Decrease of renal aquaporins 1-4 is associated with renal function impairment in pediatric congenital hydronephrosis

Background: Renal aquaporins (AQP1-4) concentration is downregulated and is in proportion to the degree of hydronephrosis graded by ultrasound in pediatric congenital hydronephrosis (CH). However, the relationship between the expression of AQP1-4 with the changes of renal function impairment (RFI) evaluated by Tc-99m-DTPA renal dynamic imaging is still unclear. This study aimed to investigate the relationship between AQP1-4 expression and degree of RFI in children with CH. Methods: The expression of AQP1-4 was evaluated in 45 children with unilateral ureteropelvic junction obstruction (28 boys and 17 girls, average age: 28+/-10 months) and 15 children undergoing nephrectomy for nephroblastoma (8 boys and 7 girls, average age: 26+/-8 months) by immunoblotting and immunohistochemistry. Renal function was graded into mild and severe RFI by Tc-99m-DTPA renal dynamic imaging. Results: One-way analysis of variance with Bonferonni's correction showed a significantly reduced protein expression of AQP1-4 in the severe RFI group compared with those in both mild RFI group and controls (AQP1: 0.52+/-0.09 vs. 0.91+/-0.06 vs. 1.23+/-0.033; AQP2: 0.68+/-0.12 vs. 1.09+/-0.06 vs. 1.52+/-0.08; AQP3: 0.59+/-0.16 vs. 0.94+/-0.08 vs. 1.31+/-0.07; AQP4: 0.64+/-0.06 vs. 1.14+/-0.07 vs. 1.61+/-0.07; P<0.001, respectively). In kidneys with severe RFI, there was a reduction in the protein concentration of all four AQP isoforms which was more pronounced compared with those seen in kidneys with mild RFI and in the controls. Conclusion: AQP1-4 expression is reduced in proportion with the impairment degree of renal function graded by Tc-99m-DTPA renal dynamic imaging in human CH. World J Pediatr 2012;8(4):335-341