Bench to Bedside

April 2016

Restoring Balance in the Brain After Concussion


As he falls to the ground from a football tackle, a boy’s brain shakes in its skull from the impact. He begins to experience dizziness and balance problems in the hours and days that follow, and a visit to his doctor confirms that he has a concussion, a mild traumatic brain injury.

The physician explains to the boy’s parents to be on the lookout during his recovery process for mood disruptions and cognitive problems such as difficulty concentrating, learning, and remembering. While these are common concussion symptoms that can be seen outwardly, much less is known about what is happening inside the brain during and after concussions.

Scientists at The Children’s Hospital of Philadelphia want to zoom in to better understand the basic science of how and why these effects occur. Their goal is to develop targeted treatments that could someday accelerate recovery and even prevent some clinical symptoms and damage.

Akiva Cohen, PhD, an investigator at CHOP and research associate professor of Anesthesiology and Critical Care at the Perelman School of Medicine at the University of Pennsylvania, is at the forefront of discovery of the neurobiology of brain injury. His lab has focused on a variety of brain regions to describe the cellular and molecular nature of impairment in emotional stability, working memory, and spatial memory, among other functions.

In a new study funded by the National Institutes of Health, Dr. Cohen and colleagues are testing whether a specific set of neurons implicated in cognitive impairment could be a useful target for future therapies to restore cognitive function after concussion.

“We are looking at specific neurons in the hippocampus that are frequently damaged by traumatic brain injury and are also important in learning and memory,” said Brian Johnson, PhD, a research associate in Dr. Cohen’s lab who leads this project.

In general, brain injuries cause shifts in the complex and delicate balance between “stop” and “go” signaling systems for activation and inhibition in different directions in different regions of the brain. The study team is focusing on CCK positive interneurons from the CA1 region of the hippocampus, which are part of the brain’s “stop” system. Like other “stop” neurons, when activated, they release the chemical GABA to signal other neurons to shut down their activity. These particular neurons shut down processes involved in learning and memory.

In the new study, Dr. Cohen and Dr. Johnson are working with an unusual model of brain injury in mice. The CCK interneurons in the hippocampus region CA1, and no other cells in the body, have been genetically altered to be responsive to a drug they can use to experimentally silence these cells’ “stop” signal without affecting the animal in any other way. (They are building this specialized model with a technique called designed receptors exclusively activated by designed drugs, or DREADDS, in which a viral vector implants only these specific cells with a receptor channel for the desired drug.)

With this experimental setup, the team can proceed with classic behavioral experiments — seeing how well or poorly the animals learn or remember to avoid a negative stimulus when their CCK interneurons are active, compared to when researchers have injected the drug intended to restore normal brain function by deactivating these cells.

“We are using behavior as a bioassay,” Dr. Cohen said. “If we take these neurons that are altered after brain injury and we make them quiescent so they can’t release GABA, will we mitigate the problem or even restore the hippocampal effects to normal?”

The team will cross-check these experiments with in vitro investigations to see if adding the designed drug to the modified CCK interneurons does indeed restore normal outputs of other cells in the hippocampus. If successful, these findings would point toward a need for further studies to find ways to target these neurons in future clinical therapies for cognitive impairment resulting from concussion.

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Young Physician-Scientist Recognized for Pediatric Kidney Stone Research


It’s often surprising for parents to learn that their child has a kidney stone, a painful condition that is more common in adults but has dramatically increased in prevalence among pediatric patients over the last 25 years. Seeing this trend firsthand as a pediatric urologist and epidemiologist at The Children’s Hospital of Philadelphia, Gregory E. Tasian, MD, MSc, MSCE, realized that more research about pediatric kidney stone disease was desperately needed.

“The fact that there has been very little prior research has led to a lot of uncertainty about how to provide the best care for these children, both surgical management and prevention strategies,” said Dr. Tasian, who also is an assistant professor at the Perelman School of Medicine at the University of Pennsylvania. “Kidney stone disease is an important area of research and is exciting to study because so much is changing in the incidence and prevalence of the disease.”

