Human - murine concordance of molecular signatures in nerve-sparing murine partial bladder outlet obstruction (NeMO)

Abstract

Recently we demonstrated the utility of a nerve-sparing mid-urethra model of partial outlet obstruction (NeMO) that has high consistency and minimal mortalities, unlike the traditional model proximal to the bladder neck. Our goal was to uncover potential therapeutic targets by investigating the genome wide transcriptional changes and pathways altered in NeMO to compare with published human bladder obstruction data. We performed RNAseq and analysed the differentially upregulated and downregulated genes for associated pathways, transcription factor binding site analysis (TFBS), upstream regulators and Gene Set Enrichment Analysis (GSEA). NeMO increased bladder mass, relative bladder mass and hyperactivity, and decreased voiding efficiency. In NeMO vs. sham, 831 genes were differentially expressed (adjusted p<0.05) and correlated significantly with at least one physiologic parameter. Gene ontology revealed an enrichment for matrix pathways in the upregulated genes, and for cardiac contraction, oxidative phosphorylation and pyruvate metabolism in downregulated genes. TFBS analysis revealed a differential regulation of up vs downregulated genes, with KLF4 strongly associated with the downregulated genes. Downregulated genes of Human bladder obstruction were also associated with the TFBS of KLF4. GSEA of the NeMO gene set confirmed the DAVID results, but also showed a cluster of cytokine activation genes. In human bladder underactive obstruction, cytokines were also highly upregulated. The common cytokine pathway upregulation provided an example of the use of RNAseq for uncovering potential new therapeutic targets. As TNF and the innate immune pathways were strongly implicated in both human and mouse, and TNF is produced by macrophages, we depletion macrophages with clodronate (CL) during NeMO. Although CL did not block hypertrophy, it significantly decreased NeMO-induced hyperactive voiding (p<0.01) and increased voiding efficiency (p<0.05). The expression of several cytokines/chemokines correlated significantly with bladder functional parameters such as residual volumes, and hyperactivity. Conclusions: Gene expression signatures of NeMO were consistent with human bladder obstruction, supporting the use of the nerve-sparing mouse obstruction model for therapeutic exploration.