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

Van der Waals Exfoliation Processed Biopiezoelectric Submucosa Ultrathin Films

Piezoelectric biomaterials have attracted significant attention due to the potential effect of piezoelectricity on biological tissues and their versatile applications. However, the high cost and complexity of assembling and domain aligning biomolecules at a large scale, and the disordered arrangement of piezoelectric domains as well as the lack of ferroelectricity in natural biological tissues remain a roadblock toward practical applications. Here, utilizing the weak van der Waals interaction in the layered structure of small intestinal submucosa (SIS), a van der Waals exfoliation (vdWE) process is reported to fabricate ultrathin films down to the thickness of the effective piezoelectric domain. Based on that, the piezoelectric property is revealed of SIS stemming from the collagen fibril, with piezoelectric coefficients up to 4.1 pm V^-1 and in-plane polarization orientation parallel to the fibril axis. Furthermore, a biosensor based on the vdWE-processed SIS film with an in-plane electrode is demonstrated that produces open-circuit voltages of ≈250 mV under the cantilever vibration condition. The vdWE method shows great potential in facilely fabricating ultrathin films of soft tissues and biosensors.

What's in the Pipeline about Bladder Reconstructive Surgery? Some Remarks on the State of the Art

The fusion of engineering with cell biology and advances in biomaterials may lead to de novo construction of implantable organs. Engineering of neobladder from autologous urothelial and smooth muscle cells cultured on biocompatible, either synthetic or naturally-derived substrates, is now feasible in preclinical studies and may have clinical applicability in the near future. The development of a bioartificial bladder would warrant the prevention of both the metabolic and neoplastic shortcomings of the intestinal neobladder. Two tissue-engineering techniques for bladder reconstruction have been tested on animals: 1) the in vivo technique involves the use of naturally-derived biomaterials for functional native bladder regeneration 2) the in vitro technique involves the establishment of autologous urothelial and smooth muscle cell culture from the host's urinary tract, after which the cells are seeded on the biodegradable matrix-scaffold to create a composite graft that is implanted into the same host for complete histotectonic regeneration. Waiting for the creation of a complete tissue-engineered bladder with a trigone-shaped base, we suggest, in surgical oncology after radical cystectomy, the realization of conduit or continent pouch using tissue-engineered material.

Renal capsule for augmentation cystoplasty in canine model: a favorable biomaterial?

PURPOSE

To evaluate effectiveness of canine renal capsule for augmentation cystoplasty.

MATERIALS AND METHODS

Ten adult dogs participated in this study. After induction of anesthesia each animal underwent bed side urodynamic study, bladder capacity and bladder pressure was recorded. Then via mid line incision abdominal cavity was entered, right kidney was identified and its capsule was dissected. Bladder augmentation was done by anastomosing the renal capsule to the bladder. After 6 months bed side urodynamic study was performed again and changes in bladder volume and pressure were recorded. Then the animals were sacrificed and the augmented bladders were sent for histopathology evaluation.

RESULTS

Mean maximum anatomic bladder capacity before cystoplasty was 334.00±11.40cc which increased to 488.00±14.83cc post-operatively (p=0.039). Mean anatomic bladder pressure before cystoplasty was 19.00±1.58cmH2O which decreased to 12.60±1.14cmH2O post-operatively (p=0.039). Histopathology evaluation revealed epithelialization of the renal capsule with urothelium without evidence of fibrosis, collagen deposits or contracture.

CONCLUSIONS

Our data shows that renal capsule is a favorable biomaterial for bladder augmentation in a canine model.

Bladder tissue engineering: a literature review

PURPOSE OF REVIEW

In bladder cancer and neuro-bladder, reconstruction of the bladder requires bowel segment grafting for augmentation cystoplasty or neo-bladder creation. However, even if currently considered as the gold standard, it is associated with potentially severe short- and long-term adverse effects. Thus, bladder tissue engineering is a promising approach to bladder reconstruction.

RECENT FINDINGS

In the last few years, progress has been made with the development of new biomaterials for bladder tissue replacement and in deciphering the role of stem cells as well as their contribution to bladder scaffold integration and tissue regeneration.

