Objective To study the microstructural change of detrusor muscle and neuromuscular junction (NMJ) after bladder functional reconstruction for atonic bladder caused by medullary cone injury and to discuss the feasibility of bladder functional reconstruction for improving the detrusor muscle degeneration. Methods A total of 104 adult female Sprague-Dawley rats (weighing, 200-250 g) were randomized divided into 3 groups: normal group (n=8), control group (n=48), and experimental group (n=48). No treatment was given in normal group; the medullary cone injury was established by sharp transection of spinal cord at L4, 5 levels in control group; and the anastomosis of bilateral L5 ventral root (VR)-S2 VR and L5 dorsal root (DR)-S2 DR was performed for bladder functional reconstruction after modeling of medullary cone injury in experimental group. After operation, the survival condition of rats was observed. At 3 days and 3 consecutive days before 1, 2, 3, 4, 5, and 6 months after operation, the residual urine volume was measured; at 1, 2, 3, 4, 5, and 6 months after operation, the detrusor muscle was harvested to measure the muscle fiber cross-sectional area by HE staining, to calculate the percentage of connective tissue by Masson trichrome staining, and to observe the ultrastructure of the detrusor muscle and the NMJ by transmission electron microscope (TEM). Results Eleven rats were supplemented because of death after operation. In control group, a significant increase of the residual urine volume was observed with the extension of time (P lt; 0.05); in experimental group, an increase was observed at the first 3 months after operation, and then gradually decreased, showing significant differences between the other time point (P lt; 0.05) except between at 3 days and at 5 months after operation (P gt; 0.05); there was significant difference between control and experimental groups at other each time point (P lt; 0.05) except at 3 days, 1 month, and 2 months (P gt; 0.05). HE staining and Masson trichrome staining indicated that the muscle fibers arranged in disorder with gradually aggravated atrophy and gradually increased connective tissue in control group, while the shape of the detrusor muscle recovered with no increased connective tissue at 4, 5, and 6 months after operation in experimental group; there was significant difference in cross-sectional area of detrusor muscle and percentage of connective tissue between normal group and experimental group, and between normal group and control group at each time point (P lt; 0.05). In control group, the cross-sectional area of detrusor muscle decreased and the percentage of connective tissue increased with the extension of time (P lt; 0.05). In experimental group, the cross-sectional area of detrusor muscle decreased at the first 3 months and then increased, and the percentage of connective tissue increased slowly with the extension of time. There was no significant difference of cross-sectional area of detrusor muscle at the first 3 months between control and experimental groups (P gt; 0.05), but the values in experimental group were significantly higher than those in control group at 4, 5, and 6 months after operation (P lt; 0.05). There were significant differences of the percentage of connective tissue between control and experimental groups at each time point (P lt; 0.05). In control group, the amount of synaptic vesicles decreased in the NMJ with time passing; vacuole like structure was observed in NMJ at 3 months; there was almost no nerve ending at 6 months. In experimental group, the amount of synaptic vesicles decreased at 1 and 3 months after operation, but obviously increased at 6 months. Conclusion The reconstruction of bladder function with L5 nerve roots above the paraplegic plane can effectively inhibit the degeneration of detrusor muscle and improve its microstructural changes after medullary cone injury.
Objective To investigate the rule of the morphological changes of the detrusor muscle and its neuromuscular junction after the medullary cone injury in rats. Methods Forty-eight SDadult rats were divided into 6 groups randomly, each of which was 8. There werenormal control group(group A), 4 weeks group(group B), 6 weeks group(group C), 8 weeks group(group D), 10 weeks group(group E) and 12 weeks group(group F) after the medullary cone injury respectively. The medullary cone injury was completed in the level of L4,5 with a sharp and transsectional way. The HE dyeing of the detrusor muscle was performed firstly to observe the changes of the section areas of muscle fibers. And the electron microscopic samples of the detrusor muscle were made to investigate the rules of the ultrastructructral changes in the detrusor muscle and its neuromuscular junction. Finally, the Masson trichromatic dyeing of the detrusor muscles was performed to calculate the percentages of the smooth muscle and the connective tissue.Results The HE dyeing of the detrusor muscle indicated the section areas of muscle fibers in groups E, F was significantly less than that in group A (P＜0.05). The gradually aggravated ultrastructructral changes of detrusor cells in groups B-F were observed in atonic bladders，such as various shape and size，malalignment, wide separation between musclecells, abundant collagen fibrils and irregular dense structures between individual cells, obvious rough endoplasmic reticulum widen and mitochondrial edema were noted．And the ultrastructructral changes of the neuromuscular junctions manifested that the similar structures in group A and the reduction of the mitochondria and synaptic vesicles was seen in groups B, C and D, the conspicuous degenerative neuromuscular junction and the obvious reduction of the synaptic vesiclesand the mitochondria was observed in group E,and the deteriorative degenerativeneuromuscular junction and the obvious reduction or disappearance of the synaptic vesicles and the mitochondria even to the degenerative corpuscle was noted in group F. The Masson trichromatic dyeing in the detrusor muscles indicated that there were significant differences in the percentage of the connective tissue in the detrusor muscles between groups E,F and group A, and between group E and group F respectively (P＜0.05). Conclusion The irreversible changes of the detrusor muscle and its neuromuscular junction canbe seen in the 10th week after medullary cone injury in rat. And the nerverepairing procedures should be performed before this.