Researchers have linked intestinal bacteria to the onset of rheumatoid arthritis, the first demonstration in humans that the chronic inflammatory joint disease is associated with a specific bacteria. The new findings by researchers in rheumatology at NYU School of Medicine add to the growing evidence that the trillions of microbes in our bodies play an important role in regulating our health.
Using DNA analysis to compare gut bacteria from fecal samples of patients, the researchers found that Prevotella copri was more abundant in patients newly diagnosed with rheumatoid arthritis than in healthy individuals or patients with chronic, treated rheumatoid arthritis. The overgrowth of P. copri was also associated with fewer beneficial gut bacteria.
“Our own results in mouse studies encouraged us to take a closer look at patients with rheumatoid arthritis, and we found this remarkable and surprising association,” says Dan Littman, MD, a professor of Pathology and Microbiology at NYU School of Medicine and a Howard Hughes Medical Institute investigator.
“At this stage, however, we cannot conclude that there is a causal link between the abundance of P. copri and the onset of rheumatoid arthritis. We are developing new tools that will hopefully allow us to ask if this is indeed the case.”
The new findings, reported in the journal eLife, were inspired by previous research in Dr. Littman’s laboratory, using mice genetically predisposed to rheumatoid arthritis. The mice resisted the disease if kept in sterile environments, but showed signs of joint inflammation when exposed to benign gut bacteria.
To test their theory, researchers took stool samples from 44 human patients with newly diagnosed rheumatoid arthritis; 26 samples from patients with chronic, treated rheumatoid arthritis; 16 samples from patients with psoriatic arthritis; and 28 samples from healthy individuals.
Three out of four samples (75%) from the patients newly diagnosed with rheumatoid arthritis carried P. copri, compared to 21.4% of samples from healthy individuals; 11.5% from chronic, treated patients; and 37.5% from patients with psoriatic arthritis.
Rheumatoid arthritis is usually treated with an assortment of medications, including antibiotics, anti-inflammatory drugs like steroids, and immunosuppressive drugs that tame immune reactions. Little is understood about how these medications affect gut bacteria.
“It could be that certain treatments help stabilize the balance of bacteria in the gut,” says co-author Jose U. Scher, MD, director of the Microbiome Center for Rheumatology and Autoimmunity at NYU Langone Medical Center’s Hospital for Joint Diseases.
“Or it could be that certain gut bacteria favor inflammation.”
Rheumatoid arthritis, an autoimmune disease that attacks joint tissue and causes painful, often debilitating inflammation, affects 1.3 million Americans. It strikes twice as many women as men and its cause remains unknown.
The researchers plan to validate their findings by obtaining stool samples from beyond New York, since gut flora can vary across geographical regions.
“We want to know if people with certain populations of gut bacteria respond better to certain treatment than others,” says Dr. Scher.
They also hope to study more people before they develop rheumatoid arthritis, to see whether overgrowth of P. copri is a cause or result of autoimmune attacks.
A recent study by researchers at Weill Cornell Medical College and The Rockefeller University found a common bacterium usually found in soil in the stool samples of multiple sclerosis (MS) patients. The bacteria produce a toxin that scientists say may trigger the autoimmune disease.