Small intestinal submucosa (SIS) graft urethroplasty: short-term results

Evolution and innovation in urethroplasty: a comprehensive narrative review of graft types and surgical techniques

Urethroplasty has evolved over last decades, with significant improvements in surgical techniques and graft types. In this narrative review, we aimed to explore the evolution of urethroplasty techniques for bulbar urethral strictures. To do this, the review is structured into three main sections: the Historical Background section highlights the seminal contribution from early pioneers to contemporary techniques, which re-gained momentum in reconstructive urology. Starting with the early techniques in the 19th and 20th centuries, we focused on the pioneering innovations of the 1990s, ultimately leading to the most recent tissue-preserving techniques. The second part presents a literature review comparing different graft types and critically evaluating surgical outcomes from multiple original articles and meta-analysis. Specifically, similar success rates were reported for oral and preputial grafts for the treatment of anterior urethral strictures, while long-term outcomes suggest graft deterioration over time. Furthermore, data on optimal surgical techniques remain limited. Lastly, Future Perspectives address ongoing innovations, including new graft and flap combinations for complex strictures, emphasizing the continuous refinement of less invasive, tissue-preserving techniques.

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.

Small intestinal submucosa graft bulbar urethroplasty is a viable technique: results compared to buccal mucosa graft urethroplasty after propensity score matching

PURPOSE

Small intestinal submucosa (SIS) graft urethroplasty has been employed to decrease buccal mucosa morbidity and facilitate the procedure. The first published series had a short follow-up, inhomogeneous patient selection, and a lack of a control group. Our purpose is to report treatment outcomes at 13 years in a propensity score-matched cohort comparing bulbar urethroplasty with SIS (SISU) or buccal mucosa (BMU).

METHODS

From our institutional database of 1132 bulbar urethroplasties, we used propensity score matching with the nearest-neighbor method without replacement to generate a study sample of 25 BMU and 25 SISU. Failure was defined as any treatment after urethroplasty. Survival analyses were used to analyze treatment failure occurrence with data censored at 156mo.

RESULTS

Matching resulted in a complete correction of bias between the two samples except for the follow-up duration, which was slightly longer in the SIS group. The cumulative treatment success probability of BMU and SISU at 156mo was 83.4% and 68%, respectively. At multivariable Cox regression, SIS graft, previous urethrotomy, stricture length, and lower postoperative Qmax (within 2mo after catheter removal) were predictors of failure. Stricture length had a more remarkable effect in SISU, with estimated survival probabilities from the Cox model lower than 80% in strictures > = 3 cm.

CONCLUSION

SIS has poorer outcomes compared to BM but may still be useful when BM grafting is not possible. The best candidates for SISU, with similar success to BMU, are patients with strictures shorter than 3 cm, preferably without a history of DVIU.

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.

Development of male and female models of long urethral strictures in swine

Background

Preclinical animal models which mimic the dimensions of long urethral strictures (>2 cm in length) encountered in the clinic are necessary to evaluate prospective graft designs for urethroplasty. The purpose of this study was to develop both male and female porcine models of long urethral strictures (∼4 cm in length) and characterize histological and functional outcomes of iatrogenic stricture formation between genders.

Methods

Focal, partial thickness urethral injuries were created over 5-6 cm long segments in male and female swine (N = 4 per gender) via electrocoagulation and the degree of stricture formation was monitored for up to 6 weeks by urethroscopy and retrograde urethrography. Animals were sacrificed following stricture confirmation and histological, immunohistochemical, and histomorphometric analyses were performed on strictured and uninjured control urethral segments to profile wound healing responses.

Results

Urethral stricture formation was detected in all female swine by 2 weeks and 100 % of male swine at 3.2 ± 1.8 weeks, post-operatively. The mean length of urethral strictures in both male and female swine was ∼4 cm. Substantial variations in the degree of stricture severity between sexes were observed with males exhibiting significant urethral stenosis and loss of α-smooth muscle actin+ smooth muscle bundles in comparison to controls, while females primarily displayed defects in pan-cytokeratin+ epithelia as well as functional urethral obstruction.

Conclusions

Electrocoagulation injury is sufficient to produce long urethral strictures in male and female swine and the degree of stricture severity and nature of urethral obstruction was observed to be dependent on gender. Animal Protocol: AUP-19-150.

Key message

Novel male and female models of long urethral strictures in swine were created to characterize histological and functional outcomes of iatrogenic stricture formation between genders.

Multifunctional Extracellular Matrix Hydrogel with Self-Healing Properties and Promoting Angiogenesis as an Immunoregulation Platform for Diabetic Wound Healing

Treating chronic wounds is a global challenge. In diabetes mellitus cases, long-time and excess inflammatory responses at the injury site may delay the healing of intractable wounds. Macrophage polarization (M1/M2 types) can be closely associated with inflammatory factor generation during wound healing. Quercetin (QCT) is an efficient agent against oxidation and fibrosis that promotes wound healing. It can also inhibit inflammatory responses by regulating M1-to-M2 macrophage polarization. However, its limited solubility, low bioavailability, and hydrophobicity are the main issues restricting its applicability in wound healing. The small intestinal submucosa (SIS) has also been widely studied for treating acute/chronic wounds. It is also being extensively researched as a suitable carrier for tissue regeneration. As an extracellular matrix, SIS can support angiogenesis, cell migration, and proliferation, offering growth factors involved in tissue formation signaling and assisting wound healing. We developed a series of promising biosafe novel diabetic wound repair hydrogel wound dressings with several effects, including self-healing properties, water absorption, and immunomodulatory effects. A full-thickness wound diabetic rat model was constructed for in vivo assessment of QCT@SIS hydrogel, in which hydrogels achieved a markedly increased wound repair rate. Their effect was determined by the promotion of the wound healing process, the thickness of granulation tissue, vascularization, and macrophage polarization during wound healing. At the same time, we injected the hydrogel subcutaneously into healthy rats to perform histological analyses of sections of the heart, spleen, liver, kidney, and lung. We then tested the biochemical index levels in serum to determine the biological safety of the QCT@SIS hydrogel. In this study, the developed SIS showed convergence of biological, mechanical, and wound-healing capabilities. Here, we focused on constructing a self-healing, water-absorbable, immunomodulatory, and biocompatible hydrogel as a synergistic treatment paradigm for diabetic wounds by gelling the SIS and loading QCT for slow drug release.

