A quantitative histological analysis of the dilated ureter of childhood

Downregulation of fibrosis related hsa-miR-29c-3p in human CAKUT

Congenital anomalies of the kidney and urinary tract (CAKUT) represent structural and functional urinary system malformations and take place as one of the most common congenital malformations with an incidence of 1:500. Ureteral obstruction-induced hydronephrosis is associated with renal fibrosis and chronic kidney diseases in the pediatric CAKUT. We aimed to construct interaction network of previously bioinformatically associated miRNAs with CAKUT differentially expressed genes in order to prioritize those associated with fibrotic process and to experimentally validate the expression of selected miRNAs in CAKUT patients compared to control group. We constructed interaction network of hsa-miR-101-3p, hsa-miR-101-5p and hsa-miR-29c-3p that showed significant association with fibrosis. The top enriched molecular pathway was extracellular matrix-receptor interaction (adjusted p = .0000263). We experimentally confirmed expression of three miRNAs (hsa-miR-29c-3p, hsa-miR-101-3p and hsa-miR-101-5p) in obstructed ureters (ureteropelvic junction obstruction and primary obstructive megaureter) and vesicoureteral reflux. The hsa-miR-29c-3p was shown to have lower expression in both patient groups compared to controls. Relative levels of hsa-miR-101-5p and hsa-miR-101-3p showed significant positive correlations in both groups of patients. Statistically significant correlation was observed between hsa-miR-101 (-3p and -5p) and hsa-miR-29c-3p only in the obstructed group. The significant downregulation of anti-fibrotic hsa-miR-29c-3p in obstructive CAKUT could explain activation of genes involved in fibrotic processes. As miRNAs are promising candidates in therapeutic approaches our results need further measurement of fibrotic markers or assessment of extent of fibrosis and functional evaluation of hsa-miR-29c.

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.

Pathological changes in ureterovesical and ureteropelvic junction obstruction explained by fetal ureter histology

The etiology of ureterovesical junction obstruction (UVJO) and ureteropelvic junction obstruction (UPJO) is obscure with an adynamic narrow segment causing the obstruction. In this study, the authors compared interstitial cells of Cajal (ICC) and collagen-to-muscle ratio (CM ratio) between UVJO, UPJO, and fetal ureters to investigate whether a maturational arrest of the fetal ureter could explain both clinical pathologies.

METHODS

Group 1 (control) involved specimens of the normal ureter (nephrectomy for trauma/tumor; n = 20), while group 2, specimens of UVJO (n = 14); group 2 was further divided into group 2a, the dilated megaureter above UVJO, and group 2b, UVJO narrow segment; group 3, UPJO narrow segment excised during pyeloplasty (n = 31); and group 4, normal fetal ureters (n = 12). The specimens were analyzed for ICC using immunohistochemistry and CM ratio on Masson's trichrome (stains collagen in blue and muscle in red).

RESULTS

The median ICC/10 high-power field was 16.1 (8.3) in the normal and 17.3 (7.9) in the dilated segment of the megaureter, with no significant difference, but was significantly less in the narrow segment of UVJO at 4.5 (2.0), narrow segment of UPJO at 5.1 (2.3), and fetal ureter at 5.0 (2.3). The median CM ratio was 0.75 (0.29) in the normal and 0.65 (0.2) in the dilated segment of the megaureter, with no significant difference between them (figure), but was significantly higher in the narrow segment of UVJO at 3.0 (0.8), narrow segment of UPJO at 2.5 (0.71), and fetal ureter at 3.1 (0.61). Overall UVJO, UPJO, and fetal ureter segment had significantly less ICC density and more collagen compared with the normal ureter (P < 0.001 by Mann-Whitney U test).

