Background and Objectives: Congenital ureteral stenosis is one of the leading causes of impaired urinary drainage and subsequent dilatation of the urinary collecting system, known as hydronephrosis or ureterohydronephrosis. The mechanism that leads to obstruction is not clearly known. Multiple studies in rat models have shown increased angiotensin II and TGFβ levels in obstructed ureteral tissue. The aim of the study is to investigate the expression of fibrosis-related genes in obstructive and normal ureteral tissue. Material and Methods: It is a monocentric pilot study in which nineteen patients were selected prospectively. 17 patients underwent Hynes-Anderson pyeloplasty due to the PUJO; two patients underwent ureteroneocystostomy due to ureterovesical junction obstruction (UVJO); and six patients were chosen for the control group: five underwent nephrectomies due to the kidney tumor and one underwent upper pole heminephrectomy due to the duplex kidney with normal pyeloureteric junctions in all. Tissue RNA was chemically extracted after freezing the biopsy samples in liquid nitrogen, with cDNA synthesis performed immediately after nucleic acid isolation. qPCR was performed to evaluate the relative expression of Tgfb1, Mmp1, Timp1, Pai1, Ctgf, and Vegfa. Expression levels of the Gapdh and Gpi genes (geometric average) were used to calculate the relative expression of the investigated genes. Outliers were removed prior to calculating confidence intervals for the experimental groups, and a Wilcoxon rank-sum test was performed to determine the statistical significance of the differences. Results: Significant differences between healthy and stenotic tissue samples in Ctgf gene expression levels were observed, with the samples from afflicted tissue showing lower expression. No statistical difference in expression levels of Tgfb1, Timp1, Vegfa, Mmp1, and Pai1 was found. Conclusions: These findings suggest that tissue fibrosis, similar to other tissues and organs, is not the leading cause of stenosis, at least at the moment of surgery. Decreased CTGF expression is indicative of the developmental origin of obstruction.

Introduction: congenital ureteral stenosis is one of the leading causes of impaired urinary drainage and subsequent dilatation of urinary collecting system, known as hydronephrosis or ureterohy-dronephrosis. Mechanism that leads to obstruction is not clearly known. Multiple studies in rat models have shown increased angiotensin 11 and TGFβ levels in obstructed ureteral tissue. The aim of the study is to investigate expression of fibrosis related genes in obstructive and normal ureteral tissue. Material and methods: it is a monocentric study in which nineteen patients were selected prospec-tively. 17 patients of which underwent Hynes-Anderson pyeloplasty due to the PUJO, 2 patients underwent ureteroneocystostomy due to ureterovesical junction obstruction (UVJO) and 6 patients were chosen for control group: 5 underwent nephrectomies due to the kidney tumor and 1- upper pole heminephrectomy due to the duplex kidney with normal pyeloureteric junctions in all. Tissue RNA was chemically extracted after freezing the biopsy samples in liquid nitrogen, with cDNA synthesis performed immediately after nucleic acid isolation. qPCR to evaluate the relative expres-sion of Tgfb1, Mmp1, Timp1, Pai1, Ctgf and Vegfa was performed. Expression levels of Gapdh and Gpi genes (geometric average) were used to calculate the relative expression of the investigated genes. Outliers were removed prior to calculating confidence intervals for the experimental groups, and Wilcoxon rank-sum test was performed to determine statistical significance of the differences. Results: significant differences between healthy and stenotic tissue samples in Ctgf gene expression levels were observed, with the samples from afflicted tissue showing lower expression. No statistical difference in expression levels of Tgfb1, Timp1, Vegfa, Mmp1, Pai1 was found. Discussion and conclusions: These findings suggest that tissue fibrosis similar to other tissues and organs is not the leading cause of stenosis, at least at the moment of surgery. Decreased CTGF ex-pression is indicative of developmental origin of obstruction.