Ureteral segmental replacement using multilayer porcine small-intestinal submucosa

The application of small intestinal submucosa in tissue regeneration

The distinctive three-dimensional architecture, biological functionality, minimal immunogenicity, and inherent biodegradability of small intestinal submucosa extracellular matrix materials have attracted considerable interest and found wide-ranging applications in the domain of tissue regeneration engineering. This article presents a comprehensive examination of the structure and role of small intestinal submucosa, delving into diverse preparation techniques and classifications. Additionally, it proposes approaches for evaluating and modifying SIS scaffolds. Moreover, the advancements of SIS in the regeneration of skin, bone, heart valves, blood vessels, bladder, uterus, and urethra are thoroughly explored, accompanied by their respective future prospects. Consequently, this review enhances our understanding of the applications of SIS in tissue and organ repair and keeps researchers up-to-date with the latest research advancements in this area.

Successful Use of Acellular Small Intestinal Submucosa Graft in Vaginal Reconstruction

PURPOSE

Various techniques for neovaginal construction have been employed in the pediatric and adult populations, including the use of intestinal segments, buccal mucosal grafts, and skin grafts. Small intestinal submucosa (SIS) extracellular matrix grafts have been described as a viable alternative, though prior experience is limited. Our purpose was to assess operative characteristics and patient outcomes with neovaginal construction using SIS grafts.

METHODS

Thirteen patients underwent vaginoplasty with acellular porcine SIS grafts at our institution between 2018 and 2022. Operative and clinical data, postoperative mold management, vaginal dilating length, and complications were reviewed.

RESULTS

Age at time of repair ranged from 13 to 30 years (median 19 years). Patient diagnosis included cloacal anomalies (n = 4), Mayer-Rokitansky-Küster-Hauser syndrome (n = 4), isolated vaginal atresia with or without a transverse vaginal septum (n = 4), and vaginal rhabdomyosarcoma requiring partial vaginectomy (n = 1). Following dissection of the neovaginal space, a silicon mold wrapped with SIS graft was placed with retention sutures and removed on postoperative day 7. Median (IQR) operative time was 171 (118-192) minutes, estimated blood loss was 10 (5-20) mL, and length of stay was 2 (1-3) days. The follow-up period ranged from 3 to 47 months (median 9 months). Two patients developed postoperative vaginal stenosis that resolved with dilation under anesthesia. Mean vaginal length on latest follow-up was 8.97 cm. All thirteen patients had successful engraftment and progressed to performing self-dilations or initiating intercourse to maintain patency. There were no cases of graft reaction or graft extrusion.

CONCLUSIONS

We conclude that acellular small intestinal submucosa grafts are effective and safe alternatives for mold coverage in neovaginal construction. Our experience demonstrates minimal perioperative morbidity, early mold removal, and progression to successful dilation with maintenance of a functional vaginal length. Future study on sexual outcomes, patient satisfaction, and comparison against alternative techniques has been initiated.

LEVEL OF EVIDENCE

IV.

TYPE OF STUDY

Retrospective Study.

Decellularization of Small Intestinal Submucosa

Small intestinal submucosa (SIS) is the most studied extracellular matrix (ECM) for repair and regeneration of different organs and tissues. Promising results of SIS-ECM as a vascular graft, led scientists to examine its applicability for repairing other tissues. Overall results indicated that SIS grafts induce tissue regeneration and remodeling to almost native condition. Investigating immunomodulatory effects of SIS is another interesting field of research. SIS can be utilized in different forms for multiple clinical and experimental studies. The aim of this chapter is to investigate the decellularization process of SIS and its common clinical application.

The promise of regenerative medicine in the treatment of urogenital disorders

Polymers and scaffolds are the most significant tools in regenerative medicine. Urogenital disorders are an important group of diseases that greatly affect the patient's life expectancy and quality. Reconstruction of urogenital defects is one of the current challenges in regenerative medicine. Regenerative medicine, as well as tissue engineering, may offer suitable approaches, while the tools needed are appropriate materials and cells. Autologous urothelial cells obtained from biopsy, bone marrow-derived stem cells, adipose stem cells and urine-derived stem cells that expressed mesenchymal cell markers are the cells that mainly used. In addition, two main types of biomaterials mainly exist; synthetic polymers and composite scaffolds that are biodegradable polymers with controllable properties and naturally derived biomaterials such as extracellular matrix components and acellular tissue matrices. In this review, we present and evaluate the most appropriate and suitable scaffolds (naturally derived and synthetic polymers) and cells applied in urogenital reconstruction.