DISCUSSION

There are conflicting reports on the etiopathogenesis of UVJO and UPJO, with several authors showing decreased ICC and increased collagen in the narrow segment. In this study, the authors found that the pathological changes at UVJ and UPJ segments resemble fetal ureter morphology. We also found that in fetal ureters, as the gestation progressed, there was an increase in the ICC density/smooth muscle, whereas the collagen content decreased. While the entire ureter has uniform embryological origin, it essentially remains an epithelial tube until the late gestation. The maturational process involves differentiation of smooth muscles cells/ICC to establish the peristaltic machinery required to functionally connect the ureter at both ends. This process, probably, starts at the mid ureter during fetal life and extends toward the UPJ and UVJ, and its failure, probably, results in UPJO or UVJO. The study's limitations are small numbers, and further larger studies are required to validate this hypothesis.

Age- and region-related changes in the biomechanical properties and composition of the human ureter

The ureter has been largely overlooked heretofore in the study of the biomechanics of soft biological tissues, although there has been significant motivation to use its biomechanical properties as inputs to mathematical models of ureteral function. Herein, we used histological analysis for quantification of collagen contents and thickness/area of ureteral layers, with concomitant geometrical analysis of zero-stress and no-load states, and inflation/extension testing to biomechanically characterize with the Fung-type model the ureters from cadavers. The effects of age and gender on the regional distribution of those properties were examined. Tissue properties did not differ (p>0.05) between the left and right ureter. Regional heterogeneity was established that was profoundly age-related but seldom gender-related, based on the following evidence: 1) In younger subjects, the axial stress-circumferential strain curves of upper ureter were shifted to smaller stresses and model parameter a₂ representing axial stiffness was smallest (p<0.05), i.e. upper ureter was the least stiff region axially; 2) upper ureter underwent axial stiffening with advanced age, evidenced by the increasing (p<0.05) parameter a₂, and the stress-strain curves were uniformly exhibited along the ureter, evidenced by the non-varying (p>0.05) parameters C,a₁,a₂,anda₄; 3) aging raised (p<0.05) the collagen content of upper ureter to favor a near-uniform regional distribution; 4) wall thickness increased with age, unlike the opening angle and residual strains, reflecting the thickening of outer (muscular) vs. inner (mucosal) layers in aged subjects, with significant differences (p<0.05) in some regions; and 5) gender affected little (p>0.05) the opening angle and morphometry of no-load and zero-stress states.

MMP9 overexpression is associated with good surgical outcome in children with UPJO: Preliminary results

BACKGROUND

Ureteropelvic junction obstruction (UPJO) diagnosed prenatally occurs in 1:150 - 1:1200 pregnancies. Although many studies investigating the molecular changes of this obstructed segment have been performed, the underlying mechanisms are still unclear. The role of extracellular matrix (ECM) components remains controversial, and the investigations in the field of ECM changes, might help the better understanding of the pathogenesis of this common condition. The aim of the present study was to investigate for the first time in the literature whether MMP9 and its specific inhibitors, TIMP1 and RECK, are expressed in a reproducible, specific pattern in UPJ.

METHODS

UPJO specimens were obtained from 16 children at the time of dismembered pyeloplasty due to intrinsic UPJ stenosis. Expression levels of the three genes (MMP9, TIMP1 and RECK) were analyzed by quantitative real-time polymerase chain reaction (qRT-PCR). Then correlated the expression levels of the genes according to grade study population that was divided in 2 categories according to Society of Fetal Urology classification, grade 3 (moderate) and 4 (severe). For DTPA we subdivided the childrens in 2 groups, obstructive (T 1/2 more than 20 min) and partial obstructive (T 1/2 between 10 and 20 min) and success in a surgery was defined as decrease in T 1/2 to less than 20 min, absence of symptoms, improving renal function and decreasing dilatation on successive exams.

RESULTS

MMP9 was underexpressed and TIMP1 and RECK were overexpressed in children with obstructive DTPA but the differences were not statistically significant. Overexpression of MMP9 was higher among patients with severe grade of UPJ compared to those with moderate grade. Surprisingly expression levels of MMP-9 was three times higher in children who were successfully treated by surgery (n = 10) (p = 0.072), so those who were followed for at least 1 year after surgery and remained with improvement in renal function and decreasing dilation on intravenous urogram and TIMP-1 was underexpressed in 100 % of this cases (p = 0.00).

