MIT finds cysteine triggers gut repair

MIT researchers said a common dietary amino acid, cysteine, can help the small intestine repair itself after injury in mouse experiments and lab-grown tissue models. The study, published in Nature on October 1, 2025, traced the effect to an immune signaling pathway that boosts intestinal stem-cell repair capacity. Ömer H. Yilmaz, an MIT biologist and director of the MIT Stem Cell Initiative, said the findings could eventually inform efforts to reduce intestinal damage caused by radiation or chemotherapy, though the work was done in mice, not people. Fangtao Chi, a Koch Institute postdoctoral researcher, was the paper’s lead author. ### What exactly did the MIT team find? MIT said cysteine had the strongest regenerative effect when researchers compared diets enriched with each of 20 amino acids in mice. The amino acid increased activity in intestinal stem cells and progenitor cells, which are the immature cells that give rise to the gut lining. Nature described the core result as enhanced intestinal stem-cell-mediated repair after injury. MIT said the effect was seen in the small intestine and was linked to faster regrowth of intestinal tissue after damage. The institute said the work builds on earlier Yilmaz lab studies showing that fasting and high-fat diets can alter intestinal stem-cell behavior, but called this the first study to identify a single nutrient with this regenerative effect. ### How does cysteine appear to trigger repair? Nature said cysteine contributes to coenzyme A biosynthesis in intestinal epithelial cells. That metabolic change promoted the expansion of intraepithelial CD8αβ+ T cells and increased their production of interleukin-22, or IL-22, a signaling molecule tied to tissue repair. MIT said that IL-22 signaling then directly increased the reparative capacity of intestinal stem cells after injury. (news.mit.edu) The paper also tested the pathway mechanistically: coenzyme A supplementation reproduced cysteine’s effect, while disrupting the cystine transporter SLC7A11 in epithelial cells blocked it. Mice lacking IL-22 in CD8αβ+ T cells, or depleted of those T cells, did not show the same regenerative benefit with cysteine treatment. (nature.com) ### What evidence did they show in animals and cell models? MIT said the study used mice as the main in vivo model and also relied on intestinal organoids, the miniature gut tissues grown from mouse or human intestinal stem cells. In the organoid work, cysteine exposure increased the tissues’ ability to regrow, according to MIT’s summary of the experiments. (nature.com) Radiation injury was one of the main test cases. MIT said regeneration stimulated by a cysteine-rich diet helped repair radiation damage to the intestinal lining in mice. The institute also said unpublished follow-up work suggested a similar regenerative effect after treatment with the chemotherapy drug 5-fluorouracil, but that result was not part of the Nature paper. (news.mit.edu) ### Why are researchers focused on the intestinal lining? The small intestine depends on rapidly renewing LGR5-positive intestinal stem cells to maintain the epithelial lining that absorbs nutrients and protects against injury. Nature said a central question in physiology is how diet changes the behavior of those cells during normal maintenance and after damage. Yilmaz told MIT that the study suggests cysteine-rich diets or supplementation might eventually help limit chemotherapy- or radiation-induced intestinal injury if similar effects are confirmed in humans. (biology.mit.edu) He said, “The beauty here is we’re not using a synthetic molecule; we’re exploiting a natural dietary compound.” ### What comes next? (nature.com) MIT said the current findings were generated in mice, and any clinical use would require future research in humans. The paper identifies named molecular targets — including SLC7A11, CD8αβ+ T cells and IL-22 — that can now be tested further in injury and regeneration studies. The October 1, 2025 Nature paper, “Dietary cysteine enhances intestinal stemness via CD8+ T cell-derived IL-22,” lists Chi and Yilmaz among the authors, and MIT’s coverage links readers to the published study and related materials. (news.mit.edu) (nature.com)