Microbiota Changes Related to Outcomes in Kidney Transplantation

Chronic kidney disease affects approximately 10% of the world population. End-stage renal disease (ESRD) is associated with immune dysregulation, chronic inflammation, and alteration of the gut and urinary microbiota. Kidney transplantation is the reference treatment for ESRD, but required immunosuppressive therapy further aggravates immune dysregulation and is associated with cardiovascular, metabolic and infectious complications. The gut microbiota plays a central role in modulating systemic immunity. In ESRD, microbiota composition is strongly altered. A recent study showed an association between gut dysbiosis and all-cause mortality in over 1,300 kidney transplant recipients. However, the mechanisms underlying deleterious microbiota modifications in transplant recipients remain poorly understood, particularly the respective roles of immunosuppressive treatment and renal function recovery. The MICRO-KT study hypothesizes that the programmed introduction of immunosuppressive therapy followed by partial or complete correction of ESRD after living-donor kidney transplantation induces quantitative and qualitative modifications of the fecal microbiota, and that specific microbial signatures are associated with clinical and immunological transplant outcomes. This prospective, single-center, longitudinal, interventional, single-arm cohort study will evaluate microbiota dynamics in 30 adult patients before and after living-donor kidney transplantation. Fecal samples are collected at 14 days before transplantation (before immunosuppression), the day before transplantation (after 4 days of immunosuppression), and 3 months post-transplantation. Urinary samples are collected at transplantation. Blood samples (serum, plasma, PBMCs) are collected at 3 timepoints for immunological and metabolomic analyses. The primary endpoint is to describe fecal microbiota beta-diversity dynamics (Bray-Curtis and Jaccard indices at genus level) across three timepoints. Secondary objectives evaluate associations between microbiota composition and clinical outcomes (rejection, infection, survival), immunosuppressant tolerance, drug levels, PBMC immunological profiles, metabolomic signatures, and dietary patterns.