Gracilis muscle flap with a tissue-engineered lining For experimental bladder wall reconstruction

Objective To assess a pedicled gracilis muscle flap prelaminated with autol ogous, in vitro-expanded urothelial cells to reconstruct an entire supratri gonal bladder-wall defect in rats. Materials and methods A gracilis muscle flap was harvested from 36 male Wis tar rats, transposed into the abdomen and wrapped around a silicon-block sp ace holder, Urothelial cells were harvested and expanded ex vivo. Cells wer e then suspended in fibrin glue and seeded into the gracilis muscle pocket. One week later this pre-laminated nap was transposed into a surgically cre ated supratrigonal bladder-wall defect. All animals underwent such a pre-la minated gracilis nap bladder reconstruction and were categorized into three experimental groups. All surviving animals with urothelial-culture pre-lam inated gracilis flap bladder reconstruction were killed 12 weeks (group I) later. Control rats had gracilis naps with no cell seeding and treated only with fibrin glue (group 2) or a standard culture medium (group 3) before r econstruction. Results Specimens stained with haematoxylin and eosin, and a specific immun ohistochemical staining (AE(1) and AE(3)-anti-cytokeratin monoclonal antibo dy stain) showed a continuous, multilayered functioning urothelial lining a long the transposed pre-laminated gracilis flap in group 1. All animals in group 1 with an intact urothelial lining on the gracilis muscle survived, i n contrast to most animals in groups 2 and 3, where eight and all 12 animal s died, respectively. The surviving four animals in group 2 had no detectab le urothelial lining. Conclusion Successful urinary reconstruction requires a contractile neo-res ervoir resistant to resorption over time and a stable, protective urothelia l lining. A gracilis muscle flap can be seeded with autologous cultured uro thelial cells suspended in fibrin glue. This pre-laminated flap can be safe ly transposed on its pedicle and be successfully integrated into the remain ing bladder wall, with a urothelial lining and the potential to contract. F urther studies in larger animals, with a urodynamic assessment, are warrant ed to determine if this type of bladder-wall replacement technique is suita ble for urinary reconstruction in humans.