Researchers at Utah State University are using silkworm silk to grow skeletal muscle cells, improving on traditional methods of cell culture and hopefully leading to better treatments for muscle atrophy.
When scientists are trying to understand disease and test treatments, they generally grow model cells on a flat plastic surface (think petri dish). But growing cells on a two-dimensional surface has its limitations, primarily because muscle tissue is three-dimensional. Thus, USU researchers developed a three-dimensional cell culture surface by growing cells on silk fibers that are wrapped around an acrylic chassis. The team used both native and transgenic silkworm silk, the latter produced by silkworms modified with spider silk genes.
Native silkworm silks have been used previously as three-dimensional cell culture models, but this is the first time that transgenic silkworm silk has been used for skeletal muscle modeling. Elizabeth Vargis, Matthew Clegg, and Jacob Barney of the Biological Engineering Department, and Justin Jones, Thomas Harris, and Xiaoli Zhang of the Biology Department published their findings in ACS Biomaterials Science & Engineering.
Cells grown on silkworm silk proved to more closely mimic human skeletal muscle than those grown on the usual plastic surface. These cells showed increased mechanical flexibility and increased expression of genes required for muscle contraction. Silkworm silk also encouraged proper muscle fiber alignment, a necessary element for robust muscle modeling.
Skeletal muscle is responsible for moving the skeleton, stabilizing joints, and protecting internal organs. The deterioration of these muscles can happen for myriad reasons, and it can happen swiftly. For example, after only two weeks of immobilization, a person can lose almost a quarter of their quadricep muscle strength. Understanding how muscles can atrophy so quickly must begin at a cellular level, with cells grown to better represent reality.
“The overarching goal of my research is to build better in vitro models,” said Elizabeth Vargis, associate professor of biological engineering at USU. “Researchers grow cells on these 2D platforms, which aren’t super realistic, but give us a lot of information. Based on those results, they usually transition into an animal model, then they move onto clinical trials, where a vast majority of them fail. I’m trying to add to that first step by developing more realistic in vitro models of normal and diseased tissue.”

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Materials provided by Utah State University. Original written by Anessa Pennington. Note: Content may be edited for style and length.

Some of Princeton’s leading cancer researchers were startled to discover that what they thought was a straightforward investigation into how cancer spreads through the body — metastasis — turned up evidence of liquid-liquid phase separations: the new field of biology research that investigates how liquid blobs of living materials merge into each other, similar to the movements seen in a lava lamp or in liquid mercury.
“We believe this is the first time that phase separation has been implicated in cancer metastasis,” said Yibin Kang, the Warner-Lambert/Parke-Davis Professor of Molecular Biology. He is the senior author on a new paper featured on the cover of the current issue of Nature Cell Biology.
Not only does their work tie phase separations to cancer research, but the merging blobs turned out to create more than the sum of their parts, self-assembling into a previously unknown organelle (essentially an organ of the cell).
Discovering a new organelle is revolutionary, Kang said. He compared it to finding a new planet within our solar system. “Some organelles we have known for 100 years or more, and then all of a sudden, we found a new one!”
This will shift some fundamental perceptions of what a cell is and does, said Mark Esposito, a 2017 Ph.D. alumnus and current postdoc in Kang’s lab who is the first author on the new paper. “Everybody goes to school, and they learn ‘The mitochondria is the powerhouse of the cell,’ and a few other things about a few organelles, but now, our classic definition of what’s inside a cell, of how a cell organizes itself and controls its behavior, is starting to shift,” he said. “Our research marks a very concrete step forward in that.”
The work grew out of collaborations between researchers in the labs of three Princeton professors: Kang; Ileana Cristea, a professor of molecular biology and leading expert in the mass spectroscopy of living tissue; and Cliff Brangwynne, the June K. Wu ’92 Professor of Chemical and Biological Engineering and director of the Princeton Bioengineering Initiative, who pioneered the study of phase separation in biological processes.

