Schistosoma haematobium egg-induced bladder urothelial abnormalities dependent on p53 are modulated by host sex.

INTRODUCTION AND
OBJECTIVE: The bladder urothelium changes dramatically during Schistosoma haematobium infection (urogenital schistosomiasis). These alterations include hyperplasia, ulceration, dysplasia, squamous metaplasia and frank carcinogenesis. Defining the pathways underpinning these urothelial responses will contribute to a deeper understanding of how S. haematobium egg expulsion, hematuria, and bladder cancer develop in humans. The tumor suppressor gene p53 is of particular interest, given its role in many cancers, including bladder cancer generally and schistosomal bladder cancer specifically.
METHODS: Transgenic mice featuring tamoxifen-inducible Cre recombinase activity in cells expressing the urothelial-specific gene uroplakin-3a (Upk3a-GCE mice) were crossed with either TdTomato-floxed-EGFP reporter or p53-floxed mice. Mice were administered tamoxifen or vehicle control to induce excision of floxed genes. TdTomato-EGFP reporter mice were sacrificed and their bladders harvested, sectioned, and imaged by fluorescence microscopy. p53-floxed mice underwent bladder wall injection with S. haematobium eggs or vehicle controls. Three months later, mice were sacrificed and their bladders subjected to histological analysis (H&E staining).
RESULTS: We first confirmed the phenotypic fidelity of Upk3a-GCE mice by crossing them with TdTomato-floxed-EGFP reporter mice and administering tamoxifen to their progeny. As expected, these progeny switched from TdTomato to EGFP expression in their bladder urothelium. Having confirmed the phenotype of Upk3a-GCE mice, we next crossed them to p53-floxed mice. The resulting progeny were given tamoxifen or vehicle control to render them urothelial p53-haploinsufficient or -intact, respectively. Then, we injected S. haematobium eggs or control vehicle into the bladder walls of these mice. Male p53-intact, egg-injected mice exhibited similar histological changes as their p53-haploinsufficient counterparts, including urothelial hyperplasia and ulceration. In contrast, female p53-intact, egg-injected mice featured no urothelial ulceration, whereas their p53-haploinsufficient counterparts often had significant ulceration.
CONCLUSIONS: Urothelial p53 signaling indeed seems to affect urothelial homeostasis during S. haematobium infection, albeit in a sex-specific manner. Ongoing work seeks to determine whether p53 mediates associated alterations in urothelial cell cycle status and frank carcinogenesis in the setting of urogenital schistosomiasis.