Mechanical induction of bi-directional orientation of primary porcine bladder smooth muscle cells in tubular fibrin-poly(vinylidene fluoride) scaffolds for ureteral and urethral repair using cyclic and focal balloon catheter stimulation

To restore damaged organ function or to investigate organ mechanisms, it is necessary to prepare replicates that follow the biological role model as faithfully as possible. The interdisciplinary field of tissue engineering has great potential in regenerative medicine and might overcome negative side effects in the replacement of damaged organs. In particular, tubular organ structures of the genitourinary tract, such as the ureter and urethra, are challenging because of their complexity and special milieu that gives rise to incrustation, inflammation and stricture formation. Tubular biohybrids were prepared from primary porcine smooth muscle cells embedded in a fibrin gel with a stabilising poly(vinylidene fluoride) mesh. A mechanotransduction was performed automatically with a balloon kyphoplasty catheter. Diffusion of urea and creatinine, as well as the bursting pressure, were measured. Light and electron microscopy were used to visualise cellular distribution and orientation. Histological evaluation revealed a uniform cellular distribution in the fibrin gel. Mechanical stimulation with a stretch of 20% leads to a circumferential orientation of smooth muscle cells inside the matrix and a longitudinal alignment on the outer surface of the tubular structure. Urea and creatinine permeability and bursting pressure showed a non-statistically significant trend towards stimulated tissue constructs. In this proof of concept study, an innovative technique of intraluminal pressure for mechanical stimulation of tubular biohybrids prepared from autologous cells and a composite material induce bi-directional orientation of smooth muscle cells by locally and cyclically applied mechanical tension. Such geometrically driven patterns of cell growth within a scaffold may represent a key stage in the future tissue engineering of implantable ureter replacements that will allow the active transportation of urine from the renal pelvis into the bladder.

Tissue Engineering of Ureteral Grafts: Preparation of Biocompatible Crosslinked Ureteral Scaffolds of Porcine Origin

The surgical reconstruction of ureteric defects is often associated with post-operative complications and requires additional medical care. Decellularized ureters originating from porcine donors could represent an alternative therapy. Our aim was to investigate the possibility of manufacturing decellularized ureters, the characteristics of the extracellular matrix (ECM) and the biocompatibility of these grafts in vitro/in vivo after treatment with different crosslinking agents. To achieve these goals, native ureters were obtained from pigs and were decellularized. The success of decellularization and the ECM composition were characterized by (immuno)histological staining methods and a DNA-assay. In vitro: scaffolds were crosslinked either with carbodiimide (CDI), genipin (GP), glutaraldehyde, left chemically untreated or were lyophilized. Scaffolds in each group were reseeded with Caco2, LS48, 3T3 cells, or native rat smooth muscle cells (SMC). After 2 weeks, the number of ingrown cells was quantified. In vivo: crosslinked scaffolds were implanted subcutaneously into rats and the type of infiltrating cells were determined after 1, 9, and 30 days. After decellularization, scaffold morphology and composition of ECM were maintained, all cellular components were removed, DNA destroyed and strongly reduced. In vitro: GP and CDI scaffolds revealed a higher number of ingrown 3T3 and SMC cells as compared to untreated scaffolds. In vivo: at day 30, implants were predominantly infiltrated by fibroblasts and M2 anti-inflammatory macrophages. A maximum of MMP3 was observed in the CDI group at day 30. TIMP1 was below the detection limit. In this study, we demonstrated the potential of decellularization to create biocompatible porcine ureteric grafts, whereas a CDI-crosslink may facilitate the remodeling process. The use of decellularized ureteric grafts may represent a novel therapeutic method in reconstruction of ureteric defects.

Intestinal seromuscular tunneling: a novel method for ureteral replacement--an experimental design

BACKGROUND

Long-segment ureteral injuries may have different etiologies. Although multiple procedures have been previously used for ureteral replacement, none of them had optimum results, and replacement of long segments of injured ureter is still a challenging surgical problem. In this article, we have hypothesized that it may be possible to use intestinal seromuscular tunneling as a novel method for ureteral replacement.

METHODS

This experimental study was conducted on eight dogs. After cutting the ureter at about its mid-part and ligating the distal part, a 10-cm tunnel was made in the seromuscular layer of small intestine using a metallic probe, and a catheter was passed through it. Proximal and distal ends of the tunnel were anastomosed to proximal end of ureter and urinary bladder, respectively. After 8 weeks, the dogs were killed, and their whole urinary system was sent for histopathologic examinations.

RESULTS

No complication was noted during the post-op period. Histopathologic examinations confirmed that the seromuscular tunnel was well patent, lined by pseudostratified transitional epithelium and without any inflammatory reaction.

CONCLUSION

Our study shows that ureteral replacement by intestinal seromuscular tunneling is anatomically possible at least in animal model. However, more well-designed prospective studies are needed to confirm its long-term functional results.

Recent advances in ureteral tissue engineering

Reconstruction of long ureteral defects often warrants the use of graft tissue and extensive surgical procedures to maintain the safe transport of urine from the kidneys to the urinary bladder. Complication risks, graft failure-related morbidity, and the lack of suitable tissue are major concerns. Tissue engineering might offer an alternative treatment approach in these cases, but ureteral tissue engineering is still an underreported topic in current literature. In this review, the most recent published data regarding ureteral tissue engineering are presented and evaluated, with a focus on cell sources, implantation strategies, and (bio)materials.

