Complete Unilateral Ureteral Obstruction in the Fetal Lamb. Part II: Long-Term Outcomes of Renal Tissue Development

Early detection of ureteropelvic junction obstruction in neonates with prenatal diagnosis of renal pelvis dilatation using 1H NMR urinary metabolomics

Renal pelvis dilatation (RPD) is diagnosed in utero on prenatal ultrasonography (US) and can resolve spontaneously. However, isolated RPD can also reflect ureteropelvic junction obstruction (UPJO), which requires surgical treatment to prevent progressive renal deterioration. The diagnosis of UPJO can only be confirmed after birth with repeat US and renal isotope studies. ¹H Nuclear Magnetic Resonance spectroscopy (NMR) was performed on urine of newborns with prenatally diagnosed unilateral RPD and healthy controls to identify specific urinary biomarkers for UPJO. The original combination of EigenMS normalization and sparse partial-least-squares discriminant analysis improved selectivity and sensitivity. In total, 140 urine samples from newborns were processed and 100 metabolites were identified. Correlation network identified discriminant metabolites in lower concentrations in UPJO patients. Two main metabolic pathways appeared to be impaired in patients with UPJO i.e. amino acid and betaine metabolism. In this prospective study, metabolic profiling of urine samples by NMR clearly distinguishes patients who required surgery for UPJO from patients with transient dilatations and controls. This study will pave the way for the use of metabolomics for the diagnosis of prenatal hydronephrosis in clinical routine.

Pathological and sonographic review of early isolated severe lower urinary tract obstruction and implications for prenatal treatment

OBJECTIVE

To identify favorable renal histology in fetuses with early severe lower urinary tract obstruction (LUTO) and determine the best timing and selection criteria for prenatal surgery.

METHODS

This multicenter, retrospective study included male fetuses with severe LUTO which died before 24 weeks of gestation during the period January 2000 to December 2018. Age-matched controls were used as reference standard for renal histology. Prenatal ultrasound features and fetal serum and/or urine β2microglobulin level were retrieved and kidney histology slides (hematein-eosin-safran and α-smooth-muscle-actin (αSMA) immunostaining) were prepared and reviewed. αSMA-positive staining of the blastema is due to its aberrant differentiation into myofibroblastic cells. Cases were sorted into histopathologic groups (favorable or unfavorable) according to the blastema's morphology and αSMA labeling and the data of these groups were compared.

RESULTS

Included in the study were 74 fetuses with a median gestational age at outcome of 17 + 6 (range, 13 + 0 to 23 + 5) weeks. Parenchymal organization was preserved in 48% of the kidneys. A blastema was present in 90% of the kidneys, but it was morphologically normal in only 9% and αSMA-negative in only 1% of them. Most (82%) fetuses had an unfavorable prognosis, and 36% of fetuses died ≤ 18 weeks and had severe renal lesions detected on histology (early unfavorable prognosis). A favorable renal prognosis was associated with an earlier gestational age (P = 0.001). Fetuses with LUTO had a significantly lower number of mature glomeruli (P < 0.001) compared with controls. However, there was no significant difference in the number of glomeruli generations between the early-unfavorable-prognosis group (≤ 18 weeks) and the group with a favorable prognosis (P = 0.19). A comparison of prenatal ultrasound features and biochemical markers between groups could not identify any prenatal selection criteria.

CONCLUSIONS

Before 18 weeks, around 30% of fetuses with severe LUTO still have potential for kidney development. Identification of these cases would enable them to be targeted for prenatal therapy. © 2021 International Society of Ultrasound in Obstetrics and Gynecology.

Quantitative Proteome of Infant Stenotic Ureters Reveals Extracellular Matrix Organization and Oxidative Stress Dysregulation Underlying Ureteropelvic Junction Obstruction

PURPOSE

Ureteropelvic junction obstruction (UPJO) is the most frequent cause of congenital hydronephrosis in child. To better investigate the molecular mechanisms of this pathological process, the stenotic ureter proteome of UPJO in infants is compared with their own normal pre-stenotic segments.

