Proteomic analysis of molecular factors associated with obstructive megaureter

Abstract

Congenital megaureter is a term used in many cases of urinary tract dilatation detected before and after birth. Prior studies have investigated histological changes such as the concomitant decrease in smooth muscle cells and increase in extracellular connective tissue. However, the underlying pathophysiology of obstructive and refluxing megaureter is poorly understood. Megaureter and normal ureter tissues were used to examine differentially expressed proteins to gain a better understanding of the pathogenesis of megaureter. Smooth muscle cells (SMCs) of obstructive megaureters were obtained from 5 patients who underwent open ureteroneocystostomy surgery and 5 control patients with low grade VUR. The obtained SMCs were cultured in M199 medium supplemented with 10% fetal bovine serum (FBS) and 1% antibiotics. To identify differently expressed proteins, protein spots separated by 2D gel electrophoresis were matched and then analyzed using PDQuest software and nanoflow LC-ESI-MS-MS. TPM1, a protein associated with the contraction and migration of SMCs, was selected among the analyzed proteins such as annexin A2, smooth muscle protein and nephronectin etc. to investigate its relationship with megaureter. When α-tropomyosin (TPM1) was artificially over-expressed in normal ureter SMCs, a significant change in morphology was observed. In addition, the rate of apoptosis was increased in transfected SMCs compared with controls. Ureter smooth muscle is known to play an important role in peristalsis and pacemaker activity. Abnormal over-expression of TPM1 in ureter SMCs may induce defects in contractility and increase apoptosis. Empty spaces caused by apoptosis may then be preferentially filled with connective tissue rather than SMCs which have a low migration rate. As a result, contractility is decreased; leading to the development a dilated ureter.From the results of this study, over-expression of TPM1 gives new insights on potential molecular mechanisms associated with the development of megaureter and is expected to be a potentially exploitable protein as putative prognostic biomarkers of fibrosis in ureters and other tissues.