The Genomic Architecture of Bladder Exstrophy Epispadias Complex

Exstrophy-epispadias complex: are the kidneys and kidney function spared?

BACKGROUND

Exstrophy-epispadias complex (EEC) is a complex malformation of the lower abdominal wall, bladder, and pelvic floor, which necessitates multiple successive reconstruction procedures. Surgical and infectious complications are frequent. Our aim was to evaluate kidney function in these patients.

METHODS

This cross-sectional study included patients with EEC, followed since birth in a pediatric urology clinic, who underwent nephrological evaluation (blood pressure (BP) measurement and blood and urine chemistries) and imaging studies (urinary tract ultrasound and DMSA kidney scan) during 2017-2020.

RESULTS

Forty-three patients (29 males), median age 9 years (interquartile range 6-19), were included. Eleven (26%) used clean intermittent catheterization (CIC) for bladder drainage. At least one sign of kidney injury was identified in 32 (74%) patients; elevated BP, decreased kidney function (estimated glomerular filtration rate (eGFR) < 90 ml/min/1.73 m2), and proteinuria/albuminuria were detected in 29%, 12%, and 36% of patients, respectively. Urinary tract dilatation (UTD) was found in 13 (37%) ultrasound examinations. Parenchymal kidney defects were suspected in 46% and 61% of ultrasound and DMSA scintigraphy, respectively. UTD was significantly associated with DMSA-proven kidney defects (p = 0.043) and with elevated BP, 39% vs. 20% in those without UTD. Decreased eGFR and elevated BP were less frequent among patients on CIC than among patients who voided spontaneously: 10% vs. 14% and 18% vs. 36%, respectively. Recurrent UTIs/bacteriuria and nephro/cystolithiasis were reported by 44% and 29% patients, respectively.

CONCLUSION

The high rate of signs of kidney injury in pediatric patients with EEC dictates early-onset long-term kidney function monitoring by joint pediatric urological and nephrological teams. A higher resolution version of the Graphical abstract is available as Supplementary information.

Inflammatory Expression Profiles in Bladder Exstrophy Smooth Muscle: Normalization Over Time

OBJECTIVE

To test the hypothesis that phenotypes in bladder exstrophy result from alterations in detrusor smooth muscle cell (SMC) gene expression.

METHODS

We generated primary human bladder smooth muscle cell lines from patients with classic bladder exstrophy (CBE) undergoing newborn closure (n = 6), delayed primary closure (n = 5), augmentation cystoplasty (n = 6), and non-CBE controls (n = 3). Gene expression profiles were then created using RNA sequencing and characterized using gene set enrichment analysis (GSEA).

RESULTS

We identified 308 differentially expressed genes in bladder exstrophy SMC when compared to controls, including 223 upregulated and 85 downregulated genes. Bladder exstrophy muscle cell lines from newborn closure and primary delayed closures shared expression changes in 159 genes. GSEA analysis revealed increased expression in the inflammatory response and alteration of genes for genitourinary development in newborn and delayed closure SMC. However, these changes were absent in SMC from older exstrophy patients after closure.

CONCLUSION

Bladder exstrophy SMC demonstrate gene expression changes in the inflammatory response and genitourinary development. However, gene expression profiles normalized in exstrophy SMC from older patients after closure, suggesting a normalization of exstrophy SMC over time. Our in vitro findings regarding the normalization of exstrophy SMC gene expression following bladder closure suggest that the development of poor detrusor compliance in bladder exstrophy has a complex multifactorial etiology. Taken together, our findings suggest that alterations in SMC gene expression may explain abnormalities in the exstrophy bladder seen prior to and immediately after closure and suggest that surgical closure may allow exstrophy SMC to normalize over time.

Narrowing the chromosome 22q11.2 locus duplicated in bladder exstrophy-epispadias complex

INTRODUCTION

Bladder exstrophy-epispadias complex (BEEC) comprises a spectrum of anterior midline congenital malformations, involving the lower urinary tract. BEEC is usually sporadic, but families with more than one affected member have been reported, and a twin concordance study supported a genetic contribution to pathogenesis. Moreover, diverse chromosomal aberrations have been reported in a small subset of individuals with BEEC. The commonest are 22q11.2 microduplications, identified in approximately 3% of BEEC index cases.

OBJECTIVES

We aimed to refine the chromosome 22q11.2 locus, and to determine whether the encompassed genes are expressed in normal developing and mature human urinary bladders.

RESULTS

Using DNA from an individual with CBE, the 22q11.2 duplicated locus was refined by identification of a maternally inherited 314 kb duplication (chr22:21,147,293-21,461,017), as depicted in this image. Moreover, the eight protein coding genes within the locus were found to be expressed during normal developing and mature bladders. To determine whether duplications in any of these individual genes were associated with CBE, we undertook copy number analyses in 115 individuals with CBE without duplications of the whole locus. No duplications of individual genes were found.

DISCUSSION

The current study has refined the 22q11.2 locus associated with BEEC and has shown that the eight protein coding genes are expressed in human bladders both during antenatal development and postnatally. Nevertheless, the precise biological explanation as to why duplication of the phenocritical region of 22q11 confers increased susceptibility to BEEC remains to be determined. The fact that individuals with CBE without duplications of the whole locus also lacked duplication of any of the individual genes suggests that in individuals with BEEC and duplication of the 22q11.2 locus altered dosage of more than one gene may be important in BEEC etiology.

CONCLUSIONS

The study has refined the 22q11.2 locus associated with BEEC and has shown that the eight protein coding genes within this locus are expressed in human bladders.