The roles of extracellular matrix proteins, apoptosis and c-kit positive cells in the pathogenesis of ureteropelvic junction obstruction

Critical analysis of pyeloplasty role in adults with late diagnosis of ureteropelvic junction obstruction-a comparative study

PURPOSE

Due to the data paucity about the functional outcomes post pyeloplasty for patients diagnosed with ureteropelvic junction obstruction (UPJO) with a preoperative age above the age of 45 years and according to the elderly definition (age ≥ 65 years), we conducted this study to clarify the different outcomes in adults presented with late hydronephrosis.

METHODS

We included patients who were managed by pyeloplasty with a preoperative age ≥ 45 years. We further subdivided those patients into; group (A) patient's age ≥ 65 years and group (B) patient's age ≥ 45 and < 65 years. Split renal function (SRF) difference was evaluated by the changes between the last follow-up and the baseline renogram, where 5% change was considered a significant change. Functional outcomes and factors predicting the functional recoverability post pyeloplasty were evaluated.

RESULTS

A total of 119 patients were included. The mean age was 62.3 ± 16.4 years. Group (A) and group (B) included 47 and 72 patients, respectively. After 24 months, GFR and SRF were increased at the last follow-up (P = 0.32 and 0.57, respectively). No significant functional changes were noted between both groups. Sixty two, 7 and 13 patients showed static, decreased and improved renal function. Lower preoperative SRF was the only predictor for poor functional recoverability in patients with age ≥ 45 years who were managed by pyeloplasty.

CONCLUSION

Elderly patients should not be excluded from the corrective surgery for UPJO. Lower preoperative SRF was the only predictor for renal function deterioration post pyeloplasty.

Urethral leiomyoma: A rare neoplasm

Extrauterine leiomyoma is a rare benign tumor, originating from smooth muscle cells, most often localized in the uterus. Extrauterine localization of leiomyoma is extremely rare. The presence of a neoplasm near the urethra always poses a challenge for differential diagnosis. Variety of pathologies sharing similar clinical findings requires further diagnostic testing and doctor alertness. We present the clinical case of urethral leiomyoma in a female patient aged 42 years complaining of frequent urination and vulval mass. The patient underwent neoplasm removal with further histologic examination revealing urethral leiomyoma. The article features the diagnosis and treatment of this rare pathology.

Comparison of different pathological markers in predicting pyeloplasty outcomes in children

PURPOSE

To compare the efficacy of pathological markers like Interstitial cells of Cajal (ICC), neurons and Collagen to Muscle ratio (CM ratio), in predicting pyeloplasty outcomes.

METHODS

Histological sections from 31 patients with UPJO were analyzed for ICC & neurons on immuno-histochemistry and CM ratio on Masson's trichrome staining. Post-operative outcomes were analyzed at 1-year follow up; expressed as excellent, moderate or mild improvement, static and deterioration based on the three factors: ultrasound grade, differential renal function and renogram drainage pattern. The pathological findings were correlated with clinical outcomes.

RESULTS

The study group (n = 31) had a mean age 2.9 (0.6) years (M: F = 22:9). UPJ segment had significantly less ICC/neurons and more collagen compared to normal ureter (p = 0.001). Pathological parameters at the anastomosed end of ureter had a better correlation than those at UPJ with clinical outcome. CM ratio with a stronger correlation (r = - 0.94; p = 0.001) was a better predictor of prognosis than ICC (r = 0.76; p = 0.01) or neuron (r = 0.83; p = 0.01) density. ICC >10/HPF, neurons >6/HPF and CM ratio <1.2 at ureteric end anastomosed were predictors of success.

CONCLUSIONS

CM ratio analysis at anastomosed ureter is a superior marker for predicting pyeloplasty outcomes.

LEVEL OF EVIDENCE

Type 2: Development of diagnostic criteria in a consecutive series of patients.

iTRAQ-based proteomics and in vitro experiments reveals essential roles of ACE and AP-N in the renin-angiotensin system-mediated congenital ureteropelvic junction obstruction

OBJECTIVE

Ureteropelvic junction obstruction (UPJO) is a common renal obstructive disorder, but its pathogenic mechanisms remain largely unclear. We aimed to investigate the potential involvement of the renin-angiotensin system in congenital UPJO pathogenesis.

