Researchers Finally Solve a Decades-Old Mystery About Cellular Aging

 A new study identifies the molecular switch that determines when aging cells permanently stop dividing.

Every time a human cell divides, the tips of its chromosomes get a little shorter. Those tips, called telomeres, act like protective caps. Once they shrink too far, the cell treats the exposed chromosome ends as DNA damage and stops dividing for good.

That shutdown, known as replicative senescence, is one of the body’s built-in defenses against cancer. By forcing damaged or risky cells into permanent arrest, it can stop early cancer clones before they become full tumors. A new study in Molecular Cell now shows that this safety mechanism depends entirely on ATM kinase, a signaling protein that senses DNA breaks and helps protect genomic stability.

The work also helps explain a puzzle that has bothered cell biologists for decades. Cells grown in standard lab air, which contains far more oxygen than most tissues in the body, stop dividing sooner than cells kept at lower oxygen levels. According to the new findings, high oxygen makes ATM unusually reactive, causing cells to become less tolerant of short telomeres.

“Our results have illuminated the mechanism underlying the aging of human cells through replicative senescence,” says Titia de Lange, head of the Laboratory of Cell Biology and Genetics. “These insights are critical for understanding how this tumor suppression pathway prevents cancer.”

Creating the right conditions

Replicative senescence begins when telomeres can no longer recruit enough TRF2, a shelterin protein that helps hide chromosome ends from the DNA damage machinery. Without sufficient TRF2, telomeres start to look like broken DNA, setting off the signal that brings cell division to a halt.

This matters because short telomeres are not only a sign of cellular aging. They are also a warning that a cell may be entering dangerous territory. By stopping such cells from dividing, replicative senescence helps prevent early-stage cancers from expanding.

“Replicative senescence is a remarkably effective tumor suppressor pathway,” de Lange says. “We know this from patients with long telomeres in which this system does not work properly. These patients can get as many as five different cancers before the age of 70, indicating that in people with normal-length telomeres, the telomere tumor suppressor pathway prevents many cancers.”

Even so, the exact wiring of this cancer prevention system had remained unclear. Earlier studies suggested that either ATM or ATR, two major DNA damage signaling pathways, might be involved. Oxygen added another complication. Researchers had long known that cells cultured at about 20 percent oxygen reach senescence faster than cells grown at more body-like levels, roughly 1 to 8 percent oxygen. The obvious explanation, that high oxygen simply makes telomeres erode faster, had already been ruled out.

o solve the problem, de Lange and colleagues followed replicative senescence in primary human fibroblasts grown at either 3 percent or 20 percent oxygen. The lower oxygen condition was closer to what many cells experience inside the body, but it also made the experiments much more demanding. Even routine steps such as moving plates, adding reagents, or breaking open cells had to be done quickly to avoid exposing the samples to ordinary air.

“Any time the cells or the reagents are outside of the special low-oxygen incubator, they are exposed to 20 percent oxygen, which can change the molecular environment within minutes,” says Alexander Stuart, a former graduate student in the de Lange lab who now holds a postdoc position at Harvard. “That means you’re often in a race to do all the standard protocol steps extremely quickly so you can keep the samples at low oxygen as much as possible.”

Stuart found that ATM alone was responsible for enforcing senescence at both oxygen levels. When ATM was inhibited, or when TRF2 was overproduced, cells continued dividing past the point where they would normally stop. Blocking ATM signaling in already arrested cells also allowed them to resume growth, showing that the arrest was reversible and fully dependent on ATM.

The impact of high oxygen

The next question was why oxygen changed the timing of senescence so strongly. Stuart and de Lange found that high oxygen does not simply age cells faster in a general way. Instead, it puts ATM into a hyperactive state.

That difference changed how cells responded to extremely short telomeres. At 3 percent oxygen, cells could keep dividing even after many telomeres had become very short. When those same cells were shifted to 20 percent oxygen, ATM responded much more aggressively, treating the short telomeres as serious DNA damage and pushing the cells into senescence.

“I don’t think of it as low oxygen extending the lifespan of human cells—that’s the physiological state of our bodies. Rather, the question was: why do high oxygen conditions shorten cellular lifespan? One could then extend that question: why aren’t high oxygen conditions accurate systems for studying senescence?” Stuart says. “We’ve now shown that high oxygen represents a hyperactive ATM setting, which leads to fewer divisions than cells would naturally undergo.”

