The change of bladder compliance and morphology post-spinal cord transection at different time points in rats

Abstract

Objective To observe the bladder compliance and morphological changes in rats post-suprasacral spinal cord transection at different time points. Methods Seventy-two female Wistar rats were randomly divided into four groups: group A (sham group of 6 weeks); group B (suprasacral spinal cord transaction group of 6 weeks), group C (sham group of 12 weeks), and group D (suprasacral spinal cord transaction group of 12 weeks). Spinal cord transection at T10 level was done in spinal cord transaction groups, while group A and group C underwent sham operaion. Urodynamics was detected at 6th or 12th week after surgery. The changes of smooth muscle, collagen and elastic fibers ratio in the area of bladder wall were observed by hematoxylin-eosin (HE) staining and Verhoeff-Van Gieson staining. Results The rats in spinal cord transaction groups had motor and voiding dysfunction. The bladder compliance in group B was significantly higher than in group A (P<0.05). The bladder compliance in group D was significantly lower than in group C (P<0.05). The morphologic changes of the bladder wall in spinal cord injury groups, including the muscle fibers arranged at random and the increased collagen were aggravated with time. As compared with group B, the bladder compliance in group D was significantly decreased [(0.046±0.023) ml/cmH2O vs. (0.146±0.107) ml/cmH2O (1 cmH2O=0.098 kPa), P<0.01], the proportion of detrusor cross-sectional area was significant decreased [(46.137±4.085)% vs. (55.260±6.873)%, P<0.01], and the proportion of collagen fibers was significantly increased [(19.757±2.071)% vs. (11.104±1.125)%, P<0.01]. Conclusion The bladder compliance in the T10 spinal cord injury rats was increased first, then decreased. The fibrosis of the bladder wall, especially the proportion of collagen fibers was increased, which might be the pathological basis of the reduced bladder compliance. Key words: Spinal cord injury; Neurogenic bladder; Bladder compliance; Collagen fiber