Tag Archives: Fibrosis

Microbiology

Scarring to the collagen framework causes dysfunction in Duchenne muscular dystrophy

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Reviewed by Emily Henderson, B.Sc.May 11 2023

Muscles that ache after a hard workout usually don’t hurt for long, thanks to stem cells that rush to the injured site along “collagen highways” within the muscle and repair the damaged tissue. But if the cells can’t reach their destination, the damaged tissue can’t regenerate. Over time, it breaks down completely and ceases to function.

In a study recently published in npj Regenerative Medicine, a group of researchers led by biochemists at UCLA show for the first time that scarring to the collagen framework that carries these healing cells causes muscles to gradually stop working in Duchenne muscular dystrophy. The discovery in mice illuminates one reason stem cell therapy has not been effective for the disorder: The cells simply can’t get where they’re needed most.

Duchenne muscular dystrophy is the most common -; and one of the most severe -; hereditary muscular dystrophies. The muscle-wasting disease, which usually affects boys, begins in childhood and inevitably ends in death as the muscles that power the heart, lungs and other vital organs fail. It is caused by a mutation in the gene for the dystrophin protein, which regulates the organization of muscle cells. In healthy people, dystrophin helps bundles of muscle cells called myofibers attach to the collagen framework -; the extracellular matrix that gives muscles their shape, holds them together and provides the “highway” for stem cells to repair and regenerate damaged tissue.

Rachelle Crosbie, a UCLA professor of integrative biology and physiology who is looking for ways to treat Duchenne muscular dystrophy, suspected that the dysfunction caused by this mutation led to scarring and stiffening of the extracellular matrix, a process known as fibrosis.

Crosbie and Kristen Stearns-Reider, a postdoctoral fellow in Crosbie’s laboratory, designed a unique experiment to find out. Using facilities at UCLA’s California NanoSystems Institute, they devised a process to “wash” all the cells off the collagen extracellular matrix in healthy mice and those with Duchenne muscular dystrophy.

Under a microscope, the two cell-free matrices, which Crosbie calls “myoscaffolds,” appeared very different: The healthy one looked like delicate lace, while the Duchenne one looked more like a dense sponge.

Next, the researchers seeded each myoscaffold with stem cells and watched as the cells tried to grow muscle tissue. Muscle stem cells grew on the myoscaffolds exactly as they would in healthy and diseased muscle: In the healthy, lacy myoscaffold, cells migrated along the smooth threads and deposited themselves in evenly spaced holes. However, the bumpy, thickened surfaces of the Duchenne myoscaffold made travel difficult and threw up roadblocks that caused the cells to pile up in clumps; the cells were stressed an unable to progress efficiently.

Like suburban commuters, resident stem cells live on outskirts of the muscle fiber and travel along the muscle fiber to damaged areas and regenerate muscle. The extracellular matrix is the highway they use. It’s like the difference between driving to work on a regular day versus the day a landslide fell on the freeway.”

Rachelle Crosbie, UCLA professor of integrative biology and physiology

This is the first time scientists have imaged living cells in a fibrotic myoscaffold, revealing specifically how fibrosis disrupts cell behavior, Crosbie said.

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The thin, supple threads of the healthy scaffold also yielded slightly as stem cells attached to them, a deformation critical to the successful development of muscle tissue. The stem cells were unable to deform the thick, stiff fibers of the Duchenne scaffold. Tissue grown on the Duchenne scaffold showed large clumps of myofibers interspersed with even larger clumps of collagen instead of the evenly distributed myofibers seen in the healthy sample.

Protein sarcospan offers a potential way forward

The research team then tested cell behavior on a Duchenne myoscaffold that was created using a therapeutic protein called sarcospan, which is known to stabilize the extracellular matrix. Stem cell function improved once sarcospan had minimized the formation of fibrotic scars.

“The results made it really clear why stem cell therapies have proven challenging for Duchenne muscular dystrophy,” Crosbie said. “Finding ways to prevent or reduce scarring on the extracellular matrix could make them more effective.”

These myoscaffolds offer several broad possibilities for studying stem cell–extracellular matrix interactions, stem cell niche formation, the microenvironments that influence stem cell behavior, muscle maturation and disease modeling, said study co-authors Michael Hicks, a UCLA postdoctoral fellow, and April Pyle, a UCLA professor of microbiology, immunology, and molecular genetics.

Crosbie also noted that because the new method requires only very small samples, these studies could potentially be extended to include individual patients, using tissue from a muscle biopsy to study treatments before they are administered and identifying ones more likely to be effective.

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Source:

University of California – Los Angeles

Journal reference:

Stearns-Reider, K. M., et al. (2023). Myoscaffolds reveal laminin scarring is detrimental for stem cell function while sarcospan induces compensatory fibrosis. Npj Regenerative Medicine. doi.org/10.1038/s41536-023-00287-2.