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“Ileana is a biochemist, Cliff is a biophysicist and engineer, and I am a cancer biologist — a cell biologist,” Kang said. “Princeton is just a wonderful place for people to connect and collaborate. We have a very small campus. All the science departments are right next to each other. Ileana’s lab is actually on the same floor of Lewis Thomas as mine! These very close relationships, among very diverse research areas, allow us to bring in technologies from many different angles, and allow breakthroughs to understanding the mechanisms of metabolism in cancer — its progression, metastasis and the immune response — and also come up with new ways to target it.”
The latest breakthrough, featuring the as-yet unnamed organelle, adds new understanding to the role of the Wnt signaling pathway, a system whose discovery led to the 1995 Nobel Prize for Eric Wieschaus, Princeton’s Squibb Professor in Molecular Biology and a professor in the Lewis-Sigler Institute for Integrative Genomics. The Wnt pathway is vital to embryonic development in countless organisms, from tiny invertebrate insects to humans. Wieschaus discovered that cancer can co-opt this pathway, essentially corrupting its ability to grow as rapidly as embryos must, to grow tumors.
Subsequent research has revealed that the Wnt signaling pathway plays multiple roles in healthy bone growth as well as in cancer metastasizing to bones. Kang and his colleagues were investigating the complex interplay between Wnt, a signaling molecule called TGF-b, and a relatively unknown gene named DACT1 when they discovered this new organelle.
Think of it as panic-shopping before a storm, said Esposito. Buying up bread and milk before a blizzard — or hoarding hand sanitizer and toilet paper when a pandemic is looming on the horizon — aren’t just human traits, it turns out. They happen on the cellular level, too.
Here’s how it works: The panicked shopper is DACT1, and the blizzard (or pandemic) is TGF-ß. The bread and hand sanitizer are Casein Kinase 2 (CK2), and in the presence of a storm, DACT1 grabs up as much of them as possible, and the newly discovered organelle sequesters them away. By hoarding CK2, the shopper prevents other folks from making sandwiches and sanitizing their hands, i.e. preventing the healthy operation of the Wnt pathway.

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Through a series of detailed and complex experiments, the researchers pieced together the story: bone tumors initially induce Wnt signaling, to disseminate (spread) through the bone. Then, TGF-b, which is abundant in bones, inspires the panicked shopping, suppressing Wnt signaling. The tumors then stimulate the growth of osteoclasts, which scrub away old bone tissue. (Healthy bones are constantly being replenished in a two-part process: osteoclasts scrub away a layer of bone, then osteoblasts rebuild the bone with new material.) This further increases the TGF-b concentration, prompting even more DACT1 hoarding and subsequent Wnt suppression that has been shown to be important in further metastasis.
By discovering the roles of DACT1 and this organelle, Kang and his team have found new possible targets for cancer drugs. “For example, if we have a way to disrupt the DACT1 complex, perhaps the tumor will disseminate, but it will never be able to ‘grow up’ to be life-threatening metastasis. That’s the hope,” Kang said.
Kang and Esposito recently co-founded KayoThera to pursue the development of medications for patients with late-stage or metastatic cancers, based on their work together in the Kang lab. “The kind of fundamental study that Mark is doing both presents groundbreaking science findings and can also lead to medical breakthroughs,” said Kang.
The researchers have found that DACT1 plays many other roles as well, which their team is only beginning to explore. The mass spectrometry collaboration with Cristea’s team revealed more than 600 different proteins in the mysterious organelle. Mass spectrometry allows scientists to find out the exact components of almost any substance imaged on a microscope slide.
“This is a more dynamic signaling node than just controlling Wnt and TGF-b.” said Esposito. “This is just the tip of the iceberg on a new field of biology.”
This bridge between phase separations and cancer research is still in its infancy, but it already shows great potential, said Brangwynne, who was a co-author on the paper.
“The role that biomolecular condensates play in cancer — both its genesis but particularly its spread through metastasis — is still poorly understood,” he said. “This study provides new insights into the interplay of cancer signaling pathways and condensate biophysics, and it will open up new therapeutic avenues.”

Smoke from local wildfires can affect the health of Colorado residents, in addition to smoke from fires in forests as far away as California and the Pacific Northwest.
Researchers at Colorado State University, curious about the health effects from smoke from large wildfires across the Western United States, analyzed six years of hospitalization data and death records for the cities along the Front Range, which reaches deep into central Colorado from southern Wyoming.
They found that wildfire smoke was associated with increased hospitalizations for asthma, chronic obstructive pulmonary disease and some cardiovascular health outcomes. They also discovered that wildfire smoke was associated with deaths from asthma and cardiovascular disease, but that there was a difference in the effects of smoke from local fires and that from distant ones.
Long-range smoke was associated with expected increases in hospitalizations and increased risk of death from cardiovascular outcomes.
But when the research team separated out health effects of smoke from local wildfires in early summer 2012 from long-range smoke from late summer 2012 and summer 2015, they found that local wildfires were associated with meaningful decreases in hospitalizations, especially for asthma.
The study, “Differential Cardiopulmonary Health Impacts of Local and Long-Range Transport of Wildfire Smoke,” was recently published in GeoHealth, a journal from the American Geophysical Union.