EXPERIMENTAL DESIGN

Data independent acquisition-based proteomics are performed to compare proteome between pre-stenotic and stenotic ureter from nine UPJO infants. Gene ontology analysis, hierarchical cluster analysis, and network interaction are performed to characterize biological functions of significantly altered proteins. Selected significantly altered proteins are validated by western blot on another three UPJO infants.

RESULTS

15 proteins are up-regulated and 33 proteins are down-regulated during stenotic pathology. Significantly altered proteins are involved in decreased extracellular matrix and cytoskeleton organization, increased regulation of oxidative activity, and altered inflammatory associated exocytosis. Significant expression of biglycan, fibulin-1, myosin-10, cytochrome b5 are validated providing possible mechanism in UPJO which could be associated impaired smooth muscle cell, epithelial integrity, and increased oxidative stress. CONCLUSIONS AND CLINICAL RELEVANCE: This study provides molecular evidence of dysregulated extracellular matrix organization, impaired smooth muscle cell, and oxidative stress during UPJO pathology, indicating that biglycan, fibulin-1, myosin-10, cytochrome b5 might reflect the pathology of UPJO.

PAX2 may induce ADAM10 expression in renal tubular epithelial cells and contribute to epithelial-to-mesenchymal transition

Purpose

We sought to investigate the role of PAX2 in renal epithelial-to-mesenchymal transition (EMT), examining the influence of PAX2 on ADAM10 expression during renal EMT and ADAM10 expression in fibrotic kidneys.

Methods

A rat renal tubular epithelial cell line, NRK52E, was transfected with lentivirus carrying PAX2, and E-cadherin and α-SMA expressions were measured. The influence of PAX2 on ADAM10 promoter activity was evaluated using chromatin immunoprecipitation (CHIP) and dual-luciferase reporter assay. We also treated NRK52E with ADAM10-specific over-expression vector and inhibitors and measured E-cadherin and α-SMA expression. In vivo, Wistar rats (n = 36) were subjected to unilateral ureteral obstruction (UUO) (n = 18) or sham surgery (n = 18), with tissues from post-operative day 3, 7, and 14 days examined, and PAX2/ADAM10 activity measured. ADAM10 expression was also assessed in kidneys from patients with chronic kidney disease (CKD).

Results

In NRK52E overexpressing PAX2, ADAM10 and α-SMA levels were increased, while E-cadherin levels were decreased. CHIP and dual-luciferase reporter assay showed that PAX2 directly bound to a specific site within the ADAM10 promoter, and over-expression of PAX2 significantly activated ADAM10 transcription. NRK52E with ADAM10 over-expression also significantly decreased E-cadherin and increased α-SMA levels. In the fibrotic kidneys of rats with UUO, E-cadherin levels were increased and α-SMA levels were decreased, and expression of PAX2 and ADAM10 increased. ADAM10 expression also elevated in the renal tissues of CKD patients.

Conclusions

PAX2 directly increased expression of ADAM10, the presence of which contributed to EMT in renal tubular epithelia and hence plays an important role in renal fibrosis.

Less expression of prohibitin is associated with increased paired box 2 (PAX2) in renal interstitial fibrosis rats

