Cell-Seeded Acellular Artery for Reconstruction of Long Urethral Defects in a Canine Model

Scaffold-based tissue engineering strategies for urethral repair and reconstruction

Urethral strictures are common in urology; however, the reconstruction of long urethral strictures remains challenging. There are still unavoidable limitations in the clinical application of grafts for urethral injuries, which has facilitated the advancement of urethral tissue engineering. Tissue-engineered urethral scaffolds that combine cells or bioactive factors with a biomaterial to mimic the native microenvironment of the urethra, offer a promising approach to urethral reconstruction. Despite the recent rapid development of tissue engineering materials and techniques, a consensus on the optimal strategy for urethral repair and reconstruction is still lacking. This review aims to collect the achievements of urethral tissue engineering in recent years and to categorize and summarize them to shed new light on their design. Finally, we visualize several important future directions for urethral repair and reconstruction.

The search for an optimal tissue-engineered urethra model for clinical application based on preclinical trials in male animals: A systematic review and meta-analysis

Tissue engineering has emerged as a promising avenue for reconstructive urology, though only a limited number of tissue-engineered urethral constructs have advanced to clinical testing. Presently, there exists a dearth of agreement regarding the most promising constructs deserving of implementation in clinical practice. The objective of this review was to provide a comprehensive analysis of preclinical trials findings of a tissue-engineered urethra and to identify the most promising constructs for future translation into clinical practice. A systematic search of the Pubmed, Scopus, and PMC databases was conducted in accordance with the PRISMA statement. Manuscripts published in English between 2015 and 2022, reporting on the methodology for creating a tissue-engineered urethra, assessing the regenerative potential of the scaffold in a male animal model, and evaluating the clinical and histological outcomes of treatment, were included. A total of 48 manuscripts met the inclusion criteria, with 12 being eligible for meta-analysis. Meta-analysis revealed no significant benefit of any matrix type in terms of complication rates. However, acellular matrices demonstrated significant advantage over cellular matrices in case of no postoperative stricture formation (odds ratio = 0.06 [95% CI 0.01; 0.23], p < 0.01). Among all subgroups (animal models and scaffold types), the usage of acellular matrices resulted in advantageous effects. The meta-regression analysis did not show a significant impact of defect length (β1 = -0.02 [-0.28; 0.23], p = 0.86). We found that decellularized materials may carry less relevance for urethral reconstruction due to unfavorable preclinical outcomes. Natural polymers, used independently or with synthetic materials, resulted in better postoperative outcomes in animals compared to purely synthetic constructs. Acellular scaffolds showed promising outcomes, matching or exceeding cellular constructs. However, more studies are needed to confirm their clinical effectiveness.

The Regenerative Microenvironment of the Tissue Engineering for Urethral Strictures

Urethral stricture caused by various reasons has threatened the quality of life of patients for decades. Traditional reconstruction methods, especially for long-segment injuries, have shown poor outcomes in treating urethral strictures. Tissue engineering for urethral regeneration is an emerging concept in which special designed scaffolds and seed cells are used to promote local urethral regeneration. The scaffolds, seed cells, various factors and the host interact with each other and form the regenerative microenvironment. Among the various interactions involved, vascularization and fibrosis are the most important biological processes during urethral regeneration. Mesenchymal stem cells and induced pluripotent stem cells play special roles in stricture repair and facilitate long-segment urethral regeneration, but they may also induce carcinogenesis and genomic instability during reconstruction. Nevertheless, current technologies, such as genetic engineering, molecular imaging, and exosome extraction, provide us with opportunities to manage seed cell-related regenerative risks. In this review, we described the interactions among seed cells, scaffolds, factors and the host within the regenerative microenvironment, which may help in determining the exact molecular mechanisms involved in urethral stricture regeneration and promoting clinical trials and the application of urethral tissue engineering in patients suffering from urethral stricture.

Cell-Based Therapy for Urethral Regeneration: A Narrative Review and Future Perspectives

Urethral stricture is a common urological disease that seriously affects quality of life. Urethroplasty with grafts is the primary treatment, but the autografts used in clinical practice have unavoidable disadvantages, which have contributed to the development of urethral tissue engineering. Using various types of seed cells in combination with biomaterials to construct a tissue-engineered urethra provides a new treatment method to repair long-segment urethral strictures. To date, various cell types have been explored and applied in the field of urethral regeneration. However, no optimal strategy for the source, selection, and application conditions of the cells is available. This review systematically summarizes the use of various cell types in urethral regeneration and their characteristics in recent years and discusses possible future directions of cell-based therapies.

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.