New methods of bladder augmentation

Pericardial bioscaffold coated with ECM gels and urothelial cells for the repair of a rabbit urinary bladder defect

Repair of damaged or faulty complex modular organs such as the urinary bladder is a current clinical challenge. The design of constructs for reconstructive urological surgery can draw advantage from the bioactivity of natural extracellular matrix (ECM) bioscaffolds, as well as the activity provided by cells seeded into constructs. Considering these benefits, this work compares the performance of pericardial ECM bioscaffolds and constructs seeded with gel-supported urothelial cells in the repair of urinary bladder defects in rabbits. The bioscaffolds considered in this study are of porcine (pM) and bovine (bM) origin and exhibited a residual composition that confers bioactivity in mesh presentation. Coating an ECM gel on the bioscaffolds promoted the adhesion and viability of urothelial cells. Repairing a full-thickness urinary bladder defect in a rabbit model with the bioscaffolds and constructs resulted in the integration with the host bladder; meanwhile, bladder volumetric capacity was promoted using bM and constructs. Although no contribution of gel/cell seeding to the failure of mechanical properties of the urinary neobladder was observed, this seeding technique is suitable for integration with different strategies to engineer constructs for urinary bladder reconstructive surgery.

BLADDER TRANSPLANTATION: THE NEW FRONTIER IN ABDOMINAL ORGAN TRANSPLANTATION

Lower urinary tract abnormalities are directly implicated in the etiology of renal dysfunction in 6 to 24% of dialytic patients. These patients require bladder capacity and compliance readjustment before being considered viable candidates for renal transplantation. Vesical augmentation surgeries often involve the use of intestinal segments. Although these procedures can effectively restore bladder capacity and compliance, they present various issues related to maintaining mucous absorption and secretion capacity. Acidosis, recurrent urinary tract infections, and stone formation are extremely common, leading to frequent hospitalizations and graft function loss. Urinary tissue is certainly ideal for these reconstructions; however, bladder augmentation using ureter and renal pelvis are feasible only in a minority of cases. Experimental studies have been conducted to establish the groundwork for vascularized bladder transplantation. Last year, for the first time, this procedure was performed on a brain-dead patient. During this intervention, cystectomy was performed with preservation the vascular pedicle, followed by organ reimplantation. The graft remained viable for a period of 12 hours post-transplant. However, this intervention utilized a robotic platform, making it less reproducible in a multi-organ procurement setting as well as for most transplant centers. Moreover, it is debatable whether the benefits of exclusive bladder transplantation outweigh the risks associated with immunosuppression. For patients needing renal transplantation and requiring lower urinary tract reconstruction, however, utilizing the donor's bladder may offer an attractive alternative, avoiding the inherent complications of enterocystoplasty without increasing immunological risk. Combined kidney and bladder transplantation has the potential to emerge as the next frontier in abdominal organ transplants.

Urinary Bladder Patch Made with Decellularized Vein Scaffold Seeded with Adipose-Derived Mesenchymal Stem Cells: Model in Rabbits

BACKGROUND

To evaluate tissue regeneration of the urinary bladder after the implantation of a decellularized vein sown with autologous adipose-derived mesenchymal stem cells (ASC) on luminal surfaces.

METHODS

New Zealand rabbits (n = 10) were distributed in two groups: Group Bioscaffold alone (G1)-decellularized vena cava (1 cm2) was implanted, and Group Bioscaffold plus ACSs (G2)-decellularized vena cava (1 cm2) containing ASCs were implanted. ASCs were expanded, characterized, and maintained for one week in culture with a decellularized vein scaffold. The implants were performed under general anesthesia using a continuous suture pattern. Afterward, 21 d (day) specimens were collected and analyzed by hematoxylin and eosin (HE) histology and scanning electron microscopy (SEM).

RESULTS

The integrity of the urinary bladder was maintained in both groups. A superior regenerative process was observed in the G2 group, compared to the G1 group. We observed a greater urothelial epithelialization and maturity of the mucosa and submucosa fibroblasts. Furthermore, SEM demonstrated a notable amount of urothelial villus in the G2 group.