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Residents protect themselves from local fires
Sheryl Magzamen, lead author of the study and an associate professor in the Department of Environmental and Radiological Health Sciences at CSU, said the team believes that evacuation efforts and related media coverage of local wildfires may have helped protect residents from adverse health effects of smoke exposure as well as direct impacts of the fires.
“There’s a lack of communication about smoke from distant wildfires,” said Magzamen. “Generally when there are local fires, there are advisories in the news that are associated with evacuations and local fire conditions. Due to the presence of the fire, people take measures to protect themselves. This could be why we see this lower risk of health effects from smoke associated with local fires.”
Researchers described the long-range wildfire smoke as resembling fog, which is what Magzamen said she noticed in Fort Collins in August 2015. At the time, she was collaborating on a project with Jeff Pierce, associate professor in the Department of Atmospheric Science.
“I thought it was weird to see fog on that day,” she explained. “Jeff said, ‘That’s actually smoke.’ We all took a step back.”
Smoke changes with age

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Pierce, a co-author on this study, said researchers don’t really know how harmful smoke is as it gets older, or becomes long-range smoke.
“In Fort Collins, about half the time we had smoke in late August or September 2020, this was smoke from the Cameron Peak Fire,” he explained. “This smoke was only a couple hours old when it got here. At other times, we were getting smoke from California, and the smoke from the Cameron Peak Fire was either going over our heads or further south.”
The Cameron Peak Fire was reported on Aug. 13, 2020, and burned into October, consuming 208,913 acres on the Arapaho and Roosevelt National Forests in Larimer and Jackson Counties and Rocky Mountain National Park. It was the first wildfire in Colorado history to burn more than 200,000 acres.
The average person would not notice a difference in wildfire smoke, Pierce said.
“If the smoke is even two days old, things happen chemically, which changes the smoke a lot,” he explained. “If it didn’t smell like wood burning, it was long-range smoke from California.”
Magzamen said that the team is working to better understand these chemical changes.
“As the small particles found in wildfire smoke age, they can cause more oxidative stress and more respiratory health effects,” she said. “But wildfire smoke itself is a mixture of particles and gases. Teasing apart the effects of all the components of smoke and what happens to the mixture across space and time — and how those changes impact health — is an enormous scientific challenge.”
Better air quality monitoring
Magzamen said the gap in understanding the source of wildfire smoke is because it historically has been measured by land-based sensors, which are primarily located in large urban areas and sparsely located in other regions, even along the Front Range.
“Even over the last five years, our air quality monitoring networks have been enhanced with new technologies and better measurements of real-time smoke effects,” she said.
CSU researchers are now collaborating with local government officials on messaging related to the different types of wildfire smoke, with a specific aim to reach the most vulnerable populations. This includes caretakers of young children, people experiencing homelessness and others who can’t shelter safely in place during wildfire season.
“We want people to be smoke-aware,” she said. “On the Front Range, we have wildfire smoke every summer. We may not get Cameron Peak-size type of fires every year, but we are downwind for pretty much the entire Western United States,” she said. “It’s critical that we keep people healthy and safe.”