Microbiology

NIH scientists discover an autoinflammatory disease caused by mutations in the LYN gene

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Reviewed by Emily Henderson, B.Sc.Mar 28 2023

Scientists have identified an autoinflammatory disease caused by mutations in the LYN gene, an important regulator of immune responses in health and disease. Named Lyn kinase-associated vasculopathy and liver fibrosis (LAVLI), the identification sheds light on how genes linked to certain illnesses can potentially be targets for treatment by repurposing existing drugs. The research, published in Nature Communications, was led by Adriana A. de Jesus, M.D. Ph.D., and Raphaela Goldbach-Mansky, M.D., M.H.S. of the Translational Autoinflammatory Diseases Section of the Laboratory of Clinical Immunology and Microbiology at the National Institute of Allergy and Infectious Diseases (NIAID), part of the National Institutes of Health.

LAVLI was first discovered in a pediatric patient through genetic testing, which detected a mutation in LYN, the gene that encodes the Lyn kinase protein. Two additional, unrelated pediatric patients were later discovered to have two more mutations in the same gene. All three patients developed diseases linked to the LYN genetic mutation shortly after birth. Two patients developed liver fibrosis—excessive amounts of scar tissue caused by inflammation and repeated liver damage—in the first year of life. All three patients had perinatal onset of neutrophilic cutaneous small vessel vasculitis. This is an immune disorder characterized by inflammation from high numbers of neutrophils—white blood cells of the immune system—that can damage small blood vessels.

The study revealed Lyn kinase was always active and unable to shut down in the three patients with the LYN mutation, which increased neutrophil migration, altered inflammatory signals and activated scar and fibrosis-inducing liver cells. The results of this study suggest that Lyn kinase may be a potential therapeutic target for drugs that treat forms of non-syndromic small vessel vasculitis and other types of inflammation-induced liver fibrosis.

Source:

National Institutes of Health

Journal reference:

de Jesus, A. A., et al. (2023). Constitutively active Lyn kinase causes a cutaneous small vessel vasculitis and liver fibrosis syndrome. Nature Communications. doi.org/10.1038/s41467-023-36941-y.

Microbiology

Research identifies western diet-induced microbial and metabolic contributors to liver disease

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Reviewed by Emily Henderson, B.Sc.Mar 15 2023

New research from the University of Missouri School of Medicine has established a link between western diets high in fat and sugar and the development of non-alcoholic fatty liver disease, the leading cause of chronic liver disease.

The research, based in the Roy Blunt NextGen Precision Health Building at MU, has identified the western diet-induced microbial and metabolic contributors to liver disease, advancing our understanding of the gut-liver axis, and in turn the development of dietary and microbial interventions for this global health threat.

We’re just beginning to understand how food and gut microbiota interact to produce metabolites that contribute to the development of liver disease. However, the specific bacteria and metabolites, as well as the underlying mechanisms were not well understood until now. This research is unlocking the how and why.”

Guangfu Li, PhD, DVM, co-principal investigator, associate professor in the department of surgery and Department of Molecular Microbiology and Immunology

The gut and liver have a close anatomical and functional connection via the portal vein. Unhealthy diets change the gut microbiota, resulting in the production of pathogenic factors that impact the liver. By feeding mice foods high in fat and sugar, the research team discovered that the mice developed a gut bacteria called Blautia producta and a lipid that caused liver inflammation and fibrosis. That, in turn, caused the mice to develop non-alcoholic steatohepatitis or fatty liver disease, with similar features to the human disease.

“Fatty liver disease is a global health epidemic,” said Kevin Staveley-O’Carroll, MD, PhD, professor in the department of surgery, one of the lead researchers. “Not only is it becoming the leading cause of liver cancer and cirrhosis, but many patients I see with other cancers have fatty liver disease and don’t even know it. Often, this makes it impossible for them to undergo potentially curative surgery for their other cancers.”

As part of this study, the researchers tested treating the mice with an antibiotic cocktail administered via drinking water. They found that the antibiotic treatment reduced liver inflammation and lipid accumulation, resulting in a reduction in fatty liver disease. These results suggest that antibiotic-induced changes in the gut microbiota can suppress inflammatory responses and liver fibrosis.

Li, Staveley-O’Carroll and fellow co-principal investigator R. Scott Rector, PhD, Director of NextGen Precision Health Building and Interim Senior Associate Dean for Research -; are part of NextGen Precision Health, an initiative to expand collaboration in personalized health care and the translation of interdisciplinary research for the benefit of society. The team recently received a $1.2 million grant from the National Institutes of Health to fund this ongoing research into the link between gut bacteria and liver disease.

