PGE2 binding to EP2 promotes ureteral stone expulsion by relaxing ureter via the cAMP-PKA pathway.

BACKGROUND: This study investigated the relaxation effect of PGE2 on the ureter and its role in promoting calculi expulsion following calculi development. METHODS: By using immunofluorescence and Western blot, we were able to locate EP receptors in the ureter. In vitro experiments assessed the impact of PGE2, receptor antagonists, and agonists on ureteral relaxation rate. We constructed a model of ureteral calculi with flowable resin and collected ureteral tissue from postoperative side of the ureter after obstruction surgery. Western blot analysis was used to determine the protein expression levels of EP receptors and the PGE2 terminal synthase mPGES-1. Additionally, PGE2 was added to smooth muscle cells to observe downstream cAMP and PKA changes. RESULTS: The expression of EP2 and EP4 proteins in ureteral smooth muscle was verified by Western blot analysis. According to immunofluorescence, EP2 was primarily found on the cell membrane, while EP4 was found in the nucleus. In vitro, PGE2 induced concentration-dependent ureteral relaxation. Maximum diastolic rate was 70.94 ± 4.57% at a concentration of 30µM. EP2 antagonists hindered this effect, while EP4 antagonists did not. Obstructed ureters exhibited elevated mPGES-1 and EP2 protein expression (P < 0.01). Smooth muscle cells treated with PGE2 displayed increased cAMP and phosphorylated PKA. CONCLUSIONS: PGE2 binding to EP2 induces ureteral relaxation through the cAMP-PKA pathway. This will provide a new theoretical basis for the development of new therapeutic approaches for the use of PGE2 in the treatment of ureteral stones.

Collagen 17A1 in the Urothelium Regulates Epithelial Cell Integrity and Local Immunologic Responses in Obstructive Uropathy.

Collagen 17A1 (COL17A1), an epidermal hemidesmosome component, is ectopically induced in the urothelium of mouse and human renal pelvis (RP) in parallel with urinary tract-associated lymphoid structure development. Here, COL17A1 was induced in obstructive uropathy-prone ureter of humans and cats. To ascertain its function, murine urinary organs with unilateral ureteral obstruction (UUO) were analyzed during 1 week after surgery. One day after UUO, COL17A1 expression increased in urothelial cells of RP and ureter, and was positively correlated with renal tubulointerstitial lesions. A portion of RP where the smooth muscle layer from the ureter was interrupted was sensitive to urothelium deciduation and COL17A1 induction, showing urine leaked from the RP lumen into the parenchyma. After urine stimulation, cultured immune cells expressed Cxcl2, also up-regulated in CD11b+ cells following COL17A1 stimulation. One day after UUO, CXCL2+ CD11b+ cells infiltrated the urothelium-disrupted area. However, these numbers were significantly lower in Col17a1-deficient mice. COL17A1+ urothelial cells partially co-expressed cytokeratin-14, a progenitor cell marker for urothelium, whereas Col17a1-deficient mice had lower numbers of cytokeratin-14+ cells. Gene Ontology analysis revealed that expression of epithelial- and immune-associated genes was up-regulated and down-regulated, respectively, in the ureter of Col17a1-deficient mice 4 days after UUO. Thus, COL17A1 maintains urothelium integrity by regulating urothelial cell adhesion, proliferation, and differentiation, and activates local immune responses during obstructive uropathy in mammals.

Deletion of the prorenin receptor in the ureteric bud in mice inhibits Dot1/H3K79 pathway.