Ureter regeneration-the proper scaffold has to be defined

The aim of this study was to compare two different acellular scaffolds: natural and synthetic, for urinary conduit construction and ureter segment reconstruction. Acellular aortic arch (AAM) and poly(L-lactide-co-caprolactone) (PLCL) were used in 24 rats for ureter reconstruction in both tested groups. Follow-up period was 4 weeks. Intravenous pyelography, histological and immunohistochemical analysis were performed. All animals survived surgical procedures. Patent uretero-conduit junction was observed only in one case using PLCL. In case of ureter segment reconstruction ureters were patent in one case using AAM and in four cases using PLCL scaffolds. Regeneration of urothelium layer and focal regeneration of smooth muscle layer was observed on both tested scaffolds. Obtained results indicates that synthetic acellular PLCL scaffolds showed better properties for ureter reconstruction than naturally derived acellular aortic arch.

[Avoidance and management of complications in open surgical ureter reconstruction]

Open surgical reconstruction of the ureter is a urological procedure with a potentially high risk of complications. The correct selection of patients and time of operation are important aspects regarding the treatment strategy. Position and length of the affected ureter segment to be reconstructed determine the surgical intervention possibilities. The psoas hitch procedure is a well-established technique for distal reconstruction of the ureter where most iatrogenic injuries occur. In more proximal or complex defects, several procedures are available. Partial or complete replacement of the ureter with bowel is still considered the standard for bridging long ureteral defects but is accompanied with higher intra- and postoperative complication rates. In specific patients and situations, autotransplantation of the kidney and subcutaneous pyelovesical bypasses are clinical options. Using mucosal grafts or tissue engineering may be new therapeutic prospects to cover ureteral defects but the clinical impact still needs to be clarified. All therapeutic strategies share the fact that great surgical expertise and experience are necessary as the operative technique must be mastered to avoid severe complications.

Traumatic rectourethral fistula repair: A potential application of porcine small intestinal submucosa

Rectourethral fistula is an uncommon but devastating condition. Traumatic rectourethral fistula is still uncommon and repair of traumatic rectourethral fistula involves a complex procedure. Most of the urologists would prefer to repair the fistula through perineal route especially when urethral reconstruction is also required. The repaired ends of the fistula are separated with various interposition flaps and grafts in order to prevent recurrence. Gracilis interposition muscle flap is commonly used. We describe the first case of traumatic rectourethral fistula repair in a 45-year-old man using interposition of a porcine small intestinal submucosal (Biodesign™ (Surgisis^®) graft.

Rabbit Ear Cartilage Regeneration With a Small Intestinal Submucosa Graft

OBJECTIVES/HYPOTHESIS

The objective was to demonstrate that interpositional grafting with porcine small intestinal submucosa promotes cartilage regeneration following excision of rabbit auricular cartilage.

STUDY DESIGN

Blinded, controlled study.

METHODS

Eight New Zealand white rabbits underwent excision of auricular cartilage on two sites with and two sites without preservation of perichondrium. Porcine small intestinal submucosa was implanted into one site with and one site without intact perichondrium. Remaining sites served as control sites. Histological assessment was performed at 3 (n = 4) and 6 (n = 3) months and at 1 year (n = 1) after grafting.

RESULTS

Histological evaluation showed cartilage regeneration accompanied by chronic inflammation in areas in which porcine small intestinal submucosa was implanted between layers of intact perichondrium. Other sites failed to show significant cartilage regeneration.

CONCLUSION

The results of the study using porcine small intestinal submucosa as a bioscaffold for cartilage regeneration are promising and justify further animal and human studies.

Terminal Urothelium Differentiation of Engineered Neoureter After In Vivo Maturation in the “Omental Bioreactor”

OBJECTIVE

Long ureteric defects may theoretically be repaired with the use of tissue-engineered neoureter. However, attempts to construct such a neoureter in animal models have failed because of major inflammatory response. Avoidance of such inflammation requires a well-differentiated urothelium. We investigated whether omental maturation of a seeded construct in a pig model could achieve terminal differentiation of the urothelium to allow construction of a stricture-free neoureter.

MATERIAL AND METHOD

Bladder biopsies were taken to allow urothelial and smooth muscle cell cultures. These cultured cells were used to seed small intestinal submucosa (SIS) matrix. After 2 wk of cell growth, the in vitro SIS-seeded construct was shaped around a silicone drain and wrapped by the omentum to obtain neoureters. These neoureters were left in the omentum without any contact with urine, and then harvested 3 wk later for histologic and immunohistochemical studies.

RESULTS

Before implantation, the in vitro constructs were composed of a mono- or bilayer of undifferentiated urothelium overlying a monolayer of smooth muscle cells. After 3 wk of omental maturation, these constructs were vascularized and comprised a terminally differentiated multilayered urothelium with umbrella cells over connective tissue and smooth muscle cells, with no evidence of fibrosis or inflammation.

CONCLUSION

We obtained, for the first time, with this model of in vivo maturation in the omentum, a mature neoureter composed of a well-differentiated multilayered urothelium.

