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Human Sense of Touch Consists of 16 Unique Types of Nerve Cells

The AHA! Team — Fri, 24 Jan 2025 07:50:08 +0000

Linköping University via EurekAlert! – No less than 16 different types of nerve cells have been identified by scientists in a new study on the human sense of touch. Comparisons between humans, mice and macaques show both similarities and significant differences. The study, a collaboration between researchers at Linköping University and Karolinska Institutet in Sweden and the University of Pennsylvania in the USA, has been published in Nature Neuroscience. “Our study provides a landscape view of the human sense of touch. As a next step, we want to make portraits of the different types of nerve cells we have identified,” says Håkan Olausson, Professor at Linköping University, about the study published in Nature Neuroscience. We perceive touch, temperature and pain through the somatic sensation system. A common understanding is that there is a specific type of nerve cell for each type of feeling, such as pain, pleasant touch, or cold. But the findings from the current study challenge that notion and show that bodily sensations are probably much more complicated than that. Much of the knowledge we have today about how the nervous system works comes from research on animals. But how big are the similarities between, for example, a mouse and a human? Many findings in animal studies have not been confirmed in human research. One reason for this may be that our understanding of how it works in humans is inadequate. The researchers behind the current study, therefore, wanted to create a detailed atlas of different types of nerve cells involved in human somatosensation and compare it with those of mice and macaques, a primate species. In the study, a research group at the University of Pennsylvania, led by Associate Professor Wenqin Luo, made detailed analyses of the genes used by individual nerve cells, so-called deep RNA sequencing. Nerve cells that had similar gene expression profiles were grouped together as one sensory nerve cell type. In this way, they identified 16 distinct types of nerve cells in humans. As the researchers analyse more cells, they will likely discover even more distinct types of sensory nerve cells. The nerve cell gene expression analyses provide a picture of what the cellular machinery looks like in the different cell types. The next question was how this relates to nerve cell function. If a nerve cell produces a protein that can detect heat, does that mean that the nerve cell responds to heat? The current study is the first to link gene expression in different types of nerve cells with their actual function. To investigate the function of nerve cells, a research group at Linköping University, led by Saad Nagi and Håkan Olausson, used a method that allows the researchers to listen to the nerve signalling in one nerve cell at a time. Using this method, called microneurography, the researchers can subject skin nerve cells in awake participants to temperature, touch or certain chemicals, and “listen in on” an individual nerve cell to find out if that particular nerve cell is reacting and sending signals to the brain. During these experiments, the researchers made discoveries that would not have been possible, had the mapping of the cellular machinery of different types of nerve cells not given them new ideas to test. One such discovery concerns a type of nerve cell that responds to pleasant touch. The researchers found that this cell type unexpectedly also reacts to heating and capsaicin, the substance that gives chili its heat. Reacting to capsaicin is typical of pain-sensing nerve cells, so it surprised the researchers that touch-sensing nerve cells responded to such stimulation. Further, this nerve cell type also responded to cooling, even though it does not produce the only protein so far known to signal cold perception. This finding cannot be explained by what is known about the cell’s machinery and suggests that there is another mechanism for detection of cold, which has not yet been discovered. The authors speculate that these nerve cells form an integrated sensory pathway for pleasant sensations. “For ten years, we’ve been listening to the nerve signals from these nerve cells, but we had no idea about their molecular characteristics. In this study, we see what type of proteins these nerve cells express as well as what kind of stimulation they can respond to, and now we can link it. It’s a huge step forward”, says Håkan Olausson. Another example is a type of very rapidly conducting pain-sensing nerve cell, which was found to respond to non-painful cooling and menthol. “There’s a common perception that nerve cells are very specific – that one type of nerve cell detects cold, another senses a certain vibration frequency, and a third reacts to pressure, and so on. It’s often talked about in those terms. But we see that it’s a lot more complicated than that,” says Saad Nagi, Associate Professor at Linköping University. And what about the comparison between mice, macaques and humans? How similar are we? Many of the 16 types of nerve cells that the researchers identified in the study are roughly similar between the species. The biggest difference the researchers found was in very rapidly conducting pain-sensing nerve cells that react to stimulation that can cause injury. These were first discovered in humans in 2019 by the same group at Linköping using microneurography. Compared to the mouse, humans have many more pain nerve cells of the type that send pain signals to the brain at high speed. Why this is so, the study cannot answer, but the researchers have a theory: “The fact that pain is signalled at a much higher velocity in humans compared to mice is probably just a reflection of body size. A mouse doesn’t require such rapid nerve signalling. But in humans, the distances are greater, and the signals need to be sent to the brain more rapidly; otherwise, you’d be injured before you even react and withdraw,” says Håkan Olausson. The study is a collaboration between Patrik Ernfors’ research group at Karolinska Institutet, Wenqin Luo’s research group at the University of Pennsylvania and Håkan Olausson and Saad Nagi’s research group at Linköping University. Financial support for the study was provided by the National Institutes of Health, the Swedish Research Council, ALF Grants Region Östergötland, and the Knut and Alice Wallenberg Foundation. Article: Leveraging Deep Single-soma RNA Sequencing to Explore the Neural Basis of Human Somatosensation, Huasheng Yu, Saad S. Nagi, Dmitry Usoskin et al. (2024). Nature Neuroscience, published online November 4 2024, doi: 10.1038/s41593-024-01794-1 Journal Nature Neuroscience DOI 10.1038/s41593-024-01794-1 To read the original article click here.

