 Clinical Relevance: Hair has feelings too
Even hair follicles want to ‘stay in touch’ with their roots. Research just published in Science Advances suggests that the structures that anchor individual strands of hair in place are capable of a sensory experience that was previously unknown to science. Beyond making sure that hair stays put, hair follicles also help regulate temperature and manage sweat. While humans don’t use whiskers to feel around the same way animals like cats and dogs do, our sense of touch is advanced enough to assist us in navigating the world and even process emotions. THE MANE RESULTS It works like this: special nerve cells in the skin send touch information to the brain. So do other skin cells. In the new study, Imperial College London explored the interaction between these nerve cells and human hair follicles to see what and how they experienced touch. The researchers started by collecting scalp skin samples from men aged 23 to 54 who were undergoing hair transplant surgeries and also gathering up leftover skin from abdominoplasties to establish keratinocyte cultures. A keratinocyte is a skin cell that produces keratin, the protein that makes up the outer layer of skin, hair, and nails. The researchers then processed the samples using various techniques. They used whole-mount immunolabeling to highlight specific tissue parts for microscopic viewing. Volumetric imaging captured detailed 3D tissue pictures. They also analyzed RNA extractions for gene expression. Additionally, they cultured different cell types and subjected them to a variety of treatments to observe the responses. This complex set of experimental methods helped demonstrate how the nerve cells sent signals to the brain that process touch sensitivity. Cells known as outer root sheath, or ORS, cells in the hair follicles interacted with these nerve cells. When something pressed against or moved the ORS cells, they released chemicals like serotonin and histamines to help modulate the response of the nerve cells. “This is a surprising finding as we don’t yet know why hair follicle cells have this role in processing light touch,” said lead author Claire Higgins, a professor at the Imperial College London’s department of bioengineering. “Since the follicle contains many sensory nerve endings, we now want to determine if the hair follicle is activating specific types of sensory nerves for an unknown but unique mechanism.”  A human hair follicle surrounded by nerve endings. Credit | Julia Agramunt EVEN MORE IN TOUCH Further testing showed just how sensitive the ORS cells were. The number of times something touched the hair follicle influenced the amount of serotonin and histamine released. More frequent brushups led to a greater chemical release. Compared to how skin cells react to contact, the researchers noted that while both types of cells respond to touch by releasing histamine, only the ORS cells released serotonin. This implies that hair follicles have a unique way of sensing and responding to touch compared to the rest of the skin. Interestingly, the researchers observed that ORS cells also had the ability to revert into regular skin cells when needed, like during wound healing, but still maintained their unique touch-sensing abilities. Previous research on ORS cells found that they emit ATP (Adenosine Triphosphate), a molecule that serves as a signaling agent to communicate with nerve cells. The new findings add complexity to this model by showing that the communication between ORS cells and nerve cells isn’t just a one-way street with ATP as the only traffic light. There might be other molecules or mechanisms involved, making the process more intricate than originally observed. SKIN DEEP SCIENCE These insights into the touchy feely powers of hair follicles could potentially lead to new treatments for conditions related to touch sensitivity or insensitivity. They might have implications for treating other types of skin problems as well. “This is interesting as histamine in the skin contributes to inflammatory skin conditions such as eczema, and it has always been presumed that immune cells release all the histamine. Our work uncovers a new role for skin cells in the release of histamine, with potential applications for eczema research,” Higgins said. The researchers say they need to conduct further experiments on living organisms to validate the study’s results. Since some nerve receptors exist only in hairy skin, the team will explore specialized signaling mechanisms within the hair follicle for these nerves. from Psychiatrist.com