CONCLUSION

Decellularized vena cava scaffolds were able to maintain the integrity of the urinary bladder in the proposed model. In addition, ASCs accelerated the regenerative process development, observed primarily by the new urothelial epithelization and the maturity of mucosa and submucosa fibroblasts.

Biomaterials assisted reconstructive urology: The pursuit of an implantable bioengineered neo-urinary bladder

Urinary bladder is a dynamic organ performing complex physiological activities. Together with ureters and urethra, it forms the lower urinary tract that facilitates urine collection, low-pressure storage, and volitional voiding. However, pathological disorders are often liable to cause irreversible damage and compromise the normal functionality of the bladder, necessitating surgical intervention for a reconstructive procedure. Non-urinary autologous grafts, primarily derived from gastrointestinal tract, have long been the gold standard in clinics to augment or to replace the diseased bladder tissue. Unfortunately, such treatment strategy is commonly associated with several clinical complications. In absence of an optimal autologous therapy, a biomaterial based bioengineered platform is an attractive prospect revolutionizing the modern urology. Predictably, extensive investigative research has been carried out in pursuit of better urological biomaterials, that overcome the limitations of conventional gastrointestinal graft. Against the above backdrop, this review aims to provide a comprehensive and one-stop update on different biomaterial-based strategies that have been proposed and explored over the past 60 years to restore the dynamic function of the otherwise dysfunctional bladder tissue. Broadly, two unique perspectives of bladder tissue engineering and total alloplastic bladder replacement are critically discussed in terms of their status and progress. While the former is pivoted on scaffold mediated regenerative medicine; in contrast, the latter is directed towards the development of a biostable bladder prosthesis. Together, these routes share a common aspiration of designing and creating a functional equivalent of the bladder wall, albeit, using fundamentally different aspects of biocompatibility and clinical needs. Therefore, an attempt has been made to systematically analyze and summarize the evolution of various classes as well as generations of polymeric biomaterials in urology. Considerable emphasis has been laid on explaining the bioengineering methodologies, pre-clinical and clinical outcomes. Some of the unaddressed challenges, including vascularization, innervation, hollow 3D prototype fabrication and urinary encrustation, have been highlighted that currently delay the successful commercial translation. More importantly, the rapidly evolving and expanding concepts of bioelectronic medicine are discussed to inspire future research efforts towards the further advancement of the field. At the closure, crucial insights are provided to forge the biomaterial assisted reconstruction as a long-term therapeutic strategy in urological practice for patients' care.

Dynamically crosslinked polydimethylsiloxane-based polyurethanes with contact-killing antimicrobial properties as implantable alloplasts for urological reconstruction

