Intraperitoneal incubation of bladder acellular matrix grafts improves bladder smooth muscle regeneration via neovascularization

The objective of this study was to investigate whether intraperitoneal incubation improves the regenerative capacity of bladder acellular matrix grafts (BAMGs) in a rat model of bladder augmentation. After 2 weeks of incubation in the peritoneum of male rats, BAMG flaps with vascular pedicles were harvested for autologous bladder augmentation. As the control, BAMGs were directly used for bladder augmentation without intraperitoneal incubation. Histological analyses of the incubated BAMGs demonstrated extensive cell growth and vasculature in homogeneous collagen bundles. The cells were positive for vimentin and negative for α-smooth muscle actin and pan-cytokeratin AE1/AE3. Cystography revealed smoother contours of the augmented bladders in the incubated group at 4 and 12 weeks postoperatively. However, the bladder capacity was not significantly different between the two groups. In both groups, the entire urothelium regenerated well without obvious differences. At both time points, compared with the control group, increased numbers of smooth muscle cells (SMCs) and blood vessels were found in the incubated group. At 12 weeks, the SMCs in the incubated group were more similar to those in the native smooth muscle fiber bundles of the bladder. Taken together, our results demonstrated that BAMGs preincubated in the peritoneum promote the regeneration of bladder smooth muscle via neovascularization in a rat bladder augmentation model.