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Scleroderma: Summaries of Research

Posted May 22 2010 12:00am

Study Examines Early Immune System Targets in Scleroderma

As is the case with most diseases, the best chance of treatment success with scleroderma is early in the process of the disease, before it has had the chance to cause irreparable damage. If doctors knew what started scleroderma - the initial targets of self-directed antibodies that seem to set the disease in motion - they might be able to diagnose it earlier and begin treatment earlier with specifically targeted therapies, says Judith James, M.D., Ph.D., Lou Kerr Chair in Biomedical Research and professor of medicine at University of Oklahoma Health Sciences Center.

To better understand these initial immune system targets, Dr. James and her colleagues have examined an antibody that is present in patients with scleroderma as well as those with systemic lupus erythematosus (SLE), another autoimmune disease. In preliminary research, they found that the specific targets, or epitopes (the portions of a protein that are bound by antibody) in people with scleroderma were different from those in people with lupus. "What that means is that both SLE and scleroderma patients make antibodies directed against the whole protein, but the specific discrete regions targeted are different in these patient groups," says Dr. James. When the researchers looked at the antibody in people with mixed connective tissue disease (MCTD), a condition with features of both scleroderma and lupus, they found antibody responses to regions targeted in both diseases.

Dr. James and her colleagues have developed a methodology that enables them to construct overlapping peptides (compounds containing two or more linked amino acids) from a whole protein and then expose those peptides to patients' serum to look for antibodies that react with any of the individual peptides. They have now looked at more than 1,000 different peptides, trying to identify regions that are targeted by antibodies in people with scleroderma that are not present in people with lupus or healthy individuals. By finding that initial target of the antibodies, they can begin to learn why the immune systems of people with lupus begin to make those antibodies.

"Patients often live decades and decades without any symptoms whatsoever, and then, based on some preliminary data we have in lupus, it looks like they make the autoantibodies first and then develop the disease," says Dr. James. "And so if we can identify what are the first targets of these abnormal immune responses, perhaps we can figure out how they are triggered."

Ideally, the results of their research might one day lead to a better diagnostic test for scleroderma. Currently, doctors test for antinuclear antibodies (ANA), antibodies directed against the cells' nuclei that are commonly found in the blood of people with scleroderma. The problem is a positive ANA is nonspecific to scleroderma: the antibodies are also common in people with some other autoimmune diseases, including lupus, as well as a small percentage of healthy people. If doctors could test for specific peptides that were always targeted in people with scleroderma, they could diagnose the disease and begin treatment earlier, says Dr. James. Identifying specific triggers could also help doctors modulate people's immune systems so they wouldn't make the abnormal immune response that leads to scleroderma.

Mouse Model Helps Researchers Understand Fibrosis

One of the greatest tools for researchers trying to understand a disease and test treatments for it is to have a mouse strain that develops problems similar to those of people with the disease. Researchers at Case/University Hospitals of Cleveland are using such a model to better understand the process of tissue hardening that occurs in scleroderma.

Because many of the problems with scleroderma are similar to that of a variant of graft-versus-host disease (GVHD, a condition that occurs when transplanted tissue causes an immune response to the tissue's recipient, which results in fibrosis), researchers decided to create a mouse model of GVHD by transplanting cells from one strain of mice to another. The mice get thick skin and lung fibrosis, or thickening of the lung tissue, much like that experienced by people with scleroderma, says principal investigator Anita C. Gilliam, M.D., Ph.D.

Among the things the scientists are trying to learn from the mice are early changes that would predict severe disease and what types of therapies would be effective. One type of therapy, latency-associated peptide, has already been shown to be effective in mice, says Dr. Gilliam. Latency-associated peptide inhibits a cytokine, or chemical messenger, called TGF-beta, which is high in these mice and which helps to drive the skin fibrosis by causing fibroblasts (cells that give rise to connective tissue) to make more collagen. The scientists also found that giving the mice antibodies to TGF-beta stopped the disease. This finding was important, she says, not only because they stopped they disease but helped confirm that TGF-beta was in fact playing a role in it.

The group is now using a technique called gene array to identify specific molecules that are either upregulated (producing more of a substance than they should) or downregulated (producing less than they should) in the skin of mice. They are examining mice from the time they receive transplanted cells to the time they develop fibrosis to try to determine what happens early in the disease process. "It takes about a month for the mice to develop thick skin, and so during that month, you would ask what is going on? What events could you interrupt that might stop the disease process?" Dr. Gilliam says.

