[Urinary biomarkers in kidney transplant recipients: From technological innovations to clinical development]

In kidney transplantation, the assessment of individual risks remains highly imperfect and highlights the need for robust noninvasive biomarkers with the overall goal to improve patient and graft outcomes. In the field of noninvasive biomarkers discovery, urinary biomarkers are promising tools which use easily accessible biological fluid. During the past decades, the technical revolution in the fields of genetics and molecular biology, and advances in chemistry and data analysis have led to a wealth of studies using urinary cell pellets or supernatants from kidney transplant recipients. Transcriptomic, proteomic and metabonomic analyses have suggested numerous signatures for the diagnoses of acute rejection, delayed-graft function or interstitial fibrosis. Nevertheless, the translation and validation of exploratory findings and their implementation into standard clinical practice remain challenging. This requires dedicated prospective interventional trials demonstrating that the use of these biomarkers avoids invasive procedures and improves patient or transplant outcomes.