Healing and Sealing: New Surgical Sealant Derived from Human Protein Seals Without Sutures
The most common complication after lung surgery is air leakage. Patients who experience air leaks after surgery may need a chest tube to drain the lung, which can put them at increased risk for infection, longer hospital stays and higher health care costs. Current synthetic sealants that have been approved by the Food and Drug Administration have drawbacks and limitations – some are complex to apply, others are elastic but don’t adhere well in the dynamic environment of the lung. And no commercially available sealant has been approved for use without sutures or staples. A newly engineered material, developed and tested by researchers from Brigham and Women’s Hospital and their collaborators at Northeastern University, Beth Israel Deaconess Medical Center and the University of Sydney, could become the first suture-less sealant for wound closure. In laboratory tests of the material, known as a MeTro sealant, the team demonstrated complete sealing of severely leaking lung tissue, as well as evidence that the material could help promote wound healing. Their results are published this week in Science Translational Medicine.
“A good surgical sealant needs to have a combination of characteristics: it needs to be elastic, adhesive, non-toxic and biocompatible,” said lead author Nasim Annabi, PhD, who holds a joint appointment at Northeastern University and is a lecturer at BWH. Annabi is also affiliated with the Wyss Institute. “Most sealants on the market possess one or two of these characteristics, but not all of them. We set out to engineer a material that could have all of these properties.”
MeTro is shorthand for methacryloyl-substituted tropoelastin – a protein derived from the elastic fibers that make up human tissue. Because the substance is laboratory-modified tissue rather than synthetic, it is much more biocompatible than other sealants. After a short exposure to light, it can form a highly elastic and adhesive layer on the wound. The research team tested the MeTro sealant in preclinical models, including rat and porcine models, finding that the sealant had no toxicity and controlled in vivo degradation. The team also found that the sealant provided higher tensile strength, elongation, and better adhesive strength and burst pressure resistance than several commercially available sealants. In previous work, the team found that the MeTro gel was an excellent candidate for regenerating tissue, meaning that it could potentially help to heal as well as seal incisions.
The team plans to launch the first phase of clinical trials in humans and will investigate other adhesion mechanisms for the MeTro sealant to guide the next-generation of its formulation.
Funding for this work was provided by the NIH (EB023052, AR057837, DE021468, D005865, AR068258, AR066193, EB022403, and EB021148) and the Office of Naval Research, Presidential Early Career Award for Scientists and Engineers, the NIH (EB014283), the Australian Research Council, and the National Health and Medical Research Council. N.A. acknowledges the support from the American Heart Association (16SDG31280010), FY17 TIER 1 Interdisciplinary Research Seed Grants from Northeastern University and a postdoctoral funding from the German Heart Foundation, Frankfurt, Germany.
Uncovering Why Psoriasis Recurs
New research by investigators at Brigham and Women’s Hospital and Rockefeller University helps address a longstanding question about the inflammatory skin condition psoriasis: Why do skin lesions that have resolved with therapy recur in the same locations after a patient stops using topical steroids? According to BWH physician scientist Rachael Clark, MD, PhD, of the Department of Dermatology, researchers have been searching for years for a cell population that continues to smolder after psoriasis appears to resolve. It’s been challenging to zoom in on the population of T cells driving the disease in part because when psoriasis is active, lesions are flooded with diverse T cells. But Clark and her colleagues have taken a new approach: instead of looking during the height of activity, they examined lesion sites after treatment, and identified T cell receptors of cells at these sites that were shared across psoriatic patients but not found in healthy individuals or those with other skin conditions. The team’s findings are reported in The Journal of Clinical Investigation.
“When psoriasis is treated, T cells that flooded in during inflammation recede like the tide,” said Clark who is the corresponding author of the paper. “They leave behind a population of cells that stand out.”
The population of T cells that remains are tissue resident memory cells, which live long term in skin and, when functioning properly, should be fighting infection. But for patients with psoriasis, these cells may be the source of the misguided immune response that leads to red, inflamed patches on the skin. To identify this T cell population, the researchers took biopsies at the sites of active lesions before treatment and biopsies of the same skin areas after the lesions had cleared on therapy. Using high-throughput sequencing and immunostaining, the research team found that resolved lesions contained populations of T cells derived from just a few cells (known as oligoclonal populations) that produced IL-17, a telltale marker of inflammation. These cells also shared stretches of genetic sequence that code for the same antigen receptors. These shared T cell antigen receptors were found only among cells from psoriatic patients, not in cells from healthy controls or people with skin conditions such as atopic dermatitis. This work highlights the fact that most psoriasis treatments do not kill these disease causing T cells but instead temporarily suppress their activation.
Now that they have identified the long lived, skin resident T cell population that appears to be driving recurrence, the team plans to search for new therapies that can deplete these resident T cells, potentially driving the disease into long term remission.
“We believe these resident memory T cells are the root of the problem. Imagine these cells are teenagers throwing a party. They invite lots of other cells to the site of the party, making it hard to identify them while the party is in full swing. It’s only after inflammation dies down and everyone else goes home that we can see these culprits,” said Clark. “A small number of cells can cause so much trouble. But depleting this population of cells may be the key to slowing down this disease or preventing its recurrence.”
This work was supported by NIH/National Institute of Arthritis and Musculoskeletal and Skin Diseases (NIAMS) R01 AR063962, NIH/NIAMS R01 AR056720, NIH/NIAMS P30 AR069625, National Institute of Allergy and Infectious Diseases (NIAID) R01 AI097128, R01 CA203721, T32 AR-07098-36, the National Psoriasis Foundation, the American Skin Association, and an AstraZeneca Foundation/Faculty of Medicine of the University of Lisbon research grant.