CONCLUSIONS

We showed an increase in expression of MMP9 and a decrease in expression of TIMP1 in children who improving renal function and decreasing dilation after surgery. We believe that the higher expression of MMP9 in these cases can reflect an increase in degradation and remodeling process that could be used as a marker for surgical outcome.

Altered expression of interstitial cells of Cajal in primary obstructive megaureter

OBJECTIVE

A marked decrease in the density of interstitial cells of Cajal (ICC) has been shown in patients with ureteropelvic junction obstruction. ICC may also play a role in primary obstructive megaureter (POM). An immunohistochemical study was conducted to investigate the density of ICC in ureterovesical junction (UVJ) segments resected from patients with POM and from control autopsy specimens.

MATERIALS AND METHODS

Resected UVJ segments from 11 patients operated for POM comprised the study group. Control UVJs were obtained from autopsy specimens of 7 children who died from causes other than urogenital pathology. The UVJs including the narrowest parts were studied using immunohistochemical staining for C-kit positive cells.

RESULTS

The number of ICC was significantly lower in the UVJs of the POM compared to the control group. The UVJs of the POM group had 1.75 ± 1.14 ICC (mean ± 1SD), whereas the control group had 5.76 ± 2.99 ICC (mean ± 1SD).

CONCLUSION

The number of ICC was decreased in the UVJs of the patients with POM compared to the normal control group. As dilation of the ureter during fetal life is a common condition and ureteral dilation is often self limiting, we hypothesize that ureteral peristalsis is a maturational event including the maturational development of ICC.

Extracellular matrix degradation and reduced neural density in children with intrinsic ureteropelvic junction obstruction

OBJECTIVES

To investigate the extracellular matrix microenvironment and nerve supply of ureteropelvic junctions (UPJs) in children with intrinsic UPJ obstruction. Congenital UPJ obstruction is the most common cause of neonatal hydronephrosis. Although many studies investigating the molecular changes within this segment have been performed, the underlying mechanisms of UPJ obstruction are still unclear.

METHODS

Specimens were obtained from 21 children with a mean age of 103.2 months undergoing dismembered pyeloplasty. Control samples included 9 archival specimens from age-matched children without any history of urologic disease. Paraffin-embedded sections were immunostained to detect matrix metalloproteinase 2 (MMP-2), tenascin C (TN-C), and S-100 (for the neuronal supply). Expression patterns were investigated using semiquantitative high-power field magnification analyses, and the MMP-2 and TN-C immunoreactivity were scored. Differences between the 2 groups were examined statistically.

RESULTS

All UPJ specimens displayed a resolved muscular coat and replacement of smooth muscle cells by connective tissue. The degree of MMP-2 expression representing matrix turnover was statistically significantly elevated. Similarly, TN-C expression was found to be higher in obstructed specimens. Additionally, the mean S-100 staining was lower than in controls. Although S-100-positive nerve-fibers were more predominant in the adventitia with minimal submucosal and absent intramuscular staining in patient specimens, they were abundant in both adventitia and submucosa with minimal intramuscular staining in the controls.

CONCLUSIONS

In intrinsic UPJ obstruction samples, a dissolved smooth muscular coat and an overexpression of extracellular matrix proteins, together with depleted nerve supply, was demonstrable.

Investigation of histopathologic changes in the ureter walls in vesicoureteral reflux

PURPOSE

This study aimed to determine the histopathologic changes in ureteral walls (UWs) in children with vesicoureteral reflux (VUR).

METHODS

Twenty ureteral specimens taken from children were divided into 2 groups, refluxing (R) and control (C) groups, each containing 10 specimens. Wall thickness of the ureter, tunica muscularis of the ureter, mucosal thickness of the ureter (uroepithelium), collagen thickness of the ureter, mucosal change, and inflammation were evaluated in resected distal UWs in children with VUR.

