Outcome of small intestinal submucosa graft for repair of anterior urethral strictures

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.

Tissue Engineering of the Urethra: From Bench to Bedside

Tissue engineering (TE) is a promising approach for repair/substitution of damaged tissues and organs. Urethral strictures are common and serious health conditions that impair quality of life and may lead to serious organ damage. The search for ideal materials for urethral repair has led to interest of scientists and surgeons in urethral TE. Over the last decades, a significant amount of preclinical studies and considerable progress have been observed. In contrast, urethral TE has made slow progress in clinical practice so far. To address this, we conducted a systematic review of the literature on clinical applications of TE constructs for urethral repair in the last three decades. In summary, the TE approach is promising and effective, but many issues remain that need to be addressed for broader adoption of TE in urethral repair. Better design of trials, better cooperation of research groups and centralization could lead to reduction of costs and slowly proceed to commercialization and routine use of TE products for urethral reconstruction.

Ureteral reconstruction with decellularized small intestinal submucosa matrix for ureteral stricture: A preliminary report of two cases

Objective

To determine the feasibility of decellularized small intestinal submucosa (SIS) matrix in repairing ureteral strictures.

Methods

Two patients with ureteral stenoses underwent ureteral reconstruction with SIS matrix at the Zhejiang Provincial Corps Hospital of Chinese People's Armed Forces between June 2014 and June 2016. The ureteral stenoses were repaired with a semi-tubular SIS matrix and the postoperative recoveries were observed.

Results

Both operations were successfully completed. The average operative time was 90 min and the average length of hospital stay was 15 days. No fevers, incision infections, intestinal obstruction, graft rejection, or other serious complications were noted. After 2 months, ureteroscopic examinations showed that the surfaces of the original patches were covered by mucosa and there were no apparent stenoses in the lumens. The ureteral stents were replaced every 2 months postoperatively and removed 12 months postoperatively. No infections or urinary leakage occurred after removal of the stents. Intravenous urography was performed 6 and 12 months postoperatively. The results showed that the ureters were not obstructed and there was no apparent stenosis at the anastomosis sites. The average follow-up time was >12 months. Long-term follow-up is still ongoing, and computed tomography examinations of the urinary tract have been conducted in the outpatient department of our hospital 1, 3, and 6 months after removal of the double-J stents, suggesting the absence of hydronephrosis. The serum creatinine levels remained stable during the follow-up.

Conclusion

SIS matrix reconstruction is a feasible method to repair ureters stenosis.

Urethra-inspired biomimetic scaffold: A therapeutic strategy to promote angiogenesis for urethral regeneration in a rabbit model

Limited angiogenesis and epithelialization make urethral regeneration using conventional tissue-engineered grafts a great challenge. Consequently, inspired from the native urethra, bacterial cellulose (BC) and bladder acellular matrix (BAM) were combined to design a three dimensional (3D) biomimetic scaffold. The developed BC/BAM scaffold was engineered for accelerating urethral regeneration by enhancing angiogenesis and epithelialization. The BC/BAM scaffold reveals the closest mimic of native urethra in terms of the 3D porous nanofibrous structure and component including collagen, glycosaminoglycans, and intrinsic vascular endothelial growth factor (VEGF). In vitro studies showed that the bioinspired BC/BAM scaffold promoted in vitro angiogenesis by facilitating human umbilical vein endothelial cells (HUVECs) growth, expression of endothelial function related proteins and capillary-like tube formation. Effect of the BC/BAM scaffold on angiogenesis and epithelialization was studied by its implantation in a rabbit urethral defect model for 1 and 3 months. Results demonstrated that the improved blood vessels formation in the urethra-inspired BC/BAM scaffold significantly promoted epithelialization and accelerated urethral regeneration. The urethra-inspired BC/BAM scaffold provides us a new design approach to construct grafts for urethral regeneration. STATEMENT OF SIGNIFICANCE: Findings in urethral regeneration demonstrate that an ideal tissue-engineered urethra should have adequate angiogenesis to support epithelialization for urethral regeneration in vivo. In this study, inspired from the native urethra, a bioinspired bacterial cellulose/bladder acellular matrix (BC/BAM) scaffold was developed to promote angiogenesis and epithelialization. The designed scaffold showed the closest physical structure and component to natural urethra, which is beneficial to angiogenesis and regeneration of urethral epithelium. This is the first time to utilize BC and dissolved BAM to develop biomimetic scaffold in urethral tissue engineering. Our biomimetic strategy on urethra graft design provided enhanced angiogenesis and epithelialization to achieve an accelerated and successful rabbit urethral repair. We believe that our urethra-inspired biomimetic scaffold would provide new insights into the design of urethral tissue engineering grafts.

Staged male genital reconstruction with a local flap and free oral graft: a case report and literature review

Background

Male genital skin loss is a common disease in urology. However, male genital skin loss accompanying a penile urethra defect is rarely reported. Herein, we describe a novel surgical technique using a composite local flap and oral mucosal graft to reconstruct the penis, which may provide a new solution for patients with similar conditions.