Scientists at Washington University School of Medicine in St. Louis have implicated a type of immune cell in the development of chronic lung disease that sometimes is triggered following a respiratory viral infection. The evidence suggests that activation of this immune cell — a type of guardian cell called a dendritic cell — serves as an early switch that, when activated, sets in motion a chain of events that drives progressive lung diseases, including asthma and chronic obstructive pulmonary disease (COPD).
The new study, published in The Journal of Immunology, opens the door to potential preventive or therapeutic strategies for chronic lung disease. More immediately, measuring the levels of these dendritic cells in clinical samples from patients hospitalized with a viral infection, such as influenza or COVID-19, could help doctors identify which patients are at high risk of respiratory failure and death.
Studying mice with a respiratory viral infection that makes the animals prone to developing chronic lung disease, the researchers showed that these dendritic cells communicate with the lining of the airway in ways that cause the airway-lining cells to ramp up their growth and inflammatory signals. The inflammation causes airway-lining cells to grow beyond their normal boundaries and turn into cells that overproduce mucus and cause inflammation, which in turn causes cough and difficulty breathing.
“We’re trying to understand how a viral infection that seems to be cleared by the body can nevertheless trigger chronic, progressive lung disease,” said senior author Michael J. Holtzman, MD, the Selma and Herman Seldin Professor of Medicine. “Not everyone experiences this progression. We believe there’s some switch that gets flipped, triggering the bad response. We’re identifying that switch and ways to control it. This work tells us that this type of dendritic cell is sitting right at that switch point.”
Holtzman’s past work had implicated the lining of the airway — where the viral infection takes hold — as the likely trigger for this process.
“But this study suggests that the cascade starts even further upstream,” said Holtzman, also director of the Division of Pulmonary and Critical Care Medicine. “Dendritic cells are telling the cells lining the airway what to do. There’s more work to be done, but this data tells us that the dendritic cells play an important role in getting the airway-lining cells onto the wrong path.”
Holtzman calls this dendritic cell a type of sentinel because its job is to detect an invading virus and trigger the body’s initial immune response against the infection. The problem comes when the cell doesn’t shut down properly after the threat has passed.
“Many people never develop chronic lung disease after a viral infection,” Holtzman said. “But others have a genetic susceptibility to this type of disease. People who are susceptible to virus-triggered disease include patients with asthma, COPD, and viral infections such as COVID-19. It’s really critical to look for ways to fix this disease response and prevent the problems that might occur after the virus has gone.”
In the meantime, Holtzman said, high levels of these dendritic cells and their products in the lungs of hospitalized patients could serve as a warning to doctors that such patients are likely to develop severe disease and should be provided with respiratory interventions and other supportive therapies that are precisely tailored to their disease process.
“Similarly, if this process is not underway, the patient might be more likely to avoid these types of long-term problems,” Holtzman said. “We’re pursuing this line of research to help improve prediction of severe lung disease after infection and to provide companion therapies that could prevent this switch from being flipped or flip it back to reverse the disease.”
This work was supported by the National Institute of Allergy and Infectious Diseases (NIAID), grant number R01 AI130591 and the National Heart, Lung, and Blood Institute (NHLBI), grant number R35 HL145242, both of the National Institutes of Health (NIH); the Cystic Fibrosis Foundation; and the Hardy Trust and Schaeffer Funds.

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Materials provided by Washington University School of Medicine. Original written by Julia Evangelou Strait. Note: Content may be edited for style and length.

Every 12 minutes, someone in the United States dies of pancreatic cancer, which is often diagnosed late, spreads rapidly and has a five-year survival rate at approximately 10 percent. Treatment may involve radiation, surgery and chemotherapy, though often the cancer becomes resistant to drugs.
Researchers at University of California San Diego School of Medicine and Moores Cancer Center, in collaboration with Sanford-Burnham-Prebys Medical Discovery Institute and Columbia University, demonstrated that a new tumor-penetrating therapy, tested in animal models, may enhance the effects of chemotherapy, reduce metastasis and increase survival.
The study, published online March 9, 2021 in Nature Communications, showed how a tumor-targeting peptide, called iRGD, can sneak inside the armor that the tumor built to protect itself and use the fibrous tissue as a highway to reach deeper inside, destroying the tumor from within.
The pancreas is a large gland located behind the stomach. It makes enzymes that aid digestion and hormones that regulate blood-sugar levels. Pancreatic ductal adenocarcinoma (PDAC) is a subtype of pancreatic cancer that is highly drug-resistant due, in part, by the hard shell-like outer layer surrounding the tumor.
“This type of tumor is made up of a dense fibrous tissue that acts as a barrier to drugs trying to get through. Many drugs can reach the vessels of the tumor, but they are not able to get deep into the tissue, making treatment less effective, and that is one reason why this type of cancer is so challenging to treat,” said Tatiana Hurtado de Mendoza, PhD, first author of the study and assistant project scientist at UC San Diego School of Medicine and Moores Cancer Center.
“Our study found that the tumor-penetrating peptide iRGD is able to use this fibrous network to deliver chemotherapy drugs deep into the tumor and be more effective.”
The research team examined the microenvironment of PDAC tumors in a mouse model. They found that after targeting the tumor blood vessels, iRGD binds to high levels of β5 integrin, a protein produced by cells known as carcinoma-associated fibroblasts (CAFs) that produce much of the tumor’s protective fibrous cover.
“We were able to closely replicate human disease in our mouse model and found that when iRGD was injected with chemotherapy in mice with high levels of β5 integrin, there was a significant increase in survival and a reduction in the cancer spreading to other organs in the body compared to chemotherapy alone. This could be a powerful treatment strategy to target aggressive pancreatic cancer,” said Andrew Lowy, MD, co-corresponding author of the study, professor of surgery at UC San Diego School of Medicine and chief of the Division of Surgical Oncology at Moores Cancer Center at UC San Diego Health.
“What is also exciting about this finding is the iRGD therapy did not produce any additional side effects. This is critically important when considering treatments for patients.”
The researchers said next steps include a national human clinical trial. They estimate the trial could begin in one year.
“The knowledge gained from our study has the potential to be directly applied to patient care. We also believe that the levels of β5 integrin within a pancreatic cancer could tell us which patients would benefit the most from iRGD-combination therapy,” said Lowy.

