Molecular Profiling of Inflammatory Processes in a Mouse Model of IC/BPS: From the Complete Transcriptome to Major Sex-Related Histological Features of the Urinary Bladder

Abstract

Animal models are invaluable in the research of the pathophysiology of interstitial cystitis/bladder pain syndrome (IC/BPS), a chronic aseptic urinary bladder disease of unknown etiology that primarily affects women. Here, a mouse model of IC/BPS was induced with multiple low-dose cyclophosphamide (CYP) applications and thoroughly characterized by RNA sequencing, qPCR, Western blot, and immunolabeling to elucidate key inflammatory processes and sex-dependent differences in the bladder inflammatory response. CYP treatment resulted in the upregulation of inflammatory transcripts such as Ccl8, Eda2r, and Vegfd, which are predominantly involved in innate immunity pathways, recapitulating the crucial findings in the bladder transcriptome of IC/BPS patients. The JAK/STAT signaling pathway was analyzed in detail, and the JAK3/STAT3 interaction was found to be most activated in cells of the bladder urothelium and lamina propria. Sex-based data analysis revealed that cell proliferation was more pronounced in male bladders, while innate immunity and tissue remodeling processes were the most distinctive responses of female bladders to CYP treatment. These processes were also reflected in prominent histological changes in the bladder. The study provides an invaluable reference dataset for preclinical research on IC/BPS and an insight into the sex-specific mechanisms involved in the development of IC/BPS pathology, which may explain the more frequent occurrence of this disease in women.

Sex-Dependent Differences in Blood–Urine Barrier Are Subtle but Significant in Healthy and Chronically Inflamed Mouse Bladders

“…The Kyoto Encyclopedia of Genes and Genomes (KEGG) analysis obtained from our previously published RNA seq data [21] showed minimal differences between the sexes in the enrichment of cell junction-related pathways ('Tight junctions', 'Adherens junctions', 'Gap junctions') after treatment with CYP. However, as shown in Figure 3A, all processes were more enriched (indicated by bubble color) and contained a higher number of genes (indicated by bubble size) in females than in males.…”

“…The mRNA transcriptome data from our previously published study [21] (available in the NCBI Gene Expression Omnibus database (https://www.ncbi.nlm.nih.gov/geo/) with the accession number GSE221783; accessed on 17 March 2023) were used. For the relevant gene sets, the information on Fragments Per Kilobase Million (FPKM) was extracted for each gene.…”

“…We previously demonstrated sex-specific differences in the mouse bladder transcriptome following cyclophosphamide (CYP)-induced bladder inflammation [21]. In the present study, we sought to find out whether sex-dependent differences exist in the urothelial permeability barrier of healthy mice that might contribute to a greater predisposition of females to chronic bladder inflammation.…”