RESULTS

The mean wall thickness of the ureter, mean tunica muscularis of the ureter, and mean uroepithelium values of the UWs in the R group were not significantly lower compared to those in the C group. Collagen thickness values in the R group were significantly lower than those in the C group.

CONCLUSIONS

Our data suggest that wall thickness (tunica muscularis and uroepithelium) was not significantly decreased, but collagen thickness of the ureter was decreased in the UWs of children with VUR.

Investigation of histopathologic changes in the ureter walls in experimental congenital obstructive uropathy

BACKGROUND/PURPOSE

The aim of this study is to determine the histopathologic changes in the ureter wall in experimental urinary bladder hypoplasia and agenesis.

METHODS

Timed pregnant rats were randomly divided and received intraperitoneal Adriamycin (ADR) at 2 mg/kg on gestational days (GD) 6 to 9 (ADR group) and saline at 2 mL/kg on GD 6 to 9 (SF group). The control (C) group did not receive any medication in their pregnancy. Fetuses were harvested near term on GD 21 and dissected under a dissecting microscope and examined for urinary system abnormalities.

RESULTS

Diameter of ureter lumen was significantly increased, but wall thickness, tunica muscularis, and epithelial thickness of the ureter were decreased in the ADR group as compared with the C and SF groups.

CONCLUSIONS

Diameter of the ureter lumen was increased, but wall thickness, tunica muscularis, and uroepithelium of the ureter were decreased in the ADR group in the intrauterine period. The diameter of the ureter lumen and wall thickness of ureter (tunica muscularis of ureter and uroepithelium) were increased following obstructive uropathy after the birth.

Upper urinary tract dilatation: prenatal diagnosis, management and outcome

Upper urinary tract dilatation is one of the most common abnormalities detected on prenatal ultrasound scanning. It is commonly due to transient urine flow impairment (UFI) at the level of the pelvi-ureteric and vesico-ureteric junctions, which improves with time in most cases. It is usually in the neonatal period that the diagnosis is confirmed and during the first 18 months of life that the prognosis of the dilatation is defined.

Myocyte Apoptosis in Primary Obstructive Megaureters: The Role of Decreased Vascular and Neural Supply

PURPOSE

We compared myocyte apoptosis index, microvessel density and nerve supply as well as muscular and collagen composition in the obstructed ureteral endings of children with primary obstructive megaureter and normal controls.

MATERIALS AND METHODS

Tissue specimens were obtained during ureteral reimplantation in 16 patients with primary obstructive megaureter. For the control group normal ureteral endings were taken at autopsy from 19 age and sex matched children. In all specimens we determined the myocyte apoptosis index, number of CD31 positive microvessels, alpha-actin positive muscular component and number of nerve terminals. The collagen fibers were also specifically stained.

RESULTS

The myocyte apoptosis index was higher in obstructed vesicoureteral junctions (10.14%+/-1.03%) compared to controls (2.11%+/-0.21%, p<0.001). Mean number of vascular elements per microscopic field was lower in ureteral endings of patients with obstructive megaureter compared to controls (p<0.001). The number of nerve endings was also significantly lower in obstructed ureteral endings. There was a negative correlation between the number of microvessels and myocyte apoptosis index in both study groups. In obstructed megaureters the number of nerve endings was also negatively correlated with myocyte apoptosis index but positively correlated with the number of microvessels. In obstructed vesicoureteral junctions the proportion of muscular component was lower and the proportion of collagen fibers was higher compared to normal controls. Positive correlation was found between the myocyte apoptosis index and the percentage of collagenous component in both study groups.

CONCLUSIONS

Congenital defective vascular development may result in myocyte apoptosis, and reduction of neural elements and muscular components in obstructed vesicoureteral junctions. Subsequent substitution of connective tissue may lead to functional obstruction in primary obstructive megaureter.