METHODS

Differentially expressed proteins in exosomes isolated from amniotic fluid of patients with congenital UPJO were characterized using iTRAQ (isobaric tags for relative and absolute quantification)-based proteomics. The expressions of angiotensin-converting enzyme (ACE) and aminopeptidase N (AP-N) in HK2 cells were inhibited by quinapril and siRNA, respectively. Cell proliferation and reactive oxygen species were measured by EdU staining and flow cytometry, respectively. Gene expression was detected by Western blot or qRT-PCR. The inflammatory factors were measured through ELISA. Mice that underwent unilateral ureteral obstruction were used as the animal model.

RESULTS

The identity of exosomes from amniotic fluids was confirmed by the expression of CD9 and CD26. In total, 633 differentially expressed proteins were identified in the amniotic fluid-derived exosomes from patients with UPJO, including 376 up- and 257 down-regulated proteins associated with multiple biological processes. Of them, ACE and AP-N were significantly decreased in the amniotic fluid exosomes. Inhibition of ACE and AP-N resulted in suppressed cell proliferation; repressed IARP, AT1R, and MAS1 expression; elevated ROS production; and increased IL-1β, TNF-α, and IL-6 levels in HK2 cells. Decreased ACE expression and elevated IL-1β levels were also observed in the mouse model.

CONCLUSION

Suppression of ACE and AP-N expression mediates congenital UPJO pathogenesis by repressing renal tubular epithelial proliferation, promoting ROS production, and enhancing inflammatory factor expression.

Comparative Proteome Analyses of Ureteropelvic Junction Obstruction and Surrounding Ureteral Tissue

Ureteropelvic junction (UPJ) obstruction is a common problem in children, but its etiology remains unclear. In this study, the proteome profiles of the obstructed segment and its surrounding distal and proximal parts were comparatively evaluated. Twelve children younger than 2 years of age with unilateral intrinsic UPJ obstruction were included. The excised operational tissue was divided into three parts immediately after resection: the obstructed part (Obst), the distal normal ureteral part (Dist), and the proximal part of the obstructed segment (Prox). Proteins extracted from the tissue samples were subjected to two-dimensional gel electrophoresis analysis to identify differentially regulated proteins. Spot analysis revealed that four proteins, namely tropomyosin beta and alpha-1 chains, actin and desmin, were upregulated in Obst in comparison to Dist. A similar analysis between Obst and Prox showed that heat shock protein beta-1 and carbonic anhydrase-1 were upregulated in Obst, while tropomyosin alpha 3 chain and ATP synthase beta were upregulated in Prox. The last comparative analysis between Dist and Prox revealed upregulation of annexin-A5 and annexin-A1 in Dist and vimentin, mitochondrial ATP synthase subunit-beta, peroxiredoxin-2, and apolipoprotein-A1 in Prox. Bioinformatics analysis using the STRING server indicated that the differentially regulated proteins, altogether, point to the changes occurring in muscle filament sliding pathway. When regulations occurring in each group were mutually compared, a change in lipase inhibition activity was detected by STRING. This is the first study scrutinizing changes occurring in protein profiles in UPJ.

A Rapid Special Staining Technique for Identification of Normal Ureter by Frozen Section in Children With Ureteropelvic Junction Obstruction

BACKGROUND

The exact etiology of ureteropelvic junction obstruction (UPJO) is unknown, and inadequate excision of the narrow segment has been proposed as a cause of failure in 5% to 7% of cases of pyeloplasty.

AIMS

To study whether frozen section can be useful to detect normal ureter distal to UPJO during pyeloplasty.

METHODS

Histological sections from 31 patients with UPJO were analyzed for collagen to muscle ratio (CMR) on conventional (formalin) and rapid (frozen section) Masson's trichrome staining. Pathological findings were correlated with postoperative outcomes analyzed at 1-year follow-up and expressed as excellent, moderate, or mild improvement, static and deterioration based on ultrasound grade, differential renal function, and renogram drainage pattern.

RESULTS

There was a very strong positive correlation (r = .94; P = .001) between CMR by conventional and rapid frozen Masson's trichrome staining. There was a very strong negative correlation between pyeloplasty outcomes and CMR on conventional staining (r = -.94; P = .001) or rapid frozen Masson's trichrome staining (r = -.91; P = .001). Regression analysis revealed that a CMR of 1.2 or less (95% confidence interval: 1.9-0.7) was associated with a successful outcome.

CONCLUSIONS

It is feasible to intraoperatively identify normal ureter distal to UPJO using CMR analysis on the novel rapid frozen section technique reported.

