin secretory function. “Generating hiPSCs is an important step forward because we cannot obtain beta cells from living patients. These cells will allow us to do many experiments that otherwise would not be possible,” says Dr. Kulkarni.
The scientists also plan to explore ways to correct the genetic defect and use the beta cells derived from the “repaired” hiPSCs to test various treatments. “If we find medications that improve beta cell function, we can go back to the clinic and use them to treat patients,” says Dr. Kulkarni. “It will allow us to tailor treatments to a patient’s unique characteristics and provide personalized medicine to diabetes patients.”
New stroke gene discovery could lead to tailored treatments
A study led by King’s College London has identified a new genetic variant associated with stroke. By exploring the genetic variants linked with blood clotting – a process that can lead to a stroke – scientists have discovered a gene which is associated with large vessel and cardioembolic stroke but has no connection to small vessel stroke.
Published in the journal Annals of Neurology, the study provides a potential new target for treatment and highlights genetic differences between different types of stroke, demonstrating the need for tailored treatments.
Approximately 152,000 people in Britain have a stroke each year, costing the UK over £8.2 billion. While there are thought to be 1.2 million stroke survivors in the UK, more than half have been left with disabilities that affect their daily lives.
A stroke occurs when the blood supply to the brain is cut off, often due to a blood clot blocking an artery that carries blood to the brain, which then leads to brain cell damage. Coagulation (blood clotting) abnormalities, particularly easy clotting of the blood, are therefore common contributing factors in the development of stroke.
Dr Frances Williams, Senior Lecturer from the Department of Twin Research and Genetic Epidemiology at King’s and lead author of the paper, said: ‘Previous studies have demonstrated the influence of genetic factors on the components of coagulation. The goal of this study was to extend these observations to determine if they were further associated with different types of stroke.’
The research was carried out in three stages. The first consisted of a genome-wide association study (GWAS) in 2100 healthy volunteers which identified 23 independent genetic variants that were involved in coagulation. The second stage examined the 23 variants in 4200 stroke and non-stroke cases from centres across Europe (Wellcome Trust Case Control Consortium 2 and MORGAM collections) and found that a particular mutation on the ABO gene was significantly associated with stroke.
Stage three of the study used the MetaStroke cohort, a project of the International Stroke Genetics Consortium which comprises 8900 stroke cases recruited from centres in the Europe, USA and Australia, whose DNA has been collected and undergone GWA scan. It was confirmed that a variant in the ABO blood type gene was associated with stroke, a finding specific to large vessel and cardioembolic stroke.
Dr Williams said: ‘The discovery of the association between this genetic variant and stroke identifies a new target for potential treatments, which could help to reduce the risk of stroke in the future. It is also significant that no association was found with small vessel disease, as this suggests that stroke subtypes involve different genetic mechanisms which emphasises the need for individualised treatment.’
Treatment to prevent Alzheimer’s disease moves a step closer
A new drug to prevent the early stages of Alzheimer’s disease could enter clinical trials in a few years’ time according to scientists.
Alzheimer’s is the most common type of dementia, which currently affects 820,000 people in the UK, with numbers expected to more than double by 2050. One in three people over 65 will die with dementia.
The disease begins when a protein called amyloid-β (Aβ) starts to clump together in senile plaques in the brain, damaging nerve cells and leading to memory loss and confusion.
Professor David Allsop and Dr Mark Taylor at Lancaster University have successfully created a new drug which can reduce the number of senile plaques by a third, as well as more than doubling the number of new nerve cells in a particular region of the brain associated with memory. It also markedly reduced the amount of brain inflammation and oxidative damage associated with the disease.
The drug was tested on transgenic mice containing two mutant human genes linked to inherited forms of Alzheimer’s, so that they would develop some of the changes associated with the illness. The drug is designed to cross the blood-brain barrier and prevent the Aβ molecules from sticking together to form plaques.
Professor Allsop, who led the research and was the first scientist to isolate senile plaques from human brain, said: “When we got the test results back, we were highly encouraged. The amount of plaque in the brain had been reduced by a third and this could be improved if we gave a larger dose of the drug, because at this stage, we don’t know what the optimal dose is.”
The drug needs to be tested for safety before it can enter human trials, but, if it passes this hurdle, the aim would be to give the drug to people with mild symptoms of memory loss before they develop the illness.
“Many people who are mildly forgetful may go on to develop the disease because these senile plaques start forming years before any symptoms manifest themselves. The ultimate aim is to give the drug at that stage to stop any more damage to the brain, before it’s too late.”
