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Heparin has long been used as a blood thinner, or anticoagulant, for patients with blood clotting disorders or after surgery to prevent complications. But the medication remains difficult to dose correctly, potentially leading to overdosing or underdosing.
A team of Penn State researchers combined heparin with a protein fragment, peptide, to slow down the release of the drug and convey the medication directly to the site of a clot. They published their findings in the journal Small.
“We wanted to develop a material that can gradually deliver heparin over time rather than the current iteration that gets cleared from the body in a couple of hours,” said corresponding author Scott Medina, Penn State associate professor of biomedical engineering. “We also wanted to deliver the drug through the skin instead of through an IV.”
When mixed, positively charged peptides and negatively charged heparin bind to create a nanogranular paste that can be injected under the skin, forming a cache of material that is then diffused in the circulatory system and travels to blood clots when they appear. The turbulent flow of fluid near a blood clot triggers the two materials to separate, allowing heparin to begin its anticoagulating action.
“The peptide is ideal for pairing with heparin because it essentially blocks heparin’s action until it is needed in the body,” said Atip Lawanprasert, doctoral student in biomedical engineering and first author on the paper. “The peptide also has some anticoagulating properties on its own: It binds to platelets in the blood, enabling action at the clotting site.”
Without an added bonding agent, heparin applies its anti-clotting properties indiscriminately, not just at blood clot sites, and clears quickly, its half-life only 60 to 90 minutes. Using preclinical animal trials, researchers determined that the addition of peptide allows for a dramatic increase of heparin’s half-life, to up to nearly 24 hours.
“The peptide increases heparin’s effects by more than ten times longer than what is currently being used,” Medina said. “The increased half-life allows for sustained treatments for patients, less medication waste and more accurate dosing. Eventually, this could allow the medication to be injected under the skin just once a day, rather than an all-day IV drip.”
Next, researchers plan to replicate the study in a clinical setting, as well as study the effect of the medication’s toxicity in the body if administered over multiple days.
In addition to Medina and Lawanprasert, the co-authors include Sopida Pimcharoen, undergraduate student in biomedical engineering, Connor T. Watson and Keefe B. Manning, graduate students in biomedical engineering, and Sarah E. Sumner and Girish S. Kirimanjeswara, Department of Veterinary and Biomedical Sciences, all at Penn State.
The U.S. Department of Agriculture and the National Institutes of Health supported this work.

During mesenchymal migration, a cancer cell moves like a gecko on a wall.
Before choosing this mode of movement, the cell sizes up the surface to which it may stick, explained physicist Nadir Kaplan. If the surface isn’t too stiff or soft and the path forward isn’t too constricting, the round cell will rapidly grow protrusions that act like temporary limbs, jutting forward and sticking to the surface. The cell will then pull itself forward and retract its rear and repeat the process.
This migration mode is one of the ways cancer cells navigate tissue during metastasis. In a study published by Biophysical Journal, postdoctoral physics fellow Wenya Shu and Kaplan, an assistant professor of physics in the College of Science, explored mesenchymal migration through cell simulations and mathematical modeling. Their aim: to learn more about how cancer cells size up surrounding tissue for stiffness and adapt their gecko-like movements in response.
The model and its insights on mesenchymal migration are a first step in learning how cancer cells migrate on the whole, Shu said. Cell migration is complex: Cells make use of multiple modes of migration, both individually and in colonies. “That’s the advantage of coming up with a computational model here,” he said. “We can dissect the effects of many ingredients at play.”
Experiments show that during mesenchymal migration, cells adapt how they navigate tissue based on stiffness: They’re drawn to tissue surfaces — or substrates — that are not too stiff or too soft. Cells can’t grow and attach their protrusions efficiently to too-stiff substrates, and if cells grab onto too-soft tissue, they’ll end up pulling it back toward their bodies, rather than using it to pull themselves forward. Shu and Kaplan’s cell simulations backed these experimental findings.
Their simulations confirmed to the researchers that cells distinguish between soft and stiff surfaces by comparing them to the physical properties of their own soft bodies. Substrate material properties will then affect the directions cells take as well as how efficiently they move.

