3

INCREASED INTRAGRAFT ANGIOTENSINOGEN GENE EXPRESSION IN POST-TRANSPLANT RECURRENT FSGS

We have initiated studies to test the hypothesis that altered intra-renal NF_KB regulation and increased expression of NF_KB-regulated proteins such as IL-8 and angiotensinogen are involved in the pathogenesis of post-transplant recurrent FSGS. I_KBa binds to NF_KB, preventing this nuclear factor from upregulating the expression of proinflammatory proteins. Steroids enhance I_KBa gene expression. Altered NF_KB regulation could result in increased expression of NF_KB-regulated factors, allowing pathological processes to be resistant to steroid therapy. We used reverse transcription-assisted competitive PCR to quantify the magnitude of intragraft gene expression of NF_KB (p65), I_KBa, angiotensinogen, IL-8 in 65 pediatric renal allograft biopsies including 20 with FSGS and 45 without FSGS. Results are expressed as mean ± s.e. for the quantitative ration of target gene expression corrected for expression of GAPDH. Our results show elevated intragraft expression of NF_KB/I_KBa ratio, IL-8, and angiotensinogen in FSGS vs. NON-FSGS, although only angiotensinogen reached statistical significance:

In order to perform combined gene analysis, samples were deemed positive for a target gene if the amount of target gene expression was above the 95% upper confidence limit of gene expression for NON-FSGS. Samples positive for 2 or more target genes were separated from samples positive for one or no genes. Of all the FSGS samples, 55% of samples were observed in the group with 2 genes positive while only 17.8% of NON-FSGS samples were observed in this group (x² = 9.274, p<0.005). These preliminary results demonstrate altered expression of NF_KB and NF_KB-regulated accounts for the variable clinical picture of recurrent FSGS post-transplantation. Angiotensin II, the final end-product of angiotensinogen may mediate the steroid-resistant proteinuria and progressive glomerular damage characteristic of this disorder. Further correlation of intragraft IL-8 and angiotensinogen gene-expression with clinical status will provide opportunities for innovative therapeutic trials.

Asher D. Schachter, Jurgen Strehlau, Lauro Vasconcellos, Xin Xiao Zheng, William E. Harmon, John T. Herrin, Amir Tejani, and Terry B. Strom, Nephrology Division. The Children’s Hospital; Immunology Division, Beth Israel Deaconess Medical Center and Harvard Medical School, Boston, MA; and SUNY Health Science Center, Brooklyn, NY, in cooperation with the North American Renal Transplant Cooperative Study (NAPRTCS)