Prohibitin (PHB) and paired box 2 (PAX2) are associated with the development of renal interstitial fibrosis (RIF). This study was performed to investigate whether or not the PHB could regulate the PAX2 gene expression in unilateral ureteral obstruction (UUO) in rats. Eighty Wistar male rats were randomly divided into two groups: sham operation group (SHO) and model group subjected to unilateral ureteral obstruction (GU), n = 40, respectively. The model was established by left ureteral ligation. Renal tissues were collected at 14-day and 28-day after surgery. RIF index, protein expression of PHB, PAX2, transforming growth factor-βl (TGF-β1), α-smooth muscle actin (α-SMA), collagen-IV (Col-IV), fibronectin (FN) or cleaved Caspase-3, and cell apoptosis index in renal interstitium, and mRNA expressions of PHB, PAX2 and TGF-β1 in renal tissue were detected. When compared with those in SHO group, expression of PHB (mRNA and protein) was significantly reduced, and expressions of PAX2 and TGF-β1 (protein and mRNA) were markedly increased in the GU group (each p < 0.01). Protein expressions of α-SMA, Col-IV, FN and cleaved Caspase-3, and RIF index or cell apoptosis index in the GU group were markedly increased when compared with those in the SHO group (each p < 0.01). The protein expression of PHB was negatively correlated with protein expression of PAX2, TGF-β1, α-SMA, Col-IV, FN or cleaved Caspase-3, and RIF index or cell apoptosis index (all p < 0.01). In conclusion, less expression of PHB is associated with increased PAX2 gene expression and RIF index in UUO rats, suggesting that increasing the PHB expression is a potential therapeutic target for prevention of RIF.

Association of PAX2 with cell apoptosis in unilateral ureteral obstruction rats

Renal interstitial fibrosis (RIF) is the final common pathway for chronic kidney disease. Cell apoptosis is a critical detrimental event that leads to renal fibrosis. Paired box 2 (PAX2) plays a major role in the development of the kidney. This study was performed to investigate whether PAX2 was associated with cell apoptosis in the progression of RIF in unilateral ureteral obstruction (UUO) rats. Eighty Wistar male rats were divided into two groups randomly: sham operation group (SHO) and model group subjected to UUO (GU), n = 40, respectively. The model was established by left ureteral ligation. Renal tissues were collected 14 and 28 days after surgery. Protein expressions of PAX2, transforming growth factor-β1 (TGF-β1), α-smooth muscle actin (α-SMA), collagen-IV (Col-IV), fibronectin (FN), and caspase-3 were detected using immunohistochemical analysis; mRNA expression of PAX2 in renal tissue was detected by real-time reverse transcription polymerase chain reaction; and RIF index and cell apoptosis index in renal interstitium were also calculated. When compared with those in the SHO group, expressions of PAX2 (protein and mRNA) were markedly increased in the GU group (each p < 0.01). Protein expressions of TGF-β1, α-SMA, Col-IV, FN, and caspase-3 and RIF index and cell apoptosis index in the GU group were remarkably increased when compared with those in the SHO group (each p < 0.01). The protein expression of PAX2 was positively correlated with the protein expressions of TGF-β1, α-SMA, Col-IV, FN, and caspase-3 and with RIF index and cell apoptosis index (all p < 0.01). The apoptotic cell in our observation was mainly derived from renal tubular epithelial cells. In conclusion, the increased expression of PAX2 is associated with cell apoptosis in the progression of RIF in UUO rats, suggesting that PAX2 is a potentially therapeutic target for prevention of RIF. Tian-Biao Zhou and Yuan-Han Qin wish it to be known that, in their opinion, they should be regarded as joint first authors.

Congenital ureteropelvic junction obstruction: human disease and animal models

Ureteropelvic junction (UPJ) obstruction is the most frequently observed cause of obstructive nephropathy in children. Neonatal and foetal animal models have been developed that mimic closely what is observed in human disease. The purpose of this review is to discuss how obstructive nephropathy alters kidney histology and function and describe the molecular mechanisms involved in the progression of the lesions, including inflammation, proliferation/apoptosis, renin-angiotensin system activation and fibrosis, based on both human and animal data. Also we propose that during obstructive nephropathy, hydrodynamic modifications are early inducers of the tubular lesions, which are potentially at the origin of the pathology. Finally, an important observation in animal models is that relief of obstruction during kidney development has important effects on renal function later in adult life. A major short-coming is the absence of data on the impact of UPJ obstruction on long-term adult renal function to elucidate whether these animal data are also valid in humans.

