Urine proteomics in kidney transplantation.

The transplanted kidney, through its urinary output, provides a medium through which the molecular constitution can provide insight into either the healthy function or developing dysfunction of a newly transplanted organ. An assay that would detect the aberration of early biomarkers of allograft injury using only urine samples from patients would provide many advantages over the current use of creatinine and tissue biopsies, as these means are either relatively non-specific or very invasive. Several urine biomarkers have been correlated with allograft injury, including CXCL9, CXCL10, CCL2, NGAL, IL-18, cystatin C, KIM-1 and Tim-3. The recent results of the CTOT-01 trial serve to validate the predictive value of the CXCL9 biomarker as a non-invasive biomarker for rejection and a prognostic indicator of graft function. There is now a preponderance of evidence showing a value of urinary monitoring of CXCL9 and CXCL10 with respect to detection of acute kidney allograft rejection. The value of the assay has been validated as a means of reducing the need for kidney transplant biopsy and applying biopsy in a more targeted manner. Additional goals for non-invasive monitoring would include predictive value prior to creatinine elevation that in turn would permit earlier, preemptive treatment of rejection.