Dr. Tasian’s epidemiological findings published in Environmental Health Perspectives gained attention for suggesting that rising temperatures due to climate change could offer a possible explanation for why kidney stones may increase in the future for individuals who are predisposed to the condition. In recognition of this novel insight, Dr. Tasian recently received the 2016 Young Physician-Scientist Award at a joint meeting of the Association of American Physicians, the American Society for Clinical Investigation, and the American Physician Scientists Association held in Chicago.

Dr. Tasian presented meeting attendees with highlights from the 2014 study, which showed that the delay between high daily temperatures and kidney stone presentation was short, peaking within three days of exposure to hot days. Sizzling temps could contribute to dehydration, which leads to a higher concentration of calcium and other minerals in the urine that promote the formation of kidney stones.

Kidney stones may grow over time, be washed out of the kidney by urine flow, and end up trapped within the ureter. Stones usually begin causing symptoms, such as pain in the sides, abdomen, or groin area, when they block the outflow of urine from the kidney to the bladder. About half of patients who are diagnosed with a kidney stone will have a recurrence within five to 10 years.

“The goal of my research is ultimately to lead to personalized, targeted interventions to increase fluid intake and decrease the risk of recurrence,” Dr. Tasian said. “If we can identify those periods of risk, then we also can identify interventions to offset that risk.”

Based on the preliminary results, Dr. Tasian is extending this research by comparing two methods of measuring temperature exposure. Dry bulb temperature, commonly known as air temperature, is indicated by a thermometer not affected by the moisture of the air. Wet bulb temperature incorporates both humidity and air temperature into one unit of measurement. Most of the research focusing on kidney stones so far has relied on dry bulb temperature alone, but Dr. Tasian wants to find out if wet bulb temperature could be a more accurate way to predict future stone prevalence.

Another line of research that Dr. Tasian is pursuing involves dietary determinants of kidney stones in children. Research studies with adult participants have suggested that high levels of fructose and salt could increase the chance of developing kidney stones, but the diets of children and adolescents can be much different than what their older family members consume. Dr. Tasian aims to identify certain dietary factors that may be contributing to why kidney stone disease is starting earlier in life.

“Your risk of kidney stones is the intersection between the things you can’t change — genetics, age, sex — and the things you can change — like drinking more water and fluids to decrease dehydration and modifying your diet. More research will help us to understand how all those pieces come together and how we might be able to develop strategies to reduce the risk of reoccurrence.”

In order to help families understand the many factors that are unique to the diagnosis and treatment of children with kidney stones, the Pediatric Kidney Stone Center, a program within the Divisions of Urology and Nephrology at CHOP, is solely dedicated to the management of kidney stones and treats nearly 300 patients each year.

Read more about Dr. Tasian’s kidney stones research here.

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CHOP Oncologist Appointed to Blue Ribbon Panel for National Cancer Moonshot


Peter Adamson, MD, a pediatric oncologist at The Children’s Hospital of Philadelphia and chair of the Children’s Oncology Group (COG), has joined a key group of scientific experts, cancer leaders, and patient advocates in advising the scientific direction and goals of Vice President Joe Biden’s National Cancer Moonshot Initiative.

On April 4, the National Cancer Institute (NCI), part of the National Institutes of Health, announced Dr. Adamson among the membership of this new Blue Ribbon Panel. The panel will serve as a working group of the presidentially appointed National Cancer Advisory Board (NCAB). Dr. Adamson, one of the nation’s leading pediatric oncologists, was previously named to the NCAB in June 2015 by President Obama.

“Thanks to advances in science, we are now in a historically unique position to make profound improvements in the way we treat, detect, and prevent cancer,” said NIH Director Francis S. Collins, MD, PhD in the NIH announcement of the Blue Ribbon panel.

The panel will consider how to advance themes and approaches in cancer research that have been proposed to date, including cancer vaccines, highly sensitive approaches to early detection, immunotherapy and combination therapies, single-cell genomic profiling of cancer cells and cells in the tumor microenvironment, enhanced data sharing, and new approaches to the treatment of pediatric cancers. The panel will make recommendations to the NCAB, which will in turn make recommendations to the NCI.

“I am very pleased that there will be pediatric oncology representation on this important panel, and am honored to join colleagues in helping to support this effort,” said Dr. Adamson, who is also a professor of Pediatrics at the Perelman School of Medicine at the University of Pennsylvania.