8/15/2023 Why does your hair curl in the summer? A chemist explains the science behind hair structure The three layers of hair If you have curly hair, you know that every day is a new adventure. What will my hair do today? Why does it curl better on some days than others? And even those without naturally curly hair might notice their hair curling—or, let's be honest, frizzing—a bit on humid summer days. As a person with curly hair, I'm always looking for the best way to care for and understand my hair. As a chemist, I'm interested in the science behind how my hair behaves at the molecular level. There are different hair types, from straight to curly, and they behave differently depending on their structure. But what hairs are made up of at the molecular level is the same. Hair structure Hair begins growing under the skin's surface, but it's what happens after it pokes through the skin that determines whether you have a good hair day or a bad one. Each hair can have three layers—the medulla, the cortex and the cuticle. You can think of each hair like a tiny tree trunk. The innermost, or core layer, is the medulla. This layer holds moisture, much like the pith in the center of a tree trunk. This layer is also very fragile, but only thick or coarse hairs contain this part—so those with thin or blond hair typically don't have the medulla layer in their hairs. Next is the cortex, which makes up most of a hair and is analogous to the wood of a tree. The cortex is made up of spring-shaped protein molecules that lie in parallel rows in a cylindrical bundle. The exact shape of that bundle is determined by the hair follicle, which is a pore on the skin from where the hair grows. How the hair grows out of the follicle influences the distribution of its proteins. So a straight follicle produces straight hair and a curved follicle produces curly hair. The less evenly distributed the squiggly proteins are, the curlier the hair. Your genetic code also plays a role in the shape of the cortex and, therefore, the shape and thickness of your hair.  A hair’s cuticle under a microscope. Lastly, the outermost layer of a hair is called the cuticle. The cuticle is like the bark of a tree—and it even looks like bark under a microscope. It's the cuticle's job to protect the cortex, but the cuticle is very easily damaged. Imagine lifting or removing the bark from a tree. Doing so would leave the wood inside susceptible to moisture loss, exposure to the environment and damage. The same is true for each hair. When the cuticle is damaged from brushing, chemicals, wind or heat, the proteins of the cortex have a much more difficult time lying smoothly together. This means they can lose moisture, gain moisture, fray like a rope—this causes split ends—and even break. All these factors can influence how your hair looks at any given moment. Hair in the summer So what does all of this have to do with humidity? Well, hair proteins contain many permanent chemical bonds. Only chemical treatments like perms or straightening can change these bonds. But there's another natural phenomenon that keeps the protein molecules in the cortex in line—something called hydrogen bonding. The long, stringy protein molecules in the cortex contain tiny positive and negative charges throughout their structure. Because opposite charges attract each other, entire rows of proteins can be attracted to each other like tiny, weak magnets. Heating or wetting your hair breaks the magnetlike attraction between these rows of proteins. So, heat and water can rearrange the proteins in your hair by breaking the hydrogen bonds that keep their structure together. Water is one of the best molecules at hydrogen bonding. So when a molecule of water has the opportunity to hydrogen bond with something, it will. In your hair, water can form hydrogen bonds between the rows of proteins in your hair's cortex. It is the extent to which this happens that determines your hair's fate. When just a little water enters the hair, like it might in lower humidity conditions or when the cuticle is healthy and able to keep too much water out of the cortex, your hair may curl. When humidity is high, or the cuticle is damaged, more water enters the hair. Too much water can swell and crack the cuticle, making hair look frizzy. Many people consider high humidity to be the problem behind frizzy hair, but styling your hair under high humidity and then entering a less humid environment can also be an issue. Water molecules leaving the hair's cortex can also lead to a change in hair behavior. Treating summer hair A damaged cuticle layer leaves the cortex more susceptible to water molecules creeping in or out and wreaking havoc on your hair. Anytime water molecules travel in or out, your hair's structure suffers and your hairstyle may be ruined. When the cuticle is healthy, it can protect the cortex, making your hair less susceptible to changes in the weather or environment. The bottom line is that a healthy hair cuticle helps keep proper moisture in the cortex. Heat from styling tools is the most common culprit behind damaged cuticles, but chemical treatments, brushing, sun and wind can also cause damage. Avoiding these activities can help, but some things, such as exposure to the sun, can't be avoided. You can also take care of your scalp—a clean, healthy scalp leads to healthy hair cuticles. Using moisturizing products on your hair can help maintain cuticle health as well. Oils and moisturizing treatments can even restore damaged cuticles. The good news is that by understanding your hair and treating it well, you can help prevent the undesired effects of humidity. from PHYS.org
