Bladder Acellular Matrix Grafts Seeded with Adipose-Derived Stem Cells and Incubated Intraperitoneally Promote the Regeneration of Bladder Smooth Muscle and Nerve in a Rat Model of Bladder Augmentation

The objective of this study was to investigate the feasibility of bladder acellular matrix grafts (BAMGs) seeded with adipose-derived stem cells (ASCs) followed by intraperitoneal incubation for bladder reconstruction in a rat model of bladder augmentation, and to explore the underlying mechanism. Autologous CM-DiI-labeled ASC-seeded (experimental group) and unseeded (control group) BAMGs were incubated in the peritoneum of male rats for 2 weeks and then harvested for bladder augmentation. Histological analysis of the incubated BAMGs revealed numerous cells growing in homogeneous collagen bundles in both groups. In the control BAMGs, these cells were mesenchyme derived, while in the ASC-seeded BAMGs, myofibroblasts and mesothelial cells were found inside and on the surface of the scaffold, respectively. Immunofluorescence analysis demonstrated that some of the myofibroblasts were transdifferentiated from the ASCs after 2 weeks of intraperitoneal incubation. The greater bladder capacity was found in the experimental group than the control group both 4 and 14 weeks postoperatively. Histological analysis revealed that the entire urothelium regenerated well both in the experimental group and the control group without significant difference 4 weeks and 14 weeks postoperatively. From the quantitative data of immunohistochemical and immunofluorescence staining, the smooth muscle cells (SMCs) regenerated significantly better in the experimental group than the control group both 4 weeks and 14 weeks postoperatively. Also significantly more nerve cells were found in the experimental group 14 weeks postoperatively. At 4 weeks postoperatively, the immunofluorescence double staining revealed that some SMCs in the BAMG were transdifferentiated from the implanted ASCs, but no CM-DiI labeling of ASCs was detected 14 weeks postoperatively. Taken together, our results demonstrate that ASC-seeded and peritoneally incubated BAMGs promote not only the morphological regeneration of the bladder smooth muscle and nerve, but also the bladder capacity, which indicates their potential for bladder regeneration.