Tissue engineering for urinary tract reconstruction and repair: Progress and prospect in China

An update on alternative therapy for Escherichia coli causing urinary tract infections; a narrative review

BACKGROUND

Urinary tract infections (UTIs) are the most common type of nosocomial infection and severe health issues because of the difficulties and frequent recurrence. Today, alternative methods such as sonodynamic therapy (SDT), photodynamic therapy (PDT) and herbal materials use for treating infections like UTI in many countries.

METHOD

We conducted searches of the biomedical databases (Google Scholar, Scopus, PubMed, and Web of sciences) to identify related studies from 2008 to 2023.

RESULT

SDT aims to use ultrasound to activate a sonosensitizer, which causes a biological effect by raising reactive oxygen species (ROS). When bacteria are exposed to ROS, several important effects occur: oxidative damage, DNA damage, protein dysfunction etc. SDT with herbal medicine significantly reduced the number of colony-forming units and bactericidal activity for Klebsiella pneumonia and E. coli. PDT is a promising treatment for cancer and microbial infections, combining a photosensitiser, light and tissue molecular oxygen. It involves a photosensitizer, light source, and oxygen, with variations affecting microbial binding and bactericidal activity. Factors affecting antibacterial properties include plant type, growing conditions, harvesting, and processing. This review highlights the recent advancements in sonodynamic, photodynamic, herbal, and bio-material-based approaches in the treatment of E. coli infections.

CONCLUSIONS

These alternative therapies offer exciting prospects for addressing UTIs, especially in cases where traditional antibiotic treatments may be less effective. Further research and clinical studies are warranted to fully explore the potential of these innovative treatment modalities in combating UTIs and improving patient outcomes.

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.

Tailor-made natural and synthetic grafts for precise urethral reconstruction

Injuries to the urethra can be caused by malformations, trauma, inflammation, or carcinoma, and reconstruction of the injured urethra is still a significant challenge in clinical urology. Implanting grafts for urethroplasty and end-to-end anastomosis are typical clinical interventions for urethral injury. However, complications and high recurrence rates remain unsatisfactory. To address this, urethral tissue engineering provides a promising modality for urethral repair. Additionally, developing tailor-made biomimetic natural and synthetic grafts is of great significance for urethral reconstruction. In this work, tailor-made biomimetic natural and synthetic grafts are divided into scaffold-free and scaffolded grafts according to their structures, and the influence of different graft structures on urethral reconstruction is discussed. In addition, future development and potential clinical application strategies of future urethral reconstruction grafts are predicted.

Electrospun PLGA and PLGA/gelatin scaffolds for tubularized urethral replacement: Studies in vitro and in vivo

To investigate the biocompatibility of polylactic acid-glycolic acid copolymer (PLGA) and PLGA/gelatin scaffolds and their suitability for tubular urethral replacement in a canine model. PLGA and PLGA/gelatin scaffolds was constructed by electrospinning. Microstructural differences between the scaffolds was examined by Scanning electron microscopy (SEM) followed by mechanical properties testing. Biocompatibility of the material was evaluated using SEM 4, 8, 12 and 72 h after PLGA and PLGA/gelatin scaffolds co-culture with urothelial cells. And confocal analysis was also used to showed the cell adhesive and growth at 12 h. Approximately 2 cm of the anterior urethra of twelve dogs were removed and replaced with a scaffold. After the surgery for 1 month performed urethrography and for 3 month perform hematoxylin-eosin (H&E) and Masson. The results indicated that PLGA and PLGA/gelatin scaffolds had a void microfilament structure, similar to that of normal acellular matrix tissue. And the tensile strength was decreased whereas the tensile deformation and suture retention strength was increased in PLGA/gelatin scaffolds compared to that in PLGA scaffolds Urothelial cells grew well on both scaffolds. Postoperatively, animals recovered well and urinated spontaneously. However, urethrography showed varying degrees of urethral strictures in the reconstructed urethras. H&E and Masson showed that multilayer urothelial cells were formed in both the proximal and distal segments of the reconstructed urethras but without continuity. There was a small amount of smooth muscle and blood vessels under the epithelium, but regenerative urothelial cells at the midpoint of the reconstructed segment did not continue. Lots of lymphocyte infiltration was observed under the epithelium, some collagen tissue was deposited under the neo-urethral epithelium were observed. In conclusion, PLGA and PLGA/gelatin scaffolds are not suitable for tubularized urethral replacement in the canine model.

