The urothelium contributes to bladder function by communicating with the central nervous system via afferent nerves. We determined whether progressively more extensive decentralization surgeries would increase the frequency of urinary tract infections (UTIs) and if preservation of the urothelium provides defense against microorganisms through reactive oxygen species (ROS)-generating Nox enzymes.

Two groups of female mixed-breed hounds with progressively more extensive pelvic decentralization were studied. In the first group, animals underwent bilateral transection of all dorsal and ventral sacral spinal roots and the hypogastric nerves (N=6). In the second group, animals underwent bilateral transection of all dorsal and ventral sacral spinal roots, the hypogastric nerves and the dorsal root of L7 (N=7). Sham-operated canines (N=6) were used as controls. Urination postures and frequency of UTIs were monitored. Hematoxylin and eosin stain and TUNEL assay were used to assess tissue histopathology and to evaluate apoptotic rate, respectively. Superoxide production in bladder tissue was detected and quantified using Dihydroethidium (DHE) fluorescence and Lucigenin-enhanced chemiluminescence.

Animals with intact L7 afferent bladder innervation showed no evidence of UTIs up to a year after surgery. Of the 7 animals with additional L7 dorsal root transections, 4 consistently showed culture confirmed bacteriuria up to one year after surgery. Bladder tissue of decentralized canines with the additional transected L7 dorsal roots showed increased signs of inflammation and increased rate of apoptosis in the urothelial layer, compared to controls. DHE fluorescence revealed intracellular superoxide production with greatest density in the mucosa layer. Lucigenin assay showed that NADPH-dependent superoxide production levels in bladder mucosa of decentralized animals were decreased, compared to that of sham-operated animals.

The absence of UTIs in animals decentralized by transection of all sacral roots plus hypogastric nerves indicates that removal of the major of sympathetic bladder innervation has no apparent effect on susceptibility to UTIs. Occurrence of UTIs in more than 50% of the animals that underwent additional transection of bladder afferents by including L7 dorsal root transection suggests that elimination of afferent innervation of the bladder predisposes the bladder to UTIs. The increase in the signs of inflammation and apoptotic rate in urothelium of the later group of canines indicates that elimination of afferents to the bladder disrupts the integrity of its urothelial layer. Since animals that showed bacteriuria due to eliminated afferents to their bladders subsequently exhibited lower levels of urothelial superoxide production, compared to controls, we speculate that afferent nerve disruption may impair urothelial function and antibacterial defense mechanisms possibly through loss of cellular stress response and tolerance capacity mediated by ROS.

Afferent–urothelial interactions are essential for the regulation of normal bladder function and its disruption impairs epithelial function in the canines with long-term lower spinal cord injury. Our preliminary results demonstrate that the mechanism by which urothelial dysfunction after decentralization of bladders creates susceptibility to UTIs may involve Nox-driven superoxide redox processes.