Previously, we have reported that direct injection of single autologous adipose-derived mesenchymal stem cells (AdMSCs) into cryo-injured urethra could restore structure and function. However, major issue with the direct injection of single cells was low survival and retention rates. Therefore, the present study was designed to enhance the therapeutic potential of AdMSCs by delivering it into biofabricated structures.

Adipose tissues harvested from 10-weeks old female New Zealand White rabbits were cultured and labeled with a fluorescent cell linker, PKH26. After the culture, the adherent proliferating cells were seeded into 96-well plates (4×104 cells/well/100μl) to form cell-aggregation called spheroid. The formed spheroids were assembled according to a designed C-type shape by a robotic biofabrication system. The biofabricated structures were perfusion cultured for 7 days. Exposed urethra was sprayed with liquid nitrogen for 20 seconds, and small incision within the frozen region was made. Following, the biofabricated C-type AdMSCs structure was immediately implanted into the incision, and then the incision was closed (n=4). As control, sham operations without the structure were performed in the similar manner (n=4). Two and four weeks after biofabricated AdMSCs structure implantation and sham operation, the urethras were harvested for histological and immunohistological analysis.

Prior to implantation, the cultured cells expressed the mesenchymal cell marker STRO1, but not muscle cell markers, Myoglobin and SMA. At 2 weeks after implantation, the biofabricated AdMSCs C-type structures were survived within the cryo-injured regions. At 4 weeks after implantation, the cells within the implanted structures differentiated into skeletal (Fig. A) or smooth muscle cells (Fig. B). These cells also formed layered muscle structures at the surrounding neighborhood of implanted structure.

Histological investigations showed that there were presences of distinct and regenerated muscle structures at 4 weeks after implantation. Also, the reconstructed skeletal and smooth muscle regions in AdMSCs C-type structures implantation group were more developed than those of sham-operated control group. The implanted PKH26 labeled C-type AdMSCs within the structure were positive for endothelial cell maker antibody, von Willebrand factor (vWF, Fig. C) or nerve cell marker antibody, S100 (Fig. D). In addition, some cells within the implanted structures secreted nerve growth factor (NGF, Fig. E), vascular endothelial growth factor (VEGF, Fig. F).

Our results demonstrated that autologous biofabricated C-type AdMSCs structures might have potential to reconstruct the urethra and treatment of various urethral injuries and dysfunctions by differentiating into skeletal muscle cells, smooth muscle cells, blood vessels, nerve cells and/or secretion of growth factors. Furthermore, spheroids based three-dimensional biofabrication of AdMSCs structures could be the simple and effective strategy of cell delivery for stem cell therapy for reconstruction of the damaged urethra.