SUMMARY

This review of recently published articles allows us to forecast the characteristics of efficient and safe bladder biomaterials. However, several factors, such as native bladder traits, the specific involvement of urine, and bladder tissue replacement indications, have to be assessed with caution before including bladder tissue engineering in clinical trials. Many authors agree that these challenging techniques could deliver significant benefits with clinical application, reducing morbidity and global long-term costs.

Biomatrices for bladder reconstruction

There is a demand for tissue engineering of the bladder needed by patients who experience a neurogenic bladder or idiopathic detrusor overactivity. To avoid complications from augmentation cystoplasty, the field of tissue engineering seeks optimal scaffolds for bladder reconstruction. Naturally derived biomaterials as well as synthetic and natural polymers have been explored as bladder substitutes. To improve regenerative properties, these biomaterials have been conjugated with functional molecules, combined with nanotechology, or seeded with exogenous cells. Although most studies reported complete and functional bladder regeneration in small-animal models, results from large-animal models and human clinical trials varied. For functional bladder regeneration, procedures for biomaterial fabrication, incorporation of biologically active agents, introduction of nanotechnology, and application of stem-cell technology need to be standardized. Advanced molecular and medical technologies such as next generation sequencing and magnetic resonance imaging can be introduced for mechanistic understanding and non-invasive monitoring of regeneration processes, respectively.

Human urinary bladder regeneration through tissue engineering - an analysis of 131 clinical cases

Replacement of urinary bladder tissue with functional equivalents remains one of the most challenging problems of reconstructive urology over the last several decades. The gold standard treatment for urinary diversion after radical cystectomy is the ileal conduit or neobladder; however, this technique is associated with numerous complications including electrolyte imbalances, mucus production, and the potential for malignant transformation. Tissue engineering techniques provide the impetus to construct functional bladder substitutes de novo. Within this review, we have thoroughly perused the literature utilizing PubMed in order to identify clinical studies involving bladder reconstruction utilizing tissue engineering methodologies. The idea of urinary bladder regeneration through tissue engineering dates back to the 1950s. Many natural and synthetic biomaterials such as plastic mold, gelatin sponge, Japanese paper, preserved dog bladder, lyophilized human dura, bovine pericardium, small intestinal submucosa, bladder acellular matrix, or composite of collagen and polyglycolic acid were used for urinary bladder regeneration with a wide range of outcomes. Recent progress in the tissue engineering field suggest that in vitro engineered bladder wall substitutes may have expanded clinical applicability in near future but preclinical investigations on large animal models with defective bladders are necessary to optimize the methods of bladder reconstruction by tissue engineering in humans.

Bladder augmentation with small intestinal submucosa leads to unsatisfactory long-term results

PURPOSE

To evaluate the use of small intestinal submucosa (SIS) for bladder augmentation in a series of select patients.

MATERIAL AND METHODS

Six patients (age 6.5-15.4, mean 9.8 years) underwent bladder augmentation with SIS: one after a cloacal exstrophy repair, one after multiple surgery of the bladder because of vesicoureteral reflux, two with spina bifida, two after bladder exstrophy repair. All suffered from a microbladder with a mean volume of 61.5 ml (range 15-120, 7-36% of expected bladder capacity for age). Preoperative bladder compliance ranged from 1.0 to 3.3 (mean 1.3) ml/cmH2O.

RESULTS

Follow-up time ranged from 4.6 to 33.5 (mean 24.4) months. An increase of bladder volume was achieved in four patients (53-370 ml, 16-95% of expected bladder capacity for age). Bladder compliance postoperatively ranged from 0.9 to 5.6 (mean 3.0) ml/cmH2O. Histological examinations showed a complete conversion of SIS, leaving irregular urothelial lining and bladder wall containing muscular, vascular and relatively thick connective tissue in four patients and regular urothelium in two patients. Major complications were bladder stones in two patients and a bladder rupture in one patient.

CONCLUSION

Bladder augmentation with SIS in humans failed to fulfill the hopes raised by animal studies. Due to the insufficient increase in bladder compliance and therefore failure to accomplish sufficient protection of the upper urinary tract, bladder augmentation with SIS cannot be recommended as a substitute for enterocystoplasty.

