Altered expression of interstitial cells of Cajal in congenital ureteropelvic junction obstruction.

PURPOSE: Peristaltic contractions in the upper urinary tract serve to move urine from the kidney through the ureter to the bladder. Ureteropelvic junction (UPJ) obstruction is the most common cause of congenital hydronephrosis in children. To our knowledge the pathophysiology of UPJ obstruction is unknown. C-kit positive interstitial cells of Cajal (ICCs) are pacemaker cells that facilitate active propagation of electrical events and mediate neurotransmission. We investigated the expression of c-kit positive cells in the muscle layer of normal and obstructed UPJ specimens.

MATERIALS AND METHODS: A total of 19 human formalin fixed, paraffin embedded specimens of intrinsic UPJ obstruction from children with a mean age of 2.3 years (range 2 months to 12 years) and 7 control samples from children with a mean age of 4.5 years (range 11 months to 9 years) were investigated immunohistochemically for the expression of c-Kit oncoprotein and peripherin by light and laser scanning microscopy. Quantification of immunolabeled structures was quantified using computerized image analysis.

RESULTS: Peripherin immunoreactivity was strong in the muscle layer of normal UPJ specimens, while in UPJ obstructed specimens there was a decrease in peripherin positive nerve fibers. In normal UPJ specimens there were many c-Kit positive ICCs between the muscle bundles. The density of ICCs was markedly decreased in the muscle layers of UPJ obstructed specimens.

CONCLUSIONS: To our knowledge this study shows for the first time the immuno-expression of c-Kit positive ICCs in the proximal part of the normal human upper ureter. The altered density of c-Kit positive cells in UPJ obstruction may have a role in the failure of transmission of peristaltic waves across the UPJ.