Paper cited: Matos TR et al. “Clinically resolved psoriatic lesions contain psoriasis-specific IL-17–producing αβ T cell clones” JCI DOI: 10.1172/JCI93396.
Combined Immunotherapy: Two is Better than One in the Fight Against Glioblastoma
Advancements in combined cancer immunotherapy approaches – treatments that use the body’s own immune system to fight cancer – have led to recent, promising results. With this knowledge, Brigham and Women’s Hospital principal investigator Sean Lawler, PhD, of the Department of Neurosurgery, and his team evaluated the effectiveness of combining two immunotherapy agents to treat an aggressive form of brain cancer in a preclinical model. This pairing ultimately provided the chemotherapy and immune stimulation needed to protect against tumor growth.
Cancer cells hijack certain molecules that help regulate the immune system’s ability to recognize “foreign” invaders, including tumor cells themselves. These checkpoint proteins—such as PD-L1—have become the targets for new drugs known as immune checkpoint inhibitors (ICIs). Several ICIs have been shown to promote long-term clinical responses in several different types of tumors. However, with the number of patients exhibiting durable outcomes at less than 30 percent, effort has turned to combining ICIs with chemotherapy, or other therapies that specifically target the inhibitory cells, to promote better outcomes.
For this immunotherapy treatment, researchers chose gene-mediated cytotoxic immunotherapy (GMCI) combined with anti-PD-1, an immune checkpoint blocking agent. GMCI is a gene transfer method for glioblastoma, the most common malignant primary brain tumor. The effects of GMCI on PD-L1 expression in glioblastoma were investigated in vitro and in vivo on two genetically similar mouse models. Ultimately, this therapeutic combination resulted in the activation of Type I immune responses—a major function of which is to kill cancer cells or cells infected with bacteria or viruses. The combination produced immune responses to protect against tumor growth by prompting DNA damage and cell death in the tumors.
In both mouse models, a higher percentage of long-term survivors was observed in mice treated with the GMCI/anti-PD-1 treatment (85 percent) relative to single treatments (30 percent). Here, “long-term” refers to mice that are essentially cured; the animal’s immune system eliminated the tumor and prevented regrowth if the animals were challenged again with the same tumor. The data suggest that anti-PD-1 treatment improves the effectiveness of GMCI, and the treatment is effective and well tolerated in the glioblastoma mouse models. These results support evaluation of this specific combination in human glioblastoma patients.
“This study adds to the increasing body of literature showing that immunostimulatory approaches, in this case a prodrug metabolizing gene therapy agent, can significantly enhance the effectiveness of immune checkpoint blockade in many cancer types. We are excited that a clinical trial investigating this therapeutic combination in brain tumors will start at the Brigham later this year,” said Lawler.
This work was supported by NIH PO1CA069246 (EAC, XOB, RW), the ABTA Medical Student
Summer Fellowship in honor of Collegiate Charities Dropping the Puck on Cancer and Joggin for Jill (A-KA), and the DFCI Neurooncology Core (EAC).
Paper Cited: Lawler E et al. “Preclinical investigation of combined gene-mediated cytotoxic immunotherapy and immune checkpoint blockade in glioblastoma.”
New Genetic Cause Discovered for Photosensitive Blood Disorder
Researchers from Brigham and Women’s Hospital have uncovered a new genetic cause for erythropoietic protoporphyria (EPP), a photosensitive blood disorder. In the past, the most well-known causes for EPP were two specific genetic disorders, but using an extended pedigree from France, the investigators found that EPP can also be caused by changes in another gene. In a paper published in Proceedings of the National Academy of Science, BWH principal investigator, Barry Paw, MD, PhD, of the Divisions of Newborn Medicine and Hematology, his team, and international collaborators describe a mechanism through which a mutation in the gene CLPX results in a functional defect that causes excess porphyrin, the protein in red blood cells, and ultimately intermediates and contributes to EPP.
The research team initially identified a family from Northern France in which the proband, or starting point for the genetic study of the family, suffered from EPP of unknown cause. The data collected from the proband indicated that she was affected by an unusual form of EPP. Among the proband’s family members, only her father and uncle presented with indicators associated with mild photosensitivity but showed no clinical symptoms of EPP.
CLPX is a gene that controls mitochondrial unfoldase, an enzyme that carries out a balancing step in the active unfolding of selected proteins for “protein quality control” during heme biosynthesis. It accomplishes this by catalytically activating the rate-limiting step enzyme, ALAS, or degrading ALAS protein. Researchers found that a dominant mutation in CLPX inherited by members of this family reduced the degradation associated with one of its target proteins, ALAS, which subsequently led to the accumulation of protoporphyrin IX (PPIX). Abnormal accumulation of PPIX is known to lead to EPP.
Past research by the team showed that there are several genes promoting PPIX overproduction and EPP including mitochondrial AAA+ unfoldase and ClpX. The current findings identify yet another gene promoting EPP and continue to expand the complex gene network that contributes to heme metabolism disorders.
“It is our hope that further understanding of the complex network of enzyme and cofactor interactions controlling heme synthesis will continue to contribute ideas for therapeutic strategies to treat diseases caused by aberrant regulation of heme metabolism,” the authors write.
This work was supported by grants from The Netherlands Society for Biochemistry and Molecular Biology (Nora Baart Foundation) and the Dutch Stomach Liver Bowel Foundation; the Public Health and Consumer Protection Directorate Public Health Executive Agency of the European Commission; the ANR-GIS Maladies rares; the Laboratoire d’Excellence Gr-Ex; the Howard Hughes Medical Institute; and the National Institutes of Health.
Paper cited: Yien Y et al. “A mutation in human CLPX elevates levels of δ-aminolevulinate synthase and protoporphyrin IX to promote erythropoietic protoporphyria” PNAS