There was a lot of research on molecules mechanisms underlying congenital intrinsic UPJO, but it is still poorly understood (11). Researches demonstrated that a Shh-Ptch-Gli3 dependent mechanism caused murine intrinsic UPJO and implicated dysregulated this signaling in the pathogenesis of human UPJO (5). Shh signaling was consisted of ligands membrane of Ptch receptors, downstream target genes and pathway regulation proteins (4). During renal development, the Shh and its receptor Ptch were expressed in stromal cells and tubular epithelium. Shh bound to Ptch and relieved a transmembrane protein expressed on the cell surface (6). In presence of Shh, GLI proteins (Gli3) translocated to the nucleus, acting as transcriptional activators (12).
It had been previously shown that Shh signaling controlled cellular differentiation during ureter formation. The defection in urothelial differentiation could cause UPJO in mice (13). Previous studies found increased Shh and decreased Gli3 expression (4), Shh might compensatory increase because the downstream target was disturbed. While the Shh receptor was Ptch, the signal was blocked in this phase, so the next downstream target Gli3 was decreased. What had happened in the intermediate passage? We were inconclusive. Recent researches were focused on the Ptch structure (8,11). But it had still not proved that the expression of Ptch (P1 and P2) was abnormal in UPJO. Gupta et al found that the expression of P1 in hydronephrotic model was high as compared to normal mice (10), his research was based on artificial mutant mice, not the real UPJO patients. In Sheybani’s research, P1 was increased in a single patient out of eight (5), but the control tissue was contiguous UPJO segment. So, these results could not describe a real pathogenic mechanism underlying congenital UPJO.
Here we obtained 20 intrinsic UPJO tissues and 10 ureters from patients with Wilms tumor, Specimen was strictly collecting and obtaining UPJ segments in two groups. Even so, the results were depressing, our results demonstrated that P1 and P2 were not changed in the quantity of UPJO patients through immunofluorescence, western blot and PCR. We also found that age was not related with quantity of both. All the results were negative and we reached an impasse in our research as well. Previous studies found that P1 was removed from cilia after binding of the Shh ligand to P1 and allowing Smoothened (A G-coupled transmembrane protein) to enter cilia and become activated. If P1 was not removed, it would prevent Smoothened’s localization to cilia and disrupt the Gli transcription activator/Gli3 repressor (Gli3R) balance (7). According to this molecular biology, the P1’s distribution may be abnormal in the UPJO patients if this pathway had been disturbed. We turned back to examine the immunofluorescence of P1 again, found that red-stained P1 were diffused in control group (Fig. 1B), but were mainly surrounding the nucleuses of smooth muscle cells in UPJO. Based on our previous findings, we inferred that P1’s quantity was unchanged, but the movement was restricted in UPJO. Thus, the whole Shh pathway was disturbed. It was only a hypothesis that we inferred from our founds, and it was needed further study to confirm this.
P2 in the shh signaling pathway remains ambiguous. Researches had shown that the two homologs had overlapping functions. But it cannot compensate for the loss of P1 activity (14). Studies found that P2 does not play a functional role in regulating Shh signaling activity during kidney development, but serves as a specific marker of the onset of UPJO (5). In some studies, P2 was increased in UPJO (5), but in our research, P2 was not changed and we could not find any regularities of distribution. We strictly followed the rules of specimen collection of uretero-pelvic-junction in UPJO and control groups, but in other researches, they were not quite exactly the human uretero-pelvic-junction in control group.