To ensure that the model accurately simulated cancer cell migration, Kaplan and Shu built in not only how cells respond to the substrate mechanics of tissue, but also how they tune their internal biochemical signals. While navigating tissue, cells may also respond chemically to the secretions of a nutrition source in the body. The researchers’ model is the first to simulate how both of these drivers of cell motion play out, Shu said.
The researchers found that cells prefer moving in the direction determined by their strong internal chemical signaling, whether or not the overall motion is efficient. But without a strong chemical signal to follow, they focus on substrate properties.
By piecing these elements of mesenchymal migration together and reproducing them in a model, Kaplan sees a move toward better understanding and pinpointing how and where metastasis may occur.
Metastasis also may involve multiple cell migration modes. Mesenchymal migration tends to be the initial mode of migration through tissue and into vessels, but cells often pivot to amoeboid migration. Whereas cells move like geckos in the former mode, the latter has them moving more like tank treads. “They just roll forward,” Kaplan said.
Chemotherapy works well against cancer cells in mesenchymal migration, Kaplan said, but not as well when the cells switch to amoeboid migration. For experimentalists to understand that transition, they first need a better grasp of the mesenchymal mode.
That is what we have made progress toward here,” Kaplan said.
Next, Shu and Kaplan hope to use the model to look at how cell-cell interactions may affect migration, as individual cells bump into one another and set off changes in their direction. They also want to learn how cells negotiate more curved, narrow channels in their microenvironment.
Each effort to more closely model cell migration brings the team closer to understanding how cancer cells invade the body. “We want to come up with a predictive model that can produce new types of qualitative behaviors, to explain more measurements and motivate new experiments,” Kaplan said.
“Experiments are quite comprehensive, but they significantly benefit from simulations. For instance, when it comes to resolving very small time scales in the dynamics of these cell deformations. We are basically discerning all those components,” he said.

Hospitals have strict hygiene and sanitation protocols to protect patients from bacteria that rarely sicken healthy people but can be deadly for vulnerable patients already hospitalized with serious illnesses. Nearly 100,000 people die every year in U.S. hospitals of infections they develop after being admitted. But despite intense infection-control efforts, new strains of bacteria keep on emerging, seemingly out of nowhere, to sicken people in hospitals worldwide.
Researchers at Washington University School of Medicine in St. Louis have found evidence pointing to an unexpected source of such bacteria: the hospitalized patients themselves. Studying mice, the researchers discovered that urinary tract infections (UTIs) can arise after sterile tubes, called catheters, are inserted into the urinary tract, even when no bacteria are detectable in the bladder beforehand. Such tubes are commonly used in hospitals to empty the bladders of people undergoing surgery. In the mice, inserting the tubes activated dormant Acinetobacter baumannii (A. baumannii)bacteria hidden in bladder cells, triggering them to emerge, multiply and cause UTIs, the researchers said.
The findings, published Jan. 11 in Science Translational Medicine, suggest that screening patients for hidden reservoirs of dangerous bacteria could supplement infection-control efforts and help prevent deadly infections.
“You could sterilize the whole hospital, and you would still have new strains of A. baumannii popping up,” said co-senior author Mario Feldman, PhD, a professor of molecular microbiology. “Cleaning is just not enough, and nobody really knows why. This study shows that patients may be unwittingly carrying the bacteria into the hospital themselves, and that has implications for infection control. If someone has a planned surgery and is going to be catheterized, we could try to determine whether the patient is carrying the bacteria and cure that person of it before the surgery. Ideally, that would reduce the chances of developing one of these life-threatening infections.”
A. baumannii is a major threat to hospitalized people, causing many cases of UTIs in people with urinary catheters, pneumonia in people on ventilators, and bloodstream infections in people with central-line catheters into their veins. The bacteria are notoriously resistant to a broad range of antibiotics, so such infections are challenging to treat and easily can turn deadly.
Feldman teamed up with co-senior author Scott J. Hultgren, PhD, the Helen L. Stoever Professor of Molecular Microbiology and an expert on UTIs, to investigate why so many A. baumannii UTIs develop after people receive catheters.
Most UTIs among otherwise healthy people are caused by the bacterium Escherichia coli (E. coli). Research has shown that E. coli can hide out in bladder cells for months after a UTI seems to have been cured, and then re-emerge to cause another infection.
