Credit: Lori Chertoff
People with rheumatoid arthritis (RA) often have trouble getting out of bed in the morning, let alone getting to the rheumatologist for a checkup or participating in a research study. This makes a deeper understanding of the mysterious autoimmune disease all the more difficult. That's a significant problem, because RA affects more than 1.5 million people in the U.S. and 18 million people worldwide-and as of now, there's no cure.
No one knows this better than Dana Orange, a physician-scientist in the Laboratory of Molecular Neuro-oncology at Rockefeller University. Orange splits her time between lab research on the molecular mechanisms underlying RA-in which antibodies attack the lining of joints-and patient care in the Inflammatory Arthritis Center at the Hospital for Special Surgery.
A few years ago, when she realized her research was being stymied by the physical limitations RA imposed on her patients, she developed an at-home finger-prick RNA sequencing test to enable them to take part in studies from home. Using this groundbreaking method, she's uncovered a number of significant discoveries, including why common medications don't work for many people with RA and the surprising way that dental health is linked to the disease.
Since then, her work has pinpointed hundreds of changes in gene expression that precede a flare-or sudden onset of symptoms such as swelling and pain-generating invaluable insights that may also apply to related conditions such as osteoarthritis.
We spoke to Orange, the Chapman Perelman Associate Professor of Clinical Investigation at Rockefeller, about how her research may help predict flares, provide precise drug targets, and enable effective interventions before symptoms begin.
What causes rheumatoid arthritis?
A mix of genetics and environmental factors. It's estimated that about 30% of the risk is probably genetic, and most of the associated genes are linked to how the immune system recognizes and responds to the body's own tissues. So the larger category is environmental. While we haven't been able to draw a direct line to specific triggers, epidemiology studies have shown that inhaled toxins are the biggest environmental risk factor, with smoking being the best-established link. Exposure to air pollution, coal dust, and silica particles are all common as well. This suggests that the initial insult to the immune system takes place at the mucosal barrier of the mouth and the lung.
Who is affected most?
Women account for about 70% of cases in the premenopausal phase of life, when the ratio is four women to one man, but in postmenopausal years, the ratio is two to one. That suggests to me that there's some hormonal component to the disparity. My group is in the process of teasing apart sex differences.
What is the most vexing challenge in researching rheumatoid arthritis?
Understanding and predicting flares. They tend to come on gradually, but the time frame depends on the person. It could unfold over the course of a couple of days or over a couple of weeks.
I designed my at-home test partly to look for molecular changes preceding flares-and during them. We got hundreds of samples from the enrollees, some during flares, and some not. That's what allowed us to compare gene expression.
What did you find?
We found really robust gene expression changes a week to two before. It was very surprising, because these changes were related to cells that usually build tissue architecture. You do not expect to find structural cells for tissue in blood!
That led us to discover that adaptive immune cells called B-cells were being activated, and that was followed by this unexpected group of structural cells that we called pre-inflammatory mesenchymal cells, or PRIME. They build up in the blood a week or two before a flare, and eventually migrate out of the blood into the synovial tissue that lines the joints, where they cause inflammation.
Could the presence of PRIME cells be used to predict a flare?
It's potentially a really promising biomarker. And it could be used not just for rheumatoid arthritis but for other diseases that wax and wane, such as psoriatic arthritis, inflammatory bowel disease, lupus, and multiple sclerosis. People with psoriatic arthritis and inflammatory bowel disease also have expanded populations of PRIME cells in their blood.
Incidentally, we also made a second important discovery through this study: Patients with periodontal disease had oral bacteria in their blood, and this triggers rheumatoid arthritis inflammation.
How did you make that insight?
People did the finger-prick test just before bed-probably around the time they brushed their teeth-so we think brushing allowed oral bacteria to get into their blood, which was then picked up by our test. We were intrigued, because it was known that people who have both periodontal disease and rheumatoid arthritis don't get much pain relief from RA treatments-but no one knew why. When we looked deeper, we found that oral bacteria and proteins targeted by autoantibodies in arthritis undergo a similar shift in amino acids, which alerts the immune system to take action. So when the immune system encounters the bacteria, it goes on the attack-but over time, it pivots to attacking the body's own proteins, which causes rheumatoid arthritic flares. This was really good news, because that suggests that for some patients, being treated for gum disease could help prevent some flares.