Functional evaluation of the grafted wall with porcine-derived small intestinal submucosa (SIS) to a stomach defect in rats

BACKGROUND

Small intestinal submucosa (SIS) represents a novel bio-scaffolding material that may be used to repair hollow-organ defects. However, it is unclear whether neurophysiologic responses return to SIS-grafted areas in the gut. We evaluated the functional recovery of a stomach defect grafted with the porcine-derived SIS.

METHODS

Twelve rats had a full-thickness defect created in the stomach. SIS was secured to the gastric wall. After 6 months, muscle strips were harvested from within the grafted area to perform both a histologic and a functional study. Additional full-thickness muscle strips were harvested from the posterior in the same stomach as controls. A dose response curve was obtained with carbachol (CCH) or sodium nitroprusside (SNP). Activation of intrinsic nerves was achieved by electrical field stimulation (EFS).

RESULTS

The response to CCH and amplitude in EFS showed tonic contraction in both controls and SIS strips in a concentration-dependent and frequency-dependent manner. The magnitude after each stimulation was significantly lower in SIS strips compared with controls (P < .01). However, the contraction ratio of EFS to ED(50) of CCH was not significantly different between the groups. Additionally, SNP produced relaxation in both strips in a concentration-dependent manner. Histologic findings revealed that an insufficient amount of smooth-muscle cells existed in the muscularis propria, whereas compensated growth was observed in the submucosa with nerve regeneration.

CONCLUSIONS

This study demonstrates that SIS provides a template for nerve migration to the graft in the rodent stomach. Innervations showed a similar distribution to that observed in the controls. The clinical implications of such findings warrant additional investigation.

The Artificial Conduit for Urinary Diversion in Rats: A Preliminary Study

OBJECTIVES

Small intestinal submucosa forms a scaffold for tubular construction. The aim of this study was to build the artificial conduit using small intestinal submucosa (SIS) and 3T3 fibroblasts for urinary diversion in rats.

MATERIALS AND METHODS

3T3 fibroblasts were multiplied to a total of 10(9). Two groups consisted of three Wistar rats each. The left ureters were separated from the bladder and anastomosed to the proximal end of the tubular scaffold. No splitting of the ureteral junction or drainage was done. The distal end of the scaffold was implanted into a previously performed channel in the abdominal wall. Cell-seeded grafts were used in the first group and acellular SIS scaffolds in the second group. Rats were sacrificed after 2 and 4 weeks. X-ray pyelography was performed. Hematoxylin and eosin staining was prepared from conduit cross sections.

RESULTS

All animals survived the observation. An inflammatory reaction was observed within the peritoneal cavity in both groups. It was difficult to dissect the adhesions in the cell-seeded group. The ureteral-conduit anastomoses were tight in five cases, except there was leakage and pseudocyst formation after 14 days in one cell-seeded graft. No ureterohydronephrosis was observed in two acellular conduits after 14 or 30 days, and in one case of a cell-seeded graft. A neovascularisation process was observed in the acellular conduit after a month. Multilayered epithelium covered the conduit lumen near the anastomosis at the distal end of acellular conduit, a small islet-forming epithelial layer was observed after a month.

CONCLUSIONS

3T3 fibroblasts cannot serve as a "feeder layer" for ureteral augmentation. It seems that there is no need to split the ureteral-conduit junction. An SIS scaffold was used for tubular construction for urinary diversion in an animal model.

Small intestinal submucosa as a potential bioscaffold for intervertebral disc regeneration

STUDY DESIGN

To evaluate the capacity of porcine small intestine submucosa to support the in vitro proliferation of human disc cells and the synthesis of extracellular matrix that could restore the biochemical properties of the disc.

OBJECTIVE

To evaluate if porcine small intestine submucosa is a potential bioactive scaffold for rescuing degenerative disc cells.

SUMMARY OF BACKGROUND DATA

Discogenic back pain is associated with alterations of the disc and abnormal turnover of the disc extracellular matrix. We hypothesize that a biodegradable and biocompatible acellular scaffold such as small intestine submucosa, which contains entrapped growth factors, may stimulate disc cells to synthesize extracellular matrix, thereby arresting the degeneration, or even promoting the regeneration, of the disc.

METHODS

Human degenerative anulus and nucleus cells were seeded onto small intestine submucosa scaffolds, and evaluated over a 3-month period for cell growth (proliferation assay, deoxyribonucleic acid content) and matrix composition (glycosaminoglycan and collagen contents).

RESULTS

As hematoxylin and eosin staining revealed, more than 70% of seeded cells attached to the small intestine submucosa surface and invaded throughout the scaffold. The macroscopic appearance of cell-seeded scaffolds was dramatically modified over time. Cell metabolic activity was confirmed for up to 3 months. Seeded scaffolds showed a higher glycosaminoglycan content as compared to control scaffolds. Toluidine blue staining detected large areas of proteoglycans. Positive gene expression for collagens I, II, and X, aggrecan, and Sox-9 confirmed deposition of new extracellular matrix components.

CONCLUSIONS

This pilot study shows that small intestine submucosa is a promising bioactive material that could potentially serve as a temporary scaffold for intervertebral disc regeneration.

