Bi-layered Adipose Mesenchymal Cell Sheets Improve Bladder Compliance in Spinal Cord-Injured Rats

To improve bladder compliance in patients with low-compliance bladders, augmentation cystoplasty with the intestinal tract is performed. However, the use of the intestinal tract often leads to serious surgical complications. Tissue engineering technologies have the potential to improve bladder compliance without using the intestinal tract. In this study, we fabricated bi-layered adipose-derived mesenchymal cell (AMC) sheets and then determined whether the bi-layered AMC sheets could improve bladder compliance in rats with spinal cord injury (SCI). The abdominal adipose tissues of green fluorescence protein (GFP)-transfected Sprague-Dawley (SD) rats were harvested, and the attached and proliferating cells on type I collagen were used as AMCs. The AMCs were then cultured on temperature-responsive culture dishes. After reaching over-confluence, the AMCs that maintained cell-cell contacts were detached from the dishes and applied to a gelatin hydrogel sheet. Then, another detached AMC monolayer was accumulated on the AMC monolayer-applied gelatin. Prior to 4 weeks of transplantation, the levels of T8-9 in the spinal cords of recipient SD rats were partially transected. After producing the bi-layered AMC sheets and the rats with SCI, the detrusor muscles of the anterior bladder walls of the rats with SCI were incised, and the bi-layered AMC sheet was patch-transplanted onto the exposed bladder epithelium (n = 8). As a control, the sham operation was performed (n = 7). Four weeks after the transplantation, bladder capacity and bladder compliance in AMC sheet-transplanted SCI rats were significantly higher than those in sham-operated control SCI rats. The smooth muscle layers in AMC sheet-transplanted bladders were significantly larger than those in control bladders. In addition, the collagen fibers in the AMC sheet-transplanted bladders were significantly smaller than those in the control bladders. Some GFP-positive transplanted AMCs differentiated into smooth muscle actin- or desmin-positive cells. Furthermore, GFP-positive cells secreted transforming growth factor-beta 1 or vascular endothelial growth factor. Therefore, this study showed that bi-layered AMC sheets could improve bladder compliance and bladder tissues in SCI rats. Impact Statement To improve bladder compliance, bi-layered adipose-derived mesenchymal cell (AMC) sheets were fabricated and patch-transplanted onto the exposed bladder epithelium of spinal cord-injured (SCI) rats. Four weeks after transplantation, bladder capacity and compliance in sheet-transplanted SCI rats were higher than those in sham-operated control SCI rats. In the sheet-transplanted bladders, the smooth muscle layers were larger, and the collagen fibers were smaller than those in the control bladders. Some transplanted AMCs differentiated into smooth muscle cells. In addition, other AMCs secreted growth factors. Therefore, we concluded that bi-layered AMC sheets could improve bladder compliance.