They say the new insights point the way toward potentially developing drugs for the disease, which affects approximately 100,000 people in the United States.
"Until now we've had little insight and no effective treatment strategies for systemic sclerosis, and many patients die within a year of diagnosis," says Hal Dietz, a professor in the Institute of Genetic Medicine and director of the Smilow Center for Marfan Syndrome Research at Johns Hopkins.
"Our group created mouse models that allowed us to learn about the sequence of events that leads to the disease's symptoms, and we hope drugs can be developed that target one or more of these events." The Dietz team's results are described in the Oct. 10 issue of Nature.
Patients with systemic sclerosis, also known as systemic scleroderma, experience a sudden hardening, or fibrosis, of the skin. For some patients, this hardening occurs only in limited areas, but for others, it quickly spreads across the body and to organs such as the heart, intestines and kidneys. It is this fibrosis of the internal organs that is often fatal.
Systemic sclerosis rarely runs in families, Dietz says, making the gene for the disease, if it exists, very difficult to find. Without a known genetic mutation, researchers had not been able to create a genetically altered mouse with which to study the condition. But Dietz's group was struck by the similarities between systemic sclerosis and a less severe, much rarer condition called stiff skin syndrome (SSS), which does run in families, and they suspected that learning more about SSS would also shed light on systemic sclerosis.
In a previous experiment , they pinpointed the genetic mutation responsible for SSS in a gene for a protein called fibrillin-1, which plays a role in other connective tissue disorders. In certain types of tissues, including skin, fibrillin-1 helps make up the scaffolding for cells. The specific changes in fibrillin-1 seen in SSS patients were predicted to impair the ability of cells to make contact with fibrillin-1 through bridging molecules called integrins.
In the current study, M.D./Ph.D. student Elizabeth Gerber created a line of mice with a genetic variant similar to that found in SSS patients. To test the group's hypothesis, Gerber also created a line of mice with a variant the team knew would prevent fibrillin-1 from interacting with integrin. As the team expected, both groups of mice developed patches of stiff skin, along with elevated levels of proteins and cells involved in the immune response—much like humans with SSS or systemic sclerosis. "It seemed we were right that the SSS mutation causes the condition by blocking fibrillin's interaction with integrin," Dietz says. "Something else we found was that both types of mice had high levels of integrin in their skin, which made us think their cells were trying to compensate for the lack of fibrillin-integrin interaction by making more and more integrin."
This still left open the question of what was ultimately causing fibrosis, however: Was it the integrin levels or the immune response? Dietz's group delved deeper into the question by creating mice that had both the SSS mutation and artificially low levels of integrin, and found that the mice never developed fibrosis or an abnormal immune response. "They looked normal," Dietz says.
The team next tried waiting until mice with the SSS mutation had developed fibrosis, then treating them with a compound known to block a key molecule with known connections to both fibrosis and the immune response. This reversed the mice's skin fibrosis and immunologic abnormalities. The team also tested the compounds on lab-grown human skin cells with systemic sclerosis, with the same results. This raises the possibility that systemic sclerosis patients could eventually be treated with similar compounds in humans, Dietz says. A number of the compounds that proved effective in SSS mice and systemic sclerosis cells are currently being explored by drug companies for the treatment of other conditions, prominently including cancer.
The results raised another big question for the team: Which of the several types of skin cells were responsible for the runaway immune response and fibrosis? They traced the activity to so-called plasmacytoid dendritic cells, or pDCs, a cell type known to either tamp down or ramp up immune response, depending on the circumstances.
"Dietz's work gives scleroderma patients hope that we have gained fundamental insights into the process of fibrosis in scleroderma. In particular, I am confident that within a relatively short time, novel therapies can be tested in patients, and I am optimistic that such treatments will have a profound effect," says Luke Evnin, Ph.D., chairman of the board of directors of the Scleroderma Research Foundation and a scleroderma patient.
Other authors on the study were Elizabeth E. Gerber, Elena M. Gallo, Stefani C. Fontana, Fredrick M. Wigley and David L. Huso, all of the Johns Hopkins University School of Medicine, and Elaine C. Davis of McGill University.
The study was funded by the Scleroderma Research Foundation, the National Institute of Arthritis and Musculoskeletal and Skin Diseases (grant numbers RO1-AR41135 and PO1-AR049698), the National Marfan Foundation, the Smilow Center for Marfan Syndrome Research, and the Howard Hughes Medical Institute.
Shawna Williams | EurekAlert!
Hot cars can hit deadly temperatures in as little as one hour
24.05.2018 | Arizona State University
3D images of cancer cells in the body: Medical physicists from Halle present new method
16.05.2018 | Martin-Luther-Universität Halle-Wittenberg
A research team led by physicists at the Technical University of Munich (TUM) has developed molecular nanoswitches that can be toggled between two structurally different states using an applied voltage. They can serve as the basis for a pioneering class of devices that could replace silicon-based components with organic molecules.
The development of new electronic technologies drives the incessant reduction of functional component sizes. In the context of an international collaborative...
At the LASYS 2018, from June 5th to 7th, the Laser Zentrum Hannover e.V. (LZH) will be showcasing processes for the laser material processing of tomorrow in hall 4 at stand 4E75. With blown bomb shells the LZH will present first results of a research project on civil security.
At this year's LASYS, the LZH will exhibit light-based processes such as cutting, welding, ablation and structuring as well as additive manufacturing for...
There are videos on the internet that can make one marvel at technology. For example, a smartphone is casually bent around the arm or a thin-film display is rolled in all directions and with almost every diameter. From the user's point of view, this looks fantastic. From a professional point of view, however, the question arises: Is that already possible?
At Display Week 2018, scientists from the Fraunhofer Institute for Applied Polymer Research IAP will be demonstrating today’s technological possibilities and...
So-called quantum many-body scars allow quantum systems to stay out of equilibrium much longer, explaining experiment | Study published in Nature Physics
Recently, researchers from Harvard and MIT succeeded in trapping a record 53 atoms and individually controlling their quantum state, realizing what is called a...
The historic first detection of gravitational waves from colliding black holes far outside our galaxy opened a new window to understanding the universe. A...
02.05.2018 | Event News
13.04.2018 | Event News
12.04.2018 | Event News
24.05.2018 | Ecology, The Environment and Conservation
24.05.2018 | Medical Engineering
24.05.2018 | Physics and Astronomy