Dr. Adamson has chaired the COG, the world’s largest organization devoted exclusively to childhood and adolescent cancer research, since 2010. At CHOP, he served as chief of the Division of Clinical Pharmacology and Therapeutics, and director of the Office of Clinical and Translational Research. Prior to joining CHOP in 1999, he was a member of the Pediatric Oncology Branch of the NCI.

“We are deeply honored that Dr. Adamson has received this national acknowledgment of his profound expertise as a clinician and researcher in children’s cancer, and we applaud his continued commitment to advancing treatment for children,” said Madeline Bell, president and CEO of CHOP.

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Teaching a Computer to See Like a Dermatologist


A picture is worth a thousand words in most places, but not at the dermatologist’s office.

“Usually when I’m in clinic, I’m looking at photos and comparing photos,” said Leslie Castelo-Soccio, MD, PhD, an attending dermatologist at The Children’s Hospital of Philadelphia and assistant professor at the Perelman School of Medicine at the University of Pennsylvania. “There hasn’t been a really good way for us to say other than just visually, are things improving or getting worse? We want to have more ways to put an easy score on each of the images.”

Dr. Castelo-Soccio and computer scientist Elena Bernardis, PhD, are now developing computational imaging tools to examine photos of the condition alopecia areata and analyze changes automatically. Their system will eventually identify new quantifiers to convert photographs into more comprehensive and useful numerical scores. They received a new grant from the National Alopecia Areata Foundation to pursue this work.

Alopecia areata is an autoimmune condition that causes the body to attack its own hair, causing varied patterns of hair loss. It can occur at any age, from infancy through adulthood. In addition to causing psychological distress among patients upset by the change to their appearance, the condition also comes with the risk of other co-occurring autoimmune conditions.

Dermatologists have some numerical scoring systems to measure and track alopecia improvement or worsening, but these methods have significant shortcomings. They are time-consuming for busy clinicians because generating a score requires a trained clinician to manually assess a photograph in detail. And, because the scores only measure the percentage area of hair loss and hair growth, they fail to take into account many characteristics that clinicians perceive as clinically relevant, such as hair pigmentation, type, and texture.

“The ultimate goal would be that, when testing new therapeutics, there would be a standard tool that we could use for research studies to go beyond just calculating percentages of density,” Dr. Castelo-Soccio said. “We want a tool that is faster and easier to use, that perceives more refined detail than existing scoring methods, and that generates consistent results among different users.”

To build that tool, Dr. Castelo-Soccio is equipping Dr. Bernardis with the clinical knowledge she needs to teach a computer to think like a dermatologist. As a first step, they have developed a computer program that can accurately score images using the existing method of quantifying an area of hair loss, known as the SALT score.

“Elena is pretty unique in that I don’t know any other dermatology programs that have a computer scientist that is part of the section that can do this kind of work,” Dr. Castelo-Soccio said. “Most clinicians, even researchers like myself, don’t have this training and ability. But I can tell her what I’m looking for, and she can tell the computer to do that, which is pretty amazing.”

Computers do not see and interpret images in the same way humans do automatically, let alone in the specific ways an experienced clinician does. By uploading a set of standardized images, Dr. Bernardis is training the computer algorithm to understand differences between hair and scalp when it encounters new images. Such uses of computer vision algorithms are extremely rare in dermatology. Dr. Bernardis is applying methods that have originally been developed for complex texture analysis and cell counting in microscopic image analysis. These methods require the computer to automatically create pixel groupings for image regions that have very faint and fuzzy boundaries.

“A person can actually interpret a lot of things from the images, but if you zoom in and look at a pixel level, they are just a blobs of colors,” said Dr. Bernardis, who is a research associate in the Dermatology Section at CHOP. “Trying to get information out in a coherent way from the pixels, trying to figure out how to group them together, gets extremely challenging without telling the algorithm that you’re looking for hair. It doesn’t actually know what I’m looking for.”

In later stages of the project, she will train the algorithm to detect other subtle differences in hair appearance that the SALT score does not consider. For instance, progression of disease or remission might be detectable through changes in hair thickness or color. Eventually, she hopes to build in computer vision capabilities so the program will see beyond what the clinician sees — detecting differences in hair appearance that may be useful predictors of disease progression or recovery, but that dermatologists do not consciously note in their observations.

