Single-staged in vivo co-transplantation of autologous muscular and urothelial micrografts as a composite tissue tube for urogenital reconstruction

Tissue-engineered grafts conventionally rely on resource-intensive ex vivo cellularization. Perioperative autologous micrografting allows for direct single-staged graft cellularization omitting laboratory-based in vitro propagation. For urogenital reconstruction, where a muscular layer may be desirable, co-transplanting muscular and urothelial micrografts has previously shown to inhibit urothelial micrograft expansion. This study aimed to assess the effects of adding muscular micrografts in a separate compartment in a tubular collagen-based urinary graft. Autologous tissue from twelve minipig bladders was used for implanting tubular grafts that were constructed and implanted subcutaneously as a single-staged in vivo procedure. Each animal received four grafts: two containing urothelial micrografts only (urothelial group) and two containing both urothelial and detrusor muscle micrografts (co-transplanted group). Six weeks post-implantation, 74% of the urothelial group and 64% of the co-transplanted tubular grafts demonstrated luminal pancytokeratin-positive epithelium (p = 0.524). Grafts were analyzed histologically and by immunoassays for identification of epithelium (pancytokeratin), differentiated urothelium (uroplakin II), smooth muscle (α-SMA & desmin), inflammation (CD68 & apoptosis assay), and vascularization (CD31+ vessels). No significant differences in cellular markers or epithelization were observed between groups. Our findings indicate that muscular micrografts can be co-transplanted in a separate compartment in a collagen-based tubular graft without inhibiting co-transplanted urothelial micrograft expansion.