The treatment practices for anterior urethral strictures in China: A case-based survey

Objective

To investigate the treatment concept of Chinese urologists for anterior urethral strictures based on actual cases.

Methods

A self-designed case-based questionnaire was distributed to the members of Official WeChat account of Learning Union from March 19, 2020, to April 10, 2020. Questionnaires requested respondents' demographic information and responses to five cases of anterior urethral stricture: short obliterative bulbar urethral stricture caused by straddle injury (Case 1), idiopathic bulbar urethral stricture after failure of multiple endoscopic therapy (Case 2), iatrogenic long penile urethral stricture (Case 3), lichen sclerosis-related urethral stricture (Case 4), and anterior urethral stricture in indwelling catheter after multiple failure of endoscopic surgery (Case 5). Data was described by frequency and percentage.

Results

A total of 1,267 valid anonymous questionnaires were received. Urethroplasty was recommended more frequently than endoscopic surgery (Case 1: 47.8% vs. 32.8%,Case 2: 42.5% vs. 33.8%, Case 3: 36.1% vs. 26.7%). Referrals patients to other urologists engaged in urethral repair and reconstruction account for a high portion of the treatment (Case 1:18.4%, Case 2:23.1%, Case 3:36.5%, Case 4:27.7%,Case 5:9.3%). Excision and primary anastomosis urethroplasty (EPA) was preferred for treatment of Case 1 (42.5%). For Case 2, the most popular choice was EPA (30.6%). Although the patient has a history of failure in endoscopic surgery, 33.8% of urologists continue to choose endoscopic surgery. For Case 3, 20.0% of urologists would perform oral mucosal urethroplasty. Surprisingly, 5.9% chose EPA. For Case 4, 37.3% of urologists selected meatotomy, 30.4% suggested that glans and urethral biopsies should be performed. 21.0% chose to use steroid ointment after surgery. For Case 5, 26.3% of the respondents believed that urethrography should be performed after removing catheter more than one week, if the urine is obstructed during the period, performing cystostomy firstly.

Conclusions

In China, the concept of urethroplasty is more widely accepted than endoscopic surgery for the treatment of anterior urethral strictures. The concept of referral has been widely formed among Chinese urologists. Better understanding of the comprehensive treatment of lichen sclerosis related anterior urethral stricture and the principle of urethral rest should be strengthened.

Tissue Engineering and Regenerative Medicine in Pediatric Urology: Urethral and Urinary Bladder Reconstruction

In the case of pediatric urology there are several congenital conditions, such as hypospadias and neurogenic bladder, which affect, respectively, the urethra and the urinary bladder. In fact, the gold standard consists of a urethroplasty procedure in the case of urethral malformations and enterocystoplasty in the case of urinary bladder disorders. However, both surgical procedures are associated with severe complications, such as fistulas, urethral strictures, and dehiscence of the repair or recurrence of chordee in the case of urethroplasty, and metabolic disturbances, stone formation, urine leakage, and chronic infections in the case of enterocystoplasty. With the aim of overcoming the issue related to the lack of sufficient and appropriate autologous tissue, increasing attention has been focused on tissue engineering. In this review, both the urethral and the urinary bladder reconstruction strategies were summarized, focusing on pediatric applications and evaluating all the biomaterials tested in both animal models and patients. Particular attention was paid to the capability for tissue regeneration in dependence on the eventual presence of seeded cell and growth factor combinations in several types of scaffolds. Moreover, the main critical features needed for urinary tissue engineering have been highlighted and specifically focused on for pediatric application.

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.

Oral Mucosa vs. Penile Skin Flap in Substitution Urethroplasty for Anterior Urethral Strictures: A Systematic Review and Meta-Analysis

Background: The purpose of this study is to compare the effectiveness and safety of oral mucosa and penile skin flaps in the treatment of anterior urethral stricture. Methods: This meta-analysis was carried out according to the principle of preferred reporting items for systematic reviews and meta-analysis (PRISMA) and registered at PROSPERO (CRD42021277688). The Cochrane Library, PubMed, Embase, CKNI databases were searched and reviewed up to Sep 2021. Quality evaluation was performed with Newcastle-Ottawa Scale (NOS) system for non-randomized studies and Cochrane stools for randomized studies. Data synthesis was conducted with RevMan 5.4 software (Cochrane) and a Stata 15.0 environment (Stata Corpor, College Station, TX, USA). Results: After the research screening, eight studies (comprising 445 patients) were finally included in the quantitative analysis. In the success rate comparison, there was no significant difference between oral mucosa and penile skin flaps (oral mucosa vs. penile skin flap, Mantel-Haenszel statistic [M-H] fixed model, OR: 0.80, 95% CI: 0.47-1.34, P = 0.39). There was no significant difference in the post-operative complication comparison (oral mucosa vs. penile skin flap, Mantel-Haenszel statistic [M-H] fixed model, OR: 0.68, 95% CI: 0.40-1.16, P = 0.15). However, considering that the site of oral mucosa is far from the anterior urethra, it may have advantages in operation time through simultaneous operations (oral mucosa vs. penile skin flap, MD: -40.05, 95% CI: -79.42, -0.68, P = 0.046). Conclusion: When the oral mucosal graft was used in the anterior urethra urethroplasty, it had a similar success rate and post-operative complication rate, and oral mucosa substitution had a shorter operation time. This evidence-based medical research further supports the view that oral mucosa is the preferred substitution material for the anterior urethra urethroplasty.

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.

Double-Modified Bacterial Cellulose/Soy Protein Isolate Composites by Laser Hole Forming and Selective Oxidation Used for Urethral Repair

In this study, a double-modified bacterial cellulose/soybean protein isolate (DMBC/SPI), a new type of urethral tissue engineering scaffold with good biocompatibility, biodegradability, and cell-oriented growth, was prepared. Bacterial cellulose (BC) was physically and chemically modified by laser hole forming and selective oxidation to obtain the double-modified bacterial cellulose (DMBC). The soybean protein isolate (SPI) was compounded on DMBC to obtain DMBC/SPI with better biocompatibility. DMBC/SPI was used to repair the damaged urethra in rabbits. The results showed that DMBC/SPI was beneficial to heal the damaged urethra and did not cause a milder inflammatory response. The repaired urethra was smooth and continuous. DMBC/SPI has a good urethral repair effect and is expected to be used as a new urethral reconstruction material in clinical applications. In addition, FT-IR spectroscopy, SEM, static contact angle measurements, mechanical property investigation, and cell experiments were also performed to characterize the properties of DMBC/SPI composites.