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Schizophrenia is a neurodevelopmental disorder that disrupts brain activity producing hallucinations, delusions, and other cognitive disturbances. Researchers have long searched for genetic influences in the disease, but genetic mutations have been identified in only a small fraction — fewer than a quarter — of sequenced patients. A new study now shows that “somatic” gene mutations in brain cells could account for some of the disease neuropathology.
The study, led by senior author Jeong Ho Lee, MD, PhD, at Korea Advanced Institute of Science and Technology and the team of Stanley Medical Research Institute, appears in Biological Psychiatry, published by Elsevier.
Traditional genetic mutations, called germline mutations, occur in sperm or egg cells and are passed on to offspring by their parents. Somatic mutations, in contrast, occur in an embryo after fertilization, and they can appear throughout the body or in isolated pockets of tissues, making them much harder to detect from blood or saliva samples, which are typically used for such sequencing studies.
Recently, more-advanced genetic sequencing techniques have allowed researchers to detect somatic mutations, and studies have shown that even mutations present at very low levels can have functional consequences. A previous study hinted that brain somatic mutations were associated with schizophrenia (SCZ), but it was not powerful enough to cement such an association.
In the current study, the researchers used deep whole-exome sequencing to determine the genetic code of all exomes, the parts of genes that encode proteins. The scientists sequenced postmortem samples from 27 people with schizophrenia and 31 control participants both from brain and from liver, heart or spleen tissue, allowing them to compare the sequences in the two tissues. Using a powerful analytic technique, the team identified an average of 4.9 somatic single-nucleotide variants (SNV), or mutations, in brain samples from people with SCZ and 5.6 somatic SNVs in brain samples from control subjects.
Although there was no significant quantitative difference in somatic SNVs between SCZ and control tissues, the researchers found that the mutations in SCZ patients were found in genes already associated with SCZ. Of the germline mutations that had previously been associated with schizophrenia, the genes affected encoding proteins associated with synaptic neural communication, particularly in a brain region called the dorsolateral prefrontal cortex.
The researchers then determined which proteins might be affected by the newly identified somatic mutations. Remarkably, a protein called GRIN2B emerged as highly affected, and two patients with SCZ carried somatic mutations on the GRIN2B gene itself. GRIN2B is a protein component of NMDA-type glutamate receptors, which are critical for neural signaling. Faulty glutamate receptors have long been suspected to contribute to SCZ pathology; GRIN2B ranks among the most-studied genes in schizophrenia.
John Krystal, MD, Editor of Biological Psychiatry, said of the work, “The genetics of schizophrenia has received intensive study for several decades. Now a new possibility emerges, that in some cases, mutations in the DNA of brain cells contributes to the biology of schizophrenia. Remarkably this new biology points to an old schizophrenia story: NMDA glutamate receptor dysfunction. Perhaps the path through which somatic mutations contribute to schizophrenia converges with other sources of abnormalities in glutamate signaling in this disorder.”
Dr. Lee and the team next wanted to assess the functional consequences of the somatic mutations. Because of the location of the GRIN2B mutations found in SCZ patients, the researchers hypothesized that they might interfere with the receptors’ localization on neurons. Experiments in cortical neurons from mice showed that the mutations indeed disrupted the receptors’ usual localization to dendrites, the “listening” ends of neurons, which in turn prevented the formation of normal synapses in the neurons. The finding suggests that the somatic mutations could disrupt neural communication, contributing to SCZ pathology.
The somatic mutations identified in the study had a variant allele frequency of only about 1 percent, indicating that the mutations were rare among brain cells as a whole. Nevertheless, they have the potential to create widespread cortical dysfunction.
Dr. Lee said of the findings: “Besides the comprehensive genetic analysis of brain-only mutations in postmortem tissues from schizophrenia patients, this study experimentally showed the biological consequence of identified somatic mutations, which led to neuronal abnormalities associated with SCZ. Thus, this study suggests that brain somatic mutations can be a hidden major contributor to SCZ and provides new insights into the molecular genetic architecture of SCZ.”