Understanding roles of porcine small intestinal submucosa in urinary bladder regeneration: identification of variable regenerative characteristics of small intestinal submucosa

Neuropathic bladders are the result from damages to the central or peripheral nervous system, and ultimately may require surgical reconstruction to increase bladder volumes and to reduce the risk of damages to the kidneys. Surgical reconstruction through bladder augmentation has traditionally been practiced using a segment of the ileum, colon, or stomach from the patient through enterocystoplasty. However, the use of gastrointestinal segments can lead to serious adverse consequences. Porcine small intestinal submucosa (SIS), a xenogeneic, acellular, biocompatable, biodegradable, and collagen-based bioscaffold is best known to encourage bladder regeneration without ex vivo cell seeding before implantation in various experimental and preclinical animal models. Although it has been demonstrated that SIS supports bladder cell growth in vitro, and SIS-regenerated bladders are histologically and functionally indistinguishable from normal functional tissues, clinical utilization of SIS for bladder augmentation has been hampered by inconsistent preclinical results. Several variables in SIS, such as the age of pigs, the region of the small intestine, and method of sterilization, can have different physical properties, biochemical characteristics, inflammatory cell infiltration, and regenerative capacity due to cellular responses in vitro and in vivo. These parameters are particularly important for bladder regeneration due to its specific biological function in urine storage. Clinical application of SIS for surgical bladder reconstruction may require graft materials to be prepared from a specific region of the small intestine, or to be further formulated or processed to provide uniform physical and biochemical properties for consistent, complete, and functional bladder regeneration.

Tissue engineering for the oncologic urinary bladder

Urinary diversion after radical cystectomy in patients with bladder cancer normally takes the form of an ileal conduit or neobladder. However, such diversions are associated with a number of complications including increased risk of infection. A plausible alternative is the construction of a neobladder (or bladder tissue) in vitro using autologous cells harvested from the patient. Biomaterials can be used as a scaffold for naturally occurring regenerative stem cells to latch onto to regrow the bladder smooth muscle and epithelium. Such engineered tissues show great promise in urologic tissue regeneration, but are faced with a number of challenges. For example, the differentiation mesenchymal stem cells from various sources can be difficult and the smooth muscle cells formed do not precisely mimic the natural cells.

Bladder augmentation using tissue-engineered autologous oral mucosal epithelial cell sheets grafted on demucosalized gastric flaps

BACKGROUND

At present, autologous intestinal segments are often used for bladder reconstruction. However, the gastrointestinal mucosa often causes various complications.

METHODS

Oral mucosal tissues were obtained from the buccal cavity of beagle dogs. Primary oral mucosal epithelial cells were cultured on temperature-responsive culture dishes with a mitomycin C-treated 3T3 feeder layer for 2 weeks. Cultured epithelial cells were harvested as contiguous sheets by reducing the temperature to 20°C. The study consisted of three groups. In group 1, oral mucosal epithelial cell sheets were autografted on demucosalized gastric flaps. Next, the gastric flaps with the oral mucosal epithelial cell sheets were used for bladder reconstruction. Bladder reconstruction was once immediately and then 5 days after epithelial cell sheet grafting in groups 2 and 3, respectively. Three weeks after bladder reconstruction, the gastric flaps with the oral mucosal epithelial cell sheets were examined by immunohistology.

RESULTS

Flaps grafted with oral mucosal epithelial cell sheets showed epithelial regeneration in groups 1 and 3. Regenerated epithelia were stratified and similar to native oral mucosa. However, the regenerated epithelium was absent from the reconstructive segment, and urothelial ingrowth was observed in group 2. Macroscopically, all reconstructive segments showed contracture.

CONCLUSIONS

We successfully performed a bladder reconstruction using oral mucosal epithelial cell sheet-grafted flaps that exhibited epithelial regeneration. Further study should consider shrinkage prevention.

Rat Bladders Augmented with a Novel Bovine Pericardium-Derived Biomaterial Reconstruct Functional Tissue Structures

OBJECTIVES

To determine if rat bladders augmented with an acellular Japanese bovine pericardium-derived biomaterial (CardioDISC [CD]) could support bladder reconstruction, and increase bladder volume and compliance.