Source: ScitechDaily

Bridging diet, microbes, and metabolism: Implications for metabolic disorders

 Mounting evidence suggests that the secret to understanding human health and combating metabolic diseases lies hidden within the microscopic world of our gut bacteria. Recent research by scientists at the Boyce Thompson Institute (BTI) and Cornell University reveals that a specific fatty acid produced by gut bacteria directly influences fat metabolism in animals. This research is pivotal as it sheds light on the complex interplay between the diet, gut microbiota, and host metabolic health, offering insights that could open new avenues in our approach to managing metabolic disorders.

The researchers focused on certain gut bacteria that produce fatty acids with a special chemical structure, known as a cyclopropane ring, and showed that these can be converted into signals that turn on fat desaturation in the nematode C. elegans, a model organism often used to study human biology. Intriguingly, C. elegans itself produces a chemically similar fatty acid compound that regulates the same metabolic pathway as the bacterial cyclopropane fats.

"Our research suggests that the host organism may have acquired the ability to produce its own signaling molecule, mimicking bacterial biochemistry, through a gene obtained from bacteria -- a process known as horizontal gene transfer," shared Bennett Fox, a post-doctoral researcher at BTI and first author of the study.

The research, recently published in Nature Communications, showed that both the bacterial and endogenous fatty acids activate a host receptor that functions as a central regulator of overall fat metabolism. This direct link between microbiota metabolites and host lipid metabolism offers insight into how our bodies could harness beneficial gut bacteria to regulate vital processes like obesity and metabolic dysfunction.

"Microbiota-dependent metabolites regulate virtually every aspect of animal physiology, including development, metabolism, and immune responses. Despite the life-sustaining importance of these metabolites, many of their structures remain unknown," noted Frank Schroeder, a professor at BTI and senior author of the study.

The fact that chemicals produced by bacteria can influence the metabolism of their host is a promising area of research. Further studies can investigate host-bacterial interactions to better understand -- and potentially improve -- metabolic health.

"The devil is in the details. As we gain clarity regarding the molecular mechanisms of fat metabolism and its regulation by specific diet-derived compounds, we step closer to harnessing this knowledge for better health outcomes in humans," said Fox. "This research not only broadens our understanding of basic biological processes but also highlights potential pathways for future exploration in human health and disease management."

Want to learn more? Dr. Fox has prepared an in-depth synopsis of the research paper, Evolutionarily related host and microbial pathways regulate fat desaturation in C. elegans, available here.

This research was supported in part by the National Institutes of Health and the Howard Hughes Medical Institute.

Source: Sciencedaily

New research in fatty liver disease aims to help with early intervention

 A new study brings researchers closer to better understanding the pathology of the fatty liver disease MASH, which stands for metabolic dysfunction-associated steatohepatitis.

MASH is a consequence of poor diet and obesity and results in severe damage to the liver. In MASH, the liver becomes filled with active and rapidly multiplying T cells, which are a type of immune cell.

In today's study, published in Hepatology, researchers examine what these T cells look like and how they work in people with liver cirrhosis (a late stage of liver disease) and in an animal model of MASH.

"Our goal is to provide a more thorough understanding of the mechanisms that drive MASH. A better understanding can lead to people being diagnosed earlier or before the disease is at such a late stage that a liver transplant may be the only treatment option," said the paper's senior author Matthew Burchill, PhD, associate professor of medicine at the University of Colorado Anschutz Medical Campus.

MASH is a slow killer in that the progression of the disease takes place over the course of decades. Despite this, MASH is rapidly becoming the most prevalent liver disease worldwide. It's estimated that approximately 40 percent of the adult population in the United States is obese, and approximately 14 percent of asymptomatic middle-aged individuals in the US have biopsy proven MASH, according to a recent study in the Journal of Hepatology.

Burchill and his team found during MASH, T cells multiply and change in function in response to harmful substances associated with poor diet.

The study showed that like infections such as Hepatitis C virus, clonally expanded CD8+ T cells accumulate in the livers of both humans and mice with MASH. This suggests a potential role for antigen-activated CD8+ T cells in the pathogenesis of MASH.