Esophageal replacement in rat using porcine intestinal submucosa as a patch or a tube-shaped graft

This study compares the efficacy of porcine intestinal submucosa (SIS) patch graft versus SIS-tube graft in esophageal replacement, using a novel esophageal regeneration model. Clinical function, as well as macroscopic and microscopic morphology were evaluated in both SIS-treated groups. We performed semi-circumferential esophageal excision followed by repair of the defect using either a SIS-patch graft (group I) or segmental esophageal excision followed by a SIS-tube interposition graft (group II) in rats. The 28-day survival rate was significantly different between the SIS-treated groups (100% in group I vs. 0% in group II). Unlike the rats in group II, which died within the first postoperative month due to esophageal dysfunction, all surviving animals in group I resumed a normal solid diet within a few days after surgery, without signs of esophageal dysfunction and gained weight. Barium swallow studies showed no evidence of fistula, significant stenosis or diverticula. No hematological or serum biochemistry abnormalities were found. By day 150 the SIS patch was replaced by esophageal-derived tissues. In the rat model, a patch graft technique using SIS appeared to induce esophageal regrowth and provided an initial and long-term satisfactory function, while a tube-shaped graft technique using SIS was unsuccessful.

First prize: ureteral segmental replacement revisited

BACKGROUND AND PURPOSE

Long strictures of the proximal ureter are difficult to manage, and circumferential replacement with various natural and synthetic materials has been unsuccessful. We sought to use cultured autologous cells seeded onto graft material for proximal-ureteral replacement. Additionally, we wished to determine if urothelial cell-seeded de-epithelialized small bowel would generate adequate ureteral replacement.

MATERIALS AND METHODS

Three sets of experiments were performed. First, autologous pig-bladder smooth-muscle and urothelial cells were expanded in culture on large sheets of multilayer small-intestinal submucosa (SIS). These sheets were then tubularized and used to replace a 5-cm segment of proximal ureter in pigs. Second, autologous cells harvested from the bladders of Beagle dogs were cultured and seeded on porcine ureteral acellular matrix, which was used to replace a 3-cm segment of ureter in dogs. Segments were wrapped in omentum to enhance vascularity. Third, a de-epithelialized small-bowel segment seeded with autologous bladder-epithelial cells was transversally retubularized (Monti) into a 4-cm ureteral replacement. Follow-up studies consisted of retrograde pyelography, serum chemistry assays, hematoxylin/eosin studies, and immunohistopathologic examination using antibodies against alpha-smooth-muscle actin and pancytokeratin AE1-AE3.

RESULTS

Coculture of urinary-tract cells on large segments of SIS failed to create adequate ureteral replacement. All grafts were contracted and stenotic, with complete obstruction of the ipsilateral renal unit. Similar results were seen in the Beagles. Despite clinical obstruction and gross contraction of the graft, a circumferential muscular ureteral wall lined with multilayer transitional epithelium was present. Urotheliumseeded de-epithelialized Monti bowel segments resulted in patent ureteral replacement without hydroureteronephrosis and with normal renal function, serum electrolytes, and acid-base balance. However, bowel mucosa fully regenerated, with multilayer transitional epithelium growing adluminally in continuity with the proximal and distal anastomotic sites.

CONCLUSIONS

Seeding of ureteral grafts with autologous bladder cells does not promote success in two largeanimal models using different xenogenic acellular matrices. However, muscle and urothelium regeneration occurs with ureteral acellular matrix in the dog. Urothelium-seeded de-epithelialized Monti bowel segments may be an acceptable substitute for long proximal ureteral segments. Further technical refinements are required to replace the bowel mucosa completely with normal urothelium.

Tissue Engineering in Urology: Between Basic Research and Clinical Applications

Tissue engineering follows the principles of cell and tissue culture, cloning and stem cell production, and materials science to develop biological substitutes, which could repair and maintain normal function. The biomaterials must be able to control the structure and function of engineered tissue by interacting with both transplanted and host cells. Either natural or synthetic biodegradable materials have been used as cell delivery scaffolds. The stem cell field is also advancing rapidly, opening new options for regenerative medicine. In the genitourinary system, tissue engineering has been applied experimentally for the reconstitution of pelvis, ureter, bladder, urethra, penile corpora cavernosa and testis. This literature review underlines recent advances that have occurred in tissue engineering and describes their clinical repercussions, particularly in offering novel therapies in urogenital pathology.

Xenogeneic extracellular matrix as a scaffold for tissue reconstruction

Bioscaffolds derived from xenogeneic extracellular matrix (ECM) have been used in numerous tissue engineering applications. The safety and efficacy of such scaffolds when used for the repair and reconstruction of numerous body tissues including musculoskeletal, cardiovascular, urogenital and integumentary structures has been shown in both preclinical animal studies and in human clinical studies. More than 200,000 human patients have been implanted with xenogeneic ECM scaffolds. These ECM scaffolds are typically prepared from porcine organs such as small intestine or urinary bladder, which are subjected to decellularization and terminal sterilization without significant loss of the biologic effects of the ECM. The composition of these bioscaffolds includes the structural and functional proteins that are part of native mammalian extracellular matrix. The three-dimensional organization of these molecules distinguishes ECM scaffolds from synthetic scaffold materials and is associated with constructive tissue remodeling instead of scar tissue. The biologic response to these xenogeneic bioscaffolds, including the immune response, is discussed herein.