Case presentation

A 36-year-old male with a penile urethra defect and a large area of genital skin loss required urethral reconstruction. The meatus had descended to the penoscrotal junction. This procedure was divided into three stages. The first stage of the surgery involved burying the nude penile shaft beneath the skin of the left anteromedial thigh for coverage of the skin defect. The second stage consisted of releasing the penis and expanding the size of the urethral plate for further urethroplasty. The third stage consisted of reconstruction of the anterior urethra 6 months later. Postoperatively, the patient reported satisfactory voiding. The maximal flow rate (MFR) was 22.2 ml/s with no postvoiding residual urine at the 24-month follow-up visit. No edema, infection, hemorrhage, or cicatricial retraction were observed. The patient’s erectile function was satisfactory, and his international index of erectile function-5 score (IIEF-5 score) was 23 at the 24-month follow-up visit. Additionally, the presence of nocturnal penile tumescence demonstrated that he had normal erectile function.

Conclusions

This procedure is an effective surgical option for men with complete foreskin and penile urethra defects. It could also be extended as a treatment strategy when composite local or pedicle transposition flaps and free grafts are needed for specific patients.

A smart bilayered scaffold supporting keratinocytes and muscle cells in micro/nano-scale for urethral reconstruction

Rationale: In urethral tissue engineering, the currently available reconstructive procedures are insufficient due to a lack of appropriate scaffolds that would support the needs of various cell types. To address this problem, we developed a bilayer scaffold comprising a microporous network of silk fibroin (SF) and a nanoporous bacterial cellulose (BC) scaffold and evaluated its feasibility and potential for long-segment urethral regeneration in a dog model. Methods: The freeze-drying and self-assembling method was used to fabricate the bilayer scaffold by stationary cultivation G. xylinus using SF scaffold as a template. The surface morphology, porosity and mechanical properties of all prepared SF-BC scaffolds were characterized using Scanning electron microscopy (SEM), microcomputed tomography and universal testing machine. To further investigate the suitability of the bilayer scaffolds for tissue engineering applications, biocompatibility was assessed using an MTT assay. The cell distribution, viability and morphology were evaluated by seeding epithelial cells and muscle cells on the scaffolds, using the 3D laser scanning confocal microscopy, and SEM. The effects of urethral reconstruction with SF-BC bilayer scaffold was evaluated in dog urethral defect models. Results: Scanning electron microscopy revealed that SF-BC scaffold had a clear bilayer structure. The SF-BC bilayer scaffold is highly porous with a porosity of 85%. The average pore diameter of the porous layer in the bilayer SF-BC composites was 210.2±117.8 μm. Cultures established with lingual keratinocytes and lingual muscle cells confirmed the suitability of the SF-BC structures to support cell adhesion and proliferation. In addition, SEM demonstrated the ability of cells to attach to scaffold surfaces and the biocompatibility of the matrices with cells. At 3 months after implantation, urethra reconstructed with the SF-BC scaffold seeded with keratinocytes and muscle cells displayed superior structure compared to those with only SF-BC scaffold. Principal Conclusion: These results demonstrate that the bilayer SF-BC scaffold may be a promising biomaterial with good biocompatibility for urethral regeneration and could be used for numerous other types of hollow-organ tissue engineering grafts, including vascular, bladder, ureteral, bowel, and intestinal.

Fabrication of Tissue-Engineered Bionic Urethra Using Cell Sheet Technology and Labeling By Ultrasmall Superparamagnetic Iron Oxide for Full-Thickness Urethral Reconstruction

Urethral strictures remain a reconstructive challenge, due to less than satisfactory outcomes and high incidence of stricture recurrence. An “ideal” urethral reconstruction should establish similar architecture and function as the original urethral wall. We fabricated a novel tissue-engineered bionic urethras using cell sheet technology and report their viability in a canine model. Small amounts of oral and adipose tissues were harvested, and adipose-derived stem cells, oral mucosal epithelial cells, and oral mucosal fibroblasts were isolated and used to prepare cell sheets. The cell sheets were hierarchically tubularized to form 3-layer tissue-engineered urethras and labeled by ultrasmall super-paramagnetic iron oxide (USPIO). The constructed tissue-engineered urethras were transplanted subcutaneously for 3 weeks to promote the revascularization and biomechanical strength of the implant. Then, 2 cm length of the tubularized penile urethra was replaced by tissue-engineered bionic urethra. At 3 months of urethral replacement, USPIO-labeled tissue-engineered bionic urethra can be effectively detected by MRI at the transplant site. Histologically, the retrieved bionic urethras still displayed 3 layers, including an epithelial layer, a fibrous layer, and a myoblast layer. Three weeks after subcutaneous transplantation, immunofluorescence analysis showed the density of blood vessels in bionic urethra was significantly increased following the initial establishment of the constructs and was further up-regulated at 3 months after urethral replacement and was close to normal level in urethral tissue. Our study is the first to experimentally demonstrate 3-layer tissue-engineered urethras can be established using cell sheet technology and can promote the regeneration of structural and functional urethras similar to normal urethra.

Graft surgery in extensive urethral stricture disease

Surgical treatment of long urethral stricture disease remains one of the most challenging problems in urology. In recent years there has been continuous discussion with regard to the etiology, location, length, and management of extensive urethral stricture disease. Various tissues such as genital and extragenital skin, buccal mucosa, lingual mucosa, small intestinal submucosa, and bladder mucosa have been proposed for urethral reconstruction. The most frequent questions pertain to the optimal technique for urethroplasty and the optimal graft for substitution urethroplasty, as judged by both patient satisfaction and outcome success. We review the recent literature with respect to any new information on graft urethroplasty for extensive urethral stricture.