So far, they have found that inflammatory changes occur early in the disease process and as the disease progresses, there are fewer inflammatory cells and more collagen produced. "My hypothesis is that treatment for scleroderma will be most effective in early stages when treatments for inflammation may stop or slow the process," says Dr. Gilliam. She hopes that findings of studies with the mice will enable researchers to identify potentially serious cases of scleroderma early on and prescribe treatment before inflammation has ceased and the damage is done.

Study Downplays Persistent Infection as Cause of Scleroderma

Some infections can linger in the body for a lifetime. For the most part they cause no problems, but if reactivated - such as the childhood chickenpox virus that lies dormant for decades until it resurfaces as shingles later in adulthood - they can cause great suffering. Some research has suggested that scleroderma may be the result of such an infection - that a persistent bacterial infection of the skin or small blood vessels may be to blame for the problems scleroderma causes. But new research led by Maureen Mayes, M.D., M.P.H., professor of medicine in the division of rheumatology at the University of Texas, Houston, Medical School, shows that is probably not the case.

With a grant from NIAMS, Dr. Mayes and her colleagues took skin biopsies and blood samples from people with scleroderma and looked for the equivalent of bacterial genes (evidence of an infection) and also attempted to see if the people's immune cells would react with some of the products of bacterial infection. Initially, the group had a positive biopsy, she says, but on subsequent biopsies the scientists were unable to reproduce their findings. "We are still doing a final analysis, but thus far it looks like a negative study," Dr. Mayes says. "Although it is sort of disappointing, we will at least publish the negative results once they are analyzed so other people won't go down the same pathway."

Dr. Mayes and her team are now turning their sights to a different factor in the development of scleroderma: genetics. With the help of a genetic registry of scleroderma patients and, when possible, their parents, she is looking for genes that predispose people to the disease. There are two ways of looking at genetic predisposition, says Dr. Mayes. One is to compare the genes of people with scleroderma to those of healthy controls. The other is to look at trios consisting of a person with scleroderma and his or her two parents, and then to try to identify which genes are preferentially transmitted from the parents to the patient in multiple trios.

The registry, which was started 5 years ago, now has about 660 scleroderma patients, as well as parents for 180 of them. "Certainly for the next 2 or 3 years, we are trying to collect not only as many scleroderma patients as we can but also patients with the different subsets of the disease," says Dr. Mayes. "There are at least two subsets, and the genetics might be different for these subsets."

Scientists Discover Role of Antibodies to RNA in Scleroderma

Many people with scleroderma and virtually all people with mixed connective tissue disease - a disease with features of both scleroderma and systemic lupus erythematosus - produce antibodies against ribonucleic protein, one of the body's own proteins.

Why people with these diseases produce antibodies to the protein and people without diseases don't is not known, but that's what Robert W. Hoffman, D.O., chief of the division of rheumatology and professor of medicine, microbiology and immunology at the University of Miami, is trying to find out. The goal of Dr. Hoffman's NIAMS-supported research was to investigate the nature of the immune response against this particular protein of one's own body, he says. His suspicion was that the protein somehow was altered to be more immunogenic (or capable of inducing an immune response), perhaps through oxidation (a chemical reaction in which oxygen is added to an element or compound) or apoptosis (a systematic process by which cells kill themselves). "These events occur normally," Dr. Hoffman says. "But we thought they might be altered in scleroderma or mixed connective tissue disease."

In laboratory studies, the researchers looked at how antibodies present in the serum of patients with scleroderma reacted with biochemically isolated self-proteins and found that there were antibodies reactive against one form of cellular modification, apoptosis. "During this process, the proteins were cleaved or cut into smaller fragments," says Dr. Hoffman, "and those smaller fragments seem to be very potent."

Dr. Hoffman and his team further learned that a particular fragment of the protein was important in the disease process, and in a subsequent study they were able to make the protein in the laboratory and then inject it into mice. The mice in turn developed inflammatory cells in their lungs, a characteristic feature of mixed connective tissue disease in people.

"This is actually the first model of this condition that has ever been described and we could show that the development of the disease was actually linked to whether the mice developed an immune response to that protein or not," says Dr. Hoffman Having a mouse model of the disease will give the researchers more insights into the disease process. The next step is to isolate the precise cells that are causing inflammation. The researchers then can look for ways to disrupt the inflammatory process to prevent the mice getting lung disease.

Scientists Learn How Chemicals May Cause Scleroderma

For years, researchers have suspected a link between exposure to certain chemicals and the development of scleroderma. But exactly what exposure might cause or contribute to the development of scleroderma was unknown. A NIAMS-supported study offers some potential answers.