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Deforestation may cause an initial increase in malaria infections across Southeast Asia before leading to later decreases, a study published today in eLife suggests.
The results may help malaria control programs in the region develop better strategies for eliminating malaria infections and educating residents on how to protect themselves from infection.
Mosquitos spread the malaria parasite to humans causing infections that can be severe and sometimes deadly. In the area along the Mekong river in Southeast Asia, many residents hunt or harvest wood in the surrounding forests, which can increase their risk of infection. Yet recent outbreaks of malaria in the region have also been linked to deforestation.
“As countries in the region focus their malaria control and elimination efforts on reducing forest-related transmission, understanding the impact of deforestation on malaria rates is essential,” says first author Francois Rerolle, Graduate Student Researcher at the University of California San Francisco (UCSF), US, who works within the UCSF Malaria Elimination Initiative.
To better understand the effects of deforestation on malaria transmission, Rerolle and colleagues examined both forest cover data and village-level malaria incidence data from 2013-2016 in two regions within the Greater Mekong Sub-region.
They found that in the first two years following deforestation activities, malaria infections increased in villages in the area, but then decreased in later years. This trend was mostly driven by infections with the malaria parasite Plasmodium falciparum. Deforestation in the immediate 1-10-kilometer radius surrounding villages did not affect malaria rates, but deforestation in a wider 30-kilometer radius around the villages did. The authors say this is likely due to the effect that wider deforestation can have on human behaviour. “We suspect that people making longer and deeper trips into the forest results in increased exposure to mosquitoes, putting forest-goers at risk,” Rerolle explains.
Previously, studies on the Amazon in South America have found increased malaria infections in the first 6-8 years after deforestation, after which malaria rates fall. The difference in timing may be due to regional differences. The previous studies in the Amazon looked at deforestation driven by non-indigenous people moving deeper into the forest, while communities in the current study have long lived at the forest edges and rely on subsistence agriculture.
“Our work provides a more complete picture of the nuanced effects of deforestation on malaria infections,” says senior author Adam Bennett, Program Lead at the UCSF Malaria Elimination Initiative. “It may encourage more in-depth studies on the environmental and behavioural drivers of malaria to help inform strategies for disease elimination.”

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Spinal cord injuries can be life-changing and alter many important neurological functions. Unfortunately, clinicians have relatively few tools to help patients regain lost functions.
In APL Bioengineering, by AIP Publishing, researchers from UCLA have developed materials that can interface with an injured spinal cord and provide a scaffolding to facilitate healing. To do this, scaffolding materials need to mimic the natural spinal cord tissue, so they can be readily populated by native cells in the spinal cord, essentially filling in gaps left by injury.
“In this study, we demonstrate that incorporating a regular network of pores throughout these materials, where pores are sized similarly to normal cells, increases infiltration of cells from spinal cord tissue into the material implant and improves regeneration of nerves throughout the injured area,” said author Stephanie Seidlits.
The researchers show how the pores improve efficiency of gene therapies administered locally to the injured tissues, which can further promote tissue regeneration.
Since many spinal cord injuries result from a contusion, the biomaterial implants need to be injected in or near the injured area without causing damage to any surrounding spared tissue. A major technical challenge has been fabricating scaffold materials with cell-scale pore sizes that are also injectable.
In the researchers’ method, they injected beads of material through a small needle into the spinal cord, where the beads stick together to form a scaffold, where cells can crawl in the pore spaces between the beads. The researchers found inclusion of these larger cell-scale pores within biomaterial scaffolds improved cell infiltration, gene delivery, and tissue repair after spinal cord injury, compared to more conventional materials with nanoscale pores.
The researchers made the highly porous scaffolds using two different methods. One was simpler but created a more irregularly sized pore network. The second was more complicated but created a highly regular pore structure.
Even though both materials had the same average pore size and chemical composition, more regenerating nerves were found to infiltrate scaffolds with regularly shaped pores.
“These results inform how to maximize interfacing with the nervous system,” said Seidlits. “This has potential applications not only for developing new therapies for brain and spinal cord repair but also for brain-machine interfaces, prosthetics, and treatment of neurodegenerative diseases.”

