Epigenetic insights to pediatric uropathology: Celebrating the fundamental biology vision of Tony Khoury.

ABSTRACT

INTRODUCTION: Many pediatric urology conditions affect putatively normal tissues or appear too commonly to be based solely on specific DNA mutations. Understanding epigenetic mechanisms in pediatric urology, therefore, has many implications that can impact cell and tissue responses to settings, such as environmental and hormonal influences on urethral development, uropathogenic infections, obstructive stimuli, all of which originate externally or extracellularly. Indeed, the cell's response to external stimuli is often mediated epigenetically. In this commentary, we highlight work on the critical role that epigenetic machinery, such as DNA methyltransferases (DNMTs), Enhancer of Zeste Polycomb Repressive Complex 2 Subunit (EZH2), and others play in regulating gene expression and cellular functions in three urological contexts. DESIGN: Animal and cellular constructs were used to model clinical pediatric uropathology. The hypertrophy, trabeculation, and fibrosis of the chronically obstructed bladder was explored using smooth muscle cell models employing disorganised vs. normal extracellular matrix (ECM), as well as a new animal model of chronic obstructive bladder disease (COBD) which retains its pathologic features even after bladder de-obstruction. Cell models from human and murine hypospadias or genital tubercles (GT) were used to illustrate developmental responses and epigenetic dependency of key developmental genes. Finally, using bladder urothelial and organoid culture systems, we examined activity of epigenetic machinery in response to non uropathogenic vs. uropathogenic E.coli (UPEC). DNMT and EZH2 expression and function were interrogated in these model systems. RESULTS: Disordered ECM exerted a principal mitogenic and epigenetic role for on bladder smooth muscle both in vitro and in CODB in vivo. Key genes, e.g., BDNF and KCNB2 were under epigenetic regulation in actively evolving obstruction and COBD, though each condition showed distinct epigenetic responses. In models of hypospadias, estrogen strongly dysregulated WNT and Hox expression, which was normalized by epigenetic inhibition. Finally, DNA methylation machinery in the urothelium showed specific activation when challenged by uropathogenic E.coli. Similarly, UPEC induces hypermethylation and downregulation of the growth suppressor p16INK4A. Moreover, host cells exposed to UPEC produced secreted factors inducing epigenetic responses transmissible from one affected cell to another without ongoing bacterial presence. DISCUSSION: Microenvironmental influences altered epigenetic activity in the three described urologic contexts. Considering that many obstructed bladders continue to display abnormal architecture and dysfunction despite relief of obstruction similar to after resection of posterior valves or BPH, the epigenetic mechanisms described highlight novel approaches for understanding the underlying smooth muscle myopathy of this crucial clinical problem. Similarly, there is evidence for an epigenetic basis of xenoestrogen on development of hypospadias, and UTI-induced pan-urothelial alteration of epigenetic marks and propensity for subsequent (recurrent) UTI. The impact of mechanical, hormonal, infectious triggers on genitourinary epigenetic machinery activity invite novel avenues for targeting epigenetic modifications associated with these non-cancer diseases in urology. This includes the use of deactivated CRISPR-based technologies for precise epigenome targeting and editing. Overall, we underscore the importance of understanding epigenetic regulation in pediatric urology for the development of innovative therapeutic and management strategies.