TGF-β1 in chronic allograft nephropathy following renal transplantation

Background: Evidence from experimental models and clinical studies supports a major role for transforming growth factor-β1 (TGF-β1) in renal fibrosis. The aim of this study was to use repeated measurement of plasma TGFb1 as an indicator of persistent expression in a cohort of patients during the first 2 years post-renal transplantation and to correlate the findings with the development of chronic allograft nephropathy (CAN). Methods: Active plasma TGF-β1 was quantified in 100 consecutive renal allograft recipients (samples/patient = 35.6 ± 12.9) under standard clinical management for a mean of 23 months (range 3.4-45 months). All patients were followed up for a minimum of 5 years. Results: By 5 years, 23 patients had developed biopsy-proven CAN (CAN+), all of whom had been positive for plasma TGF-β1. Demographic data were compared between patients who were CAN+ and CAN-negative (CAN-) and were not significantly different. TGF-β1 exposure expressed as area under the curve / day (AUC/day) was correlated with the incidence of CAN. A Cox regression model was used to investigate the interrelationship of CAN, acute cellular rejection (ACR) and TGF-β1 levels. ACR episodes were predictive of the development of CAN (log-rank test, p=0.003). After allowing for the effect of ACR (hazard ratio [HR]=3.6; 95% confidence ratio [95% CI], 1.5-8.7) between patients with and without ACR episodes, p=0.003), the independent effect of TGF-β1 was confirmed (HR=1.7; 95% CI, 1.1-2.6; per quartile; p=0.008). Conclusion: The results demonstrate that episodes of ACR are highly predictive of chronic damage in the graft. Cumulative exposure to TGF-β1 is identified as an independent predictor of CAN in the first 2 years posttransplantation.