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Astronauts face many challenges to their health, due to the exceptional conditions of spaceflight. Among these are a variety of infectious microbes that can attack their suppressed immune systems.
Now, in the first study of its kind, Cheryl Nickerson, lead author Jennifer Barrila and their colleagues describe the infection of human cells by the intestinal pathogen Salmonella Typhimurium during spaceflight. They show how the microgravity environment of spaceflight changes the molecular profile of human intestinal cells and how these expression patterns are further changed in response to infection. In another first, the researchers were also able to detect molecular changes in the bacterial pathogen while inside the infected host cells.
The results offer fresh insights into the infection process and may lead to novel methods for combatting invasive pathogens during spaceflight and under less exotic conditions here on earth.
The results of their efforts appear in the current issue of the Nature Publishing Group journal npj Microgravity.
Mission control
In the study, human intestinal epithelial cells were cultured aboard Space Shuttle mission STS-131, where a subset of the cultures were either infected with Salmonella or remained as uninfected controls.

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The new research uncovered global alterations in RNA and protein expression in human cells and RNA expression in bacterial cells compared with ground-based control samples and reinforces the team’s previous findings that spaceflight can increase infectious disease potential.
Nickerson and Barrila, researchers in the Biodesign Center for Fundamental and Applied Microbiomics, along with their colleagues, have been using spaceflight as a unique experimental tool to study how changes in physical forces, like those associated with the microgravity environment, can alter the responses of both the host and pathogen during infection. Nickerson is also a professor in the School of Life Sciences at ASU.
In an earlier series of pioneering spaceflight and ground-based spaceflight analogue studies, Nickerson’s team demonstrated that the spaceflight environment can intensify the disease-causing properties or virulence of pathogenic organisms like Salmonella in ways that were not observed when the same organism was cultured under conventional conditions in the laboratory.
The studies provided clues as to the underlying mechanisms of the heightened virulence and how it might be tamed or outwitted. However, these studies were done when only the Salmonella were grown in spaceflight and the infections were done when the bacteria were returned to Earth.
“We appreciate the opportunity that NASA provided our team to study the entire infection process in spaceflight, which is providing new insight into the mechanobiology of infectious disease that can be used to protect astronaut health and mitigate infectious disease risks,” Nickerson says of the new study. “This becomes increasingly important as we transition to longer human exploration missions that are further away from our planet.”
Probing a familiar adversary

