| Objective: The aim of this experiment is to establish a stable rat suprasacral spinal transection model of neurogenic bladder. By observing the urodynamic indicators include bladder capacity, detrusor leak point pressure and bladder compliance, measuring the bladder weight change, further morphological analysis of the structure of the bladder wall and the number of ICC-like cells after 6 weeks and 12 weeks of spinal cord transection, we intend to investigate the changes in bladder compliance and pathophysiology in different periods after injury. We also look forward to discovering the involving mechanism of ICC-like cells in the pathogenesis of neurogenic bladder, and providing some experimental basis for further study, especially the pathogenesis of low compliance bladder caused by spinal cord injury.Methods: A total of 72 female Wistar rats(190~210g) were randomly divided into four groups: Group A was sham group of 6 weeks, which had 12 rats. Group B was suprasacral spinal cord transaction group of 6 weeks, which had 24 rats. Group C was sham group of 12 weeks, which had 12 rats. Group D was suprasacral spinal cord transaction group of 6 weeks, which had 24 rats. Spinal cord transection at T10 level was built in group B and group D, while group A and group C underwent sham operaion. The main steps are as follows: the rat was weighed and fixed on board after anesthetized, and then navigated T10 spinal segments, spinal cord was exposed and transected by ophthalmic scalpel. Rat in two sham groups was only exposed T10 spinal cord, and then sutured incision. Urodynamic parameters were detected in 6 weeks(group A and B) or 12 weeks(group C and D) after surgery. Bladders of all groups were weighed after cystometry. We observed the changes of smooth muscle and fibrous connective tissue in the bladder wall and the area change of collagen and elastic fibers by hematoxylin-eosin(HE) staining and Verhoeff-Van Gieson staining. Labeling the bladder wall ICC-LC distribution by Immunofluorescence, and each sample was randomly selected five visions, and the vision photos were analyzed by the image pro6 image processing software, then calculating the average number ofICC-LC in each field, and statistical analysis.Results:1. we successfully established a stable rat suprasacral spinal transection model at T10 level provided the basis for subsequent experiments.2. After 6 weeks of surgery, there were 17 rats survived in the group B. Group A all survived. At 12 weeks, there were 18 rats survived in the group D but one of the rats accompanied with urinary tract infection and bladder stones, was not included in the study. Group C all survived. The urodynamic results showed that the bladder compliance of group B was significantly higher than group A(P<0.05); the bladder compliance of group D was significantly lower compared with group C(P<0.05); the bladder compliance of group D(12 weeks) was significantly lower than group B(6 weeks)(P < 0.01).3.The bladder structure of 6 weeks and 12 weeks spinal cord injury rat had undergone significant change, compared with the corresponding control group. The bladder weight increased(P <0.01); the bladder / weight ratio of the two experimental groups were higher than the same period in each control group(P <0.01).We found that the detrusor hypertrophy after spinal cord injury by the light microscopy, especially in the 12 weeks group, the detrusor muscle disordered, and the infiltration of collagen fibers increased among muscle bundles. The percentage composition of fibrous connective tissue of 12 weeks in the experimental group is more than that in the experimental group of 6 weeks and control group, with statistically significant difference(P <0.01); The percentage composition of fibrous connective tissue of 6 weeks in the experimental group was also higher than that in the control group, there was statistically significant difference(P <0.01). Compared the experimental group of 12 weeks with the experimental group of 6 weeks, the proportion of collagen fibers was significantly increased(P <0.01) but the difference of the proportion of the elastic fiber was not statistically significant(P > 0.05). The average number of ICC-LC under the fluorescence microscope in per field was significantly increased in the experimental group of 12 weeks compared with the control group(P <0.01); the average number of ICC-L in per field in the experimental group of 6 weeks was significantly decreased than the control group(P <0.05).Conclusions:1 We firstly reported that the bladder compliance of the T10 spinal cord injury rats increased at 6 weeks and decreased at 12 weeks.2 The urodynamic performance of the neurogenic bladder caused by spinal cord injury in rats showed that, in the early stage, the maximum capacity of bladder increased, and the bladder compliance also increased, but the increase of the bladder leak point pressure was not obvious; in the late stage, the bladder maximum capacity decreased but still higher than in the control group, and the detrusor leak point pressure significantly increased but the bladder compliance reduced.3 Neurogenic bladder caused by spinal cord injury, the tissue changes of the bladder wall of the rat, including the muscle fibers arranged at random and the increased connective tissue were aggravated with time; the fibrosis of the bladder wall, especially the proportion of collagen fibers might affect the bladder compliance.4 After spinal cord transaction in the rats, the number of the ICC-LC changed obviously at different time points, which may be involved in impacting the changes of the bladder compliance. |
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