Pacemaker Mechanisms Driving Pyeloureteric Peristalsis: Modulatory Role of Interstitial Cells

The peristaltic pressure waves in the renal pelvis that propel urine expressed by the kidney into the ureter towards the bladder have long been considered to be 'myogenic', being little affected by blockers of nerve conduction or autonomic neurotransmission, but sustained by the intrinsic release of prostaglandins and sensory neurotransmitters. In uni-papilla mammals, the funnel-shaped renal pelvis consists of a lumen-forming urothelium and a stromal layer enveloped by a plexus of 'typical' smooth muscle cells (TSMCs), in multi-papillae kidneys a number of minor and major calyces fuse into a large renal pelvis. Electron microscopic, electrophysiological and Ca²⁺ imaging studies have established that the pacemaker cells driving pyeloureteric peristalsis are likely to be morphologically distinct 'atypical' smooth muscle cells (ASMCs) that fire Ca²⁺ transients and spontaneous transient depolarizations (STDs) which trigger propagating nifedipine-sensitive action potentials and Ca²⁺ waves in the TSMC layer. In uni-calyceal kidneys, ASMCs predominately locate on the serosal surface of the proximal renal pelvis while in multi-papillae kidneys they locate within the sub-urothelial space. 'Fibroblast-like' interstitial cells (ICs) located in the sub-urothelial space or adventitia are a mixed population of cells, having regional and species-dependent expression of various Cl^-, K⁺, Ca²⁺ and cationic channels. ICs display asynchronous Ca²⁺ transients that periodically synchronize into bursts that accelerate ASMC Ca²⁺ transient firing. This review presents current knowledge of the architecture of the proximal renal pelvis, the role Ca²⁺ plays in renal pelvis peristalsis and the mechanisms by which ICs may sustain/accelerate ASMC pacemaking.

Is there a difference in the number of interstitial cells, neurons, presence of fibrosis and inflammation in ureteropelvic junction tissues of patients with ureteropelvic junction obstruction with and without crossing vessels?

OBJECTIVE

We compared the number of interstitial cells (ICs), nerves, presence of fibrosis and inflammation at the level of full-thickness human ureteropelvic junction (UPJ) tissues obtained from normal subjects, and patients with UPJ obstruction with and without crossing vessels.

MATERIAL AND METHODS

Normal UPJ tissues (n=12) histopathologically confirmed to be without tumor involvement were obtained from subjects who underwent radical nephrectomy for kidney mass. Additional UPJ tissues were obtained from patients who underwent pyeloplasty due to UPJ obstruction. Crossing vessel was identified in 17 patients. In 57 patients, no crossing-vessel was noted. ICs were stained immunohistochemically with anti-human CD117 (c-kit) antibody. Neural tissue was stained with S-100. The numbers of ICs and neurons were compared between the groups: controls with normal UPJ (Group I), Ureteropelvic junction obtruction (UPJO) with crossing vessel (Group II) and UPJ obstruction without crossing vessel (Group III). Groups were also compared in terms of the presence of fibrosis and inflammation.

RESULTS

The mean age of total population included in the study was 30.5±18.5 years. No significant differences were detected between the three groups regarding mean and median numbers of ICs at the level of UPJ (lamina propria and muscle layer) and mean and median numbers of neurons at the level of lamina propria (p>0.05). Likewise, no significant differences were detected between the three groups regarding the presence of fibrosis and inflammation (p>0.05).

CONCLUSION

Number of ICs, neurons, presence of fibrosis and inflammation seem to be similar in the intact UPJ and UPJ with obstruction with and without crossing vessel. Cellular function rather than the number ICs might play a role that warrants further research.

The molecular biology of pelvi-ureteric junction obstruction

Over recent years routine ultrasound scanning has identified increasing numbers of neonates as having hydronephrosis and pelvi-ureteric junction obstruction (PUJO). This patient group presents a diagnostic and management challenge for paediatric nephrologists and urologists. In this review we consider the known molecular mechanisms underpinning PUJO and review the potential of utilising this information to develop novel therapeutics and diagnostic biomarkers to improve the care of children with this disorder.