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Salmonella strains known to infect humans continue to ravage society, as they have since antiquity, causing around 1.35 million foodborne infections, 26,500 hospitalizations, and 420 deaths in the United States every year, according to the Centers for Disease Control. The pathogen enters the human body through the ingestion of contaminated food and water, where it attaches and invades into intestinal tissue. The infection process is a dynamic dance between host and microbe, its rhythm dictated by the biological and physical cues present in the tissue’s environment.
Despite decades of intensive research, scientists still have much to learn about the subtleties of pathogenic infection of human cells. Invasive bacteria like Salmonella have evolved sophisticated countermeasures to human defenses, allowing them to flourish under hostile conditions in the human stomach and intestine to stealthily evade the immune system, making them highly effective agents of disease.
The issue is of particular medical concern for astronauts during spaceflight missions. Their immune systems and gastrointestinal function are altered by the rigors of space travel, while the effects of low gravity and other variables of the spaceflight environment can intensify the disease-causing properties of hitchhiking microbes, like Salmonella. This combination of factors poses unique risks for space travelers working hundreds of miles above the earth — far removed from hospitals and appropriate medical care.
As technology advances, it is expected that space travel will become more frequent — for space exploration, life sciences research, and even as a leisure activity (for those who can afford it). Further, extended missions with human crews are on the horizon for NASA and perhaps space-voyaging companies like SpaceX, including trips to the Moon and Mars. A failure to keep bacterial infections at bay could have dire consequences.
Hide and Seq
In the current study, human intestinal epithelial cells, the prime target for invasive Salmonella bacteria, were infected with Salmonella during spaceflight. The researchers were keen to examine how the spaceflight setting affected the transcription of human and bacterial DNA into RNA, as well as the expression of the resulting suite of human proteins produced from the RNA code, products of a process known as translation.
The research involved the close examination of transcriptional profiles of both the pathogenic Salmonella and the human cells they attack, as well as the protein expression profiles of the human cells to gauge the effects of the spaceflight environment on the host-pathogen dynamic.
To accomplish this, researchers used a revolutionary method known as dual RNA-Seq, which applied deep sequencing technology to enable their evaluation of host and pathogen behavior under microgravity during the infection process and permitted a comparison with the team’s previous experiments conducted aboard the Space Shuttle.
The host and pathogen data recovered from spaceflight experiments were compared with those obtained when cells were grown on earth in identical hardware and culture conditions (e.g., media, temperature).
Earth and sky
Earlier studies by Nickerson and her colleagues demonstrated that ground-based spaceflight analogue cultures of Salmonella exhibited global changes in their transcriptional and proteomic (protein) expression, heightened virulence, and improved stress resistance — findings similar to those produced during their experiments on STS-115 and STS-123 Space Shuttle missions.
However, these previous spaceflight studies were done when only the Salmonella were grown in spaceflight and the infections were done when the bacteria were returned to Earth.
In contrast, the new study explores for the first time, a co-culture of human cells and pathogen during spaceflight, providing a unique window into the infection process. The experiment, called STL-IMMUNE, was part of the Space Tissue Loss payload carried aboard STS-131, one of the last four missions of the Space Shuttle prior to its retirement.
The human intestinal epithelial cells were launched into space (or maintained in a laboratory at the Kennedy Space Center for ground controls) in three-dimensional (3-D) tissue culture systems called hollow fiber bioreactors. The hollow fiber bioreactors each contained hundreds of tiny, porous straw-like fibers coated with collagen upon which the intestinal cells attached and grew. These bioreactors were maintained in the Cell Culture Module, an automated hardware system which pumped warm, oxygenated cell culture media through the tiny fibers to keep the cells healthy and growing until they were ready for infection with Salmonella.
Once in orbit, astronauts aboard STS-131 activated the hardware. Eleven days later, S. Typhimurium cells were automatically injected into a subset of the hollow fiber bioreactors, where they encountered their target — a layer of human epithelial cells.
The RNA-Seq and proteomic profiles showed significant differences between uninfected intestinal epithelial cultures in space vs those on earth. These changes involved major proteins important for cell structure as well as genes important for maintaining the intestinal epithelial barrier, cell differentiation, proliferation, wound healing and cancer. Based on their profiles, uninfected cells exposed to spaceflight may display a reduced capacity for proliferation, relative to ground control cultures.
Infections far from home
Human intestinal epithelial cells act as critical sentinels of innate immune function. The results of the experiment showed that spaceflight can cause global changes to the transcriptome and proteome of human epithelial cells, both infected and uninfected.
During spaceflight, 27 RNA transcripts were uniquely altered in intestinal cells in response to infection, once again establishing the unique influence of the spaceflight environment on the host-pathogen interaction. The researchers also observed 35 transcripts which were commonly altered in both space-based and ground-based cells, with 28 genes regulated in the same direction. These findings confirmed that at least a subset of the infection biosignatures that are known to occur on Earth also occur during spaceflight. Compared with uninfected controls, infected cells in both environments displayed gene regulation associated with inflammation, a signature effect of Salmonella infection.
Bacterial transcripts were also simultaneously detected within the infected host cells and indicated upregulation of genes associated with pathogenesis, including antibiotic resistance and stress responses.
The findings help pave the way for improved efforts to safeguard astronaut health, perhaps through the use of nutritional supplements or probiotic microbes. Ongoing studies of this kind, to be performed aboard the International Space Station and other space habitats, should further illuminate the many mysteries associated with pathogenic infection and the broad range of human illnesses for which they are responsible.
“Before we began this study, we had extensive data showing that spaceflight completely reprogrammed Salmonella at every level to become a better pathogen,” Barrila says. “Separately, we knew that spaceflight also impacted several important structural and functional features of human cells that Salmonella normally exploits during infections on earth. However, there was no data showing what would happen when both cell types met in the microgravity environment during infection. Our study indicates that there are some pretty big changes in the molecular landscape of the intestinal epithelium in response to spaceflight, and this global landscape appears to be further altered during infection with Salmonella.”