Bilateral megaureters in the Adriamycin rat model

Congenital obstructive uropathy is associated with significant morbidity and mortality in the human neonate. The pathophysiology of congenital obstructive uropathy is poorly understood. There are very few experimental models of prenatal obstruction of the urinary tract, except in the fetal lamb or inbred rats. Prenatal exposure to Adriamycin in a rat model leads to a spectrum of malformations including urinary tract anomalies. We hypothesized that Adriamycin administration during a particular time frame could yield a high incidence of urinary tract anomalies and therefore designed this study to investigate the rates of urinary tract anomalies at different windows of Adriamycin injection in rat embryos. Adriamycin (1.75 mg/kg) was administered intraperitoneally to pregnant rats at different times from days 6 to 10 of gestation. Control animals were given saline. Embryos recovered on gestational day 21 by cesarean section were examined for urinary tract anomalies, and malformations were noted. Sections were then processed for paraffin embedding, sectioned at 5 mum, and stained with hematoxylin and eosin for histological examination. Anomalies of the urinary tract occurred maximally following Adriamycin administration on days 7, 8, and 9 of gestation (91.6%) compared with 16% of controls. The most common urinary tract anomaly in the Adriamycin group was bilateral megaureters with a hypoplastic bladder (81%). Other anomalies included unilateral or bilateral ureterohydronephrosis with a normal-sized bladder, duplex kidney, and unilateral or bilateral renal agenesis. In conclusion, the critical embryologic window for the development of bilateral megaureters with a small bladder in the Adriamycin rat model occurs following Adriamycin administration on gestational days 7-9. This simple experimental model of bilateral megaureter may allow further research into the pathophysiology of this condition.

RESULTS OF TAPERED URETERAL REIMPLANTATION FOR PRIMARY MEGAURETER: EXTRAVESICAL VERSUS INTRAVESICAL APPROACH

PURPOSE

Extravesical ureteroneocystostomy is an accepted technique for the surgical treatment of vesicoureteral reflux. However, many surgeons continue to use an intravesical technique when extensive ureteral tailoring is required in the case of primary megaureter. We present our experience and outcomes with these techniques.

MATERIALS AND METHODS

A retrospective cohort study was performed of all patients who underwent tapered ureteral reimplantation between 1990 and 2002. Patient demographics, surgical technique and outcomes were recorded. Patients with ureteral dilatation secondary to bladder or urethral pathology were excluded from study. A successful postoperative outcome was defined as improved hydronephrosis and no vesicoureteral reflux.

RESULTS

A total of 53 patients with 65 megaureters were identified. Mean patient age at surgery was 4.9 years and mean followup was 3.8 years. Primary obstructive megaureter was present in 31 renal units, while refluxing megaureter was present in 34. An excisional tapering technique was performed in all cases. An extravesical reimplantation was performed in 29 renal units and an intravesical reimplantation in 36. The success rate was 86% for intravesical and 76% for extravesical reimplantation. The success rate was 90% for obstructive megaureters and 74% for refluxing megaureters. Success rate for patients with voiding dysfunction was 93% with an intravesical approach but only 50% with an extravesical approach.

CONCLUSIONS

Extensive ureteral tailoring with an extravesical ureteral reimplantation may be performed safely and effectively for primary obstructive megaureter. Patients with voiding dysfunction or preoperative vesicoureteral reflux may benefit from an intravesical ureteral reimplantation.

Anomalies of the distal ureter, bladder, and urethra in children: embryologic, radiologic, and pathologic features

Congenital anomalies of the lower urinary tract are a significant cause of morbidity in infancy. Radiologic investigation is an important source of clinical information in lower urinary tract disorders but should not inconvenience the patient, expose the patient to unnecessary radiation, or delay surgical correction. In pediatric patients with suspected underlying urologic structural anomalies, screening ultrasonography is commonly the initial diagnostic study. If dilatation of the urinary tract is confirmed, voiding cystourethrography is performed to determine the presence of vesicoureteral reflux (VUR) and other causes of upper tract dilatation. If VUR is confirmed, follow-up with nuclear cystography or echo-enhanced cystosonography may be performed. If VUR is excluded, nuclear diuresis renography is the primary test for differentiating between obstructed and nonobstructed megaureter. Intravenous urography can be used to specifically identify an area of obstruction and to determine the presence of duplex collecting systems and a ureterocele. Computed tomography and magnetic resonance (MR) imaging are unsuitable for general screening but provide superb anatomic detail and added diagnostic specificity. MR imaging is mandatory in the evaluation of associated spinal anomalies. MR urography can demonstrate ectopic extravesical ureteric insertions, thereby providing a global view of the malformation. Familiarity with anomalies of the lower urinary tract is essential for correct diagnosis and appropriate management.

