Bladder reconstruction using autologous smooth muscle cell sheets grafted on a pre-vascularized capsule

Abstract

Rationale: Construction of functional vascularized three-dimensional tissues has been a longstanding objective in the field of tissue engineering. The efficacy of using a tissue expander capsule as an induced vascular bed to prefabricate functional vascularized smooth muscle tissue flaps for bladder reconstruction in a rabbit model was tested. Methods: Skin tissue expanders were inserted into the groin to induce vascularized capsule pouch formation. Smooth muscle cells and endothelial progenitor cells were harvested and cocultured to form pre-vascularized smooth muscle cell sheet. Then repeated transplantation of triple-layer cell sheet grafts onto the vascularized capsular tissue was performed at 2-day intervals to prefabricate functional vascularized smooth muscle tissue flaps. Bladder muscular wall defects were created and repaired by six-layer cell sheet graft (sheet only), capsule flap (capsule only) and vascularized capsule prelaminated with smooth muscle cell sheet (sheet plus capsule). The animals were followed for 3 months after implantation and their bladders were explanted serially. Results: Bladder capacity and compliance were maintained in sheet plus capsule group throughout the 3 months. Tissue bath stimulation demonstrated that contractile responses to carbachol and KCl among the three groups revealed a significant difference ( p < 0.05). Histologically, inflammation was evident in the capsule only group at 1 month and fibrosis was observed in sheet only group at 3 months. The vessel density in capsule only and sheet plus capsule group were significantly higher than in the sheet only group at each time point ( p < 0.05). Comparison of the smooth muscle content among the three groups revealed a significant difference ( p < 0.05). Conclusion: These results proved that the capsule may serve as an induced vascular bed for vascularized smooth muscle tissue flap prefabrication. The prefabricated functional vascularized smooth muscle tissue flap has the potential for reliable bladder reconstruction and may create new opportunities for vascularization in 3-D tissue engineering.

Low-intensity pulsed ultrasound enhances angiogenesis in rabbit capsule tissue that acts as a novel vascular bed in vivo

“…7,8 In our previous study, the capsule tissue induced by an expander served as a novel in vivo vascular bed for cultivating smooth muscle cell sheets or buccal mucosa and fabricating vascularized and pedicled constructs that can be successfully used for bladder or urethra reconstruction. [9][10][11][12] However, according to our findings, the vascular density within the capsule tissue was highest 1 week after the full expansion, rapidly declined in the next week, and then tended to remain stable at a relatively low level. 9 This phenomenon may limit the application of the method in multilayered engineered tissues, which usually need a few weeks to stack together and form integrated tissues.…”

“…9 Subsequently, we used the capsule tissue as a vascular bed to cultivate free buccal mucosa grafts or multilayered smooth muscle cell sheets and fabricated pedicled vascularized constructs that can be successfully used for anterior and posterior urethra or bladder reconstruction, respectively. [10][11][12] The results were encouraging since the vascular pedicle continuously provided independent blood supply for the construct. However, we still encountered certain problems in the previous experiments.…”

Engineering pedicled vascularized bladder tissue for functional bladder defect repair

“…In the previous study, we were able to generate cellularized smooth muscle constructs that contain perfusable vascular networks and pedicle, leading to contractile function. 20 In this study, we fabricated full-layer bladder constructs by adding the buccal mucosa onto the pedicled vascularized smooth muscle constructs.…”

“…Although the contractibility of the engineered bladder construct was not examined in this study, it was previously assessed in the vascularized smooth muscle construct. 20 We speculated that integration of the buccal mucosa would not result in significant changes in the contractibility of the vascularized smooth muscle.…”

“…[17][18][19] Recently, we used the capsule vascular bed to cultivate smooth muscle cell (SMC) sheets and fabricate pedicled vascularized smooth muscle constructs for reliable bladder detrusor reconstruction. 20 On this foundation, we intended to generate multilayered constructs for full-thickness bladder reconstruction.…”