Surgical implantation of avulsed lumbosacral ventral roots promotes restoration of bladder morphology in rats

Injuries to the cauda equina and conus medullaris of the spinal cord commonly result in paraplegia, sensory deficits, neuropathic pain, as well as bladder, bowel, and reproductive dysfunctions. In a recently developed lower motoneuron model for cauda equina injury and repair, we have demonstrated that an acute surgical implantation of avulsed lumbosacral ventral roots into the conus medullaris is neuroprotective, promotes regeneration of efferent spinal cord axons into the implanted roots, and may result in functional reinnervation of the lower urinary tract. Here, we investigated the effects of a bilateral lumbosacral ventral root avulsion (VRA) injury and re-implantation on the morphology of the rat bladder at twelve weeks post-operatively. We demonstrated a VRA-induced overall thinning of the bladder wall, which exhibited reduced thickness of both the lamina propria and smooth muscle. In contrast, the bladder epithelium markedly increased its thickness in the injured series. Quantitative immunohistochemical studies showed a selective increase in CGRP immunoreactivity in the lamina propria after the VRA injury. Interestingly, the injury-induced changes in bladder wall morphology were ameliorated by an acute implantation of the lesioned roots into the conus medullaris. Specifically, bladders of the implanted group showed a partial restoration of the thickness of the lamina propria and epithelium as well as a return of CGRP immunoreactivity to baseline levels in the lamina propria. Our results support the notion that surgical implantation of severed ventral roots into the spinal cord may promote the recovery of a normal morphological phenotype in peripheral end organs.