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Overgrowth of Nerve Cells Appears to Cause Lingering Symptoms After Recurrent UTIs

The AHA! Team — Mon, 05 Aug 2024 08:13:54 +0000

Duke Health – DURHAM, N.C. – A perplexing problem for people with recurring urinary tract infections (UTIs) is persistent pain, even after antibiotics have successfully cleared the bacteria. Now Duke Health researchers have identified the likely cause – an overgrowth of nerve cells in the bladder. The finding, appeared March 1 in the journal Science Immunology, provides a potential new approach to managing symptoms of recurring UTIs that would more effectively target the problem and reduce unnecessary antibiotic usage. “Urinary tract infections account for almost 25% of infections in women,” said senior author Soman Abraham, Ph.D., professor in the departments of Pathology, Molecular Genetics and Microbiology, Integrative Immunobiology, and Cell Biology at Duke University School of Medicine. Urinary tract infections account for almost 25% of infections in women “Many are recurrent UTIs, with patients frequently complaining of chronic pelvic pain and urinary frequency, even after a round of antibiotics,” Abraham said. “Our study, for the first time, describes an underlying cause and identifies a potential new treatment strategy.” Abraham and colleagues collected bladder biopsies from recurrent UTI patients who were experiencing pain despite no culturable bacteria in their urine. Using biopsies from people without UTIs as a comparison, they found evidence that sensory nerves were highly activated in the UTI patients, explaining the persistent sense of pain and urinary frequency. Further studies in mice revealed the underlying events, with unique conditions in the bladder that prompt activated nerves in the lining to bloom and grow with each infection. “Typically, during every bout of UTI, epithelial cells laden with bacteria are sloughed off, and significant destruction of nearby nerve tissue occurs,” said Byron Hayes, lead author of the study and previously a postdoctoral fellow in Duke’s Department of Pathology. “These events trigger a rapid repair program in the damaged bladder involving massive regrowth of destroyed nerve cells.” This immune response, including repair activities, is led by mast cells – which are immune cells that fight infection and allergens. Mast cells release chemicals called nerve growth factor, which drive overgrowth and increase sensitivity of nerves. The result is pain and urgency. The researchers were able to address these symptoms by treating study mice with molecules that suppress production of the mast-cell generated nerve growth factor. “This work helps illuminate a puzzling clinical condition that drives medical costs and affects the quality of life of millions of people, primarily women,” Abraham said. “Understanding the crosstalk between mast cells and nerves is an essential step toward effective treatments for people suffering repeat urinary tract infections.” In addition to Abraham and Hayes, study authors include Hae Woong Choi, Abhay PS Rathore,Chunjing Bao, Jianling Shi, Yul Huh, Michael W Kim, Andrea Mencarelli, Pradeep Bist, Lai Guan Ng, Changming Shi, Joo Hwan Nho, Aram Kim, Hana Yoon, Donghoon Lim, Johanna L Hannan, J Todd Purves, Francis M Hughes Jr, and Ru-Rong Ji. The study received funding support from the National Institutes of Health (K12-DK100024, R01-DK121969, R01-DK121032, R01-GM144606), the National Research Foundation of Korea (2020R1C1C1003257), and a Korea University grant. To read the original article click here.