Scientists led by Michael S. Vincent, M.D., Ph.D., of Amgen Inc., identified in laboratory studies some human white blood cells that reacted to synthetic chemicals commonly found in the environment. The cells they found were ones that were autoreactive, meaning they had potential to react to one's own body. "The cells we found would have reacted with or without the chemicals, but the chemicals made them react more," says Dr. Vincent, formerly of Brigham and Women's Hospital in Boston.

While scientists have long known that the immune system recognizes things like sugars and proteins, Dr. Vincent's research shows that it can now recognize synthetic chemicals through a molecule called CD1 on certain white blood cells called T cells. "Previously, people had assumed or speculated that a toxic action of those chemicals was causing damage rather than causing the cells to turn against the body," says Dr. Vincent. "People didn't think that scleroderma associated with chemicals could be related to the immune system actually recognizing those chemicals." Using chemicals similar to the byproduct of vegetable oil processing that caused an outbreak of a scleroderma-like illness in Spain some years ago, these scientists are now testing this hypothesis.

Aside from better understanding of how chemicals may trigger scleroderma, the researchers' findings have implications for future treatment. "If we understood that T cells that were harmful to individuals were reacting to certain kinds of chemicals, then that might help us identify certain patients who might be better treated with one agent as opposed to another," says Dr. Vincent. "There might be other mechanisms for different toxins and even immune therapies that could specifically suppress these kinds of T cells."

Study Looks at Cell Changes That Lead to Scleroderma

Before developing thickened skin and internal organ involvement, scleroderma patients often experience Raynaud's phenomenon, a condition in which blood vessels severely constrict in response to cold temperatures or to emotional stress. Raynaud's phenomenon is caused by dysfunction of the endothelial cells lining the small blood vessels in the fingers and toes, says Bashar Kahaleh, M.D., professor of medicine and chief of rheumatology at the Medical University of Ohio. Similar dysfunction of the blood vessels progressively affects the circulation of the heart, lungs, and kidneys, causing the well-recognized and life-threatening scleroderma complications.

By studying the cells from affected blood vessels as well as healthy endothelial cells from people without the disease, Dr. Kahaleh and his colleagues are gaining new understanding about the differences between the two. Their hope is that the understanding will enable them to develop treatment that will stop or reverse the process.

"Basically what we have been working on is the fact that the cells in scleroderma seem to be defective in some functions and hyperactive in others," says Dr. Kahaleh. As a result, they make lower than normal amounts of chemicals, such as nitric oxide and prostacycline, which dilate the blood vessels and keep them healthy and higher than normal amounts of chemicals that cause blood vessels to narrow and harden, such as endothelin-1.

In further laboratory studies, the scientists have found similar differences between fibroblasts (cells from which collagen, the main component of connective tissue, arises) from the skin of people with scleroderma (even cells from unaffected sections of skin) and those from people without the disease.

These differences, the scientists have found, are caused by what are called epigenetic changes. This is the process in which the DNA in the genes is influenced in such a way that some genes (such as the ones that encode for nitric oxide or prostacycline) are silenced and others (such as those that encode for endothelin-1, which constricts blood vessels) are stimulated, says Dr. Kahaleh.

If scientists could administer an agent that would return those cells to their normal behavior, they might be able to stop the disease process those changes are causing, he says. Going back even farther, an understanding of what triggers the changes might lead to ways to prevent them in the first place.

Already, some pharmacologic agents have been shown to alter epigenetic changes in cancer cells. Once researchers confirm and better understand the changes that occur in the endothelial cells and fibroblasts in people with scleroderma, the next step is to see if agents that alter those changes are effective in clinical trials.

Studies Look at Different 'Cards' in the Scleroderma 'Hand'

Developing scleroderma can be likened to holding a hand of cards. You may be holding some of the five cards (or, in the case of scleroderma, having a few of the factors for the disease) needed for a run, but it takes the entire set of cards to complete it. In work supported by NIAMS, researchers led by J. Lee Nelson, M.D., at the Fred Hutchinson Cancer Research Center and University of Washington in Seattle are looking at some of the different cards in the scleroderma hand. Their work is focused on genetics, molecular mimicry, and microchimerism.

Genetics. Although many genes are likely to play a role in the development of scleroderma, those that encode for key immune system molecules called HLA are some of the better recognized. Scleroderma affects women more often than men, and the group has a special interest in risk factors in women. In their study population, which is primarily Caucasian women, the most commonly implicated HLA molecule is HLA-DR11. The group recently found that specific subtypes of DR11 are associated with whether a woman develops the limited or diffuse form of the disease.

Molecular mimicry. One theory about scleroderma's development is that in some people, a component of the body such as an HLA molecule mimics, or is similar to, a component of an infection the immune system is fighting. When the infection is gone, the immune system reverts back to attack that component of the body.