METHODS

Female Sprague-Dawley rats were randomly divided into three groups (n = 5 each). After partial cystectomy, bladders were closed without augmentation (non-augmentation) or augmented with porcine small intestinal submucosa (SIS) or CD, both of which are acellular. At 1, 2, 4 and 8 weeks after surgery, bladder volume and compliance were measured. The bladders were then analyzed by immunohistochemistry for smooth muscle actin (SMA), urothelium uroplakin III (UPIII), and nerve fiber S100.

RESULTS

At 4 weeks after augmentation, the SMA-positive cells from the host bladder tissues were present near the regions augmented with CD. In addition, S100-positive cells were present within the CD-augmented tissues. At 8 weeks after surgery, the CD-augmented tissues contained layered SMA-positive cells, urothelium uroplakin III -positive urothelium, and S100 fibers, similar to normal bladder tissue. The SIS-augmented bladders showed similar results. At 8 weeks after augmentation, the bladder volume of CD-augmented bladders was larger than that at 4 weeks, while the SIS-augmented bladders were the same as those at 4 weeks. The bladder volume of the non-augmented group did not increase. The bladder compliance of the CD-augmented bladders at 8 weeks was significantly higher than at earlier times. The bladder compliance of neither the non-augmented nor the SIS-augmented groups increased during the study period.

CONCLUSION

Acellular bovine pericardium-derived material could be a suitable biomaterial for bladder augmentations.

In vitro evaluation of the bioactive factors preserved in porcine small intestinal submucosa through cellular biological approaches

The objective of this study was to develop cellular biological approaches to evaluate the potential effect of bioactive factors in porcine small intestinal submucosa (SIS) on bladder regeneration and angiogenesis. For this purpose, we cultured human bladder smooth muscle cell (HBSMC) and human umbilical vein endothelial cell (HUVEC), and then used cellular biological techniques to characterize in vitro biological effect of SIS components on HBSMC and HUVEC. Our results indicated that the SIS components had stimulated the attachment, proliferation, and migration of HBSMC and HUVEC, as well as tube formation by HUVEC on Matrigel. These results implied that the SIS might have preserved a mixture of bioactive factors including cell adhesion factors, mitogenic factors, chemotactic cytokines, and angiogenic factors, and these bioactive factors would have the potential of promoting bladder regeneration and angiogenesis. In conclusion, these cellular biological approaches might be helpful and effective for evaluation of the bioactive factors preserved in porcine SIS before it is used for bladder augmentation in humans.

Urinary bladder auto augmentation using INTEGRA and SURGISIS: an experimental model

OBJECTIVE

We present our experience with an experimental urinary bladder auto augmentation model using SURGISIS and INTEGRA (collagen layer) in comparison with seromuscular enterocystoplasty. The aim of the study was to evaluate the change in compliance and elasticity of the urinary bladder.

MATERIALS AND METHODS

Eighteen lambs were divided into three different groups. Auto augmentation was performed using the seromuscular layer of small bowel, SURGISIS or the collagen layer of INTEGRA. After 3 months of the initial procedure, the lambs were re-operated, the bladder compliance was measured and the urinary bladder was submitted for histological examination and assessment of elasticity. The lambs were euthanized.

RESULTS

The postoperative period was uneventful in 17 lambs except for intestinal obstruction in one lamb from the seromuscular enterocystoplasty group. A statistically significant difference in compliance was observed with SURGISIS and the INTEGRA. Histologically, there was neovascularization in all the specimens from the SURGISIS and INTEGRA groups with the presence of fibrosis in the SURGISIS group. The INTEGRA group showed better elastic properties than the SURGISIS.

CONCLUSIONS

Urinary bladder auto augmentation using the collagen layer of INTEGRA showed better functional and histological results when compared with SURGISIS and demucosalized enterocystoplasty in the present model.

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.