Source:

University of Missouri-Columbia

Journal reference:

Yang, M., et al. (2023). Western diet contributes to the pathogenesis of non-alcoholic steatohepatitis in male mice via remodeling gut microbiota and increasing production of 2-oleoylglycerol. Nature Communications. doi.org/10.1038/s41467-023-35861-1.

Microbiology

Genetic disorder that causes immunodeficiency and susceptibility to opportunistic infections discovered

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Reviewed by Emily Henderson, B.Sc.Jan 23 2023

An international consortium co-led by Vanderbilt University Medical Center immunogeneticist Rubén Martínez-Barricarte, PhD, has discovered a new genetic disorder that causes immunodeficiency and profound susceptibility to opportunistic infections including a life-threatening fungal pneumonia.

The discovery, reported Jan. 20 in the journal Science Immunology, will help identify people who carry this in-born error of immunity (IEI). “Our findings will provide the basis for genetic diagnosis and preventive treatment for these groups of patients,” Martínez-Barricarte said.

IEIs, also known as primary immunodeficiencies, are genetic defects characterized by increased susceptibility to infectious diseases, autoimmunity, anti-inflammatory disorders, allergy, and in some cases, cancer.

To date, 485 different IEIs have been identified. It is now thought that they occur in one of every 1,000 to 5,000 births, making them as prevalent as other genetic disorders, including cystic fibrosis and Duchene’s muscular dystrophy.

Despite recent medical advances, about half of patients with IEIs still lack a genetic diagnosis that could help them avoid debilitating illness and death. That’s why this research is so important.

The error in this case is a mutation in the gene for the protein IRF4, a transcription factor that is pivotal for the development and function of B and T white blood cells, as well as other immune cells.

As a postdoctoral fellow at The Rockefeller University, Martínez-Barricarte was part of an international research team that, in 2018, identified an IRF4 mutation associated with Whipple’s disease, a rare bacterial infection of the intestine that causes diarrhea, weight loss, and abdominal and joint pain.

Martínez-Barricarte is now an assistant professor of Medicine in the Division of Genetic Medicine, and of Pathology, Microbiology & Immunology in the Division of Molecular Pathogenesis.

In 2020, after moving his lab to VUMC, he began collaborating with Aidé Tamara Staines-Boone, MD, and her colleagues in Monterrey, Mexico. They were caring for a young boy who was suffering from severe and recurrent fungal, viral, mycobacterial, and other infections.

Martínez-Barricarte and his team sequenced the protein-encoding regions of the boy’s genome and discovered a de novo IRF4 mutation, which originated in the patient and was not inherited from his parents.

Upon consulting with IRF4 experts at the Imagine Institute for the study and treatment of genetic diseases in Paris, they were told that seven other groups were independently characterizing the same mutation. They now collaborate as the IRF4 International Consortium.

In the current study, the consortium identified seven patients from six unrelated families across four continents with profound combination immunodeficiency who experienced recurrent and serious infections, including pneumonia caused by the fungus Pneumocystis jirovecii. Each patient had the same mutation in the DNA-binding domain of IRF4.

Extensive phenotyping of patients’ blood cells revealed immune cell abnormalities associated with the disease, including impaired maturation of antibody-producing B cells, and reduced T-cell production of infection-fighting cytokines.

Two knock-in mouse models, in which the mutation was inserted into the mouse genome, exhibited a severe defect in antibody production consistent with the combined immune deficiency observed in the patients.

The researchers also discovered the mutation had a “multimorphic” effect detrimental to the activation and differentiation of immune cells.

While the mutant IRF4 binds to DNA with a higher affinity than the native form of the protein (in a hypermorphic way), its transcriptional activity in common, canonical genes is reduced (hypomorphic), and it binds to other DNA sites (in a neomorphic way), altering the protein’s normal gene expression profile.

This multimorphic activity is a new mechanism for human disease. “We anticipate that variants with multimorphic activity may be more widespread in health and disease,” the researchers concluded.

Co-authors from Martínez-Barricarte’s lab included graduate students Jareb Pérez Caraballo and Xin Zhen, and research assistant Linh Tran. His research was supported by the National Institute of Allergy and Infectious Diseases of the National Institutes of Health (grant #AI171466).

Source:

Vanderbilt University Medical Center

Journal reference:

IRF4 International Consortium (2023) A multimorphic mutation in IRF4 causes human autosomal dominant combined immunodeficiency. Science Immunology. doi.org/10.1126/sciimmunol.ade7953.

Microbiology

Clinical trial to test the safety, efficacy of bacteriophages for treating P. aeruginosa infections in CF patients

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Reviewed by Emily Henderson, B.Sc.Oct 11 2022

Cystic fibrosis (CF) is an inherited disorder that causes severe damage to the lungs and other organs in the body. Nearly 40,000 children and adults in the United States live with CF, an often difficult existence exacerbated by an opportunistic bacterium called Pseudomonas aeruginosa, which is a major cause of chronic, life-threatening lung infections.