Feldman and Hultgren — along with co-first authors Jennie E. Hazen, a graduate student, and Gisela Di Venanzio, PhD, an instructor in molecular microbiology — investigated whether A. baumannii can hide inside cells like E. coli can. They studied mice with UTIs caused by A. baumannii. They used mice with weakened immune systems because, like people, healthy mice can fight off A. baumannii.
Once the infections had resolved and no bacteria were detected in the mice’s urine for two months, the researchers inserted catheters into the mice’s urinary tracts with a sterile technique. Within 24 hours, about half of the mice developed UTIs caused by the same strain of A. baumannii as the initial infection.
“The bacteria must have been there all along, hiding inside bladder cells until the catheter was introduced,” Hultgren said. “Catheterization induces inflammation, and inflammation causes the reservoir to activate, and the infection blooms.”
Since A. baumannii rarely causes symptoms in otherwise healthy people, many people who carry the bacteria may never know they’re infected, the researchers said. As part of this study, the researchers searched the scientific literature and discovered that about 2% of healthy people carry A. baumannii in their urine.
“I wouldn’t put much weight on the precise percentage, but I think we can say with certainty that some percentage of the population is walking around with A. baumannii,” Feldman said. “As long as they’re basically healthy, it doesn’t cause any problems, but once they’re hospitalized, it’s a different matter. This changes how we think about infection control. We can start considering how to check if patients already have Acinetobacter before they receive certain types of treatment; how we can get rid of it; and if other bacteria that cause deadly outbreaks in hospitals, such as Klebsiella, hide in the body in the same way. That’s what we’re working on figuring out now.”

Oregon State University College of Pharmacy scientists have demonstrated in animal models the possibility of using lipid nanoparticles and messenger RNA, the technology underpinning COVID-19 vaccines, to treat blindness associated with a rare genetic condition.
Researchers developed nanoparticles able to penetrate the neural retina and deliver mRNA to the photoreceptor cells whose proper function makes vision possible.
The study, led by OSU associate professor of pharmaceutical sciences Gaurav Sahay, Oregon State doctoral student Marco Herrera-Barrera and Oregon Health & Science University assistant professor of ophthalmology Renee Ryals, was published today in Science Advances.
The scientists overcame what had been the main limitation of using lipid nanoparticles, or LNPs, to carry genetic material for the purpose of vision therapy — getting them to reach the back of the eye, where the retina is.
Lipids are fatty acids and similar organic compounds including many natural oils and waxes. Nanoparticles are tiny pieces of material ranging in size from one- to 100-billionths of a meter. Messenger RNA delivers instructions to cells for making a particular protein.
With the coronavirus vaccines, the mRNA carried by the LNPs instructs cells to make a harmless piece of the virus’ spike protein, which triggers an immune response from the body. As a therapy for vision impairment resulting from inherited retinal degeneration, or IRD, the mRNA would instruct photoreceptor cells — faulty because of a genetic mutation — to manufacture the proteins needed for sight.

IRD encompasses a group of disorders of varying severity and prevalence that affect one out of every few thousand people worldwide.
The scientists showed, in research involving mice and non-human primates, that LNPs equipped with peptides were able to pass through barriers in the eye and reach the neural retina — where light is turned into electric signals that the brain converts to images.
“We identified a novel set of peptides that can reach the back of the eye,” Sahay said. “We used these peptides to act as zip codes to deliver nanoparticles carrying genetic materials to the intended address within the eye.”
“The peptides that we have discovered can be used as targeting ligands directly conjugated to silencing RNAs, small molecules for therapeutics or as imaging probes,” Herrera-Barrera added.
Sahay and Ryals have received a $3.2 million grant from the National Eye Institute to continue studying lipid nanoparticles’ promise in the treatment of hereditary blindness. They will lead research into using LNPs to deliver a gene editing tool that could delete bad genes in the photoreceptor cells and replace them with correctly functioning genes.
The research aims to develop solutions for the limitations associated with the current primary means of delivery for gene editing: a type of virus known as adeno-associated virus, or AAV.
“AAV has limited packaging capacity compared to LNPs and it can prompt an immune system response,” Sahay said. “It also doesn’t do fantastically well in continuing to express the enzymes the editing tool uses as molecular scissors to make cuts in the DNA to be edited. We’re hoping to use what we’ve learned so far about LNPs to develop an improved gene editor delivery system.”