Computer vision methods have reached dermatology later than other specialties, in part because human vision and analysis of photographs has been a reliable standard of the discipline for decades. At CHOP, Dr. Bernardis is collaborating on similar research on acne with Albert Yan, MD, chief of dermatology.

For alopecia areata, these methods could help shape a new phase of research. The timing is ideal because new genetically targeted medications for the condition are now in clinical trials for adults and could reach pediatrics soon.

“I think there are some subtle changes in alopecia areata, other than pure areas of hair growth, that may be important to understand which patients might respond better to those medicines, or to identify any subpopulations of patients who respond more quickly or less quickly,” Dr. Castelo-Soccio said. “I think that by measuring those changes, the tool we are developing will create more quantitative research.”

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Study Maps Early Connectivity Networks in Newborn Babies’ Brains


For parents-to-be, the third trimester of pregnancy is often a period of rapid preparation to welcome a new life into the world. Their babies are busy, too: From growing lungs that can breathe on their own, to developing neurological connections they need to feel, move, and cry, they spend those critical weeks making important preparations for life outside the womb.

Scientists are beginning to glimpse exactly how a gestating infant’s developing brain forms important connections during this period. These discoveries show the earliest scenes yet in the story of how healthy brains develop as children grow up.

“We found that brain regions are developing heterogeneously,” said Hao Huang, PhD, an investigator in radiology at The Children’s Hospital of Philadelphia and research associate professor at the Perelman School of Medicine at the University of Pennsylvania, who leads this research. “In certain periods, some brain regions develop at faster rates. Although it’s heterogeneous, it’s not random. There is a well controlled, organized pattern at work.”

Dr. Huang found that pattern places priority on early, efficient connectivity within the primary sensorimotor cortex. This prepares a baby to handle the basic needs of sensation and movement after birth.

Dr. Huang’s recent study published in the journal Cerebral Cortex mapped the functional connectivity in brains of 40 newborn infants, based on resting-state functional magnetic resonance imaging scans. He and colleagues compared the brain connectivity patterns present in babies born at various preterm ages, beginning as early as 31 postmenstrual weeks, to those born at more mature gestational ages up to full-term, or 42 postmenstrual weeks. By mapping which types of functional connectivity were present in which stages of development, they have filled an important knowledge gap about when the brain becomes organized.

Among these infants, even the youngest preterm babies’ brains had a characteristic called “small worldness” in their entire brain connectivity, a feature of networks that offer easy navigation from one area to another. In these babies’ brains, the networks through which electrical impulses can travel are analogous to well-designed road systems in a city or region. They have a useful combination of major highways interconnected with smaller side roads, so that there is always an efficient path to get from one location to another, even if there is no single direct road connecting them. If the brain networks were random or undeveloped, they would only offer the equivalent of sporadically linked side streets, making movement from one location to another slow and inefficient, riddled with meandering turns and occasional dead ends.

In addition to finding this efficient “small worldness” quality present early on in infants’ brain development, Dr. Huang and colleagues found that as gestational age increased, so did a quality called rich club structure. In rich club structure, nodes of densely connected regions make signaling more efficient within areas of the brain.

Such studies of brain connectivity in children fit into a larger context of related research that has received major investments in recent years, including President Obama’s BRAIN Initiative and the Human Connectome Project (HCP). The HCP is an ambitious NIH-funded effort to build maps of how neurons are interconnected with one another within adults’ brains, to visualize the metaphorical smaller side roads and major highways. Dr. Huang’s studies of developing brains complement the HCP, and are akin to discovering the city planners’ processes. Which roads are built first, and to what degree and in what way is the process organized?

By mapping the typical development process, Dr. Huang hopes in the future to identify biomarkers of atypical connectivity that may occur in various conditions, ranging from autism spectrum disorder to cerebral palsy. If these brain indicators can allow earlier identification of these conditions, children could potentially begin early intervention services sooner and grow up with fewer impairments related to their condition.

“We think this is a normal reference that can be used to detect certain abnormal connectivity development during this specific age period,” Dr. Huang said. “Our entire goal is to study not only this age range, but all the way from birth to adolescence.”

