Histopathological Relevance of Angiotensin II Type 1 Receptor in Renal Transplant Biopsy

The occurrence of anti-angiotensin II type 1 receptor (AT1R) antibodies is thought to be a risk factor for transplant injury, but the relationship of AT1R to graft loss in renal transplantation has not been assessed. The aim of our study was to evaluate the expression of AT1R and its relationship with graft loss in patients who had a renal transplant biopsy for cause. Methods AT1R immunoreactivity was analyzed in 170 renal transplant biopsies. Immunohistochemical evaluation of AT1R expression was performed on 4 μm-thick paraffin sections mounted on silanized slides. AT1R expression was analyzed in 5 compartments: 1. glomeruli, 2. renal blood vessels (small and intermediate arteries), 3. peritubular capillaries, 4. tubular epithelium, and 5. interstitium based on a 3-step scale. Results Initially we checked 170 consecutive samples of biopsies for the immunoreactivity of the AT1R. The study finally included 118 renal transplant patients in 1-year observation after the biopsy. The renal allograft biopsy was performed between 6 days and 24 years after transplantation and the diagnosis was based on Banff criteria. We observed positive immunostaining of AT1R in tubular epithelium in 26.3% (42/118) of patients. A total of 7 patients had staining assessed as 2 and 35 as 1. One year post-biopsy graft loss in the AT1R (+) patients was 35.7 % (15/42) compared to 14.5% (11/76) in the AT1R (-) group (P = .008). Conclusions The expression of AT1R in tubular epithelium of the biopsy for cause was associated with significantly higher graft loss. The relevance of AT1R should be considered for better transplant immunological risk assessment.