Reconstruction Of Atonic Bladder Innervation After Spinal Cord Injury: A Bladder Reflex Arc With Afferent And Efferent Pathways

Thoracolumbar fracture due to spinal cord injury（SCI） is a common clinicaldisease. It can cause atonic bladder for the sacral bladder micturition center injury. Itnot only brings inconvenience to patients’ life, but also the survey data from Hacklershow that25-year mortality in patients with spinal cord injury after injury is49%, inwhich43%of deaths are due to renal failure caused by Neuropathic bladderdysfunction. Regenerative therapy for spinal cord injury is a unsolved problem, whiletreatments like Olfactory ensheathing cell transplantation and stem celltransplantation are not yet available in human for reasons of ethics and usability, andtherefore the reduce of mortality after spinal cord injury focus on the treatment ofNeuropathic bladder dysfunction. Currently, its methods of treatment includemedications, nerve blocking or blockade, electrical stimulation therapy, intermittentcatheterization, urinary diversion surgery, catheterization, pressure voiding method,etc. in which Brindly’s method of sacral anterior root electrostimulation for recoverycontrollability urination of SCI patients achieved clinical success in United States andEurope, but it cannot carry out for reasons of expensive and extensive secondaryinjury. For better treatment of flaccid bladder problems, Stenzl, Carlsson, Sundin, etc.have tried different methods for solving the problem, but failed in clinic. Recently, onthe basis of previous studies, both the “skin-central nervous system-bladder” reflexarc model by Xiao Chuanguo and the “abdominal reflex-spinal cord central-bladder”reflex arc model by Hou Chunlin, have made certain results in the experimental stageand clinical research. They have proven that, after the primary micturition centerinjury, the normal body reflection above injury level can be used to reconstruct theflaccid bladder voiding function.But in a review of the bladder reflex arc, the defect is that it can only rebuilt efferent pathways of bladder voiding, a bladder voiding way similar to trigger point,but cannot repair the sensory afferent pathway. Therefore, one cannot perceive theurine urethral wall stretch stimulus during urination, and will not likewise be able tocomplete autonomy in the role of positive feedback regulation as physiologicalvoiding, it needs a continuous stimulation on the trigger points like skin andabdominal to keep the contraction of the detrusor to complete voiding. The same asintermittent catheterization, timed voiding is needed for bladder filling cannot beperceived, which requires a good compliance of patients. If one do not urination ontime or drink too much causing bladder over-filling exceed500ml, blood supply to thebladder wall and urethra wall, as well as bacterial resistance of bladder endometrialmay be reduced, and many negative consequences like the bladder and urinary tractinfection may be easily caused. More importantly, establishing bladder reflex arcneeds to use the healthy spinal nerves such as L5spinal nerve, which is an importantpart of composition of sciatic nerve. Whether the walking function will be affectedafter the nerve is injured has not been further studied.Thus, we constructed the bladder reflex arc with sensory afferent pathway to cureatonic bladder, and evaluated the functional changes of hind paw after establishing theartificial bladder reflex arc through the catwalk gait analysis.Part one:The CatWalk gait analysis in assessment of functionalchanges of hind paw after establish the artificial bladder reflexarc in SD rats.Objective: To assess the functional changes of hind paw after cut off the L5spinal nerve in SD rats by the CatWalk gait analysis.Methods: There were11male SD rats, of which the right side was theexperimental side, to be cut the ventral root and dorsal root of L5spinal nerve, whilethe left side without any operation.1day post-operative, to verify whether the modelwas successfully constructed by WGA-HRP in3rats, after3months postoperation, toassess the changs of parameters by using CatWalk gait analysis. Results: TheWGA-HRP-labelled motoneurons and fibers were found in posteriorhorn and anterior horn of the exprimental side of L5spinal gray matter, but not foundin left side, the results confirming the model was constructed successfully. Generalparameters, Individual paw parameters and Pain-related gait parameters can berecorded three months postoperative, and there were no statistically significantdifference compared to these parameters of1day pre-operative. However, there werestatistically significant difference in regularity index(RI) and Coupling DiagonalRH�'LF.Conclusion: These results demonstrated only a part of coordination-related gaitparameters can be influenced after cut L5spinal nerve, but the other parameters couldnot be changed. So L5spinal nerve could be used for constructing of a bladder reflexarc.Part two:Reconstruction of atonic bladder innervation afterspinal cord injury: A bladder reflex arc with afferent andefferent pathwaysObjective: To establish a bladder reflex arc equipped with sensory afferentpathway in SD rats and evaluate its effectiveness for treating atonic bladder afterspinal cord injury.Methods:There were twenty-four male SD rats, of which the right side was theexperimental side,. The operative methods of the right side: Microanastomose L5ventral root (VR) to S2VR and the distal ending of S2dorsal root (DR) to theproximal ending of L5peripheral process of dorsal ganglion, which was immediatepostganglionic zone that they weren’t merged as mixed nerve，while the left sidewithout treatment was served as a control side. In order to evaluated the validity of thebladder reflex arc, general observation, electrophysiological study and wheat germagglutinin horseradish peroxidase (WGA-HRP) method were used before and afterthe spinal cord destruction between L6and S4level at three months postoperative.Results: Twenty-one rats survived for3months after the operation, anastomotic nerves were separated successfully only in seven rats. Before and after paraplegia,compound action potentials (CAPs) of plexus vesica and bladder smooth musclecompound muscle action potentials (CMAPs) were recorded. There was nostatistically significant difference by electricity stimulated distal ending of theanastomotic stoma of the right S2DR. Moreover, their curves were similar to thecontrol side and the mean maximum amplitude reached respectively71.9%and82.4%compared to the left side when electricity stimulated the left S2DR beforeparaplegia, while the CAPs and CMAPs were not elicited after paraplegia in controlside. In addition, WGA-HRP labeled cells were observed in L5anterior horn andposterior horn on the experimental side after WGA-HRP injection.Conclusion: Reconstruction of the sensory afferent pathway in bladder reflex arccan make the axonal regeneration of motor and sensory nerves, and then they couldcontact with the anterior and posterior horn of spinal cord through parasympatheticnerves, ultimately reestablish the capability of axoplasmic transportation. Therefore,this treatment may be a prospective one in treating atonic bladder.