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Researchers Developing New Imaging Tools to Assess Placental Dysfunction


As new life forms inside a mother, the placenta becomes a key interface between maternal and fetal health. This temporary disc-shaped organ attaches to the uterine wall and transfers oxygen and nutrients to the fetus, yet the nuances of its structure and function remain enigmatic.

A multidisciplinary research team at The Children’s Hospital of Philadelphia and the Perelman School of Medicine at the University of Pennsylvania recently received a $4.2 million grant through the Human Placenta Project launched by the Eunice Kennedy Shriver National Institute of Child Health and Human Development to uncover these mysteries by developing new imaging technologies that allow for a more comprehensive understanding of blood flow and oxygenation in the placenta. Launched in 2014, the Human Placenta Project encourages researchers to explore how the placenta works and then use these insights to help predict complications in pregnancies and eventually assess interventions.

Daniel Licht, MD, one of the study team’s leaders, is in a unique position as a pediatric neurologist studying placental imaging. His research interest in this area evolved from his experience with treating babies born with congenital heart defects (CHD) who also had brain injuries. Fetal imaging has revealed that brain growth stalls in these babies around the third trimester, he noted.

“Alteration of the fetal circulation due to the CHD leads to a vulnerability for brain injury, so fetal circulation is the main problem that we have to tackle if we’re going to figure out how to manage these babies and prevent brain injury,” said Dr. Licht, who is director of the Wolfson Family Laboratory for Clinical and Biomedical Optics at CHOP. “But it’s probably not just fetal circulation; it’s also the placental circulation.”

Blood circulates from the placenta to the fetus and back to the placenta, Dr. Licht explained. If the fetus’ cardiac output is abnormal, then it is likely that this feedback loop also is abnormal, depending on the type of heart anomaly. At birth, some babies with CHD have placentas that are about half the size as would be expected. Abnormal development of the placenta also is related to other pregnancy risks, including poor fetal growth, preeclampsia, and preterm birth.

Physicians need new imaging tools to monitor development and function of the placenta throughout the organ’s lifespan. This can be difficult to accomplish because motion from the mother’s breathing and the fetus’ movement can compromise image quality. The research team will study advanced techniques and sensors in 3D ultrasound, magnetic resonance imaging, and near infrared spectroscopy (NIRS) to determine which modality or combination of modalities will be precise and easy to implement as a screening tool for placental dysfunction in early pregnancy. In the future, their goal also is to use the imaging tools to help determine how treatments, such as future drug therapies, affect the placenta.

“We are using a multimodal experiment design to tackle the problems of: How does maternal blood flow get to the placenta? How does blood flow from the placenta to get to the fetus? How does oxygen transfer occur in vivo? And how do all of these things depend on the placenta’s structure?” Dr. Licht said.

A novel part of the research project is that the team aims to develop a new imaging instrument — an ultrasound probe with optics embedded in it — so that they can measure the placenta’s structure and blood flow while at the same time making optical measurements of oxygen saturation. Part of the challenge is ensuring that the instrument is sensitive and accurate enough to be used at the bedside for pregnant bellies that vary in shapes and size.

The team will rely on a diverse range of technological and clinical expertise in radiology, bioengineering, physics, nursing, and women’s reproductive health as they refine these placental imaging methods. Other team members include co-leader of the CHOP/Penn team Nadav Schwartz, MD, an assistant professor of Maternal Fetal Medicine at Penn; Arjun Yodh, PhD, director of The Laboratory for Research on the Structure of Matter at Penn; Felix Wehrili, PhD, director of the Laboratory for Structural NMR Imaging at Penn; and John Detre, MD, director of the Center for Functional Neuroimaging at Penn.

Once the researchers are able to determine how to best measure placental volumes and changes over time during healthy pregnancies, the next phase of the research project will be to study how maternal nutritional status influences placental development and function.

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Tracing Neurons’ Migration Suggests Cause of Brain Development Defects


By following the journey of how newly born neurons migrate in the developing cerebral cortex, the part of our brain responsible for conscious thought and higher order functioning, a study team at The Children’s Hospital of Philadelphia provided new insights into how disruptions in this pathway during early brain formation may lead to neurodevelopmental defects.