A quantitative histologic analysis of collagen subtypes: the primary obstructed and refluxing megaureter of childhood

OBJECTIVES

To analyze and identify collagen subtypes in the primary obstructed and refluxing megaureter of childhood.

METHODS

Anticollagen monoclonal antibodies to collagen types I, III, and IV were used in control ureters (n = 4), obstructed (n = 7), and refluxing (n = 13) megaureters. Additionally, all were stained with Masson's trichrome to further define the extracellular matrix. After staining and serial sectioning, representative ureteral sections, focusing on the muscularis and lamina propria regions, were digitized and analyzed with a color image analysis system.

RESULTS

Immunohistochemical studies demonstrated increases in collagen types I and III for both obstructed and refluxing megaureters compared with controls (P <0.05). Collagen type IV was not detected in statistically significant amounts in any ureter. In control ureters most was type I (83% +/- 9%) collagen. Obstructed megaureters produced similar results with virtually all collagen being type I (84% +/- 26%) with very little type III collagen present, 5.3% +/- 3%. Refluxing megaureters contained only 55% +/- 15% type I collagen. However, there was an increase in type III collagen (16% +/- 4%) versus (4.5% +/- 2%) in controls (P <0.05).

CONCLUSIONS

These data suggest that the greater contribution of type III collagen may play a role in the pathophysiology of refluxing megaureters. Because type III collagen is a less distensible fiber, it may cause an intrinsically stiffer ureter and play a role in the lower surgical success in the reimplantation of refluxing megaureters.

A quantitative histological evaluation of the dilated ureter of childhood. II: Ectopia, posterior urethral valves and the prune belly syndrome

A quantitative histological study was performed on specimens of 33 ureters obtained from 14 male and 19 female patients 5 days to 14 years old (mean age 1.2 years). A high resolution color image video analysis system was used to quantify and compare collagen and smooth muscle components of the muscularis layers to normal control ureters from patients of similar ages. In comparing ureters with ectopia (7), ureters with ectopic ureteroceles (20) and control ureters (4) there was not a statistically different collagen-to-smooth muscle ratio among the groups. In the patients with posterior urethral valves the amount of collagen and smooth muscle was not statistically different from controls (p > 0.01), although the collagen-to-smooth muscle ratio was increased. The 4 patients with the prune belly syndrome had a collagen-to-smooth muscle ratio that was markedly elevated (1.21 versus 0.39) compared with controls. When this group was analyzed as 2 separate groups (obstructed versus refluxing ureters) the difference was more apparent (p < 0.004). Ureters with ectopia or ectopic ureteroceles and ureters associated with posterior urethral valves had similar quantitative amounts of smooth muscle (60%, 56% and 52%, respectively). In patients with the prune belly syndrome obstructed ureters had 65% muscle and refluxing ureters had 38% muscle on evaluation. The percentage of collagen was 33% in ureters with ectopia, 37% in those with ureteroceles and 48% in those associated with posterior urethral valves compared with 23% in controls. In the group with the prune belly syndrome there was 30% collagen in obstructed ureters and 62% collagen in refluxing ureters. Our findings demonstrate that while these dilated ureters had different etiologies the overall quantitative composition of collagen-to-smooth muscle ratios was similar except in refluxing ureters associated with the prune belly syndrome. Our study provides further insight into the pathological nature of such ureters and considerations for surgical repair.