Researchers have discovered a hidden molecular warning sign in people with inflammatory bowel disease (IBD) that may remain even when patients feel well and are in remission. By examining nearly 900 human gut biopsies and patient-derived mini-intestines, scientists found that intestinal cells can remain unusually primed to die, creating a "smoldering" defect that might contribute to future flare-ups. This discovery, led by the Walter and Eliza Hall Institute (WEHI) in partnership with the Royal Melbourne Hospital, was published in the journal Science and may help explain why IBD patients can experience sudden flare-ups even after achieving remission. Inflammatory bowel disease (IBD) includes conditions like Crohn's disease and ulcerative colitis, and affects approximately 180,000 Australians. It is a chronic condition that can cause symptoms such as rectal bleeding, abdominal pain, diarrhea, fatigue, and weight loss. While modern treatments can help many patients achieve remission, IBD remains difficult to diagnose and manage, often alternating between periods of controlled symptoms and severe flare-ups that may require hospitalization. Study co-author Dr. Andre Samson explained that even when patients feel well and their disease appears stable, intestinal cells can still be vulnerable. "Once you have the diagnosis, IBD doesn't go away," he said. "Even if you're symptom-free on current treatments, there's still a likelihood of a flare or relapse." The researchers found that in some patients, intestinal cells were primed to die, indicating a persistent issue even when symptoms were not present. The findings challenge the traditional view that cell death in IBD is solely a result of inflammation. Instead, the researchers suggest that abnormal cell death may play a role in driving the disease itself. This defect was already present during the earliest stages of IBD, even in patients with mild symptoms. Detecting it required detailed molecular analysis. The study relied entirely on human tissue and patient-derived organoids—miniature versions of human intestines grown in the lab. Researchers worked with clinicians from the Royal Melbourne Hospital to collect biopsies from about 80 people with and without IBD. These samples allowed the team to directly study the disease in human cells. Study co-author Professor Edwin Hawkins emphasized the importance of using human tissue rather than relying on mouse models, which often do not accurately reflect the human condition. "Our study is based on human tissue and patient biopsies," he said. The researchers followed the patients for more than two years and found that those with stronger intestinal cell death signals were more likely to experience a relapse. Because IBD can behave differently in each person, it's challenging to predict who will respond to specific treatments or who is most likely to relapse. Study co-author Dr. Jiyi Pang noted that the newly identified molecular signals could eventually help scientists develop more precise tools for monitoring IBD patients and selecting treatments based on the biology of their disease. "The causes of IBD are largely unknown and quite variable," Dr. Pang said. "Using mini-intestinal organoids and working with a diverse team of researchers and clinicians, we uncovered the inflammatory signals responsible for this cell death response." Study co-author Dr. Aysha Al-Ani cautioned that the findings are unlikely to lead to a new diagnostic test or therapy immediately. However, they provide a foundation for future research into better forecasting tools and potential treatments. "It opens new avenues for different prognostic tools, using more sophisticated and refined methods than are currently used clinically," she said. The research team included scientists and clinicians from several institutions, and the work was supported by various foundations and government agencies.