"Understanding this process may help identify the specific substances that trigger T cell activation and growth in the liver during MASH. This understanding could eventually result in developing a biomarker test that will allow doctors to track and treat the disease progression before it's at a late stage," adds Burchill.

The study concludes that antigenic stimulation likely drives T cell accumulation and chronic exhaustion in MASH.

The authors mention that further studies are needed to understand the timing and persistence of antigen-driven T cell responses in the liver and their role in disease progression and resolution.

Source: ScienceDaily

This ultrasound treatment may help stop arthritis before it starts

 Researchers at The University of Alabama in Huntsville (UAH), part of The University of Alabama System, have identified a promising new use for continuous low-intensity ultrasound that could one day help treat joint injuries and reduce the risk of post-traumatic osteoarthritis. Their findings suggest the non-invasive approach may shift the body's immune response away from long-lasting inflammation and toward tissue repair, offering a potential drug-free strategy for improving healing.

The study, published in the Nature journal Scientific Reports, was led by Dr. Anuradha Subramanian, professor of chemical and materials engineering. It combined biological research conducted by Dr. Shahid Khan during his doctoral studies with computational and statistical analysis developed by Dr. Satyaki Roy, professor of mathematical sciences, along with contributions from graduate student Owen Trippany. The research was funded by the National Institutes of Health through an R01 grant awarded to Subramanian.

How Ultrasound Influences Immune Cells

The team focused on macrophages, specialized immune cells that play a key role in both inflammation and tissue repair, to understand how they respond to continuous low-intensity ultrasound.

"Following injury, the body recruits inflammatory 'defender' macrophages (M1) to clear damaged tissue and healer macrophages (M2) to support repair and recovery," Subramanian explains. "Persistent dominance of defender macrophages can create a prolonged inflammatory environment that contributes to post-traumatic osteoarthritis."

The researchers wanted to determine whether ultrasound could encourage these immune cells to transition from an inflammatory state to one that promotes healing.

"In an 'M1' state, microphages promote inflammation to fight damage or infection, but prolonged M1 activity can also harm healthy tissue," Subramanian notes. "In contrast, 'M2-like' macrophages support tissue repair and recovery. Shifting macrophages toward an M2-like state is important, because it may help reduce chronic inflammation while encouraging healing in damaged joints. Our findings suggest that continuous low-intensity ultrasound may help restore this balance by promoting a more reparative macrophage response."

Roy says chronic inflammation is a major factor in the development of post-traumatic osteoarthritis.

"Post-traumatic osteoarthritis is driven in part by persistent inflammation that limits tissue repair and accelerates joint degeneration," Roy adds. "Our team is interested in continuous low-intensity ultrasound because it offers a non-pharmacological, non-invasive approach that may help regulate immune cell behavior and promote a more reparative healing environment in injured joints."

A More Realistic Model of Joint Injury

To better recreate the conditions inside an injured joint, the researchers relied on fibronectin fragments, molecules generated as damaged tissue breaks down, instead of using only conventional laboratory methods to trigger inflammation. This approach produced a model that more closely reflects the biological environment that develops after a joint injury.

The team also combined transcriptomics, the large-scale study of gene activity, with an advanced computational method known as differential clustering. Rather than analyzing genes one by one, this technique identifies groups of genes whose behavior changes together, providing a broader picture of how immune cells respond to ultrasound treatment.

"This allowed us to study not only which genes changed, but also how groups of genes changed their coordinated behavior in response to ultrasound stimulation," Roy says.

Early Results Show Reduced Inflammation

The researchers found that continuous low-intensity ultrasound lowered biological markers linked to inflammation while increasing markers associated with a more reparative, M2-like macrophage state.

Although the research is still limited to laboratory experiments, the findings suggest that non-drug, non-invasive technologies could eventually be used to influence immune cell behavior and improve healing after joint injuries. The researchers believe the technique could become part of future treatments designed to slow the progression of osteoarthritis and improve recovery after joint trauma.

"The next steps will involve validating these findings in animal models of early post-traumatic osteoarthritis and studying how ultrasound-based modulation affects long-term tissue repair in joint injury settings," Subramanian says.