Drawing on both neuroscience and developmental biology, the researchers described in the journal Cell Reports how two types of neurons — projection neurons and interneurons — take different routes to reach their destination during fetal brain development. Based on previous research, the study team reasoned that projection neurons require less energy to migrate radially than interneurons that migrate tangentially. In other words, projection neurons take the fast lane along the highway, and interneurons explore a circuitous, scenic route.

Both types of neurons have travel companions — small organelles within the cell called mitochondria — that provide the energy for their locomotion along these trips. The research team’s new work suggests that mitochondrial dysfunction could interfere with the interneurons’ progress to get from their birthplace to their station in the brain.

The study’s first author, Erika Lin-Hendel, a graduate student in the School of Veterinary Medicine at the University of Pennsylvania, consulted with CHOP experts, including Douglas Wallace, PhD, director of CHOP’s Center for Mitochondrial and Epigenomic Medicine, to figure out how to produce live images of moving mitochondria inside moving neuron cells. The movies she created showed that mitochondria shift quite actively in the tangentially migrating interneurons. Meanwhile, mitochondria appear to sit in front of the nucleus in radially migrating projection neurons without exerting as much effort.

“When a neuron migrates, its fundamental challenge is how to move its nucleus, which has very tightly packed DNA and is heavy,” explained Stewart Anderson, MD, of CHOP’s department of Psychiatry who is co-senior author of the paper and Lin-Hendel’s mentor. “Essentially it is a sack of potatoes that the neuron cell is trying to move. When projection neurons migrate radially, they grab and pull the sack behind them. They don’t need a lot of energy to do their migration. But the tangentially migrating interneurons don’t have anything to grab onto. They reach and then squeeze the cell behind the nucleus to push it forward, kind of like sliding a golf ball through a garden hose. The interneurons need a lot of energy to do this, so a bioenergetics problem could hinder their ability to get placed in the right location in the cerebral cortex.”

Once the study team saw clearly that the mitochondria localized differently in the interneurons, the next step was to demonstrate that their energetic requirements also differed. In order to accomplish this, the researchers studied mice with a mutation in a gene that encodes for a protein that is necessary to move adenosine triphosphate (ATP) outside of the mitochondria. ATP is like charged batteries that are synthesized by the tiny energy factories. In these mice, the researchers observed that since ATP could not get out of the mitochondria, the interneuron cells did not have enough oomph, and their migration slowed down and became disoriented. Yet, the projection neurons’ migration seemed to be unaffected.

They demonstrated this same concept in another way by studying migrating neurons in a petri dish and treating them with a poison that halted mitochondrial ability to transport ATP. At a very low concentration, the poison blocked interneurons’ tangential migration but did not block the projection neurons’ radial migration.

“These results provide a new way of thinking about how metabolic challenges selectively can affect populations of cells,” said Dr. Anderson, who also is an associate professor of Psychiatry in the Perelman School of Medicine at the University of Pennsylvania.

The bulk of the processes of neuronal migration occur between 10 and 30 weeks gestation. A pregnancy complication or some type of chronic oxidative stress, such as from maternal smoking, drug use, or placental dysfunction, that reduces the fetus’ mitochondrial energy production could leave the interneurons stranded. This may partly explain why many patients with mitochondrial disease, which affects about one in 5,000 people, experience neurological symptoms, like seizures, that are suggestive of a failed function by the inhibitory interneurons.

Projection neurons, which excite their targets, and interneurons, which use inhibition to balance and to shape the flow of the excitation, must work in concert. Otherwise, hypersynchronous discharge of a population of cortical projection neurons can cause conditions such as childhood epilepsy. Or, if there is not enough synchrony, then the system becomes noisy, with inadequate brain rhythms, possibly causing intellectual disability and autism spectrum disorder. An infant who has inadequate numbers of interneurons because they never arrived at the place where they are supposed to be during the brain’s formative period may not be able to achieve or maintain this delicate state of equilibrium.

“The implications of these findings are that some of the solutions may be even harder to achieve than we had previously appreciated,” Dr. Anderson said. “The idea that the problem might be altered placement versus altered function of the interneurons shifts our thinking.”

The researchers’ novel observations could help to guide new approaches to identify fetal complications earlier, reduce oxidative stress, and support placental health to help ensure that interneurons have enough energy to stay on the right course. Other future strategies that Dr. Anderson’s laboratory is at an early stage of exploring are interneuron cell replacement therapies.