Activated Hedgehog-GLI Signaling Causes Congenital Ureteropelvic Junction Obstruction

Intrinsic ureteropelvic junction obstruction is the most common cause of congenital hydronephrosis, yet the underlying pathogenesis is undefined. Hedgehog proteins control morphogenesis by promoting GLI-dependent transcriptional activation and inhibiting the formation of the GLI3 transcriptional repressor. Hedgehog regulates differentiation and proliferation of ureteric smooth muscle progenitor cells during murine kidney-ureter development. Histopathologic findings of smooth muscle cell hypertrophy and stroma-like cells, consistently observed in obstructing tissue at the time of surgical correction, suggest that Hedgehog signaling is abnormally regulated during the genesis of congenital intrinsic ureteropelvic junction obstruction. Here, we demonstrate that constitutively active Hedgehog signaling in murine intermediate mesoderm-derived renal progenitors results in hydronephrosis and failure to develop a patent pelvic-ureteric junction. Tissue obstructing the ureteropelvic junction was marked as early as E13.5 by an ectopic population of cells expressing Ptch2, a Hedgehog signaling target. Constitutive expression of GLI3 repressor in Ptch1-deficient mice rescued ectopic Ptch2 expression and obstructive hydronephrosis. Whole transcriptome analysis of isolated Ptch2⁺ cells revealed coexpression of genes characteristic of stromal progenitor cells. Genetic lineage tracing indicated that stromal cells blocking the ureteropelvic junction were derived from intermediate mesoderm-derived renal progenitors and were distinct from the smooth muscle or epithelial lineages. Analysis of obstructive ureteric tissue resected from children with congenital intrinsic ureteropelvic junction obstruction revealed a molecular signature similar to that observed in Ptch1-deficient mice. Together, these results demonstrate a Hedgehog-dependent mechanism underlying mammalian intrinsic ureteropelvic junction obstruction.

The association between impaired autophagy and the development of congenital ureteropelvic junction obstruction

OBJECTIVE

To investigate the association between impaired autophagy in smooth muscle cells and the development of congenital ureteropelvic junction (UPJ) obstruction (UPJO).

MATERIALS AND METHODS

Tissue specimens were obtained from 40 patients with unilateral UPJO and were divided into 3 sections as renal pelvis, site of obstruction, and the ureter distal to obstruction. Control specimens were obtained from the UPJ of 40 age-matched cadavers. Autophagy was evaluated by image analysis techniques for the expression of light chain 3 (LC3) after immunohistochemical staining of LC3 rabbit polyclonal antibody and Western blot analysis; additionally, myocyte apoptosis was determined using terminal deoxynucleotidyl transferase dUTP nick end labeling (TUNEL) assay, 4',6-diamidino-2-phenylindole staining, and p53 immunohistochemical staining. To assess the possible role of cell senescence, P21 and P16 immunohistochemistry staining was applied. Cellular proliferation was assessed by image analysis of proliferating cell nuclear antigen-stained specimens.

RESULTS

LC3 expression was significantly increased at the renal pelvis (P <.05). Apoptotic indices of smooth muscle cells and Bcl-2 were significantly greater at the site of UPJO (5.15 ± 0.91) compared with the UPJs of the control group (P <.001). A significant negative correlation was found between TUNEL and LC3 in all sections of the obstructed UPJ complex (P <.05). Proliferating cell nuclear antigen and LC3 were positively correlated in the renal pelvis and UPJ (P <.05); however, no specimen was stained for p16, p21, and p53.

CONCLUSION

In conclusion, impaired autophagy is associated with the development of congenital UPJO. Nonetheless, further studies are mandated to establish its etiologic role.

Hydroureternephrosis due to loss of Sox9-regulated smooth muscle cell differentiation of the ureteric mesenchyme

Congenital ureter anomalies, including hydroureter, affect up to 1% of the newborn children. Despite the prevalence of these developmental abnormalities in young children, the underlying molecular causes are only poorly understood. Here, we show that the high mobility group domain transcription factor Sox9 plays an important role in ureter development in the mouse. Transient Sox9 expression was detected in the undifferentiated ureteric mesenchyme and inactivation of Sox9 in this domain resulted in strong proximal hydroureter formation due to functional obstruction. Loss of Sox9 did not affect condensation, proliferation and apoptosis of the undifferentiated mesenchyme, but perturbed cyto-differentiation into smooth muscle cells (SMCs). Expression of genes encoding extracellular matrix (ECM) components was strongly reduced, suggesting that deficiency in ECM composition and/or signaling may underlie the observed defects. Prolonged expression of Sox9 in the ureteric mesenchyme led to increased deposition of ECM components and SMC dispersal. Furthermore, Sox9 genetically interacts with the T-box transcription factor 18 gene (Tbx18) during ureter development at two levels--as a downstream mediator of Tbx18 function and in a converging pathway. Together, our results argue that obstructive uropathies in campomelic dysplasia patients that are heterozygous for mutations in and around SOX9 arise from a primary requirement of Sox9 in the development of the ureteric mesenchyme.