Chronic urinary retention could decrease the number of suburothelial myofibroblasts in the rat bladder

To demonstrate changes in the number of suburothelial myofibroblasts in the rat bladder due to chronic urinary retention (CUR).

Bladder specimens were obtained from 12-week-old Wistar female rats that were divided into two groups: a CUR group and a sham-operated group. In the CUR rats, the urethra was intubated with a polyethylene catheter, and a double 4-0 silk ligature was placed around the proximal urethra, after which the catheter was removed. After 8 weeks, the cystometric findings and immunohistochemical staining of the suburothelial myofibroblasts were compared between the groups.

The bladder weight of the control rats was 0.20 ± 0.01 g and that of CUR rats 1.6 ± 0.4 g. The bladder capacity of the control rats was 0.5 ± 0.3 ml and that of the CUR rats 12.9 ± 3.1 ml. The number of suburothelial myofibroblasts of the control rats was 417 ± 123 and that of the CUR rats 44 ± 42. The number of suburothelial myofibroblasts in the CUR rats was significantly less than that observed in the sham-operated rats (p < 0.01).

In this study, we demonstrated that mechanical stress over a long period on the bladder wall can decrease the number of suburothelial myofibroblasts. The reduced expression of suburothelial myofibroblasts may be related to prolongation of the micturition interval by CUR.