Hypothesis / aims of study
Bladder outlet obstruction (BOO) induces significant organ remodelling accompanied by changes in bladder function. Elderly males with benign prostatic obstruction (BPO) frequently present with detrusor overactivity (DO), which often persists after de-obstruction surgery despite other functional improvements. Assessment of specific molecular alterations could aid diagnosis and optimize timing of treatment. Here for the first time we performed mRNAseq and proteomics in BPO patients with detrusor overactivity (DO) before and after TURP and correlated the mRNA profiles with functional recovery, determined by urodynamics, including persistence or disappearance of DO. Our goal was to investigate the molecular origin of persistent DO in humans with BPO.
Study design, materials and methods
Bladder dome biopsies were collected from controls (n = 5, urolithiasis patients), and patients with BPO (n = 10) during and 3 months after de-obstruction surgery (TUR-P). Bladder function was assessed by urodynamics at both time points, and all patients had urodynamically established BPO (Abrams Griffiths nomogram) with detrusor overactivity before de-obstruction. Total RNA and proteins were isolated from the biopsies, and transcriptomes and proteomes analyzed before and after TURP. Differentially expressed genes (DEGs) and proteins (DEPs) were identified by comparing each group with controls.
Results
Age-matched patients with BPO and DO had similar urodynamic parameters before TURP. Based on urodynamic studies after TUR-P, the DO group was subdivided into “DO-disappeared (DOD)” (n = 5), and “DO-persisted (DOP)” (n = 5) sub-groups. All patients showed urodynamic improvement consistent with de-obstruction. There was a striking difference in DEG profiles and activated pathways between groups before treatment: the DOD group was characterized by a significant up-regulation of genes involved in contractility, proliferation and immune pathways, whereas in the DOP group the pathways related to DNA repair were dysregulated. Specific for DOD were high smooth muscle proliferation and differentiation processes, STAT and ERK signalling.
The bladder contractility index (BCI) was higher in the DOP group before de-obstruction than in DOD group. After TURP, BCI remained unchanged in both groups. In the DOP group dysregulation of gene expression relevant for DNA repair persisted after TURP, and there was no normalization of the related pathways. We observed a significant decrease of poly(ADP-ribose) polymerase 1 (PARP1) protein levels correlated with the resolution of DO after de-obstruction. Similarly, previously elevated CHRNA10, CACNA2D1 genes, encoding regulators of acetylcholine-gated cation-selective channel and calcium current density, potentially relevant for contractility, normalised in DOD group, concomitant with resolution of DO.
Interpretation of results
Significant dysregulation of contractility markers and their normalization when DO resolves indicates a strong myogenic component in the DOD group. Normalization of genes, encoding proteins involved in regulation of extracellular matrix (TGFB2, SPP1, ITGA1, MMP1, ADAMTS4) and muscle-specific signal transduction (GEM, CHRNA10, CACNA2D1) serves as a hallmark of DO resolution. On the other hand, strong and specific dysregulation of proliferative and DNA repair pathways, and chromatin-binding proteins (PRDM11, MSX1, EGFR, ING4) in DOP group points to a more advanced organ remodelling when DO persists after TURP.