[Which management for anterior urethral stricture in male? 2021 guidelines from the uro-genital reconstruction urologist group (GURU) under the aegis of CAMS-AFU (Committee of Andrology and Sexual Medicine of the French Association of Urology)]

OBJECTIVE

The purpose of this first french guideline is to provide a clinical framework for the diagnosis, treatment and follow-up of anterior urethral strictures. The statements are established by the subgroup working on uro-genital reconstruction surgery (GURU) from the CAMS-AFU (Andrology and Sexual Medicine Committee from the French Association of Urology).

MATERIAL AND METHODS

These guidelines are adapted from the Male Urethral Stricture : American Urological Association Guideline 2016, updated by an additional bibliography from January 2016 to December 2019. Twenty-seven main scenarios seen in clinical practice are identified: from diagnosis, to treatment and follow-up. In addition, this guidelines are powered by anatomical diagrams, treatment algorithms, summaries and follow-up tables.

RESULTS

Anterior urethral strictures are a common condition (0,1 à 1,4 %) in men. The diagnosis is based on a trifecta including an examination with patient reported questionnaires, urethroscopy and retrograde urethrography with voiding cystourethrography. Short meatal stenosis can be treated by dilation or meatotomy, otherwise a urethroplasty can be performed. First line treatment of penile strictures is urethroplasty. Short bulbar strictures (<2cm) may benefit from endourethral treatment (direct visual internal urethrotomy or dilation). In case of recurrence or when the stenosis measures more than 2 cm, a urethroplasty will be proposed. Repeated endourethral treatment management are no longer recommended except in case of palliative option. Urethroplasty is usually done with oral mucosa graft as the primary option, in one or two stages approach depending on the extent of the stenosis and the quality of the tissues. Excision and primary anastomosis or non-transecting techniques are discussed for bulbar urethra strictures. Follow-up by clinical monitoring with urethroscopy, or retrograde urethrography with voiding cystourethrography, is performed at least the first year and then on demand according to symptoms.

CONCLUSION

Anterior urethral strictures need an open surgical approach and should be treated by urethroplasty in most cases. This statement requires a major paradigm shift in practices. Training urologist through reconstructive surgery is the next challenge in order to meet the demand.

Uretroplastia bulbar con injerto: Una actualización sobre las diferentes técnicas quirúrgicas

En pacientes con estrechez uretral bulbar de una longitud mayor a 2 cm, que no sean candidatos a otras técnicas, se realiza uretroplastia con injerto. Actualmente se emplean diversas técnicas, cada una con ventajas y desventajas propias.

Describir las ventajas y desventajas de las técnicas quirúrgicas empleadas actualmente en la uretroplastia con injerto, así como sus tasas de éxito.

Se hizo una búsqueda en PubMed, ClinicalKey y en ScienceDirect, utilizando las palabras claves: “urethral stricture,” “urethroplasty,” “oral graft” y “flap.” Se utilizaron los estudios más relevantes, tanto originales como revisiones sistemáticas y meta-análisis, en inglés y en español.

Las diferentes técnicas quirúrgicas ofrecen ventajas y desventajas teóricas frente a las otras, aunque las tasas de éxito en todas es cercana al 90%, sin ser una francamente superior frente a las demás.

La elección de la técnica quirúrgica a realizar depende de las preferencias y experiencia del cirujano, dado que la tasa de éxito para todas las técnicas es similar.

Anterior Urethroplasty for the Management of Urethral Strictures in Males: A Systematic Review

OBJECTIVE

To identify the currently utilised techniques of anterior urethroplasty described in literature for treatment of urethral strictures, assess the effectiveness of the identified techniques based on re-stricture and complication rates, evaluate, and suggest treatment options based on current evidence for urethral strictures at different locations and of different lengths.

METHODS

A systematic review of the MEDLINE, EMBASE, Scopus and Cochrane Library databases from conception up to September 2020 was performed. Primary outcomes included success rates measured via re-stricture rates and the post-operative maximum urinary flow rate (Qmax). Secondary outcomes included patient reported complication rates.

RESULTS

A total of 52 papers, including 7 RCTs, met the inclusion criteria. Forty studies described the use of free graft urethroplasty with a median success rate of 86.5% (IQR = 8.1). The best outcomes were found in dorsal onlay buccal mucosa grafting in the penile urethra (86.6%). Twelve described the use of pedicled flap urethroplasty with a median success rate of 76% (IQR = 14.4). Excision and Primary Anastomosis results were reported in 5 studies and showed an overall highest success rate of 89.7% (IQR = 7.0) but involved the shortest strictures of median lengths of 2.1 cm (IQR = 0.48).

CONCLUSION

Graft urethroplasty showed optimal outcomes when utilised in penile and bulbar strictures, with dorsal onlay buccal mucosa grafting presenting with the largest evidence base and best outcomes overall. Flap urethroplasty had the highest success rates in panurethral and bulbar strictures, while anastomotic urethroplasty had the greatest success in bulbar and penobulbar strictures.

Genitourinary Tissue Engineering: Reconstruction and Research Models

Tissue engineering is an emerging field of research that initially aimed to produce 3D tissues to bypass the lack of adequate tissues for the repair or replacement of deficient organs. The basis of tissue engineering protocols is to create scaffolds, which can have a synthetic or natural origin, seeded or not with cells. At the same time, more and more studies have indicated the low clinic translation rate of research realised using standard cell culture conditions, i.e., cells on plastic surfaces or using animal models that are too different from humans. New models are needed to mimic the 3D organisation of tissue and the cells themselves and the interaction between cells and the extracellular matrix. In this regard, urology and gynaecology fields are of particular interest. The urethra and vagina can be sites suffering from many pathologies without currently adequate treatment options. Due to the specific organisation of the human urethral/bladder and vaginal epithelium, current research models remain poorly representative. In this review, the anatomy, the current pathologies, and the treatments will be described before focusing on producing tissues and research models using tissue engineering. An emphasis is made on the self-assembly approach, which allows tissue production without the need for biomaterials.