Source: ScienceDaily

Identifying a new liver defender: The role of resident macrophages

 Osaka University researchers discovered liver resident macrophages' pivotal role in defending against gut bacteria and related substances entering via the portal vein, particularly under compromised intestinal barrier conditions. Identified as "sentinel macrophages," they are activated by isoallo-lithocholic acid. This finding holds promise for developing preventive and therapeutic strategies for liver chronic inflammatory diseases, such as metabolic dysfunction-associated steatohepatitis (MASH), by enhancing the function of these macrophages to mitigate inflammation and improve treatment efficacy.

The liver and intestines are directly connected via the portal vein, a blood vessel that transports nutrients absorbed in the intestines directly to the liver. The intestines harbor numerous gut bacteria, and sometimes these bacteria and their related substances can enter the liver through the portal vein. This is especially problematic when the intestinal barrier is compromised, as seen in conditions like ulcerative colitis or leaky gut syndrome, allowing many gut bacteria and related substances to reach the liver. Under normal circumstances, the liver's immune system is able to defend against the invading gut bacteria and related substances and prevent inflammation, but the exact mechanism behind this was unclear.

Using innovative technologies like in vivo imaging of the liver and analysis of single-cell gene expression while preserving tissue locational information, a research group led by Yu Miyamoto and Masaru Ishii at the Graduate School of Medicine of Osaka University has revealed that certain resident macrophages near the entrance of the liver protect it against intestinal bacteria and related substances. Their findings are illustrated in Figure 1. Dr. Miyamoto, a lead author of the study, explained, "Our technology showed that these 'sentinel macrophages' play a crucial role in protecting the liver from inflammation caused by intestinal bacteria and related substances." Additionally, the study found that isoallo-lithocholic acid (isoallo-LCA), a secondary bile acid produced by some gut bacteria, trigger the activation of these sentinel macrophages.

With the rise in conditions like leaky gut due to modern lifestyles (stress, high-fat diets, and lack of exercise), there is increasing concern about inflammation affecting various organs, including the liver. Metabolic dysfunction-associated steatohepatitis (MASH), often accompanied by the leaky gut, has been particularly concerning due to its ever increasing incidence and challenging treatment. This research shed light on how liver sentinel macrophages defend against gut commensal invaders, offering hope that enhancing their functions could lead to the development of new preventive and therapeutic strategies for liver chronic inflammatory diseases, including MASH.

Source: ScienceDaily

Physicists recreate black hole energy extraction in the lab

 More than 50 years ago, physicist Sir Roger Penrose proposed a remarkable idea: under the right conditions, it might be possible to extract energy from a rapidly spinning black hole. In his concept, a particle entering the black hole's ergosphere, a region where spacetime is dragged along by the object's rotation, could split into two. One fragment would fall into the black hole while the other escaped carrying away more energy than the original particle. Later, physicist Yakov Zel'dovich expanded on this concept, predicting that waves interacting with an object rotating fast enough could also gain energy and become amplified.

Now, researchers at the Advanced Science Research Center at the CUNY Graduate Center (CUNY ASRC) have demonstrated an experimental approach inspired by those long standing theories. Writing in the journal Nature, the team showed that wave amplification can be achieved using a device that simulates extreme rotation without physically spinning.

Synthetic Rotation Recreates Extreme Physics

Instead of rotating an object mechanically, the researchers built a radio frequency device whose properties are rapidly changed across both space and time. This carefully engineered system creates the illusion of ultrafast rotation, reaching effective rotational speeds far beyond what conventional mechanical systems can achieve. By replacing physical motion with synthetic rotation, the researchers overcame challenges that have limited experimental studies of extreme rotational physics for decades.

"Our approach facilitates a new method of wave-matter interaction in which waves with selected rotational properties extract energy from synthetic time-engineered rotation, producing a form of broadband selective amplification," said principal investigator Andrea Alù, Distinguished Professor and Einstein Professor of Physics at the CUNY Graduate Center and founding director of the CUNY ASRC's Photonics Initiative.

Lead author Hadiseh Nasari, a post-doctoral researcher with the CUNY ASRC's Photonics Initiative, said the experiment transforms a long standing theoretical concept into a practical research tool.

"This successful experiment moves ideas about extreme rotational dynamics from theory to practice and creates a versatile experimental platform for exploring a broad range of phenomena at the intersection of astrophysics, wave physics, and quantum science," said Nasari. "The work has implications for advances in fundamental science and in communications, optics and photonics."

