April 9, 2026
Fact checked by: Jordana Joy
Key Takeaways
- Engineered C. mastitidis establishes ocular-surface residence, addressing rapid tear-mediated clearance that limits conventional eye drops and enabling sustained local delivery of therapeutic proteins.
- IL10 secretion accelerated corneal wound healing in mice, and IL10 receptor blockade abrogated benefit, supporting a mechanism dependent on IL10 signaling rather than nonspecific microbial effects.
Researchers at the University of Pittsburgh School of Medicine (UPMC) have developed an experimental “living eye drop” that uses a naturally occurring ocular bacterium to support corneal wound healing, according to a proof-of-concept study published March 5, 2026, in Cell Reports.
The study, titled “Genetically engineered eye-colonizing microbes that deliver the anti-inflammatory cytokine interleukin-10 enhance corneal tissue repair,” demonstrates that Corynebacterium mastitidis, a bacterium that resides on the ocular surface, can be genetically modified to secrete the anti-inflammatory cytokine interleukin-10 (IL10). In a mouse model of corneal injury, treatment with the engineered bacteria was associated with faster healing compared with treatment using unmodified bacteria or saline.
“Despite Corynebacterium spp. having been engineered in the past, most studies have focused on engineering C. glutamicum—a soil-habiting bacterium—to produce amino acids in an industrial production setting; our study, however, focused on genetically manipulating C. mast for the purposes of generating a therapeutic delivery vehicle or an LBP,” the study authors, led by Jackie Shane, PhD, postdoctoral associate and researcher in the Ocular Microbiome and Immunology Laboratory at the University of Pittsburgh Department of Ophthalmology, stated.
“This is the first demonstration that a microbe that lives on the ocular surface could be engineered to deliver a therapeutic that improves eye health,” said senior author Anthony St. Leger, PhD, associate professor of ophthalmology and immunology and a faculty member of the UPMC Vision Institute, in a UPMC release. “It opens the door to the idea of ‘living medicine’ for the eye—something you apply once, and it stays, protects and helps the tissue heal.”
The researchers noted that conventional eye drops can be limited by rapid clearance due to tear production, often requiring frequent administration. To address this, the team engineered C. mastitidis to continuously secrete IL10, a protein involved in regulating inflammation. In mice with corneal abrasions, those treated with the modified bacteria showed improved healing outcomes. The effect was not observed when the IL10 receptor was blocked, indicating the response was dependent on IL10 activity.
In additional experiments, the researchers engineered a version of the bacterium to release human IL10. This approach improved wound closure in cultured human corneal epithelial cells and reduced inflammatory signaling in human immune cells, providing initial evidence supporting potential applicability in human systems.
“What makes this exciting is that the system is modular,” St. Leger said in the release. “We built it so you can swap in different genes—different cytokines, growth factors or other proteins—to tailor the therapy to specific eye diseases.”
The authors emphasized that the technology remains in early development and that further work is required before clinical application. This includes the development of mechanisms to safely deactivate or remove the engineered bacteria after treatment.
Conditions such as severe dry eye, ocular surface inflammatory disorders, and corneal injuries affect millions of individuals in the US. While the current findings do not establish a clinical therapy, the study provides a basis for further investigation into engineered live biotherapeutics for sustained delivery of therapeutic molecules to the eye.
“In my lab, we don’t typically build tools from the ground up,” St. Leger stated in the release. “Seeing a measurable improvement in healing in an animal model using something we engineered was incredibly rewarding, and it points us toward intriguing possibilities for future research.”
Funding was provided by the National Institutes of Health, the Hillman Innovation Exploratory Award, the Eye and Ear Foundation of Pittsburgh, and Research to Prevent Blindness.
References:
- Shane J, Evans M, Rigas Y, Shanks RMQ, St. Leger AJ. Genetically engineered eye-colonizing microbes that deliver the anti-inflammatory cytokine interleukin-10 enhance corneal tissue repair. Cell Reports. 2026;43(3):117064. https://doi.org/10.1016/j.celrep.2026.117064
- Pitt scientists engineer ‘living eye drop’ to support corneal healing. News release. University of Pittsburgh School of Medicine. Accessed April 1, 2026. https://www.medschool.pitt.edu/news/pitt-scientists-engineer-living-eye-drop-support-corneal-healing