Reconstruction of Vascular and Urologic Tubular Grafts by Tissue Engineering

Tissue engineering is one of the most promising scientific breakthroughs of the late 20th century. Its objective is to produce in vitro tissues or organs to repair and replace damaged ones using various techniques, biomaterials, and cells. Tissue engineering emerged to substitute the use of native autologous tissues, whose quantities are sometimes insufficient to correct the most severe pathologies. Indeed, the patient’s health status, regulations, or fibrotic scars at the site of the initial biopsy limit their availability, especially to treat recurrence. This new technology relies on the use of biomaterials to create scaffolds on which the patient’s cells can be seeded. This review focuses on the reconstruction, by tissue engineering, of two types of tissue with tubular structures: vascular and urological grafts. The emphasis is on self-assembly methods which allow the production of tissue/organ substitute without the use of exogenous material, with the patient’s cells producing their own scaffold. These continuously improved techniques, which allow rapid graft integration without immune rejection in the treatment of severely burned patients, give hope that similar results will be observed in the vascular and urological fields.

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.

Regenerative and engineered options for urethroplasty

Surgical correction of urethral strictures by substitution urethroplasty - the use of grafts or flaps to correct the urethral narrowing - remains one of the most challenging procedures in urology and is frequently associated with complications, restenosis and poor quality of life for the affected individual. Tissue engineering using different cell types and tissue scaffolds offers a promising alternative for tissue repair and replacement. The past 30 years of tissue engineering has resulted in the development of several therapies that are now in use in the clinic, especially in treating cutaneous, bone and cartilage defects. Advances in tissue engineering for urethral replacement have resulted in several clinical applications that have shown promise but have not yet become the standard of care.

A critical outcome analysis of Asopa single-stage dorsal inlay substitution urethroplasty for penile urethral stricture

PURPOSE

To critically report outcomes from a contemporary series of patients undergoing single-stage Asopa dorsal inlay urethroplasty for penile stricture.

METHODS

First, we retrospectively evaluated patients who underwent Asopa urethroplasty for penile stricture between 2009 and 2016 at our department. Clinical and surgical characteristics were compared across treatment groups (proximal penile, mid-penile, distal penile). Recurrence-free survival was plotted using Kaplan-Meier curves. Treatment satisfaction was assessed using a validated outcome measurement tool. Second, a literature review was performed through Medline to summarize the available evidence on Asopa urethroplasty and put our own results into context.

RESULTS

Of 125 patients, 38 (30%), 74 (59%), and 13 (10%) had distal penile, mid-penile, and proximal penile stricture, respectively. Patients with distal strictures were younger and graft length was shorter compared to other groups (P ≤ 0.009). The majority of strictures were iatrogenic (38%), followed by hypospadias related (24%), congenital (17%), traumatic (10%), inflammatory (9%), and post-infectious strictures (2.4%). At a median follow-up of 36 months, overall success rate was 70%. In sensitivity analyses, success rates were only marginally improved to 71% after exclusion of hypospadias- and lichen sclerosus-associated strictures. Patients with mid-penile strictures were significantly more satisfied compared to other groups. Overall, 272 patients from 9 studies in the literature review underwent Asopa urethroplasty and success rates ranged from 73 to 100%.

CONCLUSIONS

Success rates of Asopa urethroplasty in penile strictures are lower than previously reported. This is most likely due to both complex stricture etiology and surgical history and last resort single-stage surgery in many cases. Pre-operative counseling must consider high recurrence risk and staged urethroplasty should be discussed in selective cases to optimize patient satisfaction.

From Acellular Matrices to Smart Polymers: Degradable Scaffolds that are Transforming the Shape of Urethral Tissue Engineering

Several congenital and acquired conditions may result in severe narrowing of the urethra in men, which represent an ongoing surgical challenge and a significant burden on both health and quality of life. In the field of urethral reconstruction, tissue engineering has emerged as a promising alternative to overcome some of the limitations associated with autologous tissue grafts. In this direction, preclinical as well as clinical studies, have shown that degradable scaffolds are able to restore the normal urethral architecture, supporting neo-vascularization and stratification of the tissue. While a wide variety of degradable biomaterials are under scrutiny, such as decellularized matrices, natural, and synthetic polymers, the search for scaffold materials that could fulfill the clinical performance requirements continues. In this article, we discuss the design requirements of the scaffold that appear to be crucial to better resemble the structural, physical, and biological properties of the native urethra and are expected to support an adequate recovery of the urethral function. In this context, we review the biological performance of the degradable polymers currently applied for urethral reconstruction and outline the perspectives on novel functional polymers, which could find application in the design of customized urethral constructs.

Repair of injured urethras with silk fibroin scaffolds in a rabbit model of onlay urethroplasty

BACKGROUND

Preclinical validation of scaffold-based technologies in animal models of urethral disease is desired to assess wound healing efficacy in scenarios that mimic the target patient population. This study investigates the feasibility of bilayer silk fibroin (BLSF) scaffolds for the repair of previously damaged urethras in a rabbit model of onlay urethroplasty.

MATERIALS AND METHODS

A focal, partial thickness urethral injury was created in adult male rabbits (n = 12) via electrocoagulation and then onlay urethroplasty with 50 mm² BLSF grafts was carried out 2 wk after injury. Animals were randomly divided into three experimental groups and harvested at 2 wk after electrocoagulation (n = 3), and 1 (n = 3) or 3 (n = 6) months after scaffold implantation. Outcome analyses were performed preoperatively and at 2 wk after injury in all groups as well as at 1 or 3 mo after scaffold grafting and included urethroscopy, retrograde urethrography (RUG), and histological and immunohistochemical analyses.