The study team also included co-senior author Jeffrey Golden, MD, formerly of CHOP and currently chair of the department of Pathology at Brigham and Women’s Hospital, Harvard Medical School; and Meagan McManus, PhD, of CHOP’s Center for Mitochondrial and Epigenomic Medicine and the department of Pathology and Laboratory Medicine at Penn.

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Putting the Brakes on Allergic Response


When you have a chronic allergic disorder, it’s easy to blame the trigger — an early pollen season or furry pet — but the real culprit is your own immune system. Designed to attack foreign substances such as bacteria and viruses, T cells are the immune system’s watchdog to recognize serious threats. But sometimes T cells can be too zealous and set in motion a signaling cascade that can cause allergic reactions to everyday things and even attack your body’s healthy cells by mistake.

“Inappropriate activation of immune cells is common in autoimmunity and also in allergic disease,” said Claire O’Leary, PhD, a postdoctoral fellow at The Children’s Hospital of Philadelphia. “Your immune system needs to learn to tolerate non-pathogenic immune insults while recognizing pathogenic organisms that it should mount a strong defense against.”

As a graduate student in the Cell and Molecular Biology program at the Perelman School of Medicine at the University of Pennsylvania, Dr. O’Leary completed her research in the lab of Paula Oliver, PhD, in the Cell Pathology Division of CHOP, to learn more about what is occurring at a basic cellular level to drive inappropriate immune cell responses. Dr. Oliver also is an assistant professor of Pathology and Laboratory Medicine at Penn.

Dr. Oliver’s lab had previously demonstrated that when an enzyme, called an E3 ubiquitin ligase did not function in mice, these deficient mice developed characteristics of allergic disease. Two small adapter proteins, Ndfip1 and Ndfip2, are required to activate this E3 ubiquitin ligase, which can then send proteins to the cell’s degradation machinery. Their research revealed that if certain proteins are not degraded, then the buildup could lead to aberrant T cell responses, precipitating allergic or autoimmune disease.

Dr. O’Leary’s new work, which appeared in Nature Communications, went a step further to describe how Ndfip1 and Ndfip2 contribute to the braking system that keeps T cells from instigating hyperactivity of the immune system and producing proinflammatory cytokines that are involved in ramping up inflammation.

“We think of these proteins as being negative regulators of inappropriate activation,” Dr. O’Leary said. “In the absence of these proteins, the cells are accelerating immune reactions without a lot of guidance. They become self-directed and differentiate toward a path that is highly proliferative. They produce a lot of Th2 type cytokines associated with allergic disease.”

The research project provided novel insight into how the molecular braking system works in two distinct stages. Ndfip1 comes on early when the immune system perceives a substance as being foreign or dangerous, and its expression skyrockets as T cells are stimulated. When the T cells are re-exposed to the antigen and stimulated a second time, they initiate a more aggressive and rapid memory response that requires both Ndfip1 and Ndfip2 to be activated in order prevent an overly exuberant immune response.

“Somehow, the protein degradation complex is helping during T cell stimulation to keep the cytokine signaling limited,” Dr. O’Leary said.

The Protein and Proteomics Core Facility at CHOP’s Research Institute helped the study team to dig deeper into the protein interactions that enable T cells to proliferate and produce too much cytokine. They found that when Ndfip1 and Ndfip2 were not functioning, it halted degradation of a protein called Jak1, which is essential for signaling via certain types of cytokine receptors. Without appropriate down regulation of Jak1, expansion and survival of pathogenic effector T cells increased. The study authors suggest that Ndfip1 and Ndfip2 work together to regulate the cross talk between the T cell receptor and cytokine signaling pathways to prevent inappropriate T cell responses.

As scientists learn about the basic mechanisms of T cells’ negative regulatory pathways, these findings could point the way to future drug therapies. Already, drugs are available that inhibit the Jak1 pathway in treating immune-mediated diseases, including rheumatoid arthritis, inflammatory bowel disease, and psoriasis. However, they also disarm the immune system and reduce its ability to respond to viral or bacterial infections. An alternative could be to develop drugs that promote activity of the E3 ubiquitin ligase.

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