Electrostimulation-Based Decellularized Matrix Bladder Patch Promotes Bladder Repair in Rats.

Bladder tissue engineering offers significant potential for repairing defects resulting from congenital and acquired conditions. However, the effectiveness of engineered grafts is often constrained by insufficient vascularization and neural regeneration. This study utilized four primary biomaterials─gelatin methacryloyl (GelMA), chitin nanocrystals (ChiNC), titanium carbide (MXene), and adipose-derived stem cells (ADSC)─to formulate two types of bioinks, GCM0.2 and GCM0.2-ADSC, in specified proportions. These bioinks were 3D printed onto bladder acellular matrix (BAM) patches to create BAM-GCM0.2 and BAM-GCM0.2-ADSC patches. The BAM-GCM0.2-ADSC patches underwent electrical stimulation to yield GCM0.2-ADSC-ES bladder patches. Employed for the repair of rat bladder defects, these patches were evaluated against a Control group, which underwent partial cystectomy followed by direct suturing. Our findings indicate that the inclusion of ADSC and electrical stimulation significantly enhances the regeneration of rat bladder smooth muscle (from [24.052 ± 2.782] % to [57.380 ± 4.017] %), blood vessels (from [5.326 ± 0.703] % to [12.723 ± 1.440] %), and nerves (from [0.227 ± 0.017] % to [1.369 ± 0.218] %). This research underscores the superior bladder repair capabilities of the GCM0.2-ADSC-ES patch and opens new pathways for bladder defect repair.

A bilayer bioengineered patch with sequential dual-growth factor release to promote vascularization in bladder reconstruction.

Bladder tissue engineering holds promise for addressing bladder defects resulting from congenital or acquired bladder diseases. However, inadequate vascularization significantly impacts the survival and function of engineered tissues after transplantation. Herein, a novel bilayer silk fibroin (BSF) scaffold was fabricated with the capability of vascular endothelial growth factor (VEGF) and platelet derived growth factor-BB (PDGF-BB) sequential release. The outer layer of the scaffold was composed of compact SF film with waterproofness to mimic the serosa of the bladder. The inner layer was constructed of porous SF matrix incorporated with SF microspheres (MS) loaded with VEGF and PDGF-BB. We found that the 5% (w/v) MS-incorporated scaffold exhibited a rapid release of VEGF, whereas the 0.2% (w/v) MS-incorporated scaffold demonstrated a slow and sustained release of PDGF-BB. The BSF scaffold exhibited good biocompatibility and promoted endothelial cell migration, tube formation and enhanced endothelial differentiation of adipose derived stem cells (ADSCs) in vitro. The BSF patch was constructed by seeding ADSCs on the BSF scaffold. After in vivo transplantation, not only could the BSF patch facilitate the regeneration of urothelium and smooth muscle, but more importantly, stimulate the regeneration of blood vessels. This study demonstrated that the BSF patch exhibited excellent vascularization capability in bladder reconstruction and offered a viable functional bioengineered patch for future clinical studies.

Chitin nanocrystal-assisted 3D bioprinting of gelatin methacrylate scaffolds.

In recent years, there has been an increasing focus on the application of hydrogels in tissue engineering. The integration of 3D bioprinting technology has expanded the potential applications of hydrogels. However, few commercially available hydrogels used for 3D biological printing exhibit both excellent biocompatibility and mechanical properties. Gelatin methacrylate (GelMA) has good biocompatibility and is widely used in 3D bioprinting. However, its low mechanical properties limit its use as a standalone bioink for 3D bioprinting. In this work, we designed a biomaterial ink composed of GelMA and chitin nanocrystal (ChiNC). We explored fundamental printing properties of composite bioinks, including rheological properties, porosity, equilibrium swelling rate, mechanical properties, biocompatibility, effects on the secretion of angiogenic factors and fidelity of 3D bioprinting. The results showed that adding 1% (w/v) ChiNC to 10% (w/v) GelMA improved the mechanical properties and printability of the GelMA hydrogels, promoted cell adhesion, proliferation and vascularization and enabled the printing of complex 3D scaffolds. This strategy of incorporating ChiNC to enhance the performance of GelMA biomaterials could potentially be applied to other biomaterials, thereby expanding the range of materials available for use. Furthermore, in combination with 3D bioprinting technology, this approach could be leveraged to bioprint scaffolds with complex structures, further broadening the potential applications in tissue engineering.

Injectable, stretchable, toughened, bioadhesive composite hydrogel for bladder injury repair.

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.

Bladder Acellular Matrix Prepared by a Self-Designed Perfusion System and Adipose-Derived Stem Cells to Promote Bladder Tissue Regeneration.

The bladder patch constructed with the bladder acellular matrix (BAM) and adipose-derived stem cells (ASCs) was incubated with the omentum for bladder reconstruction in a rat model of bladder augmentation cystoplasty. A self-designed perfusion system and five different decellularization protocols were used to prepare the BAM. Finally, an optimal protocol (group C) was screened out by comparing the cell nucleus residue, collagen structure preservation and biologically active components retention of the prepared BAM. ASCs-seeded (BAM-ASCs group) and unseeded BAM (BAM group) were incubated with the omentum for 7 days to promote neovascularization and then perform bladder reconstruction. Hematoxylin and eosin and Masson's trichrome staining indicated that the bladder patches in the BAM-ASCs group could better regenerate the bladder wall structure compared to the BAM group. Moreover, immunofluorescence analyses demonstrated that the ASCs could promote the regeneration of smooth muscle, neurons and blood vessels, and the physiological function (maximal bladder capacity, max pressure prior to voiding and bladder compliance) restoration in the BAM-ASCs group. The results demonstrated that the self-designed perfusion system could quickly and efficiently prepare the whole bladder scaffold and confirmed that the prepared BAM could be used as the scaffold material for functional bladder tissue engineering applications.

Bi-layer silk fibroin skeleton and bladder acellular matrix hydrogel encapsulating adipose-derived stem cells for bladder reconstruction.

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 BSFS, prepared from silk fibroin (SF), had good mechanical properties that allowed it to maintain the scaffold shape and be used for stitching. The prepared BAM was digested by pepsin and the pH was adjusted to harvest the BAMH that provided an extracellular environment for the ASCs. The constructed BSFS-BAMH-ASCs and BSFS-BAMH scaffolds were wrapped in the omentum to promote neovascularization and then used for bladder augmentation; at the same time, a cystotomy was used as the condition for the control group. Histological staining and immunohistochemical analysis confirmed that the omentum incubation could promote scaffold vascularization. Hematoxylin and eosin and Masson's trichrome staining indicated that the BSFS-BAMH-ASCs scaffold regenerated the bladder wall structure. In addition, immunofluorescence analyses confirmed that the ASCs could promote the regeneration of smooth muscle, neurons and blood vessels and the restoration of physiological function. These results demonstrated that the BSFS-BAMH-ASCs may be a promising scaffold for promoting bladder wall regeneration and the restoration of physiological function of the bladder in a rat bladder augmentation model.