RESULTS

At 2 wk after electrocoagulation, urethroscopic and RUG evaluations confirmed urethral stricture formation in 92% (n = 11/12) of rabbits. Gross tissue assessments at 1 (n = 3) and 3 (n = 6) mo after onlay urethroplasty revealed host tissue ingrowth covering the entire implant site. At 3 mo post-op, RUG analyses of repaired urethral segments demonstrated a 39% reduction in urethral stenosis detected following electrocoagulation injury. Histological and immunohistochemical analyses revealed the formation of innervated, vascularized neotissues with α-smooth muscle actin+ and SM22α+ smooth muscle bundles and pan-cytokeratin + epithelium at graft sites.

CONCLUSIONS

These results demonstrate the feasibility of BLSF matrices to support the repair of previously damaged urethral tissues.

Tissue engineered extracellular matrices (ECMs) in urology: Evolution and future directions

Autologous gastrointestinal tissue has remained the gold-standard reconstructive biomaterial in urology for >100 years. Mucus-secreting epithelium is associated with lifelong metabolic and neuromechanical complications when implanted into the urinary tract. Therefore, the availability of biocompatible tissue-engineered biomaterials such as extracellular matrix (ECM) scaffolds may provide an attractive alternative for urologists. ECMs are decellularised, biodegradable membranes that have shown promise for repairing defective urinary tract segments in vitro and in vivo by inducing a host-derived tissue remodelling response after implantation. In urology, porcine small intestinal submucosa (SIS) and porcine urinary bladder matrix (UBM) are commonly selected as ECMs for tissue regeneration. Both ECMs support ingrowth of native tissue and differentiation of multi-layered urothelial and smooth muscle cells layers while providing mechanical support in vivo. In their native acellular state, ECM scaffolds can repair small urinary tract defects. Larger urinary tract segments can be repaired when ECMs are manipulated by seeding them with various cell types prior to in vivo implantation. In the present review, we evaluate and summarise the clinical potential of tissue engineered ECMs in reconstructive urology with emphasis on their long-term outcomes in urological clinical trials.

Graft Use in Bulbar Urethroplasty

The gold standard for bulbar urethroplasty has been excision and primary anastomosis. Application of this approach is generally limited to strictures that are 2 cm or less in the bulbar urethra due to penile shortening. Strictures greater than 2 cm are successfully treated with augmentation urethroplasty wherein the narrowed segment is not excised but widened with the use of a skin flap or a tissue graft. Buccal mucosa is the most prevalent tissue for bulbar urethral stricture repair for strictures greater than 2 cm. Outcomes for the different graft locations are similar, approximately 90%.

Thermo-sensitive hydrogels combined with decellularised matrix deliver bFGF for the functional recovery of rats after a spinal cord injury

Because of the short half-life, either systemic or local administration of bFGF shows significant drawbacks to spinal injury. In this study, an acellular spinal cord scaffold (ASC) was encapsulated in a thermo-sensitive hydrogel to overcome these limitations. The ASC was firstly prepared from the spinal cord of healthy rats and characterized by scanning electronic microscopy and immunohistochemical staining. bFGF could specifically complex with the ASC scaffold via electrostatic or receptor-mediated interactions. The bFGF-ASC complex was further encapsulated into a heparin modified poloxamer (HP) solution to prepare atemperature-sensitive hydrogel (bFGF-ASC-HP). bFGF release from the ASC-HP hydrogel was more slower than that from the bFGF-ASC complex alone. An in vitro cell survival study showed that the bFGF-ASC-HP hydrogel could more effectively promote the proliferation of PC12 cells than a bFGF solution, with an approximate 50% increase in the cell survival rate within 24 h (P < 0.05). Compared with the bFGF solution, bFGF-ASC-HP hydrogel displayed enhanced inhibition of glial scars and obviously improved the functional recovery of the SCI model rat through regeneration of nerve axons and the differentiation of the neural stem cells. In summary, an ASC-HP hydrogel might be a promising carrier to deliver bFGF to an injured spinal cord.

Silk Fibroin Scaffolds for Urologic Tissue Engineering

Urologic tissue engineering efforts have been largely focused on bladder and urethral defect repair. The current surgical gold standard for treatment of poorly compliant pathological bladders and severe urethral stricture disease is enterocystoplasty and onlay urethroplasty with autologous tissue, respectively. The complications associated with autologous tissue use and harvesting have led to efforts to develop tissue-engineered alternatives. Natural and synthetic materials have been used with varying degrees of success, but none has proved consistently reliable for urologic tissue defect repair in humans. Silk fibroin (SF) scaffolds have been tested in bladder and urethral repair because of their favorable biomechanical properties including structural strength, elasticity, biodegradability, and biocompatibility. SF scaffolds have been used in multiple animal models and have demonstrated robust regeneration of smooth muscle and urothelium. The pre-clinical data involving SF scaffolds in urologic defect repair are encouraging and suggest that they hold potential for future clinical use.

Seeding cell approach for tissue-engineered urethral reconstruction in animal study: A systematic review and meta-analysis

We systematically reviewed published preclinical studies to evaluate the effectiveness of cell-seeded tissue engineering approach for urethral reconstruction in an animal model. The outcomes were summarized by success factors in the animal experiments, which evaluate the possibility and feasibility of a clinical application in the future. Preclinical studies of tissue engineering approaches for urethral reconstruction were identified through a systematic search in PubMed, Embase, and Biosis Previews (web of science SP) databases for studies published from 1 January 1980 to 23 November 2014. Primary studies were included if urethral reconstruction was performed using a tissue-engineered biomaterial in any animal species (with the experiment group being a cell-seeded scaffold and the control group being a cell-free scaffold) with histology and urethrography as the outcome measure. A total of 15 preclinical studies were included in our meta-analysis. The histology and urethrography outcome between the experimental and control groups were considered to be the most clinically relevant. Through this systematic approach, our outcomes suggested that applying the cell-seeded biomaterial in creating a neo-urethra was stable and effective. And multi-type cells including epithelial cells as well as smooth muscle cells or fibroblasts seemed to be a better strategy. Stem cells, especially after epithelial differentiation, could be a promising choice for future researches.

Management of penile urethral strictures: Challenges and future directions

The anatomy of the penile urethra presents additional challenges when compared to other urethral segments during open stricture surgery particularly because of its unsuitability for excision and primary anastomosis and its relatively deficient corpus spongiosum. Stricture aetiology, location, length and previous surgical intervention remain the primary factors influencing the choice of penile urethroplasty technique. We have identified what we feel are the most important challenges and controversies in penile urethral stricture reconstruction, namely the use of flaps vs grafts, use of skin or oral mucosal tissue for augmentation/substitution and when a single or a staged approach is indicated to give the best possible outcome. The management of more complex cases such as pan-urethral lichen-sclerosus strictures and hypospadias “cripples” is outlined and potential developments for the future are presented.