One suspected cause of infection is cytomegalovirus, a member of the herpes virus group. The researchers noticed that the cytomegalovirus shares an amino acid sequence with the HLA-DR11 molecule. They are now looking for T cells specific to the shared amino acid sequence and will examine the types of cytokines, or chemical messengers, these cells produce. Knowing this could potentially help with developing and testing therapies to block or modify the T cell reaction without having to suppress the whole immune system.
Microchimerism. Another part of the group's work focuses on microchimerism, which refers to harboring a small number of cells from a genetically distinct individual. For example, long-term microchimerism commonly occurs as a result of cells that have crossed the placenta from mother to child and vice versa during pregnancy. For most people, these so-called microchimeric cells are not thought to have any adverse effects, but for a small percentage, the researchers believe, these cells (or fragments derived from these cells) may result in an inappropriate immune response resulting in scleroderma.

By looking at the genetics of a woman with scleroderma and the genetics of family members such as children and a woman's mother, the researchers have developed an approach in which they are able to identify microchimerism that was acquired from a prior pregnancy as well as microchimerism from the woman's mother. Previously, the scientists first reported a significant difference in levels of microchimerism from pregnancies that occurred prior to disease onset in women with scleroderma compared to healthy women.

In recent studies, they found maternal microchimerism more often but not at higher levels in women with scleroderma compared to healthy women. They suspect that both types of microchimerism can contribute to scleroderma, and that the immune system may deal with the two different types of cells differently due to the level of immunological maturity at the time the two types of microchimeric cells were acquired.

Genetics, microchimerism, and molecular mimicry. The group is working with the hypothesis that the "scleroderma hand" includes at least four cards that line up with each other and result in scleroderma. One card is the patient's genetics, with HLA-DR11 increasing risk. Two or more other cards may be microchimerism from the patient's mother, and from her children, and completing the hand, an infectious agent mimicking the woman's HLA molecule.
Mouse Models Offer Clues to Process of Skin Thickening

Thickening and hardening of the skin is a hallmark of scleroderma, which actually translates "hard skin." One hypothesis about the disease process is that there is a subset of fibroblasts (cells that give rise to collagen, the major component of connective tissue) that become activated and make more collagen than they should, says Stephen H. Clark, Ph.D., associate professor in the department of genetics and development biology at the University of Connecticut Health Center. This unchecked process continues, he says, resulting in a fibrotic condition. Dr. Clark's work is focusing on two fundamental questions: What are the factors that cause initial activation of the fibroblasts? What are the mechanisms that maintain this activated state, leading to fibrotic lesions?

Dr. Clark and his colleagues are searching for answers using two mouse models: tight skin 1, a mouse that spontaneously develops tight, hardened skin; and tight skin 2, a mouse strain created by inducing a genetic mutation that causes the development of tight skin.

To learn more about these two mice strains, they created a third: a transgenic mouse with DNA sequences associated with collagen regulation hooked to a reporter gene with a green fluorescent protein, which enabled them to monitor the gene's expression. When they mated the transgenic mice with the tight skin strains, some of the resulting progeny had normal skin and some had tight skin, but all carried the fluorescent protein that allowed the scientists to track what was going on at the molecular level and how that activity differed between the two groups.

Dr. Clark found that the tight skin not only had more fibroblasts activated (something that had not been shown in tight skin 2 before), but that the level of the fluorescent protein was activated, meaning that the each cell was also producing more protein.

Because scleroderma is likely the result of more than one gene, Dr. Clark says his goal is to identify genes in addition to the mutant gene that are upregulated in the fibroblasts. Because the dermal fibroblasts cultured cells also carry the fluorescent protein, researchers use a piece of equipment called a fluorescence activated cell sorter to separate out the cells that are fluorescing high levels of protein versus low levels - an important step identifying the molecules that are associated with collagen upregulation.

Once the scientists have identified the responsible molecules, they can begin to develop and/or test therapies specifically targeted to interfere with the harmful actions of these molecules and modify or stop the disease process.

The mission of the National Institute of Arthritis and Musculoskeletal and Skin Diseases (NIAMS), a part of the Department of Health and Human Services' National Institutes of Health, is to support research into the causes, treatment and prevention of arthritis and musculoskeletal and skin diseases; the training of basic and clinical scientists to carry out this research; and the dissemination of information on research progress in these diseases. For more information about NIAMS, call the information clearinghouse at (301) 495-4484 or (877) 22-NIAMS (free call) or visit the NIAMS Web site at http://www.niams.nih.gov/.

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