BACKGROUND: The prorenin receptor (PRR) plays a critical role in ureteric bud (UB) branching morphogenesis. DOT1 Like (DOT1L), a histone methyltransferase specific for Histone 3 lysine 79 (H3K79), is important for differentiation of the UB-derived renal collecting duct cells. In this study, we tested whether DOT1L/H3 dimethyl K79 (H3m2K79) are regulated by PRR deletion in the UB and UB-derived collecting ducts in the embryonic mouse kidneys. METHODS: Mutant Hoxb7Cre+/PRRflox/flox (PRRUB-/-) and control PRRUB+/+, mice were studied on embryonic (E) day E17.5. DOT1L mRNA and protein expression in the kidney was examined by real-time qRT-PCR and immunohistochemistry, respectively. H3m2K79 protein expression was determined by immunohistochemistry and Western blot analysis. RESULTS: DOT1L mRNA levels were decreased in mutant compared to control mice (0.68 ± 0.06 vs. 1.0 ± 0.01, p < 0.01). DOT1L and H3m2K79 immunostaining was reduced in the mutant vs. control kidneys (Dot1: 0.62 ± 0.03 vs. 1.0 ± 0.01, p < 0.05; H3m2K79: 0.64 ± 0.04 vs.1.1 ± 0.01. p < 0.05.). Western blot analysis revealed decreased H3m2K79 protein levels in mutant compared to control kidneys (1.0 ± 0.06 vs. 1.5 ± 0.02, p < 0.05). CONCLUSION: Targeted deletion of the PRR in the UB and UB-derived collecting ducts results in reduced DOT1L gene/protein and H3m2K79 protein expression in the embryonic mouse metanephroi in vivo. IMPACT: The role of histone methylation in mediating the effect of the prorenin receptor on the ureteric bud branching (UB) morphogenesis and urine acidification during kidney development is unknown. We demonstrate that histone H3 lysine (K) 79 dimethylation by methyltransferase Dot1 is reduced in the embryonic kidney of mice that lack the prorenin receptor in the UB lineage.

Isthmin-1: A critical regulator of branching morphogenesis and metanephric mesenchyme condensation during early kidney development.

Isthmin-1 (Ism1) was first described to be syn-expressed with Fgf8 in Xenopus. However, its biological role has not been elucidated until recent years. Despite of accumulated evidence that Ism1 participates in angiogenesis, tumor invasion, macrophage apoptosis, and glucose metabolism, the cognate receptors for Ism1 remain largely unknown. Ism1 deficiency in mice results in renal agenesis (RA) with a transient loss of Gdnf transcription and impaired mesenchyme condensation at E11.5. Ism1 binds to and activates Integrin α8ß1 to positively regulate Gdnf/Ret signaling, thus promoting mesenchyme condensation and ureteric epithelium branching morphogenesis. Here, we propose the hypothesis underlying the mechanism by which Ism1 regulates branching morphogenesis during early kidney development.

Use of small intestine submucosa as ureteral allograft in pigs

PURPOSE: The aim of the present study was to evaluate the biocompatibility of small intestine submucosa (SIS) in the reconstruction of the ureter in swine. MATERIALS AND METHODS: An experimental study was performed in 10 half-breed pigs weighing between 20 and 30 K, in which a previously prepared segment of SIS measuring approximately 2.0 cm was implanted in the upper third part of the right ureter. RESULTS: Of the 10 operated animals, one died 14 days after the surgery due to a dehiscence on the suture line of the implanted graft. The remaining 9 animals were submitted to ultrasound examination of the urinary tract and were sacrificed on the 40th postoperative day. The macroscopic evaluation showed no calculus, incrustation, fistula, abscesses or adhesions in the ureters with the graft. Microscopic evaluation with hematoxylin-eosin and Sirius red showed in the experimental area (graft) the presence of urothelium in 100 percent of the cases, collagen in 100 percent of the cases, and smooth muscle layer in 87.5 percent of the animals. In the area adjacent to the graft (proximal and distal), we observed 92.86 percent of urothelium, 42.86 percent of collagen and 71.43 percent of smooth muscle. In the contralateral ureter, it was found 100 percent of urothelium and smooth muscle and just 11.11 percent of collagen. The microscopic analysis of the kidneys whose ureters received the graft of SIS evidenced congestion in 55.55 percent, pelvic edema in 66.66 percent and interstitial nephritis in 77.78 percent. Hydronephrosis was present in 33.33 percent and chronic pyelonephritis in 44 percent. Only 1 animal presented total absence of glomerulus in the renal parenchyma. CONCLUSION: The SIS graft behaved as a biological tissue support, allowing the regeneration of the urothelium and smooth muscle grow, despite of chronic inflammatory process.