A systematic review of animal and clinical studies on the use of scaffolds for urethral repair

Replacing urethral tissue with functional scaffolds has been one of the challenging problems in the field of urethra reconstruction or repair over the last several decades. Various scaffold materials have been used in animal studies, but clinical studies on use of scaffolds for urethral repair are scarce. The aim of this study was to review recent animal and clinical studies on the use of different scaffolds for urethral repair, and to evaluate these scaffolds based on the evidence from these studies. PubMed and OVID databases were searched to identify relevant studies, in conjunction with further manual search. Studies that met the inclusion criteria were systematically evaluated. Of 555 identified studies, 38 were included for analysis. It was found that in both animal and clinical studies, scaffolds seeded with cells were used for repair of large segmental defects of the urethra, such as in tubular urethroplasty. When the defect area was small, cell-free scaffolds were more likely to be applied. A lot of pre-clinical and limited clinical evidence showed that natural or artificial materials could be used as scaffolds for urethral repair. Urinary tissue engineering is still in the immature stage, and the safety, efficacy, cost-effectiveness of the scaffolds are needed for further study.

Dorsal inlay buccal mucosal graft (Asopa) urethroplasty for anterior urethral stricture

Asopa described the inlay of a graft into Snodgrass’s longitudinal urethral plate incision using a ventral sagittal urethrotomy approach in 2001. He claimed that this technique was easier to perform and led to less tissue ischemia due to no need for mobilization of the urethra. This approach has subsequently been popularized among reconstructive urologists as the dorsal inlay urethroplasty or Asopa technique. Depending on the location of the stricture, either a subcoronal circumferential incision is made for penile strictures, or a midline perineal incision is made for bulbar strictures. Other approaches for penile urethral strictures include the non-circumferential penile incisional approach and a penoscrotal approach. We generally prefer the circumferential degloving approach for penile urethral strictures. The penis is de-gloved and the urethra is split ventrally to exposure the stricture. It is then deepened to include the full thickness of the dorsal urethra. The dorsal surface is made raw and grafts are fixed on the urethral surface. Quilting sutures are placed to further anchor the graft. A Foley catheter is placed and the urethra is retubularized in two layers with special attention to the staggering of suture lines. The skin incision is then closed in layers. We have found that it is best to perform an Asopa urethroplasty when the urethral plate is ≥1 cm in width. The key to when to use the dorsal inlay technique all depends on the width of the urethral plate once the urethrotomy is performed, stricture etiology, and stricture location (penile vs. bulb).

New frontiers in urethral reconstruction: injectables and alternative grafts

Contemporary management of anterior urethral strictures requires both endoscopic as well as complex substitution urethroplasty, depending on the nature of the urethral stricture. Recent clinical and experimental studies have explored the possibility of augmenting traditional endoscopic urethral stricture management with anti-fibrotic injectable medications. Additionally, although buccal mucosa remains the gold standard graft for substitution urethroplasty, alternative grafts are necessary for reconstructing particularly complex urethral strictures in which there is insufficient buccal mucosa or in cases where it may be contraindicated. This review summarizes the data of the most promising injectable adjuncts to endoscopic stricture management and explores the alternative grafts available for reconstructing the most challenging urethral strictures. Further research is needed to define which injectable medications and alternative grafts may be best suited for urethral reconstruction in the future.

The potential role of tissue-engineered urethral substitution: clinical and preclinical studies

Urethral strictures and anomalies remain among the difficult problems in urology, with urethroplasty procedures being the most effective treatment options. The two major types of urethroplasty are anastomotic urethroplasty and widening the urethral lumen using flaps or grafts (i.e. substitution urethroplasty). However, no ideal material for the latter has been found so far. Designing and selecting such a material is a necessary and challenging endeavour, driving the need for further bioengineered urethral tissue research. This article reviews currently available studies on the potentialities of tissue engineering in urethral reconstruction, in particular those describing the use of both acellular and recellularized tissue-engineered constructs in animal and human models. Possible future developments in this field are also discussed. Copyright © 2015 John Wiley & Sons, Ltd.

Decellularization technology in CNS tissue repair

Decellularization methodologies have been successfully used in a variety of tissue engineering and regenerative technologies and methods of decellularization have been developed for target tissues and organs of interest. The technology to promote regeneration and functional recovery in the CNS, including brain and spinal cord, has, however, made slow progress mainly because the intrinsic regenerative potential of the CNS is regarded as low. To date, currently available therapies have been unable to provide significant functional recovery and successful therapies, which could provide functional restoration to the injured brain and spinal cord are controversial. In this review, the authors provide a critical analysis, comparing the advantages and limitations of the major decellularization methods and considering the effects of these methods upon the biologic scaffold material. The authors also review studies that supplement decellularized grafts with exogenous factors, such as stem cells and growth factors, to both promote and enhance regeneration through decellularized allografts.

An acellular cerebellar biological scaffold: Preparation, characterization, biocompatibility and effects on neural stem cells

Biomaterial and regenerative medical research has diversified and developed rapidly. A biological scaffold consisting of an extracellular matrix (ECM) functions not only as a supportive material but also as a regulator of cellular functions. Although decellularized scaffolds have been widely applied for the repair of non-central nervous system (CNS) tissues, their efficacy in the CNS has not been extensively investigated. In this report, we describe a dynamic decellularization protocol that combined intracardial perfusion and a series of treatments to effectively remove the cellular components from the cerebellum, which is a unique and relatively simple CNS structure. The resulting cerebellar scaffold retained neurosupportive proteins and growth factors and, when tested with neural stem cells (NSCs) in vitro, was found to be cytocompatible and to stimulate the proliferation and migration of these cells. NSCs that were cultured in vitro on the scaffold differentiated into neurons and astrocytes, as indicated by their expression of βIII-tubulin and glial fibrillary acidic protein (GFAP). Through subcutaneous and intracranial implantation experiments, this preliminary study demonstrated the in vivo biocompatibility of the cerebellar scaffold and indicated its potential for future applications. Thus, our study demonstrated that the cerebellar ECM scaffold provided tissue-specific advantages for regenerative medical applications.

