Tissue engineering: recent advances and review of clinical outcome for urethral strictures

Tissue Engineering for Penile Reconstruction

The penis is a complex organ with a development cycle from the fetal stage to puberty. In addition, it may suffer from either congenital or acquired anomalies. Penile surgical reconstruction has been the center of interest for many researchers but is still challenging due to the complexity of its anatomy and functionality. In this review, penile anatomy, pathologies, and current treatments are described, including surgical techniques and tissue engineering approaches. The self-assembly technique currently applied is emphasized since it is considered promising for an adequate tissue-engineered penile reconstructed substitute.

Injectable Decellularized Extracellular Matrix-Based Bio-Ink with Excellent Biocompatibility for Scarless Urethra Repair

In recent years, decellularized extracellular matrices (dECM) derived from organs have attracted much attention from researchers due to their excellent biocompatibility, capacity to promote cell proliferation and migration, as well as pro-vascularization. However, their inferior mechanical properties, slow cross-linking, weak strengths, and poor supporting properties remain their inevitable challenges. In our study, we fabricated a novel dECM hydrogel with better crosslinking strength and speed, stronger support properties, and better mechanical properties. The hydrogel, which we named gelatin-based dECM powder hydrogel (gelatin-dECM hydrogel), was prepared by mixing dECM microparticles in gelatin solution and adding certain amount of 1-Ethyl-3-(3-dimethyl-aminopropyl-1-carbodiimide) (EDC) and N-hydroxysuccinimide (NHS). We evaluated the utility of this hydrogel by assessing the degradation rate, mechanical properties, and biocompatibility. The results showed that the gelatin-dECM hydrogel has high mechanical properties and biocompatibility and also has the ability to promote cell proliferation and migration. After injection of this hydrogel around the surgical sites of urethras in rabbits, the incorporation of dECM powder was demonstrated to promote angiogenesis as well as scarless repair by histological sections after surgery. The application of this novel hydrogel provides a new perspective for the treatment of post-traumatic urethral stricture.

De- and recellularized urethral reconstruction with autologous buccal mucosal cells implanted in an ovine animal model

OBJECTIVES

Patients with urethral stricture due to any type of trauma, hypospadias or gender dysphoria suffer immensely from impaired capacity to urinate and are in need of a new functional urethra. Tissue engineering with decellularization of a donated organ recellularized with cells from the recipient patient has emerged as a promising alternative of advanced therapy medicinal products. The aim of this pilot study was to develop an ovine model of urethral transplantation and to produce an individualized urethra graft to show proof of function in vivo.

METHODS

Donated urethras from ram abattoir waste were decellularized and further recellularized with autologous buccal mucosa epithelial cells excised from the recipient ram and expanded in vitro. The individualized urethral grafts were implanted by reconstructive surgery in rams replacing 2.5 ± 0.5 cm of the native penile urethra.

RESULTS

After surgery optimization, three ram had the tissue engineered urethra implanted for one month and two out of three showed a partially regenerated epithelium.

CONCLUSIONS

Further adjustments of the model are needed to achieve a satisfactory proof-of-concept; however, we interpret these findings as a proof of principle and a possible path to develop a functional tissue engineered urethral graft with de- and recellularization and regeneration in vivo after transplantation.

Ascorbic Acid 2-Phosphate-Releasing Supercritical Carbon Dioxide-Foamed Poly(L-Lactide-Co-epsilon-Caprolactone) Scaffolds Support Urothelial Cell Growth and Enhance Human Adipose-Derived Stromal Cell Proliferation and Collagen Production

Tissue engineering can provide a novel approach for the reconstruction of large urethral defects, which currently lacks optimal repair methods. Cell-seeded scaffolds aim to prevent urethral stricture and scarring, as effective urothelium and stromal tissue regeneration is important in urethral repair. In this study, the aim was to evaluate the effect of the novel porous ascorbic acid 2-phosphate (A2P)-releasing supercritical carbon dioxide-foamed poly(L-lactide-co-ε-caprolactone) (PLCL) scaffolds (scPLCLA2P) on the viability, proliferation, phenotype maintenance, and collagen production of human urothelial cell (hUC) and human adipose-derived stromal cell (hASC) mono- and cocultures. The scPLCLA2P scaffold supported hUC growth and phenotype both in monoculture and in coculture. In monocultures, the proliferation and collagen production of hASCs were significantly increased on the scPLCLA2P compared to scPLCL scaffolds without A2P, on which the hASCs formed nonproliferating cell clusters. Our findings suggest the A2P-releasing scPLCLA2P to be a promising material for urethral tissue engineering.

Fibrinogen/poly(l-lactide-co-caprolactone) copolymer scaffold: A potent adhesive material for urethral tissue regeneration in urethral injury treatment

Since a scarcity of sufficient grafting materials, several complications can arise after urothelial defect reconstruction surgery, including severe hypospadias. Accordingly, developing alternative therapies, such as urethral restoration via tissue engineering are needed. In the present study, we developed a potent adhesive and repairing material using fibrinogen-poly(l-lactide-co-caprolactone) copolymer (Fib-PLCL) nanofiber scaffold to achieve effective urethral tissue regeneration after seeding with epithelial cells on the surface. The in vitro result found the Fib-PLCL scaffold promoted the attachment and viability of epithelial cells on their surface. The increased expression levels of cytokeratin and actin filaments were observed in Fib-PLCL scaffold than PLCL scaffold. The in vivo urethral injury repairing potential of Fib-PLCL scaffold was evaluated using a rabbit urethral replacement model. In this study, a urethral defect was surgically excised and replaced with the Fib-PLCL and PLCL scaffolds or autograft. As expected, the animals healed well after surgery in the Fib-PLCL scaffold group, and no significant strictures were identified. As expected, the cellularized Fib/PLCL grafts have induced the luminal epithelialization, urethral smooth muscle cell remodelling, and capillary development all at the same time. Histological analysis revealed that the urothelial integrity in the Fib-PLCL group had progressed to that of a normal urothelium, with enhanced urethral tissue development. Based on the results, the present study suggests that the prepared fibrinogen-PLCL scaffold is more appropriate for urethral defect reconstruction.

Urine-Microenvironment-Initiated Composite Hydrogel Patch Reconfiguration Propels Scarless Memory Repair and Reinvigoration of the Urethra

The harsh urine microenvironment (UME), as an inherent hurdle, endangers and renders urethral repair unreachable. Innovatively, the unfavorable UME is utilized as the design source to construct a UME-responsive 3D-printed hydrogel patch for realizing scarless memory repair, wherein laser-excited reactive oxygen species (ROS) production and mechanical strength elevation using chemically crosslinked silicon quantum dots are accessible. Intriguingly, the proposed composite scaffolds can respond to Ca²⁺ in urine, cause structure reconfiguration, and repress swelling to further enhance scaffold stiffness. Systematic experiments validate that ROS birth and unexpected stiffness elevation in such UME-responsive scaffolds can realize scarless memory repair of the urethra in vivo. Comprehensive mechanism explorations uncover that the activations of cell proliferation and collagen-related genes (e.g., MMP-1 and COL3A1) and the dampening of fibrosis-related (e.g., TGF-β/Smad) and mechanosensitive genes (e.g., YAP/TAZ) are responsible for the scarless memory repair of such UME-responsive scaffolds via enhancing collagen deposition, recalling mechanical memory, decreasing fibrosis and inflammation, and accelerating angiogenesis. The design rationales (e.g., UME-initiated structure reconfiguration and antiswelling) can serve as an instructive and general approach for urethra repair.