Researchers Prevent and Reverse Fibrosis in a Mouse Model of SSS
News Oct 14, 2013
The Scleroderma Research Foundation said that researchers at The Johns Hopkins University working in a novel mouse model of Stiff Skin Syndrome have made key discoveries that may have broad implications for future scleroderma therapy.
In a report published online on October 10th in Nature, scientists show that integrin-modulating agents can arrest fibrosis in a model of scleroderma-like skin fibrosis and, more strikingly, that established fibrosis can be resolved with such agents.
Although years away from an approved drug, the conclusion stands in sharp contrast to traditional thinking about scleroderma's irreversible advance and its resistance to therapeutic intervention. The Scleroderma Research Foundation has supported the work for the past six years.
Systemic sclerosis (commonly referred to as scleroderma) is a rare autoimmune disease affecting approximately 1 in 4,000 Americans. A signature symptom is fibrosis of the skin, although the disease typically affects the lungs, kidneys and other organs with life-threatening consequences.
Like many complex, adult-onset autoimmune diseases, animal models replicate some, but not all features of the disease. This gap has slowed work in the scleroderma field.
In the Nature report, a group led by Hal Dietz, M.D., focused on a genetic fibrotic disease called Stiff Skin Syndrome to provide insights. Dr. Dietz is a Professor of Genetics at The Johns Hopkins University School of Medicine, Director of the William S. Smilow Center for Marfan Syndrome Research and an Investigator for the Howard Hughes Medical Institute. "We looked to Stiff Skin Syndrome, an ultra-rare form of inherited scleroderma-like skin fibrosis as a means to understand the very similar skin fibrosis of systemic sclerosis," explains Dietz.
Dietz continued, "Reasoning that if we could understand how a single point mutation in the fibrillin-1 (FBN1) protein causes skin fibrosis in Stiff Skin Syndrome (SSS), this would help us to understand the biological pathways involved in systemic sclerosis, a typically acquired, adult-onset autoimmune disease."
"There may be a final common pathway by which cells lose their normal control," postulates Dietz, "and even if one condition is genetic and the other is not, they may both funnel down to the same mechanism."
"Our creation of the SSS mouse model marked the first time we could breed large numbers of animals to see what is happening in the tissues at every step along the way-from predisposition to end-stage tissue failure," says Dietz. "There is a very fundamental process that goes awry: cells in the skin of the SSS mouse model lose the ability to attach to the extracellular matrix and to sense their surroundings. Those cells then become activated and stimulate an immune reaction that causes the surrounding cells to produce excessive amounts of collagen, resulting in fibrotic skin. What's most exciting is that we discovered a strategy to suppress abnormal immune cells. We also found that we could not only prevent but also reverse established skin fibrosis."
Treatment with specific integrin binding antibodies as well as with TGF-beta neutralizing antibodies both prevented and, in a separate experiment, resolved fibrotic skin in the SSS model.
The Dietz group tested the same therapeutic strategies on cells cultured from the skin of patients with systemic sclerosis and found that the same treatments that are effective in SSS mice were able to suppress collagen production in the cells from systemic sclerosis patients.
Dietz believes that "some of these treatment strategies could transition very quickly to patients as pharmaceutical companies are already exploring the targets for other conditions, including cancer."
"A key finding of this study is the unexpected discovery that fibrosis can be reversed. This is a major advance in our thinking about fibrosis. It reveals that the fibrotic process is actually quite dynamic; therefore, when a drug succeeds in preventing excessive production of collagen, existing fibrosis can be diminished," said David Botstein, Ph.D., the Anthony B. Evnin Professor of Genomics and Director of the Lewis - Sigler Institute for Integrative Genomics at Princeton University, who is also a Scientific Advisor of the Scleroderma Research Foundation. "Within eight weeks of treatment, the researchers were able to fully normalize fibrotic skin in a mouse model so that it became impossible to distinguish treated fibrotic tissue from normal tissue."
Scleroderma Research Foundation Scientific Advisor Antony Rosen, M.D., who is Director of the Division of Rheumatology at The Johns Hopkins University School of Medicine and the Mary Betty Stevens Professor of Medicine as well as a Professor of Cell Biology and Pathology added that "equally surprising is that the SSS mice have an immune response that targets the identical protein (topoisomerase I) that is targeted in systemic sclerosis. We hope that investigating that similarity-how the immune system gets stimulated and targets that molecule-will tell us a great deal about the mechanism of systemic sclerosis."
"This work really gives us hope that we have gained some fundamental insights into the process of fibrosis and, with this model, we are positioned both to determine how dysregulation of these biological processes occurs in systemic sclerosis and to rapidly and efficiently test new treatment strategies," explains Luke Evnin, Ph.D., Chairman of the Board of Directors of the Scleroderma Research Foundation and a scleroderma patient.
"Hal's expertise in genetics and connective tissue diseases, together with his phenomenal success in translating his discoveries about the action of fibrillin-1 in Marfan syndrome into therapeutic insights that directly benefit Marfan's patients inspired us to approach him and explore whether there was a productive area of overlap for us," says Evnin. Dietz adds, "I credit the Scleroderma Research Foundation with great foresight and wisdom in coming to someone with no track record in scleroderma and saying, "give us your best idea, think broadly, and see if you can help us make progress."