Tissue engineering in urothelium regeneration

The development of therapeutic treatments to regenerate urothelium, manufacture tissue equivalents or neourethras for in-vivo application is a significant challenge in the field of tissue engineering. Many studies have focused on urethral defects that, in most cases, inadequately address current therapies. This article reviews the primary tissue engineering strategies aimed at the clinical requirements for urothelium regeneration while concentrating on promising investigations in the use of grafts, cellular preparations, as well as seeded or unseeded natural and synthetic materials. Despite significant progress being made in the development of scaffolds and matrices, buccal mucosa transplants have not been replaced. Recently, graft tissues appear to have an advantage over the use of matrices. These therapies depend on cell isolation and propagation in vitro that require, not only substantial laboratory resources, but also subsequent surgical implant procedures. The choice of the correct cell source is crucial when determining an in-vivo application because of the risks of tissue changes and abnormalities that may result in donor site morbidity. Addressing an appropriately-designed animal model and relevant regulatory issues is of fundamental importance for the principal investigators when a therapy using cellular components has been developed for clinical use.

Tissue engineered buccal mucosa for urethroplasty: progress and future directions

PURPOSE

Autologous buccal mucosa is commonly utilized in the surgical treatment of urethral strictures. Extensive strictures require a larger quantity of tissue, which may lead to donor site morbidity. This review assesses progress in producing tissue engineered buccal mucosa as an alternative graft material.

RESULTS

Few clinical studies have introduced cells onto biological or synthetic scaffolds and implanted resulting constructs in patients. The available studies show that buccal mucosa cells on acellular human dermis or on collagen matrix lead to good acute stage tissue integration. Urothelial cells on a synthetic substrate also perform well. However while some patients do well many years post-grafting, others develop stricture recurrence. Acellular biomaterials used to treat long urethral defects in animals commonly lead to fibrosis.

CONCLUSIONS

Tissue engineered buccal mucosa shows promise as a substitute for native tissue. The fibrosis which occurs months post-implantation may reflect the underlying disease process recurring in these patients.

Acellular matrix in urethral reconstruction

The treatment of severe urethral stenosis has always been a challenge even for skilled urologists. Classic urethroplasty, skin flaps and buccal mucosa grafting may not be used for long and complex strictures. In the quest for an ideal urethral substitute, acellular scaffolds have demonstrated the ability to induce tissue regeneration layer by layer. After several experimental studies, the use of acellular matrices for urethral reconstruction has become a clinical reality over the last decade. In this review we analyze advantages and limitations of both biological and polymeric scaffolds that have been reported in experimental and human studies. Important aspects such as graft extension, surgical technique and cell-seeding versus cell-free grafts will be discussed.

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.

Urethral reconstruction with tissue-engineered human amniotic scaffold in rabbit urethral injury models

BACKGROUND

Mitigating urethral injury remains a great challenge for urologists due to lack of ideal biomaterials for urethroplasty. The application of amniotic membranes (AM) over other synthetic materials make it a better potential source for urethral reconstruction. We separated the basement layer of AM to obtain denuded human amniotic scaffold (dHAS) and then inoculated primary rabbit urethral epithelial cells on the surface of dHAS to define whether this strategy minimize potential rejection and maximize the biocompatibility of human AM.

MATERIAL/METHODS

After the successful acquisition of dHAS from AM, cell-seeded dHAS were prepared and characterized. Both cell-seeded dHAS and acellular dHAS were subcutaneously implanted. Immune responses were compared by histological evaluation and CD4 cell and CD8 cell infiltrations. Then they were applied as urethroplastic materials in the rabbit models of urethral injury to fully explore the feasibility and efficacy of tissue-engineered dHAS xenografts in urethral substitution application.

RESULTS

Mild inflammatory infiltration was observed in cell-seeded dHAS grafts, as revealed by fewer accumulations of CD4 cells and CD8 cells (or neutrophils or other immune cells). Urethral defects of rabbits in the urethroplastic group with dHAS implantation (n=6) were completely resolved in one month, while there were one infection and one fistula in the control group with acellular dHAS patches (n=6). Histopathological analysis revealed mild immune response in cell-seeded dHAS group (P<0.05).

CONCLUSIONS

Tissue-engineered dHAS minimize potential rejection and maximize the biocompatibility of AM, which makes it a potential ideal xenograft for urethral reconstruction.

Organ bioengineering for the newborn

Regenerative medicine has recently been established as an emerging interdisciplinary field focused on the repair; replacement or regeneration of cells, tissues and organs. It involves various disciplines, which are focused on different aspects of the regeneration process such as cell biology, gene therapy, bioengineering, material science and pharmacology. In this article, we will outline progress on tissue engineering of specific tissues and organs relevant to paediatric surgery.

Regenerative medicine in urology

Repair and reconstruction of damaged tissues and organs has been a major issue in the medical field. Regenerative medicine and tissue engineering, as rapid evolving technologies, may offer alternative treatments and hope for patients with serious defects and end-stage diseases. Most urologic diseases could benefit from the development of regenerative medicine and tissue engineering. This article discusses the role of cells and materials in regenerative medicine, as well as the status of current role of regenerative medicine for the generation of specific urologic organs.

