Pathophysiological analysis of detrusor overactivity following partial bladder outlet obstruction
Introduction: Detrusor overactivity (DO) following partial bladder outlet obstruction (PBOO) is a common urological condition in humans, with 50-70% patients with PBOO complicated with DO. The pathological mechanisms of DO following PBOO are largely unknown, but inflammatory changes may play a key role. We hypothesized that inflammation is important in the earlier pathophysiological phase before overproduction of oxidative stress in DO following PBOO. Therefore, we investigated the relationships among bladder function, ischemia, oxidative stress and inflammation in DO following PBOO in PBOO model mice. Materials and Methods: C57BL/6J male mice aged 10 to 15 weeks were used in the study. PBOO model mice were created surgically by ligation of the proximal urethra with 5-0 nylon suture under inhalation anesthesia. Sham-operated mice were used as controls. Pathophysiological changes in the bladder at 1, 3 and 5 weeks after creation of the PBOO model mice were compared with those in sham-operated mice using functional, histological, biochemical and immunohistochemical analyses. Results: Functional analysis using a pressure flow study showed increased maximum detrusor pressure at 1 week and DO from 3 to 5 weeks after creation of the PBOO model. Histological analysis using hematoxylin-eosin and Masson-Trichrome staining showed greater invasion of inflammatory cells and fibrosis in PBOO model mice compared with sham-operated mice at 3 and 5 weeks. Inflammatory cells were mainly present in interstitial tissue, and fibrosis gradually infiltrated from interstitial tissue to the muscular layer. Ischemia analysis showed significantly increased HIF-1α in PBOO model mice at all time points. Oxidative stress analysis indicated significantly increased levels of ROS from 1 week and 8-OHdG from 3weeks in PBOO model mice. An inflammation-related proteome assay showed high levels of colony stimulating factor (CSF) family proteins at 1 week and IL-2, IL-3, IL-17A, IL-23, MMP-3, MMP-9 and periostin from 3 to 5 weeks in PBOO model mice. Conclusions: Oxidative stress and inflammatory changes showed contemporaneous increase in pathophysiology of detrusor overactivity following partial bladder outlet obstruction. Especially, CSF family and ROS changes are showed in the early stage, and might be a predict marker in the pathophysiology of DO following PBOO at the early stage.