The peptide-guided LNP study was funded by the National Institutes of Health. Also participating in the research for Oregon State were College of Pharmacy faculty Oleh Taratula and Conroy Sun, postdoctoral researchers Milan Gautam and Mohit Gupta, doctoral students Antony Jozic and Madeleine Landry, research assistant Chris Acosta and undergraduate Nick Jacomino, a bioengineering student in the College of Engineering who graduated in 2020.

CAR T cell therapy, an approach which reprograms patients’ own immune cells to attack their blood cancers, may enhance the effectiveness surgery for of solid tumors, according to a preclinical study from researchers in the Perelman School of Medicine at the University of Pennsylvania.
In the study, published today in Science Advances, the researchers applied a special gel containing human CAR T cells to surgical wounds in mice following partial tumor removal. They found that in almost all cases, the CAR T cells apparently eliminated the residual tumor cells — allowing the mice to survive when they otherwise would have succumbed to tumor recurrence.
Surgery can be curative when a solid tumor cancer has not spread. However, where a tumor ends and healthy tissue begins is often very difficult for surgeons to discern. Thus, for many cancer types, post-surgical recurrence due to remaining microscopic tumor cells is common. One possible approach to this problem is to apply an anti-tumor treatment to the remaining tissue margins immediately after tumor removal, to kill any residual tumor cells. In the study, Penn researchers tested that approach using CAR T cells.
“As we continue to advance CAR T cell therapy forward, finding applications for use in solid tumors is a major goal,” said study senior author Carl June, MD, the Richard W. Vague Professor in Immunotherapy and director of the Center for Cellular Immunotherapies at Penn Medicine’s Abramson Cancer Center. “Based on the promising results in this study, our colleagues have planned a clinical trial in patients with locally advanced breast cancer.”
CAR T cells are T cells — a powerful type of immune cell — that are engineered to target specific proteins. All the CAR T treatments that have been approved for clinical use target proteins found on cancer cells. Typically, the T cells are harvested from the patient’s blood, engineered in the lab, and then put back into the patient to work as a “living drug.” June and colleagues at Penn helped develop and test what became, in 2017, the first U.S. Food and Drug Administration-approved CAR T treatment. There are now six approved CAR T cell therapies targeting a variety of blood cancers, which have provided fresh hope for patients who have run out of conventional options.
Solid tumors, so far, have been a harder target for CAR T treatments, due in part to tumor bulk and tumor anti-immune defenses. However, another group of researchers showed in a study last year, in a mouse model of brain cancer, that CAR T cells might be useful for the more limited task of clearing up residual cancer cells after surgery. In the new study, June and colleagues tried this same approach against two other cancer types: triple-negative breast cancer, which lacks all of the three major breast cancer markers, and human pancreatic ductal carcinoma, the most common type of pancreatic cancer. Both of these solid tumor types are notoriously hard to cure.
The CAR T cells were engineered to home in on the protein mesothelin, a surface marker on both types of tumor cell in the experiments. Without the CAR T cell and fibrin gel, the remaining tumor tissue grew and the mice succumbed within about seven weeks. With the gel, however, residual tumor tissue swiftly disappeared in 19 of 20 mice, and these animals survived without wound-healing complications or other apparent side effects for the remainder of the observation period.
Further experiments showed that CAR T cells targeting mesothelin have the potential to attack healthy cells bearing that protein marker after intravenous injection, and the toxicity was decreased by local injection of the CAR T cells compared to direct injection of the cells into the blood.
“This study demonstrates the promise of CAR T as an add-on to surgery for solid tumors,” June said. “We also think that this approach could be broadened to deliver other cellular therapies and anticancer agents in addition to CAR T cells, potentially boosting the antitumor effectiveness even further.”
Additional authors include Ugur Uslu, Tong Da, Charles-Antoine Assenmacher, John Scholler, Regina Young, and Julia Tchou.
Funding for the study was provided by the Mildred-Scheel-Postdoctoral Fellowship of the German Cancer Aid, the Abramson Cancer Center, and the National Institutes of Health (P01CA214278).