How the Experiment Worked

The researchers set out to answer a fundamental question: Could electromagnetic waves interacting with a completely stationary device behave as though they were encountering an object rotating at ultrafast speed and draw energy from that synthetic motion?

To investigate, they constructed a ring of electronic resonators whose properties were rapidly adjusted in a carefully synchronized sequence. Although the hardware itself never moved, these timed changes generated a traveling pattern around the ring. As a result, the electromagnetic waves effectively experienced the system as though it were spinning at extraordinary speed.

Source: ScienceDaily

Spider-like creatures help uncover the surprising origins of fatherhood

 Citizen scientists have helped researchers uncover how parental care evolved in harvestmen, a group of spider like arachnids, by contributing observations through the popular nature platform iNaturalist. The findings, published in the Zoological Journal of the Linnean Society, reveal that parental guarding behavior has appeared, disappeared, and evolved again multiple times over the group's evolutionary history.

By combining nearly 30 years of field research with observations submitted to iNaturalist, an international team led by a University of São Paulo scientist more than doubled the number of documented examples of parental care in harvestmen. The expanded dataset also allowed researchers to reconstruct, for the first time, how both maternal and paternal care evolved within the superfamily Gonyleptoidea.

Citizen science reveals the evolution of parental care

The analysis showed that parental guarding behavior has not followed a simple evolutionary path. Instead, it has emerged repeatedly, been lost in some lineages, and later reappeared.

Researchers found that maternal care evolved only from species that showed no parental care, matching patterns previously observed in insects. Paternal care, however, followed two different evolutionary routes. It arose either directly from species with no parental care or from species in which females already guarded the eggs. This suggests that different evolutionary pressures shaped the development of maternal and paternal care.

The researchers propose that when paternal care evolved from maternal care, it likely reflects a form of sexual selection known as 'enhanced fecundity', in which females favor males that are already caring for eggs.

Why harvestmen are ideal for studying fatherhood

More than 6900 species of harvestmen have been identified, making them one of the most diverse groups of arachnids. Although they account for only about 0.6% of all arthropod diversity, they represent more than half of the independently evolved examples of paternal care known among arthropods, making them an exceptional group for studying the evolution of parenting.

Lead author Glauco Machado explained:

"It's very rare in nature, paternal care, and this behavior evolved many times independently. So, by looking at harvestmen we can explore questions related to the factors that led to the evolution of this behavior. In many species where males care for the offspring alone, the caring activity is a sexually selected behavior, which means that females prefer males that are caring for the eggs."

iNaturalist dramatically expanded the dataset

Citizen science projects allow people without specialized scientific training to contribute valuable observations. Around the world, volunteers have helped monitor bird populations, rediscover lost species, and even uncover ancient writing systems through cave art. Their contributions are becoming an increasingly important source of scientific data.

Machado's team turned to the global iNaturalist platform after hearing a presentation about using citizen science in bird research. The website allows users to upload georeferenced observations of plants and animals from virtually anywhere in the world.

The results demonstrated just how quickly citizen science can accelerate research. From 1936 through 2025, published scientific studies documented parental guarding behavior in only 80 harvestman species. Using iNaturalist, the researchers more than doubled that total, including 62 new records contributed through the platform alone. Machado said the iNaturalist search itself took only two days.

Citizen science speeds research worldwide

According to Machado, iNaturalist's greatest strength is not simply the number of observations it contains but the accessibility of those records for scientists everywhere.

"It's a tremendous source of information that can improve the velocity with which we accumulate biological information. I would never be able to do this by visiting museums around the world. It would be very expensive, very time consuming, but here we conducted the search in only one week."

By eliminating many of the costs associated with museum visits and extensive fieldwork, citizen science platforms are making large scale biological research more accessible, particularly for scientists working in the Global South.

Taxonomists remain essential

Despite the growing value of citizen science, the researchers emphasize that expert taxonomists remain indispensable. Identifying species correctly, determining whether the caregiving individual is male or female, and distinguishing true parental care from similar behaviors such as mate guarding all require specialized expertise.

Machado stressed the continuing importance of taxonomy:

"I think taxonomists' role in modern science is more important than ever. We cannot preserve a species that doesn't have a name. And names are provided by taxonomists. So, it's very important."

Source: ScienceDaily