Utilização da submucosa de intestino delgado porcino como retalho para aumento da capacidade vesical em cães

Objetivo: Avaliar a biocompatibilidade de um enxerto xenogênico de SID como meio de ampliação da capacidade vesical. Métodos: Oito cães mestiços foram submetidos à laparotomia e abertura da bexiga por incisão mediana de 3cm em sua face ventral. Para aumento da capacidade vesical, bem como sua reconstituição, foi interposto um segmento de submucosa porcina, fixando-o à parede vesical. No 30°dia de pós-operatório os animais foram sacrificados e procedeu-se à análise macroscópica. As peças foram então encaminhadas para fixação, coloração e análise microscópica. Resultados: Não se observou seroma, hematoma, abscesso, fístula, deiscência, aderências, litíase e a não incorporação do enxerto. Microscopicamente observou-se em todos os casos uma proliferação do urotélio que recobriu toda a superfície do enxerto, além da presença de fibras musculares lisas no local do implante. Verificou-se proliferação conjuntiva, principalmente às custas de colágeno imaturo do tipo III e reação inflamatória crônica em todos os animais. A proliferação vascular foi acentuada e a reabsorção da membrana foram também observadas. Conclusão: Asubmucosa de intestino delgado porcino participou como um substrato para a regeneração da bexiga e pode ser uma futura alternativa na reconstrução do trato urinário.

Tissue Engineering der Harnr�hre und des Harnleiters

Congenital or acquired disorders of the urethra or ureter often require adequate tissue transfer for reconstruction. A variety of biomaterials have proved to be useful in the reconstruction of the urethra or ureter in animal models and meanwhile even clinically. Innovative tissues such as acellular matrices can be placed in the host and function as a scaffold to allow the natural process of tissue regeneration. Biodegradable scaffolds can also be used as cell transplantation vehicles for the reconstruction of urethral or ureteral tissue. One of the limitations of cell-based tissue engineering techniques however is the difficulty of growing genitourinary-associated cells in large quantities in primary cultures. It can be speculated that stem cell research might help to overcome this specific problem in the future.

Ureteral replacement using small-intestinal submucosa and a collagen inhibitor in a porcine model

PURPOSE

Small-intestinal submucosa (SIS) has been successful as an onlay graft in ureteral repair, but tubularized segment interposition of SIS has been unsuccessful. Our objective was to evaluate whether a type I collagen inhibitor, halofuginone, would prevent stricture formation in tubularized SIS interposition.

MATERIALS AND METHODS

We performed either laparoscopic partial ureteral excision followed by an SIS onlay graft (N = 5) or complete laparoscopic ureteral excision followed by an SIS interposition graft (N = 7) in domestic pigs. Animals received either no (N = 3), low-dose (N = 5), or high-dose (N = 4) halofuginone. Animals had ureteral stenting for 2 weeks after surgery and were permitted to survive for 6 or 9 weeks. An intravenous urogram (IVU) was performed prior to sacrifice. Kidneys were examined grossly and histologically.

RESULTS

One animal that received an onlay graft died of an unrelated illness. The remaining four ureteral onlay animals, including one control and two low-dose and one high-dose pig, had grossly normal kidneys at harvest. The IVU was normal in the control and high-dose animal but showed delayed excretion with mild hydroureteronephrosis in the low-dose animals. Pathologic examination of the SIS site revealed circumferential reepithelialization with inflammation and mild fibrosis. All seven tubularized interposition graft kidneys demonstrated either severe hydroureteronephrosis (N = 5) or renal atrophy (N = 2), and all had complete obstruction on IVU. Pathologic examination revealed a stenotic ureteral lumen with extensive surrounding inflammation and fibrosis.

CONCLUSIONS

An SIS onlay graft was successful in the porcine model of ureteral injury. Halofuginone, a type I collagen inhibitor, did not demonstrate a significant beneficial effect in this technique. Ureteral tubularized interpositions with SIS are unsuccessful and not improved by halofuginone.

Lichtenstein repair of inguinal hernia with Surgisis inguinal hernia matrix soft-tissue graft in immunodepressed patients

While polypropylene mesh remains the preferred prosthesis material for hernioplasties, there are some problems with infections, intestinal obstruction and fistulization, and migration particularly in immunodepressed patients. A new degradable and reabsorbable material, the porcine small intestinal submucosa (Surgisis) has been developed for hernia repairs in humans. This prospective study evaluated the safety and efficacy of Lichtenstein hernioplasty using the Surgisis inguinal hernia matrix soft-tissue graft as a mesh in ten immunodepressed subjects. Six subjects were HIV-positive in the immunodepressive phase, and the other four had undergone transplantation (three kidney, one liver). There were no intraoperative or postoperative complications, recurrences, or wound infections. Thus Lichtenstein's hernioplasty using the Surgisis inguinal hernia matrix soft-tissue graft in immunodepressed patients promises safety and efficacy.