The brain performs various cognitive and behavioral functions in everyday life, flexibly transitioning to various states to carry out these functions. Scientists view the brain as a system that performs these numerous functions by controlling its states. To better understand the properties of this control in the brain, scientists look for ways to estimate the difficulty of control, or control cost, when the brain transitions from one state to another. So a team of researchers undertook a study to quantify such control costs in the brain, and was successful in building a framework that evaluates these costs.
Controlling transitions to some states incurs greater “costs” than controlling transitions to others. With the development of a framework for quantifying transition costs, scientists will have a way to evaluate the difficulty of the shifts between various brain states. Possibly, they might also have a quantifiable measure for explaining cognitive loads, sleep-wake differences, habituation of cognitive tasks and psychiatric disorders.
The work is published in the Journal of Neuroscience.
The team worked to build a novel framework to quantify control cost that takes account of stochasticity, or the randomness, of neural activity. This stochasticity has been ignored in previous studies. The current control paradigm in neuroscience uses a deterministic framework that is unable to consider stochasticity. But it is well known that the neural dynamics are stochastic and the noise is ubiquitous throughout the whole brain. “In this work, we addressed the issue of stochasticity and first proposed a novel theoretical framework that quantifies the control cost taking account of the stochastic fluctuations of the neural dynamics,” said Shunsuke Kamiya, a doctoral student in the Graduate School of Arts and Sciences at the University of Tokyo.
In their study, the researchers established the analytical expression of the stochastic control cost, which enabled them to compute the cost in high-dimensional neural data. By the analytical expression, they discovered that the optimal control cost can be decomposed into the costs to control the mean and covariance. “This decomposition enables us to investigate how various brain areas differently contribute to controlling the transitions from one brain state to another,” said Kamiya.
The researchers also identified the significant brain regions for the optimal control in cognitive tasks in human whole-brain imaging data. They examined the significant brain regions in the optimal control of transitions from the resting state to seven cognitive task states, using human whole-brain imaging data of 352 healthy adults. They found that, with these different transitions, the lower visual areas commonly played a significant role in controlling the means, while the posterior cingulate cortex commonly played a significant role in controlling the covariances. The posterior cingulate cortex is the upper part of the limbic lobe, that region of the brain that plays an important role in memory and emotional behaviors.
In this study, the team only considered the optimal control cost where brain state transitions are controlled in an optimal manner, with minimization of stochastic control cost. However, in real neural systems, it is not likely that state transitions are controlled in an optimal manner. “An intriguing future direction will be to compare the optimally controlled dynamics and the actual dynamics using neural data during tasks,” said Masafumi Oizumi, associate professor in the Graduate School of Arts and Sciences at the University of Tokyo.
Looking ahead to future research, Oizumi explains that the ultimate goal of his lab is to understand the connection between brain dynamics and human behaviors, cognitions and consciousness. “For example, we suspect that the decrease of controllability in the brain dynamics may be related to mental fatigue or the loss of consciousness. We expect that control theoretical perspective will provide a new insight to this goal,” said Oizumi.

An Iowa State University research team has discovered a method for modifying the function of an enzyme crucial to fat production, which could lead to more effective treatments for childhood obesity and cancer.
While the research was in fruit fly larvae, being able to speed up or slow down lipid metabolism could have significant implications for human health, said Hua Bai, an associate professor of genetics, development and cell biology.
“We’ve identified what’s basically a metabolic switch. It’s like the accelerator on a car,” he said.
The focus of Bai’s research lab is the cellular and molecular mechanisms that cause animals to age. That was the initial intent of studying fatty acid synthase, an enzyme that plays a role in de novo lipogenesis, which is the process of turning excess dietary carbohydrates into fat. Typically, levels of fatty acid synthase rise and fall based on an animal’s cellular needs and diet.
Surprisingly, the researchers noticed that early in a fruit fly’s development, de novo lipogenesis increases without an accompanying boost in the expression of fatty acid synthase. That suggested there must be some other factor at play, Bai said.
After proteins such as fatty acid synthase are created based on genetic code, their function can be altered by one of several different types of post-translational modification. Bai’s team found one of those processes, acetylation, affected one of the 2,540 amino acids that combine to make fatty acid synthase, changing how effective it was at producing fat.