CR, Mauney JR. Acellular bi-layer silk fibroin scaffolds support tissue regeneration in a rabbit model of onlay urethroplasty

Acellular scaffolds derived from Bombyx mori silk fibroin were investigated for their ability to support functional tissue regeneration in a rabbit model of urethra repair. A bi-layer silk fibroin matrix was fabricated by a solvent-casting/salt leaching process in combination with silk fibroin film casting to generate porous foams buttressed by homogeneous silk fibroin films. Ventral onlay urethroplasty was performed with silk fibroin grafts (Group 1, N = 4) (Width×Length, 1×2 cm²) in adult male rabbits for 3 m of implantation. Parallel control groups consisted of animals receiving small intestinal submucosa (SIS) implants (Group 2, N = 4) or urethrotomy alone (Group 3, N = 3). Animals in all groups exhibited 100% survival prior to scheduled euthanasia and achieved voluntary voiding following 7 d of initial catheterization. Retrograde urethrography of each implant group at 3 m post-op revealed wide urethral calibers and preservation of organ continuity similar to pre-operative and urethrotomy controls with no evidence of contrast extravasation, strictures, fistulas, or stone formation. Histological (hematoxylin and eosin and Masson's trichrome), immunohistochemical, and histomorphometric analyses demonstrated that both silk fibroin and SIS scaffolds promoted similar extents of smooth muscle and epithelial tissue regeneration throughout the original defect sites with prominent contractile protein (α-smooth muscle actin and SM22α) and cytokeratin expression, respectively. De novo innervation and vascularization were also evident in all regenerated tissues indicated by synaptophysin-positive neuronal cells and vessels lined with CD31 expressing endothelial cells. Following 3 m post-op, minimal acute inflammatory reactions were elicited by silk fibroin scaffolds characterized by the presence of eosinophil granulocytes while SIS matrices promoted chronic inflammatory responses indicated by mobilization of mononuclear cell infiltrates. The results of this study demonstrate that bi-layer silk fibroin scaffolds represent promising biomaterials for onlay urethroplasty, capable of promoting similar degrees of tissue regeneration in comparison to conventional SIS scaffolds, but with reduced immunogenicity.

Epithelial-differentiated adipose-derived stem cells seeded bladder acellular matrix grafts for urethral reconstruction: an animal model

The limited amount of available epithelial tissue is considered a main cause of the high rate of urethral reconstruction failures. The aim of this study was to investigate whether epithelial-differentiated rabbit adipose-derived stem cells (Epith-rASCs) could play a role of epithelium in vivo functionally and be a potential substitute of urothelium. Substitution urethroplasty was performed to repair an anterior urethral defect in male New Zealand rabbits using Epith-rASCs seeded bladder acellular matrix grafts (BAMGs) after 5-bromo-2'-deoxyuridine (BrdU) labeling, based on the in vitro epithelial induction system we previously described. Urethroplasty with cell-free BAMGs and with undifferentiated rASCs (Und-rASCs) seeded BAMGs were performed as controls. After surgery, a notable amelioration of graft contracture and recovery of urethral continuity were observed in the Epith-rASCs/BAMG group by retrograde urethrograms and macroscopic inspection. Immunofluorescence revealed that the BrdU-labeled Epith-rASCs/Und-rASCs colocalized with cytokeratin 13 or myosin. Consistent with the results of western blotting, at early postimplantation stage, the continuous epithelial layer with local multilayered structure was observed in the Epith-rASCs/BAMG group, whereas no significant growth and local monolayer growth profile of epithelial cells were observed in the BAMG and Und-rASCs/BAMG group, respectively. The results showed that Epith-rASCs could serve as a potential substitute of urothelium for urethral tissue engineering and be available to prevent lumen contracture and subsequent complications including recurrent stricture.

SIU/ICUD Consultation on Urethral Strictures: The management of anterior urethral stricture disease using substitution urethroplasty

In this systematic review of the literature, a search of the PubMed database was conducted to identify articles dealing with augmentation/substitution urethral reconstruction of the anterior urethral stricture. The evidence was categorized by stricture site, surgical technique, and the type of tissue used. The committee appointed by the International Consultation on Urological Disease reviewed this data and produced a consensus statement relating to the augmentation and substitution of the anterior urethra. In this review article, the background pathophysiology is discussed. Most cases of urethral stricture disease in the anterior urethra are consequent on an ischemic spongiofibrosis. The choice of technique and the surgical approach are discussed along with the potential pros and cons of the use of a graft vs a flap. There is research potential for tissue engineering. The efficacy of the surgical approach to the urethra is reviewed. Whenever possible, a 1-stage approach is preferable from the patient's perspective. In some cases, with complex penile urethral strictures, a 2-stage procedure might be appropriate, and there is an important potential role for the use of a perineal urethrostomy in cases where there is an extensive anterior urethral stricture or where the patient does not wish to undergo complex surgery, or medical contraindications make this hazardous. It is important to have accurate outcome measures for the follow-up of patients, and in this context, a full account needs to be taken of patients' perspectives by the use of appropriate patient-reported outcome measures. The use of symptoms and a flow rate can be misleading. It is well established that with a normally functioning bladder, the flow rate does not diminish until the caliber of the urethra falls below 10F. The most accurate means of following up patients after stricture surgery are by the use of endoscopy or visualization by urethrography. Careful consideration needs to be made of the outcomes reported in the world literature, bearing in mind these aforementioned points. The article concludes with an overview of the key recommendations provided by the committee.

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

OBJECTIVES

To investigate the feasibility of small intestinal submucosa graft for the repair of selected anterior urethral strictures.

METHODS

From June 2009 to May 2011, 28 men (mean age 39 years) with anterior urethral strictures underwent urethroplasty using a four-layer small intestinal submucosa patch graft in an onlay or inlay fashion. The stricture was localized to the bulbar urethra in eight patients, the bulbopenile area in nine patients and the distal penile urethra in 10 patients. Failed hypospadias was observed in one patient. The mean stricture length was 4.6 cm (range 3.5-7.0 cm).

RESULTS

The mean follow-up period was 24.8 months (range 12-30 months). No postoperative complications, such as infection or rejection, were related to the use of heterologous graft material. The patients voided well postoperatively, with peak flows between 16 and 44 mL/s (mean 25.4 mL/s) in 26 patients. Two patients (7.1%) developed a urethral narrowing; this occurred at 5 months in one patient and 6 months in the other, and cystoscopy, which was carried out at 20 and 24 weeks, respectively, showed clear cicatricial tissue at the proximal anastomotic site. Dilation was carried out once every 4-6 months for recurrent stricture in one patient and lingual mucosal graft urethroplasty was carried out in the other patient at 18 months postoperatively. Biopsies were obtained in four patients at 18, 24, 36 and 42 weeks, respectively. Squamous epithelium with or without hyperkeratosis was observed on histological examination of the small intestinal submucosa-grafted areas.

CONCLUSIONS

The small intestinal submucosa matrix appears to be a safe and effective reconstructive material for selective use in urethral reconstructive surgery.