Ureteral Reconstruction in Goats Using Tissue-Engineered Templates and Subcutaneous Preimplantation

Gelatin-grafted tubular asymmetric scaffolds promote ureteral regeneration via activation of the integrin/Erk signaling pathway

Introduction: The repair of a diseased ureter is an urgent clinical issue that needs to be solved. A tissue-engineered scaffold for ureteral replacement is currently insufficient due to its incompetent bioactivity, especially in long-segment abnormalities. The primary reason is the failure of urothelialization on scaffolds. Methods: In this work, we investigated the ability of gelatin-grafted tubular scaffold in ureteral repairment and its related biological mechanism. We designed various porous asymmetric poly (L-lactic acid) (PLLA)/poly (L-lactide-co-e-caprolactone) (PLCL) tubes with a thermally induced phase separation (TIPS) method via a change in the ratio of solvents (named PP). To regulate the phenotype of urothelial cells and ureteral reconstruction, gelatin was grafted onto the tubular scaffold using ammonolysis and glutaraldehyde crosslinking (named PP-gel). The in vitro and in vivo experiments were performed to test the biological function and the mechanism of the scaffolds. Results and Discussion: The hydrophilicity of the scaffold significantly increased after gelatin grafting, which promoted the adhesion and proliferation of urothelial cells. Through subcutaneous implantation in rats, PP-gel scaffolds demonstrated good biocompatibility. The in vivo replacement showed that PP-gel could improve urothelium regeneration and maintain renal function after the ureter was replaced with an ∼4 cm-long PP-gel tube using New Zealand rabbits as the experimental animals. The related biologic mechanism of ureteral reconstruction was detected in detail. The gelatin-grafted scaffold upgraded the integrin α6/β4 on the urothelial cell membrane, which phosphorylates the focal adhesion kinase (FAK) and enhances urothelialization via the MAPK/Erk signaling pathway. Conclusion: All these results confirmed that the PP46-gel scaffold is a promising candidate for the constitution of an engineered ureter and to repair long-segment ureteral defects.

Bioengineering solutions for Ureteric disorders: Clinical need, challenges and opportunities

Objectives

To summarise the causes of ureteric damage and the current standard of care, discussing the risks and benefits of available therapeutic options. We then focus on the current and future solutions that can be provided by ureteric bioengineering and provide a description of the ideal characteristics of a bioengineered product.

Methods

We performed a literature search in February 2021 in: Google Scholar, Medline, and Web of Science. Three searches were conducted, investigating: (a) the epidemiology of ureteric pathology, (b) the current standard of care, and (c) the state of the art in ureteric bioengineering.

Results

The most‐common causes of ureteric damage are iatrogenic injury and external trauma. Current approaches to treatment include stent placement or surgical reconstruction. Reconstruction can be done using either urological tissue or segments of the gastrointestinal tract. Limitations include scarring, strictures, and infections. Several bioengineered alternatives have been explored in animal studies, with variations in the choice of scaffold material, cellular seeding populations, and pre‐implantation processing. Natural grafts and hybrid material appear to be associated with superior outcomes. Furthermore, seeding of the scaffold material with stem cells or differentiated urothelial cells allows for better function compared to acellular scaffolds. Some studies have attempted to pre‐implant the graft in the omentum prior to reconstruction, but this has yet to prove any definitive benefits.

Conclusion

There is an unmet clinical need for safer and more effective treatment for ureteric injuries. Urological bioengineering is a promising solution in preclinical studies. However, substantial scientific, logistic, and economic challenges must be addressed to harness its transformative potential in improving outcomes.

Small Ruminants and Its Use in Regenerative Medicine: Recent Works and Future Perspectives

Simple Summary

Small ruminants such as sheep and goats have been increasingly used as animal models due to their dimensions, physiology and anatomy identical to those of humans. Their low costs, ease of accommodation, great longevity and easy handling make them advantageous animals to be used in a wide range of research work. Although there is already a lot of scientific literature describing these species, their use still lacks some standardization. The purpose of this review is to summarize the general principles related to the use of small ruminants as animal models for scientific research.

