One-year follow-up of kidney transplant recipients with increased expression of mRNA for granzyme B in urinary cells.

Background: Measurement of mRNA encoding cytotoxic proteins in urinary cells is recognized as a potential noninvasive means to diagnose acute rejection in kidney allograft recipients. We sought to evaluate kidney graft function after 1 year follow-up without therapeutic intervention among patients with increased urinary expression of mRNA for granzyme B, albeit with stable graft function at the time of measurements.

Patients And Methods: The 29 randomly selected patients were at a median of 39 months (range, 10-156) after transplantation with stable graft function over the previous 3 months. The reference housekeeping gene GAPDH was used for expression measurement in a TaqMan Gene Expression Assay with the target granzyme B gene. Delta delta ct relative gene expression analysis compared results with reference samples from 10 healthy individuals. Kidney graft function was reassessed after 1 year follow-up; immunosuppression was not changed during this period.

Results: mRNA granzyme B expression was significantly higher among the group of randomly assessed out-clinic patients with stable graft function than among healthy volunteers (mean ± standard error of the mean, 6.18 ± 1.27; P < .01). Despite no therapeutic intervention, no significant changes were observed in delta glomerular filtration rate or quantitative proteinuria between groups with mRNA expression > 5× versus <2× higher than the healthy controls at 1 year of follow-up.

Conclusion: Increased mRNA expression for granzyme B in urinary cells over the medium to long term among kidney transplant recipients did not predict changes in renal allograft function after 1 year follow-up.