Urinary-Cell mRNA Profile and Acute Cellular Rejection in Kidney Allografts

Background—The standard test for the diagnosis of acute rejection in kidney transplants is the renal biopsy. Noninvasive tests would be preferable. Methods—We prospectively collected 4300 urine specimens from 485 kidney-graft recipients from day 3 through month 12 after transplantation. Messenger RNA (mRNA) levels were measured in urinary cells and correlated with allograft-rejection status with the use of logistic regression. Results—A three-gene signature of 18S ribosomal (rRNA)–normalized measures of CD3ε mRNA and interferon-inducible protein 10 (IP-10) mRNA, and 18S rRNA discriminated between biopsy specimens showing acute cellular rejection and those not showing rejection (area under the curve [AUC], 0.85; 95% confidence interval [CI], 0.78 to 0.91; P<0.001 by receiver-operatingcharacteristic curve analysis). The cross-validation estimate of the AUC was 0.83 by bootstrap resampling, and the Hosmer–Lemeshow test indicated good fit (P = 0.77). In an externalvalidation data set, the AUC was 0.74 (95% CI, 0.61 to 0.86; P<0.001) and did not differ significantly from the AUC in our primary data set (P = 0.13). The signature distinguished acute cellular rejection from acute antibody-mediated rejection and borderline rejection (AUC, 0.78; 95% CI, 0.68 to 0.89; P<0.001). It also distinguished patients who received anti–interleukin-2 receptor antibodies from those who received T-cell–depleting antibodies (P<0.001) and was diagnostic of acute cellular rejection in both groups. Urinary tract infection did not affect the signature (P = 0.69). The average trajectory of the signature in repeated urine samples remained below the diagnostic threshold for acute cellular rejection in the group of patients with no rejection, but in the group with rejection, there was a sharp rise during the weeks before the biopsy showing rejection (P<0.001). Conclusions—A molecular signature of CD3ε mRNA, IP-10 mRNA, and 18S rRNA levels in urinary cells appears to be diagnostic and prognostic of acute cellular rejection in kidney allografts

Free pentosidine and neopterin as markers of progression rate in diabetic nephropathy

Free pentosidine and neopterin as markers of progression rate in diabetic nephropathy.BackgroundPatients with diabetic nephropathy experience a progressive and usually inexorable decline in renal function. The presence of the structurally defined advanced glycation end product (AGE) pentosidine on tissue and circulating proteins has been correlated with the severity of diabetic complications.MethodsTo delineate a role for this AGE in the progression of diabetic nephropathy, glycohemoglobin and free and protein-bound pentosidine were measured in baseline stored serum and urine from a subgroup of patients with diabetes mellitus and proteinuria originally followed by the Collaborative Study Group Trial. To delineate a potential role for an immune-activation response to AGEs, the inflammatory markers, interleukin-6 (IL-6), C-reactive protein (CRP), and the monocyte activation marker neopterin were also measured at baseline. The patients chosen represented 67 subjects whose creatinine levels had “doubled” over the course of the study whether or not they later were treated with captopril, and 67 paired “non-doublers.”ResultsBaseline disease activity, as manifested by glycohemoglobin, serum creatinine and degree of proteinuria was equal in the two groups, as was protein-bound pentosidine and the immune-markers IL-6 and CRP. At baseline the “doublers” as compared to the “non-doublers” had elevated serum levels of free pentosidine and neopterin. Baseline increases in these two parameters were also associated with an increased rate of “doubling” of serum creatinine by the proportional hazards method.ConclusionDifferences in individual responsiveness to AGEs, as manifested by either the production of free pentosidine or its release from a protein-bound form, and by evidence of monocyte/macrophage activation, are associated with progression of diabetic nephropathy