Canine ureteral replacement with long acellular matrix tube: is it clinically applicable?

PURPOSE

We evaluated the effectiveness of acellular matrix used as a tube for replacement of a relatively long segment of the canine ureter.

MATERIALS AND METHODS

Acellular matrix was obtained by excision of the whole ureter of donor dogs that were sacrificed and not included in the study group. Retrieved ureters were treated to have complete cell lysis, while maintaining the fiber framework. The study included 10 mongrel dogs in which a 3 cm segment was excised from 1 ureter and replaced by a tube of acellular matrix of the same length and width. The new tube was sutured proximal and distal by watertight interrupted sutures around a 5Fr Double-J stent (Medical Engineering Corp., New York, New York) that remained for 6 weeks. Excretory urography was done 1 and 2 weeks after stent removal and the dogs were then sacrificed. Before sacrifice the ureter was exposed and carefully examined, and the whole specimen was excised for histopathological examination.

RESULTS

All dogs survived surgery except 1, which died 1 week postoperatively of a malpositioned stent and urinary ascites. There was no clinically apparent postoperative complications during the presence or after the removal of the ureteral stents. One week after stent removal excretory urography showed ipsilateral mild to moderate hydroureteronephrosis in 3 dogs and no dye excretion in 6 with a normal contralateral kidney. One week later no dye excretion was detected in all except 1 dog, which showed more radiological deterioration. At the time of sacrifice there was moderate to marked hydroureteronephrosis above the level of the new tube in all dogs. Although the graft was intact in all subjects, marked shrinkage was observed. On ureteral calibration there was significant narrowing of the lumen up to complete occlusion. At 8 weeks histopathological examination showed extensive fibrosis.

CONCLUSIONS

An acellular matrix tube is not able to replace a 3 cm segment of the canine ureter.

4 LAYER VERSUS 1 LAYER SMALL INTESTINAL SUBMUCOSA FOR CORRECTION OF PENILE CHORDEE: EXPERIMENTAL STUDY IN A RABBIT MODEL

PURPOSE

We evaluated the use of 4 vs 1 layer small intestinal submucosa (SIS) for covering defects in the ventral surface of the tunica albuginea to correct severe chordee.

MATERIALS AND METHODS

A total of 18 New Zealand white rabbits underwent implantation of a 10 x 5 mm SIS graft following excision of a rectangular area in the ventral surface of the tunica albuginea. In 9 rabbits 4 layer SIS was used to cover the defect and in the remaining animals 1 layer SIS was used. The animals were sacrificed at 2, 6 and 12-week intervals postoperatively, respectively. The surface area of the grafts was measured and the percent of contracture was calculated. Transverse sections of the penis at the graft site were stained with hematoxylin and eosin, and Masson's trichrome, and examined microscopically.

RESULTS

: None of the animals had hematoma or bleeding. At autopsy contracture was not seen in any of the rabbits with 1 layer SIS. On the contrary, there was 21% and 25% contracture at 6 and 12 weeks, respectively, in the 4 layer SIS group. At 12 weeks the 1 layer SIS graft was completely replaced by well collagenized tissue similar to that of normal tunica albuginea without inflammatory infiltrate, while the multilayer SIS graft was replaced by dense fibrous tissue with areas of chronic inflammation and other focal areas of calcification.

CONCLUSIONS

Four layer SIS undergoes contracture and calcification when used to cover defects in the tunica albuginea. On the other hand, 1 layer SIS can be safely and reliably used for corporeal grafting.

URINARY TRACT BIOMATERIALS

PURPOSE

As a result of endourological advances, biomaterials have become increasingly used within the urinary tract. This review article provides an update on the current status of urinary tract biomaterials, discussing issues of biocompatibility, biomaterials available for use, clinical applications and biomaterial related complications. Perspectives on future materials for use in the urinary tract are also provided.

MATERIALS AND METHODS

We performed a comprehensive search of the peer reviewed literature on all aspects of biomaterials in the urinary tract using PubMed and MEDLINE. All pertinent articles were reviewed in detail.

RESULTS

Any potential biomaterial must undergo rigorous physical and biocompatibility testing prior to its commercialization and use in humans. There are currently many different bulk materials and coatings available for the manufacturing of biomaterials, although the ideal material has yet to be discovered. For use in the urinary tract, biomaterials may be formed into devices, including ureteral and urethral stents, urethral catheters and percutaneous nephrostomy tubes. Despite significant advances in basic science research involving biocompatibility issues and biofilm formation, infection and encrustation remain associated with the use of biomaterials in the urinary tract and, therefore, limit their long-term indwelling time.

CONCLUSIONS

Prosthetic devices formed from biomaterials will continue to be an essential tool in the practicing urologist's armamentarium. Ongoing research is essential to optimize biocompatibility and decrease biomaterial related complications such as infection and encrustation within the urinary tract. Future advances include biodegradables, novel coatings and tissue engineering.

