FRIDAY, Dec. 29, 2006 (HealthDay News) -- Researchers believe they've developed an important new tool in understanding rheumatoid arthritis: a genetically altered mouse that closely mimics the disease in humans.
The new mouse model might also help explain why women are much more prone to the crippling illness than men.
"This is a big step forward, because for the first time, we have mice that actually have the human genes which makes humans susceptible to rheumatoid arthritis," said study author Veena Taneja, an assistant professor in the department of immunology at the Mayo Clinic, in Rochester, Minn.
The importation of these human genes into the rodent means that "any treatment which is studied in this mouse would be a relevant treatment in humans," she explained.
Taneja's team reported the advance in the January issue of Arthritis & Rheumatism.
According to the Arthritis Foundation, more than 2 million Americans suffer from rheumatoid arthritis, most of whom initially begin coping with this autoimmune disease between the ages of 30 and 50.
While 70 percent of patients are women, the illness tends to be more aggressive in men.
Nailing down the exact cause of rheumatoid arthritis has been tough. Researchers have started to explore the possibility that the degenerative joint disease may, in fact, be the product of several different pathologies.
Once under way, rheumatoid arthritis harnesses the patient's otherwise healthy immune system to behave abnormally -- attacking healthy tissue as if it were a foreign invader.
The disease typically strikes the smaller joints of the hand, wrist and fingers first. Accompanying symptoms include fatigue, stiffness (especially in the morning), weakness and muscle pain, weight loss, depression and flu-like complications.
To date, there is no known cure. Treatments focus on pain relief and the reduction of joint inflammation but do not halt the illness.
Efforts to get at a cure have run into one major roadblock: The most useful and available study subjects -- mice -- do not naturally mimic the human course of rheumatoid arthritis.
In their work, Taneja's team sought to build a better lab mouse for the study of the illness. They focused first on a specific human gene mutation previously associated with a higher risk for rheumatoid disease.
The gene is known to provoke the activation of certain auto-antibodies, a step immediately preceding the onset of rheumatoid arthritis.
Working with both female and male mice, the authors removed the mouse equivalent of this gene -- "knocking" it out -- and replaced it with the relevant human gene.
The offspring of these genetically altered rodents were then induced to develop arthritis by injecting collagen into their systems.
Taneja and her colleagues found that all of the mice who went on to develop arthritis produced an immune response that strongly resembled that seen in human disease.
As well, female mice were found to have triple the likelihood for developing rheumatoid arthritis -- just as is found among humans.
The researchers believe the new mice are ideal models for the study of human rheumatoid arthritis.
"I'm very excited about this achievement, because by studying these mice, hopefully, we can put together some new treatment strategies and make some real headway with this disease," said Taneja.
Dr. Hayes Wilson, chief of rheumatology at Piedmont Hospital in Atlanta as well as a national medical adviser for the Arthritis Foundation, said the new mouse model is a real breakthrough.
"Any time that we can mimic disease in an experimental way that more closely resembles it in our own experience, we're better off," he said. "Of course, it doesn't necessarily translate into a health improvement for humans, but I think it's the best we can do."
"So, this sounds to me like an exciting development," Hayes added. "I'm optimistic that it will lead to better understanding and better treatment, and perhaps, ultimately, the cure we'd all like to find."
More information
For additional information on rheumatoid arthritis, visit the Arthritis Foundation.