P. aeruginosa infections are not easily treated. The pathogen can be resistant to most current antibiotics. However, an early-stage clinical trial led by scientists at University of California San Diego School of Medicine, with collaborators across the country, has launched to assess the safety and efficacy of treating P. aeruginosa lung infections in CF patients with a different biological weapon: bacteriophages.

Bacteriophages are viruses that have evolved to target and destroy specific bacterial species or strains. Phages are more abundant than all other life forms on Earth combined and are found wherever bacteria exist. Discovered in the early 20th century, they have long been investigated for their therapeutic potential, but increasingly so with the rise and spread of antibiotic-resistant bacteria.

In 2016, scientists and physicians at UC San Diego School of Medicine and UC San Diego Health used an experimental intravenous phage therapy to successfully treat and cure colleague Tom Patterson, PhD, who was near death from a multidrug-resistant bacterial infection. Patterson’s was the first documented case in the U.S. to employ intravenous phages to eradicate a systemic bacterial infection. Subsequent successful cases helped lead to creation of the Center for Innovative Phage Applications and Therapeutics (IPATH) at UC San Diego, the first such center in North America.

In 2020, IPATH researchers published data from 10 cases of intravenous bacteriophage therapy to treat multidrug-resistant bacterial infections, all at UC San Diego. In 7 of 10 cases, there was a successful outcome.

The new phase 1b/2 clinical trial advances this work. The trial is co-led by Robert Schooley, MD, professor of medicine and an infectious disease expert at UC San Diego School of Medicine who is co-director of IPATH and helped lead the clinical team that treated and cured Patterson in 2016.

It will consist of three elements, all intended to assess the safety and microbiological activity of a single dose of intravenous phage therapy in males and non-pregnant females 18 years and older, all residing in the United States.

The dose is a cocktail of four phages that target P. aeruginosa, a bacterial species commonly found in the environment (soil and water) that can cause infections in the blood, lungs and other parts of the body after surgery.

For persons with CF, P. aeruginosa is a familiar and sometimes fatal foe. The Cystic Fibrosis Foundation estimates that roughly half of all people with CF are infected by Pseudomonas. Previous studies have indicated that chronic P. aeruginosa lung infections negatively impact life expectancy of CF patients, who currently live, on average, to approximately 44 years.

In the first stage of the trial, two “sentinel subjects” will receive one of three dosing strengths of the IV bacteriophage therapy. If, after 96 hours and no adverse effects, the second stage (2a) will enroll 32 participants into one of four arms: the three doses and a placebo.

After multiple follow-up visits over 30 days and an analysis of which dosing strength exhibited the most favorable safety and microbiologic activity, i.e. most effective at reducing P. aeruginosa, stage 2b will recruit up to 72 participants to either receive that IV dose or a placebo.

Enrollment will occur at 16 cystic fibrosis clinical research sites in the United States, including UC San Diego. It is randomized, double-blind and placebo-controlled. The trial is being conducted through the Antibacterial Resistance Leadership Group and funded by the National Institute of Allergy and Infectious Diseases, part of the National Institutes of Health, with additional support for the UC San Diego trial site from the Mallory Smith Legacy Fund.

Mallory Smith was born with cystic fibrosis and died in 2017 at the age of 25 from a multidrug-resistant bacterial infection following a double lung transplant.

Mallory’s death was a preventable tragedy. We are supporting the IPATH trial through Mallory’s Legacy Fund because Mark and I deeply believe in the promise of phage therapy to save lives by combatting multidrug-resistant bacteria.”

Diane Shader Smith, Mother

In an article published in 2020 in Nature Microbiology, Schooley and Steffanie Strathdee, PhD, associate dean of global health sciences and Harold Simon Professor in the Department of Medicine and IPATH co-director, describe phages as “living antibiotics.”

As such, said Schooley, researchers need to learn how to best use them to benefit patients through the same systematic clinical trials employed to evaluate traditional antibiotics.

The primary objectives of the new trial are first to determine the safety of a single IV phage dose in clinically stable patients with CF who are also infected with P. aeruginosa, said Schooley.

“Second, it’s to describe the microbiological activity of a single IV dose and third, to assess the benefit-to-risk profile for CF patients with P. aeruginosa infections. This is one study, with a distinct patient cohort and carefully prescribed goals. It’s a step, but an important one that can, if ultimately proven successful, help address the growing, global problem of antimicrobial resistance and measurably improve patients’ lives.”

Estimated study completion date is early 2025.

Source:

University of California – San Diego