A large population of patients is reported to suffer from urinary bladder-associated irreversible physiological disorders, rationalizing a continuous surge for structural and functional substitutes of urinary tissues, including ureters, bladder-wall, and urethra. The current gold standard for bladder reconstruction, an autologous gastrointestinal graft, is proven not to be an ideal substitute in the clinic. While addressing this unmet clinical need, a unique platform of antimicrobial polydimethyl siloxane-modified polyurethanes (TPU/PDMS) is designed and developed for its potential application as a urological implant. To the best of our knowledge, this study reports for the first time the successful integration of varying contents of PDMS within the molten polyurethane matrix using in situ crosslinking methodology. Thus, compatibilized binary blends possess clinically relevant viscoelastic properties to sustain high pressure, large distensions, and surgical manipulation. Furthermore, different chemical strategies are explored to covalently incorporate quaternized moieties, including 4-vinyl pyridine (4-VP), branched-polyethyleneimine (bPEI) as well as bPEI-grafted-(acrylic acid-co-vinylbenzyltriphenyl phosphonium chloride) (PAP), and counter urinary tract infections. The modified compositions, endowed with contact killing surfaces, reveal nearly three log reduction in bacterial growth in pathogenically infected artificial urine. Importantly, the antimicrobial TPU/PDMS blends support the uninhibited growth of mitochondrially viable murine fibroblasts, in a manner comparable to the medical-grade polyurethane. Collectively, the obtained results affirmed the newly developed polymers as promising biomaterials in reconstructive urology. STATEMENT OF SIGNIFICANCE: The clinical procedure for end-stage bladder disease remains replacement or augmentation of the bladder wall with a section of the patient's gastrointestinal tract. However, the absorptive and mucus-producing epithelium of intestinal segment is liable to short- and long-term complications. The dynamically crosslinked polydimethyl siloxane-based polyurethanes proposed herein, and the associated synthesis strategies to induce polycation grafted non-exhaustive contact-killing surfaces against uropathogents, have a significant clinical prospect in reconstructive urology. As an 'off-the-shelf' available alloplastic substitute, these blends offer the potential to circumvent the challenges associated with non-urinary autografts or scaffold based regenerative engineering and, thereby, shorten as well as simplify the surgical treatment. The targeted application has been conceived for a bladder patch to assist in various urinary diseases including, bladder carcinoma, refractory overactive bladder, interstitial cystitis, etc. However, given the ease of fabrication, moldability and the wide spectrum of mechanical properties that could be encompassed, these blends also present the possibility to be manifested into artificial ureteral or urethral conduits.

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.

Use of an inflatable silicone balloon improves the success rate of bladder autoaugmentation at long-term followup

PURPOSE

Most groups have reported disappointing results with autoaugmentation or detrusor myectomy for low capacity/compliance neuropathic bladders. Failure may be due to an ischemic diverticulum or mucosal shrinkage. We investigated whether a Silimed® silicone balloon placed in the bladder after autoaugmentation could prevent these problems, improving surgical results.

MATERIALS AND METHODS

We compared the results of standard bladder autoaugmentation in 12 children (group 1) with those in 10 (group 2) who underwent the same surgery using a bladder conformer. The conformer was a silicone balloon filled with saline that remained in the bladder for 2 weeks. All patients had a neuropathic bladder with poor capacity and compliance, resulting in urinary leakage between catheterizations. Preoperative and postoperative evaluation included a voiding diary, ultrasound, voiding cystourethrogram and urodynamics.

RESULTS

In group 1 only 1 patient became dry, 4 had little improvement in continence, 4 remained unchanged and 3 became worse. In group 2, 6 patients (60%) become continent without medication, 2 (20%) become continent with oxybutynin and 2 remained unchanged. Bladder capacity and compliance did not change significantly in group 1. However, in group 2 capacity changed from a mean of 140 to 240 ml and mean ± SD compliance increased from 15.6 ± 16.8 to 34.3 ± 22.8 ml/cm H(2)O (p = 0.02).

CONCLUSIONS

The inflatable balloon improved our long-term results of bladder auto-augmentation. A larger series may be necessary to confirm procedure efficacy and safety.

Nerve distribution in rat urinary bladder after incorporation of acellular matrix graft or subtotal cystectomy

OBJECTIVE

In the treatment of reduced bladder capacity, matrix grafts have been used as a scaffold into which cell elements from the native bladder grow, eventually forming a new bladder segment. Functioning motor nerve endings in such segments in the rat have been demonstrated, although little is known about nerve distribution. We compare the pattern of nerve distribution in scaffold-augmented rat bladders with that in bladders regrown after subtotal cystectomy and that in control bladders.

MATERIAL AND METHODS

Female Sprague-Dawley rats were either subtotally cystectomized (n=7) or had a part of the bladder dome replaced by an acellular collagen (small intestinal submucosa) matrix graft (n=10). Fourteen age-matched, unoperated animals were used as controls. Two and a half to 10 months after surgery the bladders were stained for acetylcholinesterase and studied in wholemounts.

