GSE123779
RNAseq data of WT and Pparg-ablated mouse urothelium under homeostasis and during regneration
Peroxisome Proliferator-Activated Receptor-gamma (PPARG) is a nuclear hormone receptor that was originally described as a master regulator of adipogenesis but could also promote cellular differentiation in a number of epithelium. PPARG also serves as an important regulator in anti-inflammatory activity after a variety of injuries, acting in part by antagonizing the NF-kB pathway. Moreover, the expression of PPARG is strongly down regulated in the basal subtype of bladder cancer, suggesting that its removal might be essential in tumorigenesis. In urothelial cells, it has been shown that PPARG promotes urothelial differentiation in vitro, but its function in vivo remains unexplored.  The urothelium is a stratified epithelium that serves as a barrier between the urinary tract and blood. It consists of terminally differentiated umbrella cells, intermediate cells which serve as umbrella cell progenitors; and unipotent basal cells. To determine the role of PPARG in vivo, we used Cre-Lox recombination to conditionally delete the Pparg gene in the mouse urothelium using the ShhCre driver, which drives recombination in basal and intermediate cells, and their respective daughters. Interestingly, ShhCre;Ppargfl/fl mutants lack umbrella and intermediate cells, but have an abnormal cell population negative for classical urothelial markers instead. Furthermore, we observed an increase of KRT14+ population in the basal compartment and squamous features in the mutant urothelium. Expression profile analysis suggested PPARG regulates metabolism, urothelial differentiation and innate immune response.  We further challenged the Pparg mutant urothelium with acute injury. In wild type animals, urinary tract infection (UTI) with uropathogenic E.coli results in a transient innate immune response, followed by a completed regernation within 2 weeks. When ShhCre;Ppargfl/fl mutants were challenged with urinary tract infection, the innate immune response was not resolved even after several weeks and the Pparg ablated urothelium exhibited squamous metaplasia. RNAseq data suggested that PPARG plays a role in regulating squmous differentiation and NFkB signial pathway.  Together these findings suggest that PPARG is essential for the normal differentiation of the urothelium and is a potent regulator of the inflammatory response after UTI. Understanding the link between the loss of PPARG, chronic inflammation and tumorigenesis in the urothelium  could shed light on the urothelial differentiation network and pave the way for the development of therapeutic approaches to various urinary diseases. Overall design: Mouse urothelial mRNA profile of adult WT, ShhCre;Pparg (+/-, fl/fl) and K5CreER; Pparg (+/-,fl/fl) mice under homeostasis or during regeneration were generated by RNA sequencing