The research was published last month in the Proceedings of the National Academy of Sciences, a peer-reviewed journal.
In addition to its role in obesity, elevated levels of de novo lipogenesis are linked to cancer, so controlling it through a single amino acid could lead to highly targeted treatments, Bai said.
“Fine tuning the acetylation levels of fatty acid synthase would be a much more precise treatment than blocking the entire protein,” he said.
It’s not certain that the processes Bai’s team studied will work the same in humans, but the two species’ genomes are similar, which is part of the reason fruit flies are a common research subject. Still, capitalizing on the discovery to treat human disease is many years away, he said.
“The potential is high, but further testing is needed in other animals,” he said.

Vaccines that provide long-lasting protection against influenza, coronaviruses and respiratory syncytial virus (RSV) have proved exceptionally difficult to develop. In a new review article in Cell Host & Microbe, researchers from the National Institute of Allergy and Infectious Diseases (NIAID), part of the NIH, explore the challenges and outline approaches to improved vaccines. Anthony S. Fauci, M.D., former NIAID director, is an author along with Jeffery K. Taubenberger, M.D., Ph.D., and David M. Morens, M.D.
Unlike the respiratory viruses that cause measles, mumps and rubella — for which vaccination or recovery from illness provides decades-long protection against future infection — flu, RSV, SARS-CoV-2 and “common cold” coronaviruses share several characteristics that enable them to cause repeated re-infections. These include very short incubation periods, rapid host-to-host transmission and replication in the nasal mucosa rather than throughout the body. This last feature — non-systemic replication — means these viruses do not stimulate the full force of the adaptive immune response, which typically takes a week or more to mount.
A next generation of improved vaccines for mucosa-replicating viruses will require advances in understanding on several fronts, the authors say. For instance, more must be learned about interactions between flu viruses, coronaviruses and RSV and the components of the immune response that operate largely or exclusively in the upper respiratory system. Over time, these interactions have evolved and led to “immune tolerance,” wherein the human host tolerates transient, limited infections by viruses that are generally non-lethal to avoid the destructive consequences of an all-out immune system attack.
The authors note that mucosal immunization appears to be an optimal route of vaccination for the viruses of interest, when feasible. However, to develop useful mucosal vaccines, significant knowledge gaps must be filled including finding ideal vaccine formulations; determining dosage size, frequency and timing; and developing techniques for overcoming immune tolerance.
The NIAID authors urge fellow researchers to “think outside the box” to make strides toward vaccines that can elicit durable protection against these viruses of considerable public health impact. They conclude, “we are excited and invigorated that many investigators…are rethinking, from the ground up, all of our past assumptions and approaches to preventing important respiratory viral diseases and working to find bold new paths forward.”

Neuroimaging technology has been shown to hold great promise in helping clinicians link specific symptoms of mental health disorders to abnormal patterns of brain activity. But a new Yale-led study shows there are still kinks to be ironed out before doctors can translate images of the brain to psychiatric disorders such as post-traumatic stress disorder (PTSD).
Their findings are published Jan. 11 in the American Journal of Psychiatry.
Several years ago, The National Institutes of Mental Health launched a multi-billion-dollar research effort to locate biomarkers of brain activity that point to the biological roots of a host of mental health diseases, which today are typically identified by clinical evaluation of a constellation of often overlapping symptoms reported by patients.
“The idea is to forget classification of disease by symptoms and find underlying biological causes,” said Yale’s Ilan Harpaz-Rotem, professor of psychiatry and psychology and senior author of the study.
For the new study, the Yale-led team attempted to replicate the findings of an earlier nationwide neuroimaging study, in which Emory and Harvard scientists linked clusters of brain activity to a variety of outcomes among patients who had arrived at U.S. emergency departments following traumatic events. Specifically, when researchers measured patients’ brain activity during the performance of simple tasks — including ones that probe responses to threats and rewards — they detected a cluster of brain activity that showed high reactivity to both threat and reward signals and seemed to predict more severe symptoms of PTSD later on.
However, when Yale researchers analyzed similar neuroimaging data collected from recent trauma survivors in Israel, they were not able to replicate these findings. While they did identify the different clusters of brain activity observed in the earlier study, they found no association with prospective PTSD symptoms.