Tightly curled scalp hair protected early humans from the sun’s radiative heat, allowing their brains to grow to sizes comparable to those of modern humans.  A graphic showing how scientists used a thermal manikin and human hair wigs to measure heat transfer from the scalp. Credit: Melisa Morales Garcia. All Rights Reserved. Curly hair does more than simply look good — it may explain how early humans stayed cool while conserving water, according to researchers who studied the role human hair textures play in regulating body temperature. The findings can shed light on an evolutionary adaptation that enabled the human brain to grow to modern-day sizes. “Humans evolved in equatorial Africa, where the sun is overhead for much of the day, year in and year out,” said Nina Jablonski, Evan Pugh University Professor of Anthropology at Penn State. “Here the scalp and top of the head receive far more constant levels of intense solar radiation as heat. We wanted to understand how that affected the evolution of our hair. We found that tightly curled hair allowed humans to stay cool and actually conserve water.” The researchers used a thermal manikin — a human-shaped model that uses electric power to simulate body heat and allows scientists to study heat transfer between human skin and the environment — and human-hair wigs to examine how diverse hair textures affect heat gain from solar radiation. The scientists programmed the manikin to maintain a constant surface temperature of 95 degrees Fahrenheit (35 degrees Celsius), similar to the average surface temperature of skin, and set it in a climate-controlled wind tunnel.  A thermal manikin wearing tightly curled (left) and straight (right) human hair wigs. The manikin uses electric power to simulate body heat and allows scientists to study heat transfer between human skin and the environment. A new study examining the role human hair textures play in regulating body temperature found that tightly curled hair provides the best protection from the sun’s radiative heat while minimizing the need to sweat to stay cool. Credit: George Havenith, Loughborough University. All Rights Reserved. The team took base measurements of body heat loss by monitoring the amount of electricity required by the manikin to maintain a constant temperature. Then they shined lamps on the manikin’s head to mimic solar radiation under four scalp hair conditions — none, straight, moderately curled and tightly curled. The scientists calculated the difference in total heat loss between the lamp measurements and the base measurements to determine the influx of solar radiation to the head, explained George Havenith, director of the Environmental Ergonomics Research Centre at Loughborough University, U.K., who led the manikin experiments. They also calculated heat loss at different windspeeds and after wetting the scalp to simulate sweating. They ran their results through a model to study how the diverse hair textures would affect heat gain in 86-degree Fahrenheit (30 degrees Celsius) heat and 60% relative humidity, like environments in equatorial Africa. The researchers found that all hair reduced solar radiation to the scalp, but tightly curled hair provided the best protection from the sun’s radiative heat while minimizing the need to sweat to stay cool. They reported their findings yesterday (June 6) in the Proceedings of the National Academy of Sciences. “Walking upright is the setup and brain growth is the payoff of scalp hair,” said Tina Lasisi, who conducted the study as part of her doctoral dissertation at Penn State. Lasisi will start as an assistant professor of anthropology at the University of Michigan in the fall. As early humans evolved to walk upright in equatorial Africa, the tops of their heads increasingly took the brunt of solar radiation, explained Lasisi. The brain is sensitive to heat, and it generates heat, especially the larger it grows. Too much heat can lead to dangerous conditions like heat stroke. As humans lost much of their body hair, they developed efficient sweat glands to keep cool, but sweating comes at a cost in lost water and electrolytes. Scalp hair likely evolved as a way to reduce the amount of heat gain from solar radiation, thereby keeping humans cool without the body having to expend extra resources, said Lasisi. “Around 2 million years ago we see Homo erectus, which had the same physical build as us but a smaller brain size,” she said. “And by 1 million years ago, we’re basically at modern-day brain sizes, give or take. Something released a physical constraint that allowed our brains to grow. We think scalp hair provided a passive mechanism to reduce the amount of heat gained from solar radiation that our sweat glands couldn’t.” The multidisciplinary research provides important preliminary results for bettering our understanding of how human hair evolved without putting humans in potentially dangerous