Changes in Cajal cell density in ureteropelvic junction obstruction in children

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Congenital ureteropelvic junction obstruction is one the most common causes of neonatal hydronephrosis. The etiology of the ureteropelvic junction (UPJ) obstruction has not been clearly established. The presence of a hypoplastic, adynamic ureteral segment is thought to be the major cause of an UPJ obstruction. We evaluated the distribution of Cajal cells using immunohistologic methods coupled with light microscopy of the UPJ tissues in obstructed and normal UPJs. The study group consisted of 19 patients who underwent pyeloplasty for UPJ obstruction. Twelve patients who had been operated on for oncological indications constituted the control group. The sections were stained immunohistochemically using CD117 (c-kit) antibody; the numbers of CD117 (+) interstitial cells of Cajal were counted in 10 consecutive high-power fields under the light microscope and the cell density was determined for each case. The mean age of the cases who underwent dismembered pyeloplasty and the control group were 116 ± 116 months (14 male, 5 female; 6-420 months) and 279 ± 312 months (9 male, 3 female; 24-948 months) (p = 0.1), respectively. The mean interstitial Cajal cell number in the UPJ obstruction and the control groups were 2.37 ± 2.19 and 24.5 ± 9.73, respectively (p < 0.0001). Thirteen (68.4%) patients had very few, five (26.3%) patients had few, and one (5.3%) patient had many Cajal cells in the UPJ obstruction group. In the control group, all patients had more than seven cells per high-power field. We found that in cases of UPJ, obstruction the numbers of interstitial Cajal cells were decreased, being either absent or significantly reduced. Although data about the motility are currently not sufficient, the decrease in the number of Cajal cells in patients with UPJ highlights that they might be responsible for the initiation, coordination, and conduction of peristaltic activity along the pelvicalyceal system. Improvement and enhancement of contraction waves arising from the upper urinary system depend on interstitial cells of Cajal, which are the pacemaker cells in smooth muscles. We think that a decreased number of interstitial cells of Cajal have a close relationship with changing ureteral motility when we compare our UPJ obstruction cases with the limited data in the literature. Further investigations on these cells will probably give detailed information about the neurophysiology of the urinary system and the diseases that cause congenital hydronephrosis.