RESULTS

No ganglion neurons were observed in any of the bladders. On their ventral side the control bladders showed longitudinal nerve trunks, running in parallel along the longitudinally oriented muscle bundles, while on the lateral and dorsal aspects the nerves were thinner, more irregularly arranged and frequently branched. In the bladders regrown after subtotal cystectomy, the ventral nerves were seen running obliquely to the still longitudinally oriented muscle bundles, resembling the pattern of the normal bladder base; the pattern of the dorsolateral nerves was the same as that in the controls. In the matrix bladders, the muscle and nerve patterns in the native part were the same as those in controls. Muscle bundles were growing into the matrix, accompanied by nerves, which showed limited branching when entering the matrix, usually running in parallel to the muscle, but then branching within the matrix.

CONCLUSIONS

The nerves in the matrix grafts and the regrown parts of the subtotally cystectomized bladders derive from preexisting nerves in the bladder. In neither case does the nerve trunk or muscle bundle arrangement fully attain the pattern found in normal bladders.

Urological care of the spinal cord-injured patient

Spinal cord injury (SCI) is a catastrophic occurrence affecting the lives of 11,000 people in the United States every year. Urologic complications account for much of the morbidity associated with SCI and as much as 15% of the associated mortality. Spinal cord-injured patients are required to digest a plethora of self-management information during the emotionally and psychologically distressing period immediately following their injury. As a vital resource in the SCI patients' recovery process, it is crucial for the WOC nurse to have knowledge of the specialized needs of this population. This article reviews the effects of SCI on bladder function, discusses potential complications of the neurogenic bladder, and provides an overview of management options to assist the patient in adaptation and restoration of quality of life.

Feasibility study of a novel urinary bladder bioreactor

We have devised a bioreactor to simulate normal urinary bladder dynamics. The design permits a cell-seeded scaffold made from a modified porcine acellular matrix to be placed between 2 closed chambers filled with culture medium and be mechanically stimulated in a physiologically relevant manner. Specifically designed software increased hydrostatic pressure from 0 to 10 cm of water in a linear fashion in 1 chamber, resulting in mechanical stretch and strain on the scaffold. Pressure was increased over 55 min (filling) and then decreased to 0 over 10 s (voiding). Commercially available small intestinal submucosa scaffolds were used to test the mechanical capabilities of the bioreactor, and pressure waveforms were generated for up to 18 h. Scaffolds were seeded with bladder smooth muscle or urothelial cells and incubated in the bioreactor, which generated pressure waveforms for 6 h. Scaffold integrity was preserved as seen through Masson's trichrome staining. No obvious contamination of the system was noted. Hematoxylin and eosin staining showed presence of cells after incubation in the bioreactor, and immunohistochemistry and real-time reverse transcriptase polymerase chain reaction suggested continued cellular activity. Cellular orientation tended to be perpendicular to the applied pressure. Preliminary results suggest that our bioreactor is a suitable model for simulating normal physiological conditions of bladder cycling in an ex vivo system.

Incorporation of Integra in tissue defects: a pilot study in the rat model

Integra has been shown to be very useful in accelerating the growth of neodermis. It has found extensive use in case of burns as a primary dressing immediately after a burn, after release of contractures and following scar revision. It has been used to achieve cover after the debridement of extensive infective processes involving the skin. Encouraged by these results we have assessed the application of Integra to augment and/or patch defects of the urinary bladder, diaphragm and the abdominal wall in the rat model. This was a pilot study and involved the incorporation of Integra in the diaphragm, the urinary bladder (extramucosal) and the muscle layer of the abdominal wall. Eight adult Wistar rats were given general anaesthesia and Integra was implanted with absorbable sutures at the sites mentioned. The omentum was hitched to the collagen matrix surface to revascularise the graft. The silicone was left in situ. The operative period was covered with antibiotics. The anaesthesia was then reversed. Postoperatively the rats were given analgesia and feeds started immediately. The rats were sacrificed after 3 weeks. The abdominal cavity was examined for adhesions. The Integra implant along with adjacent tissue was harvested and examined histologically. There were no visible intra-abdominal adhesions. The histology revealed good degree of neovascularisation and fibrosis in and adjacent to the implant. This was comparable to the changes seen in the skin. This pilot study has shown that implanting Integra invokes a similar response in deeper tissues and it can develop neovascularisation from the omentum. Hence, this could find some application in treating congenital conditions such as diaphragmatic hernias, abdominal wall defects and for bladders requiring augmentation. Our initial results are quite encouraging and we feel that this field should be further explored.