The incorporation of poly(lactic-co-glycolic) acid nanoparticles into porcine small intestinal submucosa biomaterials

Small intestinal submucosa (SIS) derived from porcine small intestine has been intensively studied for its capacity in repairing and regenerating wounded and dysfunctional tissues. However, SIS suffers from a large spectrum of heterogeneity in microarchitecture leading to inconsistent results. In this study, we introduced nanoparticles (NPs) to SIS with an intention of decreasing the heterogeneity and improving the consistency of this biomaterial. As determined by scanning electron microscopy and urea permeability, the optimum NP size was estimated to be between 200 nm and 500 nm using commercial monodisperse latex spheres. The concentration of NPs that is required to alter pore sizes of SIS as determined by urea permeability was estimated to be 1 mg/ml 260 nm poly(lactic-co-glycolic) acid (PLGA) NPs. The 1mg/ml PLGA NPs loaded in the SIS did not change the tensile properties of the unmodified SIS or even alter pH values in a cell culture environment. More importantly, PLGA NP modified SIS did not affect human mammary endothelial cells (HMEC-1) morphology or adhesion, but actually enhanced HEMC-1 cell growth.

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.

In vivo bladder regeneration using small intestinal submucosa: experimental study

Significant side effects are correlated with bladder augmentation. Recently, small intestinal submucosa (SIS) has been proposed for clinical use. The efficacy of SIS bladder regeneration was studied in a porcine experimental model. Partial cystectomy (40-60% of bladder wall) was performed and replaced by SIS graft. Animals were planned to be killed at 2 weeks, 5 weeks and 3 months. Bladder capacity at 40 cmH(2)O pressure and macroscopic graft morphology were assessed before and after SIS implant. Histological examination was carried out with computer assisted morphometric analysis for collagen/smooth muscle ratio. Student's t test was adopted for statistical analysis. Two piglets died on the 9th and 10th post-operative day due to urinary peritonitis. The remaining piglets were killed after uneventful post-operative period at 5 weeks (two animals) and 3 months (two animals). The bladder capacity was reduced (-18%) at the 5 week follow-up and quite similar to the pre-operative volume (+2.5%) at the 3 months control. No diverticular formation, bladder calculi, mucus and urinary infection were found. The SIS graft resulted not significantly contracted. Histology at 10 days showed SIS membrane lined by transitional epithelium islands with some capillaries. At 5 weeks, transitional epithelium was fully covering the graft; new blood vessels and fibroblasts with smooth muscle cells were observed. At 3 months, the SIS was not evident. Two layers were defined: inner transitional epithelium, outer collagen with fibroblasts and muscular bundles. Computer assisted morphometric analysis showed collagen/muscle ratio 70/30% (normal bladder=56/44%, P<0.05). The SIS was effective as a scaffold for bladder wall regeneration in four out of six animals. Long-term studies are required to confirm the efficacy of the newly developed wall and for eventual clinical use.

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.

BLADDER RECONSTITUTION WITH BONE MARROW DERIVED STEM CELLS SEEDED ON SMALL INTESTINAL SUBMUCOSA IMPROVES MORPHOLOGICAL AND MOLECULAR COMPOSITION

PURPOSE

Tissue engineering has been used for bladder augmentations with small intestinal submucosa (SIS). Although favorable short-term outcomes have been reported, long-term followup has been poor. We investigate whether tissue engineering with stem cells improves the morphological and genetic composition.

MATERIALS AND METHODS

A total of 33 Lewis rats (Harlan Laboratories, Indianapolis, Indiana) were used to investigate bladder augmentations with 4-layer SIS in certain groups, including the control group (sham operation), partial cystectomy with oversewn defect group (OG), augmentation with unseeded SIS group (USG) and augmentation with stem cell seeded SIS group (SSG). Bladders from 4 rats per group were harvested 1 and 3 months after surgery. Morphological analyses were performed using Masson's trichrome and immunohistochemical staining with cytokeratin AE1/AE3, smooth muscle alpha-actin and S100. Gene expression was evaluated using quantitative real-time reverse transcriptase-polymerase chain reaction (RT-PCR) for collagen I (CI), collagen III (CIII), cytokeratins 8 and 19, and smooth muscle myosin heavy chain (MHC).