“That is not to say one set of data is right and the other is wrong, just that there is a lot of fundamental work that needs to be done to develop reliable models that could generalize across different studies,” said Yale’s Ziv Ben-Zion, a postdoctoral associate at Yale School of Medicine and the corresponding author of the study.
In fact, Yale researchers are currently working with the investigators of the original Emory-Harvard study to merge datasets “to search for common underlying patterns of brain activity associated with different responses to trauma,” Ben-Zion said.
“It took about 100 years to come up with current classifications of mental illness, but we’ve only been exploring refining psychiatric diagnoses using biomarkers for the last 10 years,” said Harpaz-Rotem. “We still have a long way to go.”

Using new microscopic methods in combination with machine learning-based image analysis, researchers from Freiburg have discovered new structures on the surface of living B cells that affect the distribution and possibly the function of their antigen receptors. The researchers’ study has been published in The EMBO Journal.
B cells are a crucial part of our immune system and recognize pathogens through specialized receptors on their surface. Scientists from the University of Freiburg could now observe how these receptors are distributed on the surface of living and moving cells. They found that the B cell surface is shaped into a characteristic landscape of interconnected ridges and protrusions. On this landscape, the IgM-class B cell antigen receptors (IgM-BCR) accumulate in specific areas. The precision of the receptors’ localization and their clustering into larger units likely constitute a mechanism that controls receptor signaling and facilitates antigen sensing and thereby the activation of B cells.
The surface of B lymphocytes is structured
In most immunological textbooks, lymphocytes are depicted as round, ball-like cells whose smooth surface carries randomly distributed receptors. The notion of a smooth unstructured B cell surface has already been challenged by electron micrographs of fixed and frozen lymphocytes, revealing thin membrane protrusions called microvilli on the cells’ surface. These tentacle-like structures help immune cells to search for molecular markers of pathogens, so-called antigens. B lymphocytes recognize such antigens through different classes of their B cell antigen receptors (BCR). These antigen receptors are complex molecular machines that, when activated, interact with other molecules to initiate a signaling cascade, leading to the differentiation of B cells into plasma cells and the production of protective antibodies.
Images of living cells at a very high speed
The research group of Prof. Dr. Michael Reth from the Clusters of Excellence BIOSS and CIBSS — Centre for Integrative Biological Signalling Studies at the University of Freiburg collaborated with the group of BIOSS and CIBSS researcher Prof. Dr. Ralf Reski, researchers at Euro-BioImaging (EMBL) and researchers at the University of Osnabrück/Germany to analyze how the IgM-BCR is distributed across the 3D surface of living B cells. For this, they used a technique called lattice light sheet microscopy, LLSM for short. “This method can capture volumetric images of living cells at a very high speed,” explains Dr. Deniz Saltukoglu from Freiburg University, the first author of the study. “In other types of high-resolution microscopy, cells need to be attached to a flat surface, which completely alters the B cells’ outer structures. LLSM allowed us to observe the cells in an environment that mimics biological tissues, meaning that the structures and movements that we saw were largely undisturbed,” she says.
The researchers then developed custom image analysis tools to quantify and objectively characterize the microscopic data. “We needed to segment the images and isolate morphological features,” describes Saltukoglu. “So far this had only been done with two-dimensional data, so we had to develop new computational tools for volumetric, time course data.” For this, the researchers drew inspiration from algorithms that are used to map geographical data for archeological surveys. With this approach, they found that the B cell surface carries a network of elevated ridges, with microvilli growing from the intersections of the network. Within this “cellular landscape,” the IgM-BCRs form clusters that concentrate along the ridges, in close proximity to the bases of the microvilli. The position of these clusters was linked with the dynamic movement of the ridges on the cells’ surface.
“We think that the 3-D location of the antigen receptors controls their activity,” says Reth. “Localization at the microvilli base may prevent their unwanted activation. Once B cells receive a danger signal, they extent their microvilli and we assume that the IgM-BCR clusters then get recruited to the tip where they are localized in an optimal position for antigen sensing.” This hypothesis is in line with other findings from Reth’s group, which suggest that the IgM-BCRs are regulated via lateral interactions with regulatory coreceptors. This means that the position and distribution of antigen receptors likely represent additional control mechanisms that affect signaling and activation of cells of the immune system.