Study of mRNA Growth Factors in Urinary Cells of Kidney Transplant Recipients as Predictors of Chronic Allograft Nephropathy

Abstract

Chronic allograft nephropathy (CAN) is responsible for a significant proportion of graft loss. Current diagnostic methods for CAN are inadequate, and noninvasive assays for detecting allograft dysfunction/rejection and predicting long-term outcomes are a priority in transplantation. Urine samples were collected from 48 kidney transplant recipients (KTR): 18 recipients with stable graft function (creatinine levels<2.0 mg/dL) and proteinuria of less than 500 mg/24 hr (Group 1); 18 recipients with stable graft function and proteinuria of greater than 500 mg/24 hr (Group 2); and 12 recipients with biopsy confirmed CAN. Urinary cell levels of transforming growth factor-beta1 (TGF-beta1) mRNA or epidermal growth factor (EGF) mRNA were measured using real-time quantitative PCR assay, and levels were correlated with renal allograft status. The integrity of RNA isolated from urine sediments was also assessed using the Agilent 2100 Bioanalyzer. Urinary cell TGF-beta1 mRNA levels were higher in the CAN group compared to Group 1 (P<0.0001) or Group 2 (P<0.0001). Urinary cell EGF mRNA levels were higher in Group 1 compared to Group 2 (P<0.0001) or the CAN group (P<0.0001). There were no significant differences in the urinary cell levels of EGF mRNA between patients with greater than 500 mg/24 hr proteinuria (Group 2) and the CAN group (P=0.75). These results demonstrate that urinary cell TGF-beta1 mRNA levels distinguish CAN patients from long-term transplant patients with stable renal function and varied levels of proteinuria. Urinary cells may be a good resource for the noninvasive diagnosis of CAN.