Analysis of the Physico-Chemical, Mechanical and Biological Properties of Crosslinked Type-I Collagen from Horse Tendon: Towards the Development of Ideal Scaffolding Material for Urethral Regeneration

Urethral stenosis is a pathological condition that consists in the narrowing of the urethral lumen because of the formation of scar tissue. Unfortunately, none of the current surgical approaches represent an optimal solution because of the high stricture recurrence rate. In this context, we preliminarily explored the potential of an insoluble type-I collagen from horse tendon as scaffolding material for the development of innovative devices for the regeneration of injured urethral tracts. Non-porous collagen-based substrates were produced and optimized, in terms of crosslinking density of the macromolecular structure, to either provide mechanical properties compliant with the urinary tract physiological stress and better sustain tissue regeneration. The effect of the adopted crosslinking strategy on the protein integrity and on the substrate physical-chemical, mechanical and biological properties was investigated in comparison with a decellularized matrix from porcine small intestinal submucosa (SIS patch), an extensively used xenograft licensed for clinical use in urology. The optimized production protocols allowed the preservation of the type I collagen native structure and the realization of a substrate with appealing end-use properties. The biological response, preliminarily investigated by immunofluorescence experiments on human adult renal stem/progenitor cells until 28 days, showed the formation of a stem-cell monolayer within 14 days and the onset of spheroids within 28 days. These results suggested the great potential of the collagen-based material for the development of scaffolds for urethral plate regeneration and for in vitro cellular studies.

SARS-CoV-2 and tissue damage: current insights and biomaterial-based therapeutic strategies

The effect of SARS-CoV-2 infection on humanity has gained worldwide attention and importance due to the rapid transmission, lack of treatment options and high mortality rate of the virus. While scientists across the world are searching for vaccines/drugs that can control the spread of the virus and/or reduce the risks associated with infection, patients infected with SARS-CoV-2 have been reported to have tissue/organ damage. With most tissues/organs having limited regenerative potential, interventions that prevent further damage or facilitate healing would be helpful. In the past few decades, biomaterials have gained prominence in the field of tissue engineering, in view of their major role in the regenerative process. Here we describe the effect of SARS-CoV-2 on multiple tissues/organs, and provide evidence for the positive role of biomaterials in aiding tissue repair. These findings are further extrapolated to explore their prospects as a therapeutic platform to address the tissue/organ damage that is frequently observed during this viral outbreak. This study suggests that the biomaterial-based approach could be an effective strategy for regenerating tissues/organs damaged by SARS-CoV-2.

Urine-derived stem/progenitor cells: A focus on their characterization and potential

Cell therapy, i.e., the use of cells to repair an affected tissue or organ, is at the forefront of regenerative and personalized medicine. Among the multiple cell types that have been used for this purpose [including adult stem cells such as mesenchymal stem cells or pluripotent stem cells], urine-derived stem cells (USCs) have aroused interest in the past years. USCs display classical features of mesenchymal stem cells such as differentiation capacity and immunomodulation. Importantly, they have the main advantage of being isolable from one sample of voided urine with a cheap and unpainful procedure, which is broadly applicable, whereas most adult stem cell types require invasive procedure. Moreover, USCs can be differentiated into renal cell types. This is of high interest for renal cell therapy-based regenerative approaches. This review will firstly describe the isolation and characterization of USCs. We will specifically present USC phenotype, which is not an object of consensus in the literature, as well as detail their differentiation capacity. In the second part of this review, we will present and discuss the main applications of USCs. These include use as a substrate to generate human induced pluripotent stem cells, but we will deeply focus on the use of USCs for cell therapy approaches with a detailed analysis depending on the targeted organ or system. Importantly, we will also focus on the applications that rely on the use of USC-derived products such as microvesicles including exosomes, which is a strategy being increasingly employed. In the last section, we will discuss the remaining barriers and challenges in the field of USC-based regenerative medicine.

Keratin - Based materials for biomedical applications

Keratin constitutes the major component of the feather, hair, hooves, horns, and wool represents a group of biological material having high cysteine content (7-13%) as compared to other structural proteins. Keratin -based biomaterials have been investigated extensively over the past few decades due to their intrinsic biological properties and excellent biocompatibility. Unlike other natural polymers such as starch, collagen, chitosan, the complex three-dimensional structure of keratin requires the use of harsh chemical conditions for their dissolution and extraction. The most commonly used methods for keratin extraction are oxidation, reduction, steam explosion, microbial method, microwave irradiation and use of ionic liquids. Keratin -based materials have been used extensively for various biomedical applications such as drug delivery, wound healing, tissue engineering. This review covers the structure, properties, history of keratin research, methods of extraction and some recent advancements related to the use of keratin derived biomaterials in the form of a 3-D scaffold, films, fibers, and hydrogels.

