A scaffold, constructed from a bi-layer silk fibroin skeleton (BSFS) and a bladder acellular matrix hydrogel (BAMH) encapsulated with adipose-derived stem cells (ASCs), was developed for bladder augmentation in a rat model.

The bladder is exposed to constant internal and external mechanical forces due to its deformation and the dynamic environment in which it is placed, which can hamper its repair after an injury. Traditional hydrogel materials have limitations regarding their use in the bladder owing to their poor mechanical and tissue adhesion properties. In this study, a composite hydrogel composed of methacrylate gelatine, methacrylated silk fibroin, and Pluronic F127 diacrylate was developed, which combines the characteristics of natural and synthetic polymers. The mechanical properties of the novel hydrogel, such as stretchability, viscoelasticity, and toughness, were improved by virtue of a particular molecular design strategy whereby covalent and non-covalent bond interactions create a cross-linking effect. In addition, the composite hydrogel has important usability properties; it can be injected in liquid format and rapidly transformed into a gel via photo-initiated crosslinking. This was demonstrated on an isolated porcine bladder where the hydrogel closed arbitrarily-shaped tissue defects within 90 s of its application, verifying its effective bioadhesive and sealing properties. This composite hydrogel has great potential for application in bladder injury repair as a tissue-engineering scaffold.

Previous studies of bladder tissue engineering simply seeded cells onto the surface of the material, which makes the cells lack protection and makes it difficult to face the complex in vivo environment. The gelatin methacryloyl (GelMA) hydrogel possesses outstanding biocompatibility and distinctive photo‐crosslinking characteristics and is capable of offering a suitable three‐dimensional growth environment for cells. This study explored the optimal concentration of GelMA for encapsulating adipose‐derived stem cells (ADSCs) and combined it with bladder acellular matrix (BAM) to create a tissue‐engineered bladder patch. Results indicated that 10% GelMA more effectively promoted ADSCs proliferation and spreading compared to 7.5% and 12.5% concentrations, which can offer a better extracellular matrix environment for cells. BAM performed as an excellent substrate with mechanical properties and stitchability similar to natural tissues. Animal experiments demonstrated that the encapsulated ADSCs in GelMA enhanced patch vascularization in vivo and BAM‐GelMA‐ADSCs tissue‐engineered bladder patch can repair large‐scale bladder defects in beagles and promote bladder tissue regeneration and functional recovery. This photocrosslinking hydrogel‐acellular matrix patch provides a protective semi‐controlled environment for ADSCs, supporting the growth and viability of encapsulated cells in vivo, while being easy to suture and preventing leakage, and has significant clinical potential.

The engineered bladder patch with a three‐layer structure was constructed from a bi‐layer silk fibroin scaffold (BSFS) and a methacrylated bladder acellular matrix hydrogel (BAMMAH) that carried induced vascular endothelial cells (VECs) and induced nerve cells (NCs). The patch was developed for bladder augmentation in a rabbit model. The prepared BSFS combined the rigidity of silk fibroin film with the elasticity of silk fibroin sponge, providing a support framework for the construction of engineered bladder. The synthesized BAMMAH exhibited a rapid gelling property, and 2% BAMMAH showed good rheological properties and an internal pore structure. Immunofluorescent staining and RT‐qPCR confirmed that the induction schemes for adipose‐derived mesenchymal stem cells (ADSCs) differentiation into VECs and NCs were feasible and stable. Immunofluorescence analysis demonstrated that incubation with omentum could promote the regeneration of the vascular network inside the engineered patch with a three‐layer structure (BSFS‐BAMMAH‐ADSCs‐VECs‐NCs). Animal experimental data showed that the engineered patch could promote the regeneration of the bladder wall and the recovery of bladder function. These results confirmed that the constructed engineered bladder patch with a three‐layer structure could regenerate the blood vessel network and neural reinnervation, providing a feasible method to solve the difficulties of vascular network and neural innervation in bladder tissue engineering research.

Congenital malformations, iatrogenic injuries, and acquired diseases of the ureter often lead to structural or functional defects, yet tissue engineering approaches for ureteral repair and reconstruction remain limited. In this study, a photo-crosslinkable bladder acellular matrix (BAMMA) was synthesized from porcine bladder acellular matrix (BAM) through enzymatic digestion and methacrylic anhydride modification. The mechanical and biological properties of GelMA, GelMA/BAMMA, and BAMMA hydrogels were comprehensively characterized, and 3D-bioprinted tubular scaffolds were fabricated using a GelMA/BAMMA hydrogel and adipose-derived mesenchymal stem cells (ADSCs) mixture as the bioink and subsequently embedded in the rat omentum. The GelMA/BAMMA hybrid hydrogel combined the favorable mechanical properties of GelMA with the biological activity of BAMMA, supporting the growth and proliferation of ADSCs. One week after omental embedding, histological and immunohistochemical analyses revealed enhanced tissue remodelling, neovascularization and mitigated local inflammatory response in the ADSC-seeded scaffolds compared with the unseeded controls. These findings demonstrate that ADSC-loaded GelMA/BAMMA bioprinted tubular scaffolds can undergo tissue remodeling and vascularization in a rat omental model, providing a feasible hydrogel bioink for ureteral tissue engineering and a foundation for future research on ureteral repair.

Medical adhesives have been extensively applied for skin wound repair and hemostasis, while the dynamically humid and complex intraperitoneal environment imposes stringent requirements on tissue adhesives. Few studies have reported the application of biological adhesives for bladder defect repair in urological practice. The GSF composite hydrogel adhesive, composed of gelatin methacryloyl (GelMA), silk fibroin methacryloyl (SilMA), and polyether F127 diacrylate (F127DA), was previously fabricated with favorable injectability, appropriate viscosity and superior mechanical toughness. To further confirm the repair efficacy, GSF was characterized in vitro for the adhesive properties and structural stability under dynamically humid conditions. Corresponding in vivo experiments were conducted on rat models with graded bladder rupture and partial bladder defects to further assess the repair performance of GSF. Results showed that GSF hydrogel retained robust interfacial adhesion and intact structural stability for 8 days under dynamically simulated humid intraperitoneal conditions and cyclic urine filling-emptying environments. GSF exhibited rapid bonding capacity and effectively shortened the operation time. Under moderate bladder injury conditions, the wound closure time of the GSF group was only 28.3% of that of the suture group in cystotomy experiment and 34.5% in cystectomy experiment. It achieved satisfactory repair of mild-to-moderate bladder ruptures and partial bladder defects. Postoperative histological and functional evaluations confirmed that GSF hydrogel facilitated bladder structural reconstruction and functional recovery. These findings highlight the significant potential of GSF hydrogel adhesives for repairing and regenerating injured bladders. Future applications of GSF will extend to adhesive repairs of organs within the humidity conditions of the abdominal cavity.