Tubularized urethral reconstruction using a prevascularized capsular tissue prelaminated with buccal mucosa graft in a rabbit model

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.

Tailor-made natural and synthetic grafts for precise urethral reconstruction

Injuries to the urethra can be caused by malformations, trauma, inflammation, or carcinoma, and reconstruction of the injured urethra is still a significant challenge in clinical urology. Implanting grafts for urethroplasty and end-to-end anastomosis are typical clinical interventions for urethral injury. However, complications and high recurrence rates remain unsatisfactory. To address this, urethral tissue engineering provides a promising modality for urethral repair. Additionally, developing tailor-made biomimetic natural and synthetic grafts is of great significance for urethral reconstruction. In this work, tailor-made biomimetic natural and synthetic grafts are divided into scaffold-free and scaffolded grafts according to their structures, and the influence of different graft structures on urethral reconstruction is discussed. In addition, future development and potential clinical application strategies of future urethral reconstruction grafts are predicted.

AK, Pennisi CP. Quality of Reporting in Preclinical Urethral Tissue Engineering Studies: A Systematic Review to Assess Adherence to the ARRIVE Guidelines

Preclinical research within the area of urethral tissue engineering has not yet been successfully translated into an efficient therapeutic option for patients. This gap could be attributed, in part, to inadequate design and reporting of the studies employing laboratory animals. In this study, a systematic review was conducted to investigate the quality of reporting in preclinical studies utilizing tissue engineering approaches for urethral repair. The scope was on studies performed in rabbits, published between January 2014 and March 2020. Quality assessment of the data was conducted according to the Animal Research: Reporting of in Vivo Experiments (ARRIVE) guidelines by the scoring of a 38-item checklist in different categories. A total of 28 articles that fulfilled the eligibility criteria were included in the study. The range of ARRIVE score was from 0 to 100, taking into consideration having reported the item in question or not. The mean checklist score was 53%. The items that attained the highest scores included the number of animals utilized, the size of control and experimental groups, and the definition of experimental outcomes. The least frequently reported items included the data regarding the experimental procedure, housing and husbandry, determination and justification of the number of animals, and reporting of adverse events. Surprisingly, full disclosure about ethical guidelines and animal protocol approval was missing in 54% of the studies. No paper stated the sample size estimation. Overall, our study found that a large number of studies display inadequate reporting of fundamental information and that the quality of reporting improved marginally over the study period. We encourage a comprehensive implementation of the ARRIVE guidelines in animal studies exploring tissue engineering for urethral repair, not only to facilitate effective translation of preclinical research findings into clinical therapies, but also to ensure compliance with ethical principles and to minimize unnecessary animal studies.

Tissue expander capsule as an induced vascular bed to prefabricate an axial vascularized buccal mucosa-lined flap for tubularized posterior urethral reconstruction: preliminary results in an animal model

Surgical repair of complex posterior urethral disruptions remains one of the most challenging problems in urology. The efficacy of using a tissue expander capsule as an induced vascular bed to prefabricate axial vascularized buccal mucosa-lined flaps for tubularized posterior urethral reconstruction in a rabbit model was tested. The experiments were performed in three stages. First, silicone tissue expanders were inserted into the groin to induce vascularized capsule pouch formation. Next, buccal mucosa grafts were transplanted into the newly formed capsular tissue supplied by axial vessels for buccal mucosa-lined flap prefabrication. Then, circumferential posterior urethral defects were created and repaired with the buccal mucosa graft (Group 1), the capsule flap (Group 2), and the prefabricated capsule buccal mucosa composite flap (Group 3). After surgery, notable contracture of the tubularized buccal mucosa graft was observed in the neourethra, and none of the rabbits in Group 1 maintained a wide urethral caliber. In Group 2, the retrieved neourethra showed little evidence of epithelial lining during the study period, and the lumen caliber was narrowed at the 3-month evaluation. In Group 3, the buccal mucosa formed the lining in the neourethra and maintained a wide urethral caliber for 3 months. The capsule may serve as an induced vascular bed for buccal mucosa-lined flap prefabrication. The prefabricated buccal mucosa-lined flap may serve as a neourethra flap for posterior urethral replacement.

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

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.