Support for the research was given by Alzheimer’s Research UK, and the results are published in the open access journal PLOS ONE.
Medical illustrators and neurological imaging experts at Johns Hopkins have figured out how night-hunting owls can almost fully rotate their heads - by as much as 270 degrees in either direction - without damaging the delicate blood vessels in their necks and heads, and without cutting off blood supply to their brains.
In what may be the first use of angiography, CT scans and medical illustrations to examine the anatomy of a dozen of the big-eyed birds, the Johns Hopkins team, led by medical illustrator Fabian de Kok-Mercado, M.A., a recent graduate student in the Department of Art as Applied to Medicine, found four major biological adaptations designed to prevent injury from rotational head movements. The variations are all to the strigid animals’ bone structure and vascular network needed to support its top-heavy head. The team’s findings are acknowledged in the Feb.1 issue of the journal Science, as first-place prize winners in the posters and graphics category of the National Science Foundation’s 2012 International Science & Engineering Visualization Challenge.
Discovery opens the door to a potential ‘molecular fountain of youth’
A new study led by researchers at the University of California, Berkeley, represents a major advance in the understanding of the molecular mechanisms behind aging while providing new hope for the development of targeted treatments for age-related degenerative diseases.
Researchers were able to turn back the molecular clock by infusing the blood stem cells of old mice with a longevity gene and rejuvenating the aged stem cells’ regenerative potential. The findings were published online in the journal Cell Reports.
The biologists found that SIRT3, one among a class of proteins known as sirtuins, plays an important role in helping aged blood stem cells cope with stress. When they infused the blood stem cells of old mice with SIRT3, the treatment boosted the formation of new blood cells, evidence of a reversal in the age-related decline in the old stem cells’ function.
“We already know that sirtuins regulate aging, but our study is really the first one demonstrating that sirtuins can reverse aging-associated degeneration, and I think that’s very exciting,” said study principal investigator Danica Chen, UC Berkeley assistant professor of nutritional science and toxicology. “This opens the door to potential treatments for age-related degenerative diseases.”
Genome-wide Atlas of Gene Enhancers in the Brain On-line
Future research into the underlying causes of neurological disorders such as autism, epilepsy and schizophrenia, should greatly benefit from a first-of-its-kind atlas of gene-enhancers in the cerebrum (telencephalon). This new atlas, developed by a team led by researchers with the U.S. Department of Energy (DOE)’s Lawrence Berkeley National Laboratory (Berkeley Lab) is a publicly accessible Web-based collection of data that identifies and locates thousands of gene-regulating elements in a region of the brain that is of critical importance for cognition, motor functions and emotion.
“Understanding how the brain develops and functions, and how it malfunctions in neurological disorders, remains one of the most daunting challenges in contemporary science,” says Axel Visel, a geneticist with Berkeley Lab’s Genomics Division. “We’ve created a genome-wide digital atlas of gene enhancers in the human brain – the switches that tell genes when and where they need to be switched on or off. This enhancer atlas will enable other scientists to study in more detail how individual genes are regulated during development of the brain, and how genetic mutations may impact human neurological disorders.”
Visel is the corresponding author of a paper in the journal Cell that describes this work. The paper is titled “A High-Resolution Enhancer Atlas of the Developing Telencephalon.”
Multiple sclerosis study reveals how killer T cells learn to recognize nerve fiber insulators
A micrograph of a killer T cell, a white blood cell that destroys germs or cancers, but that can sometimes attack the body’s own normal cells.
Misguided killer T cells may be the missing link in sustained tissue damage in the brains and spines of people with multiple sclerosis, findings from the University of Washington reveal. Cytoxic T cells, also known as CD8+ T cells, are white blood cells that normally are in the body’s arsenal to fight disease.
Multiple sclerosis is characterized by inflamed lesions that damage the insulation surrounding nerve fibers and destroy the axons, electrical impulse conductors that look like long, branching projections. Affected nerves fail to transmit signals effectively.
Intriguingly, the UW study, published this week in Nature Immunology, also raises the possibility that misdirected killer T cells might at other times act protectively and not add to lesion formation. Instead they might retaliate against the cells that tried to make them mistake the wrappings around nerve endings as dangerous.
Scientists Qingyong Ji and Luca Castelli performed the research with Joan Goverman, UW professor and chair of immunology. Goverman is noted for her work on the cells involved in autoimmune disorders of the central nervous system and on laboratory models of multiple sclerosis.