Prenatal urinary matrix metalloproteinase profiling as a potential diagnostic tool in fetal obstructive uropathy

BACKGROUND/PURPOSE

The diagnostic evaluation, patient stratification, and prenatal counseling for congenital obstructive uropathy remain sub-optimal. Matrix metalloproteinase (MMP) expression profiles are emerging as a valuable diagnostic tool in assorted disease processes. We sought to determine whether congenital obstructive uropathy impacts MMP expression in fetal urine.

METHODS

Fetal lambs (n = 25) were divided in two groups: group I (n = 12) underwent a sham operation and group II (n = 13) underwent creation of a complete urinary tract obstruction. Gelatin zymography panels for 4 MMP species were performed on fetal urine in both groups at comparable times post-operatively. Statistical analysis was by the Fisher's exact test (P < .05).

RESULTS

Overall fetal survival was 80% (20/25). A variety of significant differences in MMP expression between the two groups were identified. The following profiles were present only in obstructed animals: any MMP other than MMP-2 (P = .029), including any MMP other than 63 kDa and 65 kDa (P = .009); 2 or more MMPs excluding MMP-2s (0.029); and 3 or more MMPs (P = .029).

CONCLUSIONS

Limited matrix metalloproteinase expression is present in the urine of normal ovine fetuses. Fetal obstructive uropathy impacts urinary MMP expression in various distinguishable patterns. Prenatal urinary MMP profiling may become a practical and valuable diagnostic tool in the evaluation of congenital obstructive uropathy.

Does intervention in utero preserve the obstructed kidneys of fetal lambs? A histological, cytological, and molecular study

Ureteropelvic junction obstruction is a common cause of end-stage nephropathy in children. Our aim was to investigate whether relief of obstruction in utero can alleviate the development of nephropathy. A silastic tube was tied around the left superior segment ureter to induce unilateral partial ureteral obstruction in 22 fetal sheep at 75- 85 d of gestation. Three weeks later, the tubes were removed to relieve the obstruction in 10 of the 22 lambs. A sham operation was performed on four fetuses (the control). At birth, the lambs were killed, and their kidneys were removed to study the changes in histology, podocytes, and expression of paired-box 2 (PAX2) and VEGF. In the obstructed kidneys, we observed cysts of various sizes in the cortex, fibrosis in the interstitial tissue, much decreased number of glomeruli, severe podocyte foot process fusion, and markedly increased PAX2 and decreased VEGF expressions. However, relief of obstruction preserved the number of glomeruli, significantly increased VEGF expression, reduced fusion of the podocyte foot processes, andrestored expression of PAX2 to some extent. Thus, relief ofobstruction in utero may prevent or attenuate the development ofnephropathy in lambs.

Activated extracellular signal-regulated kinase correlates with cyst formation and transforming growth factor-beta expression in fetal obstructive uropathy

Human renal dysplasia is frequently associated with urinary tract obstruction and the abnormal expression of mitogen-activated protein kinase (MAPK). Here, we determined the renal responses and MAPK expression in developing kidneys that were obstructed in fetal lambs. Kidneys were harvested at various times after obstruction (gestation day 60) through normal term (day 145). Dilation of Bowman's capsule and proximal tubules was seen 2 days after obstruction and involved the whole cortex 18 days later, with numerous cysts present throughout the kidney at term. The proliferation marker Ki-67 and transforming growth factor-beta (TGF-beta) were detected 2 days after obstruction and progressively increased in tubules, cysts, and the interstitium. In control kidneys, p38 was expressed in tubules only during the fetal stage, whereas phosphorylated extracellular signal-regulated kinase (P-ERK) was limited to ureteric buds and collecting ducts at all stages examined. However, Jun-N-terminal kinase (JNK) was absent in the fetal kidney but present in tubules at term. In obstructed kidneys, cyst epithelia were positive for p38 and P-ERK but negative for JNK throughout all stages. These studies show that P-ERK correlated spatially and temporally with Ki-67 and TGF-beta expression, which suggests that ERK may contribute to cyst formation and fibrosis in the obstructed fetal kidney.