situations, said Jablonski. The study also shows that evolutionary anthropologists have an extra tool in the thermal manikin – normally used for testing the functionality of protective clothing – for quantifying human data that is otherwise very difficult to capture, added Havenith. “The work that’s been done on skin color and how melanin protects us from solar radiation can shape some of the decisions that a person makes in terms of the amount of sunscreen needed in certain environments,” said Lasisi. “I imagine that similar decision making can occur with hair. When you think about the military or different athletes exercising in diverse environments, our findings give you a moment to reflect and think: is this hairstyle going to make me overheat more easily? Is this the way that I should optimally wear my hair?” Also contributing to the research were James Smallcombe, Loughborough University and the University of Australia; and from Penn State Larry Kenney, professor of physiology, kinesiology and Marie Underhill Noll Chair in Human Performance; Mark Shriver, professor of anthropology; and Benjamin Zydney, previously an undergraduate research assistant and now a Penn State alum. The National Science Foundation and the Wenner-Gren Foundation supported this work. from PennStateEdu
Summary: In a new study, researchers discovered that age-related stiffness in hair follicle stem cells can inhibit hair growth. By enhancing the production of a tiny RNA, miR-205, they managed to soften these cells, encouraging hair growth in both young and old mice. These findings indicate the potential for stimulating hair growth by manipulating cell mechanics. This could pave the way for novel treatments for hair loss, with future tests set to determine whether topically delivered miR-205 can stimulate hair growth in humans. Key Facts:
Source: Northwestern University Coaxing hair growth in aging hair follicle stem cells Softening stiff hair follicle stem cells with a microRNA regrows hair  Just as people’s joints can get stiff as they age and make it harder for them to move around, hair follicle stem cells also get stiff, making it harder for them to grow hair, reports a new Northwestern Medicine study. But if the hair follicle’s stem cells are softened, they are more likely to produce hair, the scientists found. Northwestern scientists discovered how to soften up those stem cells to enable them to grow hair again. In a study in mice published this week in PNAS, the investigators report that they can soften the stem cells by boosting the production of a tiny RNA, miR-205, that relaxes the hardness of the cells. When scientists genetically manipulated the stem cells to produce more miR-205, it promoted hair growth in young and old mice. “They started to grow hair in 10 days,” said corresponding author Rui Yi, the Paul E. Steiner Research Professor of Pathology and professor of dermatology at Northwestern University Feinberg School of Medicine. “These are not new stem cells being generated. We are stimulating the existing stem cells to grow hair. A lot of times we still have stem cells, but they may not be able to generate the hair. “Our study demonstrates the possibility of stimulating hair growth by regulating cell mechanics. Because of the potential to deliver microRNA by nanoparticles directly into the skin, next we will test whether topically delivered miR-205 can stimulate hair growth first in mice. If successful, we will design experiments to test whether this microRNA can promote hair growth potentially in humans.” This study was conducted in genetically engineered mouse models. The scientists used advanced microscopy tools, including atomic force microscopy, to measure the stiffness and two-photon microscopy to monitor cell behaviors in live animals. The article is titled “MicroRNA-205 promotes hair regeneration by modulating mechanical properties of hair follicle stem cells.” Other Northwestern authors include Jingjing Wang, Yuheng Fu and Kathleen Green. Funding: This study was funded by the National Institute of Arthritis and Musculoskeletal and Skin Diseases grants AR066703, AR071435, AR043380, AR041836 and P30AR075049 of the National Institutes of Health. About this genetics research news
Author: Marla Paul Source: Northwestern University Contact: Marla Paul – Northwestern University Image: The image is credited to Neuroscience News Original Research: Open access. “MicroRNA-205 promotes hair regeneration by modulating mechanical properties of hair follicle stem cells” by Rui Yi et al. PNAS Abstract MicroRNA-205 promotes hair regeneration by modulating mechanical properties of hair follicle stem cells Stiffness and actomyosin contractility are intrinsic mechanical properties of animal cells required for the shaping of tissues. However, whether tissue stem cells (SCs) and progenitors located within SC niche have different mechanical properties that modulate their size and function remains unclear. Here, we show that hair follicle SCs in the bulge are stiff with high actomyosin contractility and resistant to size change, whereas hair germ (HG) progenitors are soft and periodically enlarge and contract during quiescence. During activation of hair follicle growth, HGs reduce contraction and more frequently enlarge, a process that is associated with weakening of the actomyosin network, nuclear YAP accumulation, and cell cycle reentry. Induction of miR-205, a novel regulator of the actomyosin cytoskeleton, reduces actomyosin contractility and activates hair regeneration in young and old mice. This study reveals the control of tissue SC size and activities by spatiotemporally compartmentalized mechanical properties and demonstrates the possibility to stimulate tissue regeneration by fine-tuning cell mechanics. 