Use of Single Layer Small Intestinal Submucosa for Long Segment Ureteral Replacement: A Pilot Study

PURPOSE

Previous studies have demonstrated successful use of small intestinal submucosa (SIS) as a tube for replacing short segment (11 mm) proximal ureteral defects. However, such small segment ureteral defects could be managed by resection re-anastomosis. We evaluated the use of 1-layer SIS as a tube for the replacement of long segment ureteral defects.

MATERIALS AND METHODS

The ureters of 5 female mongrel dogs were accessed through a median laparotomy incision. A 4 cm segment of mid ureter was resected on the right side. The right ureteral segments were replaced by tubularized SIS segments using 6-zero polydioxanone interrupted sutures. Internal pigtail stents were left for 6 weeks. All animals were sacrificed at 12 weeks. Ureteral patency was assessed by excretory urography and magnetic resonance urography 7 and 12 weeks after the initial procedures. Inflammation and regeneration were assessed histologically.

RESULTS

At 12 weeks all ureters on the experimental side were completely occluded with significant hydroureteronephrosis and the subsequent deterioration of kidney function. At autopsy there was failure to calibrate any of the experimental ureters with a 3Fr catheter. Although histologically urothelium and muscular cells had proliferated over the graft, they were embedded in an intense fibrotic and inflammatory process.

CONCLUSIONS

Technically 1-layer SIS was easily modeled, providing the conditions for watertight anastomosis. The regeneration of urothelium and muscle was induced and supported by the graft. However, functional replacement was not successful. One-layer SIS is not a suitable material for replacing long segment (4 cm) ureteral defects.

8-ply small intestinal submucosa tension-free sling: spectrum of postoperative inflammation

PURPOSE

We report a series of postoperative inflammatory reactions of a tension-free pubourethral sling procedure using an 8-ply small intestinal submucosa (SIS) and review the literature regarding inflammatory reactions with this material in genitourinary reconstruction.

MATERIALS AND METHODS

Between August 2002 and June 2003, 6 of 10 patients treated for stress urinary incontinence with 8-ply SIS had postoperative inflammatory reactions. Patients underwent a thorough evaluation, including history, physical examination and urodynamic studies, before surgical intervention.

RESULTS

All patients presented with induration and erythema at the abdominal incision site(s) and pain 10 to 39 days postoperatively. Pelvic examinations were negative. In 3 patients the inflammatory reaction resolved with minimal or no intervention. Incision and drainage of a sterile abscess were required in 1 patient. Despite 7 days of prophylactic postoperative antibiotics and anti-inflammatory drugs, 2 patients had delayed inflammatory reactions. One patient had resolution with conservative treatment, while the other had an abscess that spontaneously drained. With short-term followup (mean 7 months, range 4 to 10), 8 patients are dry, 1 is improved and 1 is incontinent.

CONCLUSIONS

While the results with the 8-ply SIS tension-free sling in the short term are encouraging, the additional morbidity is alarming and caution is warranted. It is essential that patients be made aware of potential risks and possible delayed presentation of morbidity with the use of this material. The human to 8-ply SIS interaction needs further investigation to ensure that long-term safety and efficacy will not be jeopardized. Until then we will continue to use other sling materials.

Multilayered small intestinal submucosa is inferior to autologous bowel for laparoscopic bladder augmentation

PURPOSE

Bladder augmentation is most commonly performed with ileum. However, porcine small intestinal submucosa has been reported as a substitute for bowel for incorporation into the urinary tract. We assessed the feasibility and long-term 12-month results of laparoscopic bladder augmentation with ileum or multilayered small intestinal submucosa (Cook Biotech, Spencer, Indiana) in a porcine model.

MATERIALS AND METHODS

We performed laparoscopically assisted hemicystectomy and bladder augmentation in 24 female Yucatan mini-pigs using an ileal segment (12) or multilayered small intestinal submucosa (12). The followup protocol included anesthetic bladder capacity, renal ultrasonography and serum chemistry. At 3, 6 and 12 months, respectively, 4 animals per group were scheduled for sacrifice and pathological analysis.

RESULTS

Despite longer anastomotic time in the multilayered small intestinal submucosa group (120 versus 91 minutes, p = 0.026) total operative time was similar in the 2 groups. In each group bladder capacity increased with time but by 12 months bladder capacity was significantly better in the bowel than in the small intestinal submucosa group (825 versus 431 cc, p = 0.016). At 3 months pathological evaluation revealed that the multilayered regenerated bladder patch had shrunken and by 6 months it was replaced by dense calcified scar tissue. Long-term 6 and 12-month bladder capacity in the small intestinal submucosa group was the result of the regeneration of native bladder with exclusion of the whole multilayered patch in the majority of cases.

CONCLUSIONS

Laparoscopic bladder augmentation using multilayered small intestinal submucosa produced functional and pathological results inferior to those of bowel at 12-month followup in a porcine model.