Multiple sclerosis generally first appears between ages 20 to 40. It is believed to stem from corruption of the body’s normal defense against pathogens, so that it now attacks itself. For reasons not yet known, the immune system, which wards off cancer and infection, is provoked to vandalize the myelin sheath around nerve cells. The myelin sheath resembles the coating on an electrical wire. When it frays, nerve impulses are impaired.
Depending on which nerves are harmed, vision problems, an inability to walk, or other debilitating symptoms may arise. Sometimes the lesions heal partially or temporarily, leading to a see-saw of remissions and flare ups. In other cases, nerve damage is unrelenting.
The myelin sheaths on nerve cell projections are fashioned by support cells called oligodendrocytes. Newborn’s brains contain just a few sections with myelinated nerve cells. An adult’s brains cells are not fully myelinated until age 25 to 30.
For T cells to recognize proteins from a pathogen, a myelin sheath or any source, other cells must break the desired proteins into small pieces, called peptides, and then present the peptides in a specific molecular package to the T cells. Scientists had previously determined which cells present pieces of a myelin protein to a type of T cell involved in the pathology of multiple sclerosis called a CD4+ T cell. Before the current study, no cells had yet been found that present myelin protein to CD8+ T cells.
Scientists strongly suspect that CD8+ T cells, whose job is to kill other cells, play an important role in the myelin-damage of multiple sclerosis. In experimental autoimmune encephalitis, which is a mouse model of multiple sclerosis in humans, CD4+ T cells have a significant part in the inflammatory response. However, scientists observed that, in acute and chronic multiple sclerosis lesions, CD8+T cells actually outnumber CD4+ T cells and their numbers correlate with the extent of damage to nerve cell projections. Other studies suggest the opposite: that CD8+ T cells may tone down the myelin attack.
The differing observations pointed to a conflicting role for CD8+ T cells in exacerbating or ameliorating episodes of multiple sclerosis. Still, how CD8+ T cells actually contributed to regulating the autoimmune response in the central nervous system, for better or worse, was poorly understood.
TIP dendritic cells, stained to show their physical features.
Goverman and her team showed for the first time that naive CD8+ T cells were activated and turned into myelin-recognizing cells by special cells called Tip-dendritic cells. These cells are derived from a type of inflammatory white blood cell that accumulates in the brain and the spinal cord during experimental autoimmune encephalitis originally mediated by CD4+ T cells. The membrane folds and protrusions of mature dendritic cells often look like branched tentacles or cupped petals well-suited to probing the surroundings.
The researchers proposed that the Tip dendritic cells can not only engulf myelin debris or dead oligodendrocytes and then present myelin peptides to CD4+ T cells, they also have the unusual ability to load a myelin peptide onto a specific type of molecule that also presents it to CD8+ T cells. In this way, the Tip dendritic cells can spread the immune response from CD4+ T cells to CD8+ T cells. This presentation enables CD8+ T cells to recognize myelin protein segments from oligodendrocytes, the cells that form the myelin sheath. The phenomenon establishes a second-wave of autoimmune reactivity in which the CD8+ T cells respond to the presence of oligodendrocytes by splitting them open and spilling their contents.
“Our findings are consistent,” the researchers said, “with the critical role of dendritic cells in promoting inflammation in autoimmune diseases of the central nervous system.” They mentioned that mature dendritic cells might possibly wait in the blood vessels of normal brain tissue to activate T-cells that have infiltrated the blood/brain barrier.
The oligodendrocytes, under the inflammatory situation of experimental autoimmune encephalitis, also present peptides that elicit an immune response from CD8+ T cells. Under healthy conditions, oligodendrocytes wouldn’t do this.
The researchers proposed that myelin-specific CD8+ T cells might play a role in the ongoing destruction of nerve-cell endings in “slow burning” multiple sclerosis lesions. A drop in inflammation accompanied by an increased degeneration of axons (electrical impulse-conducting structures) coincides with multiple sclerosis leaving the relapsing-remitting stage of disease and entering a more progressive state.
Medical scientists are studying the roles of a variety of immune cells in multiple sclerosis in the hopes of discovering pathways that could be therapeutic targets to prevent or control the disease, or to find ways to harness the body’s own protective mechanisms. This could lead to highly specific treatments that might avoid the unpleasant or dangerous side effects of generalized immunosuppressants like corticosteroids or methotrexate.
(Source: washington.edu)