Abstract

Medical and translational scientific research requires the use of animal models as an initial approach to the study of new therapies and treatments, but when the objective is an exploration of translational potentialities, classical models fail to adequately mimic problems in humans. Among the larger animal models that have been explored more intensely in recent decades, small ruminants, namely sheep and goats, have emerged as excellent options. The main advantages associated to the use of these animals in research works are related to their anatomy and dimensions, larger than conventional laboratory animals, but very similar to those of humans in most physiological systems, in addition to their low maintenance and feeding costs, tendency to be docile, long life expectancies and few ethical complications raised in society. The most obvious disadvantages are the significant differences in some systems such as the gastrointestinal, and the reduced amount of data that limits the comparison between works and the validation of the characterization essays. Despite everything, recently these species have been increasingly used as animal models for diseases in different systems, and the results obtained open doors for their more frequent and advantageous use in the future. The purpose of this review is to summarize the general principles related to the use of small ruminants as animal models, with a focus on regenerative medicine, to group the most relevant works and results published recently and to highlight the potentials for the near future in medical research.

Electrospinning: Application and Prospects for Urologic Tissue Engineering

Functional disorders and injuries of urinary bladder, urethra, and ureter may necessitate the application of urologic reconstructive surgeries to recover normal urine passage, prevent progressive damages of these organs and upstream structures, and improve the quality of life of patients. Reconstructive surgeries are generally very invasive procedures that utilize autologous tissues. In addition to imperfect functional outcomes, these procedures are associated with significant complications owing to long-term contact of urine with unspecific tissues, donor site morbidity, and lack of sufficient tissue for vast reconstructions. Thanks to the extensive advancements in tissue engineering strategies, reconstruction of the diseased urologic organs through tissue engineering have provided promising vistas during the last two decades. Several biomaterials and fabrication methods have been utilized for reconstruction of the urinary tract in animal models and human subjects; however, limited success has been reported, which inspires the application of new methods and biomaterials. Electrospinning is the primary method for the production of nanofibers from a broad array of natural and synthetic biomaterials. The biomimetic structure of electrospun scaffolds provides an ECM-like matrix that can modulate cells' function. In addition, electrospinning is a versatile technique for the incorporation of drugs, biomolecules, and living cells into the constructed scaffolds. This method can also be integrated with other fabrication procedures to achieve hybrid smart constructs with improved performance. Herein, we reviewed the application and outcomes of electrospun scaffolds in tissue engineering of bladder, urethra, and ureter. First, we presented the current status of tissue engineering in each organ, then reviewed electrospun scaffolds from the simplest to the most intricate designs, and summarized the outcomes of preclinical (animal) studies in this area.

Onlay Repair Technique for the Management of Ureteral Strictures: A Comprehensive Review

Ureteroplasty using onlay grafts or flaps emerged as an innovative procedure for the management of proximal and midureteral strictures. Autologous grafts or flaps used commonly in ureteroplasty include the oral mucosae, bladder mucosae, ileal mucosae, and appendiceal mucosae. Oral mucosa grafts, especially buccal mucosa grafts (BMGs), have gained wide acceptance as a graft choice for ureteroplasty. The reported length of BMG ureteroplasty ranged from 1.5 to 11 cm with success rates of 71.4%-100%. However, several studies have demonstrated that ureteroplasty using lingual mucosa grafts yields better recipient site outcomes and fewer donor site complications than that using BMGs. In addition, there is no essential difference in the efficacy and complication rates of BMG ureteroplasty using an anterior approach or a posterior approach. Intestinal graft or flap ureteroplasty was also reported. And the reported length of ileal or appendiceal flap ureteroplasty ranged from 1 to 8 cm with success rates of 75%-100%. Moreover, the bladder mucosa, renal pelvis wall, and penile/preputial skin have also been reported to be used for ureteroplasty and have achieved satisfactory outcomes, but each graft or flap has unique advantages and potential problems. Tissue engineering-based ureteroplasty through the implantation of patched scaffolds, such as the small intestine submucosa, with or without cell seeding, has induced successful ureteral regeneration structurally close to that of the native ureter and has resulted in good functional outcomes in animal models.