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Innovative Silicon Nanochip Can Reprogram Biological Tissue in Living Body

AHA Publisher — Wed, 15 Dec 2021 08:00:12 +0000

Indiana University via Newswise – A silicon device that can change skin tissue into blood vessels and nerve cells has advanced from prototype to standardized fabrication, meaning it can now be made in a consistent, reproducible way. As reported in Nature Protocols, this work, developed by researchers at the Indiana University School of Medicine, takes the device one step closer to potential use as a treatment for people with a variety of health concerns. The technology, called tissue nanotransfection, is a non-invasive nanochip device that can reprogram tissue function by applying a harmless electric spark to deliver specific genes in a fraction of a second. In laboratory studies, the device successfully converted skin tissue into blood vessels to repair a badly injured leg. The technology is currently being used to reprogram tissue for different kinds of therapies, such as repairing brain damage caused by stroke or preventing and reversing nerve damage caused by diabetes. “This report on how to exactly produce these tissue nanotransfection chips will enable other researchers to participate in this new development in regenerative medicine,” said Chandan Sen, director of the Indiana Center for Regenerative Medicine and Engineering, associate vice president for research and Distinguished Professor at the IU School of Medicine. Sen also leads the regenerative medicine and engineering scientific pillar of the IU Precision Health Initiative and is lead author on the new publication. Media kit: Access photos and video “This small silicon chip enables nanotechnology that can change the function of living body parts,” he said. “For example, if someone’s blood vessels were damaged because of a traffic accident and they need blood supply, we can’t rely on the pre-existing blood vessel anymore because that is crushed, but we can convert the skin tissue into blood vessels and rescue the limb at risk.” In the Nature Protocols report, researchers published engineering details about how the chip is manufactured. Sen said this manufacturing information will lead to further development of the chip in hopes that it will someday be used clinically in many settings around the world. “This is about the engineering and manufacturing of the chip,” he said. “The chip’s nanofabrication process typically takes five to six days and, with the help of this report, can be achieved by anyone skilled in the art.” Sen said he hopes to seek FDA approval for the chip within a year. Once it receives FDA approval, the device could be used for clinical research in people, including patients in hospitals, health centers and emergency rooms, as well as in other emergency situations by first responders or the military. Other study authors include Yi Xuan, Subhadip Ghatak, Andrew Clark, Zhigang Li, Savita Khanna, Dongmin Pak, Mangilal Agarwal and Sashwati Roy, all of IU, and Peter Duda of the University of Chicago. This research is funded by the National Institutes of Health. To read the original article click here.

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Adult Stem Cell Study Shows Fish Oil May Help With Depression

AHA Publisher — Wed, 17 Jun 2020 07:00:30 +0000

University of Illinois at Chicago via EurekAlert – A study published in Molecular Psychiatry shows that patient-derived adult stem cells can be used to model major depressive disorder and test how a patient may respond to medication. Using stem cells from adults with a clinical diagnosis of depression, the University of Illinois at Chicago researchers who conducted the study also found that fish oil, when tested in the model, created an antidepressant response. UIC’s Mark Rasenick, principal investigator of the study, says that the research provides a number of novel findings that can help scientists better understand how the brain works and why some people respond to drug treatment for depression, while others experience limited benefits from antidepressant medication. “It was also exciting to find scientific evidence that fish oil — an easy-to-get, natural product — may be an effective treatment for depression,” said Rasenick, UIC distinguished professor of physiology and biophysics and psychiatry at the College of Medicine. Major depressive disorder, or depression, is the most common psychiatric disorder. Around one in six individuals will experience at least one depressive episode in their lifetime. However, antidepressant treatment fails in about one-third of patients. In the study, the UIC researchers used skin cells from adults with depression that were converted into stem cells at Massachusetts General Hospital and then directed those stem cells to develop into nerve cells. The skin biopsies were taken from two types of patients: people who previously responded to antidepressant treatment and people who have previously been resistant to antidepressants. When fish oil was tested, the models from treatment-sensitive and treatment-resistant patients both responded. Rasenick says the response was similar to that seen from prescription antidepressants, but it was produced through a different mechanism. “We saw that fish oil was acting, in part, on glial cells, not neurons,” said Rasenick, who is also a research career scientist at Jesse Brown VA Medical Center and president and chief scientific officer at Pax Neuroscience, a UIC startup company. “For many years, scientists have paid scant attention to glia — a type of brain cell that surrounds neurons — but there is increasing evidence that glia may play a role in depression. Our study suggests that glia may also be important for antidepressant action. “Our study also showed that a stem cell model can be used to study response to treatment and that fish oil as a treatment, or companion to treatment, for depression warrants further investigation,” Rasenick said. To read the original article click here.

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