RESULTS

At 1 month trichrome staining revealed collagen admixed with indiscrete cells and morphology similar to that in controls in USG and SSG, respectively. Discrete smooth muscles fascicles and S100 staining were found in all groups except USG. Organized urothelium with increased basal cell layer staining was present in controls and SSG only. At 3 months increased collagen formation was present in OG and USG. Immunostaining showed hyperplasia of the urothelium with increased staining of the basal cell layer, discrete muscle fascicles and positive nerve staining in all groups. Using quantitative RT-PCR expression levels in SSG were more improved than in USG, especially for CI, CIII and MHC. This was further evident at 3 months when CI and CIII were over expressed in OG and USG but not in the control group or SSG. Furthermore, RT-PCR showed that cytokeratins 8 and 19, and MHC had greater expression levels in SSG than in USG.

CONCLUSIONS

Bladder reconstitution occurs more rapidly using stem cell seeded SIS. Although in USG and SSG all 3 cellular constituents appear to develop by 3 months, only SSG had gene expression levels similar to those in controls. The results suggest an explanation for the fibrosis noted in unseeded SIS bladder augmentations and the possible solution using stem cells.

Molecular, cellular and developmental biology of urothelium as a basis of bladder regeneration

Urinary bladder malfunction and disorders are caused by congenital diseases, trauma, inflammation, radiation, and nerve injuries. Loss of normal bladder function results in urinary tract infection, incontinence, renal failure, and end-stage renal dysfunction. In severe cases, bladder augmentation is required using segments of the gastrointestinal tract. However, use of gastrointestinal mucosa can result in complications such as electrolyte imbalance, stone formation, urinary tract infection, mucous production, and malignancy. Recent tissue engineering techniques use acellular grafts, cultured cells combined with biodegradable scaffolds, and cell sheets. These techniques are not all currently applicable for human bladder reconstruction. However, new avenues for bladder reconstruction maybe facilitated by a better understanding of urogenital development, the cellular and molecular biology of urothelium, and cell-cell interactions, which modulate tissue repair, homeostasis, and disease progression.

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.

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.

Single layered small intestinal submucosa in the repair of severe chordee and complicated hypospadias

PURPOSE

Severe ventral chordee often accompanies proximal hypospadias. We describe our experience with single layered small intestinal submucosa (SIS), a commercially available, acellular, collagen based biomaterial, in the repair of severe chordee as part of a multistage approach to the repair of proximal hypospadias.

MATERIALS AND METHODS

Between 2001 and 2002, 9 boys with proximal hypospadias (penoscrotal to perineal) and severe ventral chordee (greater than 40 degrees) underwent SIS grafting to correct the curvature. In each case the urethral plate was transected at the point of maximal curvature, the defect in the corporal bodies was measured, and the SIS graft was cut 2 mm wider around the perimeter of the defect and sutured into place. Skin resurfacing of the ventral penis was performed in standard fashion using Byars flaps. Recurrence of chordee was assessed by an artificial penile erection test at the time of stage 2 reconstruction.

RESULTS

Of the 9 boys 8 underwent a planned 2-stage repair with subsequent urethroplasty 6 to 12 months after the initial stage 1 chordee repair. Median age at stage 1 repair of the 8 boys was 9 months. Native meatus location was penoscrotal in 6 boys, mid scrotal in 1 and perineal in 1. A 14 month-old boy underwent 1-stage chordee correction with SIS and a transverse preputial island tube graft urethroplasty for penoscrotal hypospadias. There were no perioperative medical or surgical complications related to use of SIS for chordee repair. Median age of the 8 boys at stage 2 repair was 18 months. At stage 2 the graft site was supple and smooth without significant scarring. All chordee correction has remained durable with followup ranging from 16 to 21 months. Postoperative complications occurred in 3 cases, including meatal stenosis requiring meatoplasty, subcoronal fistula requiring repair and complete breakdown of the neourethra in the single stage repair case.

CONCLUSIONS

Although this study includes a small population of patients and has limited followup, our favorable experience with single layer SIS suggests that it is a safe and effective, commercially available material for corporal body grafting to correct severe chordee as part of a multistage surgical approach to repair complex hypospadias. A larger series of patients with longer followup is necessary to determine if the chordee correction remains durable. Our experience is insufficient to judge its efficacy in single stage repairs.