5/20/2023 Stress hormone measured in hair predicts who is likely to suffer from cardiovascular diseasesStudy in over 6,300 individuals finds hair cortisone levels were the strongest predictor of future cardiovascular disease in those aged 57 years or younger New research being presented at this year’s European Congress on Obesity (ECO) in Dublin, Ireland (17-20 May) suggests that glucocorticoid levels (a class of steroid hormones secreted as a response to stress) present in the hair of individuals may indicate which of them are more likely to suffer from cardiovascular diseases (CVD) in the future. “There is a tremendous amount of evidence that chronic stress is a serious factor in determining overall health. Now our findings indicate that people with higher long-term hair glucocorticoid levels appear significantly more likely to develop heart and circulatory diseases in particular,” says lead author Dr Eline van der Valk from Erasmus University Medical Center Rotterdam in the Netherlands. Long-term levels of scalp hair cortisol and its inactive form, hair cortisone, are increasingly used biomarkers that represent the cumulative exposure to glucocorticoids over the previous months. There is a large body of evidence indicating that the stress hormones cortisol and cortisone affect the body’s metabolism and fat distribution. But data on these stress hormone levels and their effect on long-term CVD outcomes is scarce. To find out more, researchers analysed cortisol and cortisone levels in 6,341 hair samples from adult men and women (aged 18 and older) enrolled in Lifelines—a multi-generational study including over 167,000 participants from the northern population of the Netherlands. Study participants' hair was tested, and participants were followed for an average 5-7 years to assess the long-term relationship between cortisol and cortisone levels and incident CVD. During this time, there were 133 CVD events. Researchers adjusted for factors known to be linked with increased risk of CVD including age, sex, waist circumference, smoking, blood pressure, and type 2 diabetes. The researchers found that people with higher long-term cortisone levels were twice as likely to experience a cardiovascular event like a stroke or heart attack, and this rose to over three times as likely in those aged 57 years or younger. However, in the oldest half of CVD cases (aged 57 and older), hair cortisone and cortisol were not strongly linked to incident CVD. “Our hope is that hair analysis may ultimately prove useful as a test that can help clinicians determine which individuals might be at high risk of developing cardiovascular disease. Then, perhaps in the future targeting the effects of stress hormones in the body could become a new treatment target,” says Professor Elisabeth van Rossum, the principal investigator of the study from Erasmus University Medical Center. The authors acknowledge several limitations of the study, including that it is observational and does not prove that stress causes CVD but indicate that they are linked. They also note that most participants self-identified as white and were from one area of the Netherlands so the findings might not be generalisable to other populations. And although age, sex, waist circumference, smoking, blood pressure, and type 2 diabetes were adjusted for in the analysis, there may be other unmeasured factors that may have influenced the results. For interviews with article author Eline van der Valk, Erasmus University Medical Center Rotterdam, the Netherlands please email e.vandervalk@erasmusmc.nl or contact the Erasmus MC press office at press@erasmusmc.nl T) +31 1070 33289 Alternative contact in the ECO Press Room: Tony Kirby T) + 44(0)7834 385827 E) tony@tonykirby.com Notes to editors: The authors declare no conflicts of interest. The study was funded by Elisabeth Foundation; Netherlands Organization of Scientific Research NWO. This press release is based on oral abstract 14.06 at the European Congress on Obesity (ECO). All accepted abstracts have been extensively peer reviewed by the congress selection committee. There is no full paper at this stage, but the authors are happy to answer your questions. The research has not yet been submitted to a medical journal for publication. from EurekAlert
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