Engineering pedicled vascularized bladder tissue for functional bladder defect repair

An engineered bladder construct that mimics the structural and functional characteristics of native bladder is a promising therapeutic option for bladder substitution. We previously showed that pedicled vascularized smooth muscle tissue fabricated by grafting smooth muscle cell (SMC) sheets onto an axial capsule vascular bed had the potential for reliable bladder reconstruction. In this study, we investigated the feasibility of buccal mucosa graft (BMG) integration with the pedicled vascularized smooth muscle tissue to generate a full-layer pedicled vascularized bladder construct. BMG transplanted onto vascularized smooth muscle tissue showed good survival and developed into a pedicled vascularized bladder construct with full-layer structures, appropriate thickness, abundant vascularization, and effective barrier function. Then the full-thickness bladder defects were, respectively, reconstructed by pedicled capsule tissue (pedicled capsule group), nonpedicled vascularized bladder construct (nonpedicled construct group), and pedicled vascularized bladder construct (pedicled construct group). The picrosirius red (PSR) staining and immunohistochemistry results showed minimal fibrosis, maximal smooth muscle proportion, and high vascular density in the pedicled construct group. A continuous mucosal layer was observed only in the pedicled construct group. Moreover, morphological and functional studies revealed better bladder compliance and good ductility in the pedicled construct group. Overall, these results suggested that the BMG could be well integrated with vascularized smooth muscle tissue and generated a pedicled, fully vascularized, and structurally organized bladder construct, which facilitated structural remodeling and functional recovery and could become an alternative to bladder reconstruction.