Review of clinical experience on biomaterials and tissue engineering of urinary bladder

PURPOSE

In recent pre-clinical studies, biomaterials and bladder tissue engineering have shown promising outcomes when addressing the need for bladder tissue replacement. To date, multiple clinical experiences have been reported. Herein, we aim to review and summarize the reported clinical experience of biomaterial usage and tissue engineering of the urinary bladder.

METHODS

A systematic literature search was performed on Feb 2019 to identify clinical reports on biomaterials for urinary bladder replacement or augmentation and clinical experiences with bladder tissue engineering. We identified and reviewed human studies using biomaterials and tissue-engineered bladder as bladder substitutes or augmentation implants. The studies were then summarized for each respective procedure indication, technique, follow-up period, outcome, and important findings of the studies.

RESULTS

An extensive literature search identified 25 studies of case reports and case series with a cumulative clinical experience of 222 patients. Various biomaterials and tissue-engineered bladder were used, including plastic/polyethylene mold, preserved dog bladder, gelatine sponge, Japanese paper with Nobecutane, lypholized human dura, bovine pericardium, amniotic membrane, small intestinal mucosa, and bladder tissue engineering with autologous cell-seeded biodegradable scaffolds. However, overall clinical experiences including the outcomes and safety reports were not satisfactory enough to replace enterocystoplasty.

CONCLUSION

To date, several clinical experiences of biomaterials and tissue-engineered bladder have been reported; however, various studies have reported non-satisfactory outcomes. Further technological advancements and a better understanding is needed to advance bladder tissue engineering as a future promising management option for patients requiring bladder drainage.

Ureter tissue engineering with vessel extracellular matrix and differentiated urine-derived stem cells

OBJECTIVE

To assess the possibility of ureter tissue engineering using vessel extracellular matrix (VECM) and differentiated urine-derived stem cells (USCs) in a rabbit model.

METHODS

VECM was prepared by a modified technique. USCs were isolated from human urine samples and cultured with an induction medium for the differentiation of the cells into urothelium and smooth muscle phenotypes. For contractile phenotype conversion, the induced smooth muscle cells were transfected with the miR-199a-5p plasmid. The differentiated cells were seeded onto VECM and cultured under dynamic conditions in vitro for 2 weeks. The graft was tubularized and wrapped by two layers of the omentum of a rabbit for vascularization. Then, the maturated graft was used for ureter reconstruction in vivo.

RESULTS

VECM has microporous structures that allow cell infiltration and exhibit adequate biocompatibility with seeding cells. USCs were isolated and identified by flow cytometry. After induction, the urothelium phenotype gene was confirmed at mRNA and protein levels. With the combined induction by TGF-β1 and miR-199a-5p, the differentiated cells can express the smooth muscle phenotype gene and convert to the contractile phenotype. After seeding cells onto VECM, the induced urothelium cells formed a single epithelial layer, and the induced smooth muscle cells formed a few cell layers during dynamic culture. After 3 weeks of omental maturation, tubular graft was vascularized. At 2 months post ureter reconstruction, histological evaluation showed a clearly layered structure of ureter with multilayered urothelium over the organized smooth muscle tissue.

CONCLUSION

By seeding differentiated USCs onto VECM, a tissue-engineered graft could form multilayered urothelium and organized smooth muscle tissue after ureteral reconstruction in vivo.

STATEMENT OF SIGNIFICANCE

Cell-based tissue engineering offers an alternative technique for urinary tract reconstruction. In this work, we describe a novel strategy for ureter tissue engineering. We modified the techniques of vessel extracellular matrix (VECM) preparation and used a dynamic culture system for seeding cells onto VECM. We found that VECM had the trait of containing VEGF and exhibited blood vessel formation potential. Urine-derived stem cells (USCs) could be differentiated into urothelial cells and functional contractile phenotype smooth muscle cells in vitro. By seeding differentiated USCs onto VECM, a tissue-engineered graft could form multilayered urothelium and organized smooth muscle tissue after ureteral reconstruction in vivo. This strategy might be applied in clinical research for the treatment of long-segment ureteral defect.