Initial Characterization of Exstrophy Bladder Smooth Muscle Cells in Culture

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.

New Insights on the Basic Science of Bladder Exstrophy-epispadias Complex

The exstrophy-epispadias complex is a rare congenital anomaly presenting as a wide spectrum of disorders. The complex nature of this malformation leads to continuous investigations of the basic science concepts behind it. Elucidating these concepts allows one to fully understand the mechanisms behind the disease in order to improve diagnosis, management, and treatment ultimately leading to improvement in patient quality of life. Multiple technological advancements within the last 10 years have been made allowing for new studies to be conducted. Herein, the authors conduct a literature review of studies from 2009 to 2019, considering novel theories regarding the genetics, embryology, bladder, bony pelvis, prostate, and genitalia of patients with bladder exstrophy-epispadias complex.

Functional, histological and molecular characteristics of human exstrophy detrusor

INTRODUCTION

Bladder exstrophy is a congenital anomaly involving foetal exposure and protrusion of the open bladder through an incomplete lower abdominal wall. Techniques to surgically correct exstrophy after birth have greatly improved, but it still presents a major challenge to achieve continence and a good quality of life for patients and their families as the pathophysiology of bladder dysfunction is unknown.

OBJECTIVES

A multimodal approach was used to characterise the histological and biomechanical properties of exstrophy detrusor. These were correlated with myocyte responses to agonists and an evaluation of developmental signalling pathways to evaluate the cause of bladder dysfunction in exstrophy.

STUDY DESIGN

Detrusor muscle specimens were obtained during corrective surgery from four exstrophy groups: neonatal (1-3 days, n = 8), younger children (7 months-5 years, n = 13) and older children (8-14 years, n = 11) undergoing secondary procedures and cloacal exstrophy (16 days-9 years, n = 9); control specimens were obtained from children (3 months-9 years, n = 14) undergoing surgery for other pathologies but with normal bladder function. Five lines of experiments were undertaken: measurement of connective tissue to detrusor muscle ratio, contractile responses to electrical and agonist stimulation; in vitro biomechanical stiffness, intracellular Ca²⁺ responses to contractile agonists and immunohistochemistry for proteins (MMP-7, cyclinD1, β-catenin and c-myc) involved in fibrosis generation. Exstrophy data were compared with those from the control group.

RESULTS

Exstrophy tissue demonstrated reduced smooth muscle compared with connective tissue, reduced contractile responses and greater mechanical stiffness. However, intracellular Ca²⁺ responses to agonists were maintained. These changes were greatest in neonatal and cloacal exstrophy samples and least in those from older paediatric bladders. Immunolabelled MMP-7, β-catenin and c-myc were reduced in exstrophy samples.

DISCUSSION

These results highlight the reality that newborns with exstrophy have significantly reduced compliance and bladder underactivity, which may persist or return to normal values with surgery and age. The primary cause of underactivity is increased connective tissue in relation to detrusor muscle; however, detrusor myocyte function remains normal. Finally, the increase of the smooth muscle content in the paediatric bladder group indicates a remodelling response of the bladder to surgical correction and time. Excess gestational fibrosis is associated with changed expression of key proteins in the Wnt-signalling pathway, a potential aetiological factor and therapeutic target.

CONCLUSION

Results point to connective tissue deposition as the primary pathological process that determines bladder function with normal myocyte function. Future research that reduces connective tissue deposition may lead to improvement in outcomes for these children.

New advances in the pathophysiologic and radiologic basis of the exstrophy spectrum

The exstrophy-epispadias complex is a rare spectrum of anomalies affecting the genitourinary system, anterior abdominal wall, and pelvis. Recent advances in the repair of classic bladder exstrophy (CBE) and cloacal exstrophy (CE) have resulted in significant changes in outcomes of surgical management (including higher continence rate, fewer surgical complications, and better cosmesis) and health-related quality of life in these patients. These noteworthy changes resulted from advances in the pathophysiological and genetic backgrounds of this disease and better radiologic assessment of the three-dimensional anatomy of the bony pelvis and its musculature. A PubMed search was performed with the keyword exstrophy. The resulting literature pertaining to genetics, stem cells, imaging, tissue engineering, epidemiology, and endocrinology was reviewed. The following represents an overview of the advances in basic science understanding and imaging of the exstrophy-epispadias spectrum and discusses their possible and future effects on the management of CBE and CE.