That finding opened up a new direction in my research. I'm now collaborating with the University of Newcastle in the U.K. to test the hypothesis that patients who have oral bacteria in their blood experience flares when they discontinue medication. And we're looking at longitudinal blood samples to see what changes occur in the blood of patients who flare-and whether there are any baseline biomarkers that can predict sustained remission.
Your research has also shown why about 20% of RA patients don't get any pain relief from anti-inflammatories.
That was another big surprise. From studying surgical tissue samples, we figured out that this subset of patients didn't have inflamed tissues at all. Instead, they had joint tissue fibroblasts that nurtured growth of pain-sensing neurons. So you can see why anti-inflammatories don't help these patients. And these drugs can cost upwards of $70,000 a year! That was also important to understand because to a doctor, these patients look identical to those with inflammation. Their joints appear just as swollen and tender, but the cause of their pain is very different.
Now, we're studying the various types of sensory nerves involved to identify ones that could be precise targets for nerve blockers that might reduce pain. There are multiple nerve types, and we don't want to block ones that tell you where your joint is in space or, for example, alert you to an injury.
Does anything work for these patients?
Steroids can, but steroids have so many effects on the immune system, and we don't know which ones are necessary for them to work. And because we don't understand why, we haven't been able to determine a standard steroid dose. If you ask 10 rheumatologists what a standard dose is, you'll get 10 different answers. So we're attempting to find out what changes when patients get better from steroid treatment. We are also trying to see if we can identify features in synovial fluid-the fluid that bathes the joint cavity-that can predict treatment response.
But we must do a better job of getting the right dose of the right drug to every RA patient. My research contributes to the Accelerating Medicines Partnership, where we're doing single cell RNA sequencing of these synovial tissue samples to better understand key parts of the disease process. We're also investigating how joint tissue innervation changes during inflammation to see how this correlates with gene expression in local cells. This is a difficult challenge, because the cell bodies and nuclei of the peripheral nerves that innervate joints are located near the spine-far from the joint and not included in biopsy samples-and their fine, thread-like endings follow complex paths that are difficult to visualize in histological sections. So our group is developing methods to better visualize them. All of this will help the development of better ways to control pain.
What other research projects are currently on your plate?
Because we know that RA symptoms are worse early in the day, we've been studying how circadian rhythms differ in patients who wake up with severe symptoms. So far, we see that the activation of certain white blood cells in the morning might be related to the exacerbation of symptom severity.
A lot of our findings are also applicable to related conditions, such as osteoarthritis. Unfortunately, there are few available treatments for osteoarthritis knee pain, and as a result, it is one of the more common reasons for adults to become addicted to opiates. So we are studying how nerves and joint cells relate to knee pain with the REJOIN consortium, funded by the NIH HEAL initiative, which is an effort to end opiate addiction. So far, we've identified interesting similarities between OA and RA in terms of the activation of fibroblasts and endothelial cells.
I also have another project just starting on complex regional pain syndrome. It causes such severe limb pain that patients request amputations; at my hospital, surgeons are performing these amputations about once a month. It's a really horrible problem that we're hoping to illuminate using RNA techniques we've mastered, including the three-dimensional imaging of nerves. Just as with RA, I think we'll learn a lot things that could help inform treatment across these kinds of debilitating diseases.
What about non-drug interventions? The FDA recently approved an implant that wraps around the vagus nerve and seems to tamp down autoimmune response. Do you see any promise in this direction?
Absolutely. We are entering a new era of understanding how the nervous system interacts with the immune system. The FDA approval of this implant highlights this progress. By directly modulating nerve pathways that shape immune responses, these approaches introduce an entirely new class of treatments that move beyond drugs and instead tap into the body's own regulatory networks. It's still early, but the potential is enormous, and we are only beginning to see what is possible.