Bladder Augmentation With Acellular Dermal Biomatrix in a Diseased Animal Model

PURPOSE

The use of bowel for bladder augmentation is associated with many complications. We have reported that acellular dermal biomatrix can be used successfully for directing the regeneration of each key bladder wall element in healthy domestic pigs. Before proposing that this material should be used in the human setting a final set of experiments using this scaffold to replace diseased bladder wall is necessary. We determined if acellular dermal biomatrix can be used to replace diseased bladder wall. We compared our findings to our previous results.

MATERIALS AND METHODS

Six domestic male pigs underwent urethral ligation and suprapubic tube placement. Five female pigs served as controls for bladder dynamics. Machined resistance valves of 5 and 10 cm H(2)O pressure were placed into the lumen of the cystostomy catheter for a mean of 3.3 weeks (range 3 to 4). Obstruction was then relieved and partial cystectomy was performed, followed by augmentation with a 4 x 4 cm segment of acellular dermal biomatrix of the markedly thickened and poorly compliant bladder. Animals were sacrificed 3 months following augmentation. Standard urodynamic studies were performed. Contractility and compliance were measured in freshly isolated regenerated and native bladder tissues. Histological evaluation was performed on hematoxylin and eosin, and Masson's trichrome stained sections.

RESULTS

Bladder compliance was markedly decreased after 3.3 weeks of obstruction. Mean compliance +/- SEM before obstruction was 16.28 +/- 9.21 cm H(2)O. After 3.3 weeks of obstruction average compliance was 4.13 +/- 0.98 cm H(2)O. One pig died 2 weeks following augmentation due to graft separation and sepsis. Gross examination of augmented bladders revealed the complete replacement of acellular dermal biomatrix with bladder tissue. Histological evaluation revealed extensive fibrosis with small islands of poorly organized muscle in contrast to the complete regeneration of mucosa, smooth muscle and serosa seen in augmentations previously performed in healthy animal bladders. Maximum contractile tension of the patch tissue was not different than that in the native tissue from the obstructed hypertrophied bladder but it was only approximately 10% of the tension produced by healthy tissue from nonobstructed augmented bladders. The obstructed bladder patch and native tissue was approximately 14 times stiffer than healthy bladder tissue.

CONCLUSIONS

While augmentation of healthy porcine bladder with acellular dermal biomatrix results in excellent functional bladder tissue regeneration, similar experiments in a porcine model of obstructed bladder disease failed to show favorable results. Therefore, acellular dermal biomatrix cannot be recommended at this time for human bladder dysfunction. Results support the contention that matrices designed for human bladder augmentation should be tested in a disease animal model before recommending them for human bladder dysfunction.

Colonic seromuscular augmentation cystoplasty following subtotal cystectomy for treatment of bladder necrosis caused by bladder torsion in a dog

CASE DESCRIPTION

A 5-year-old Labrador Retriever was evaluated because of a 3-day history of lethargy, anorexia, vomiting, stranguria, and anuria after routine ovariohysterectomy.

CLINICAL FINDINGS

On initial examination, signs of abdominal pain and enlargement of the urinary bladder were detected. Clinicopathologic abnormalities included leukocytosis, azotemia, and hyperkalemia. Radiography and surgical exploration of the abdomen revealed urinary bladder torsion at the level of the trigone; histologically, there was necrosis of 90% of the organ.

TREATMENT AND OUTCOME

After excision of the necrotic wall of the urinary bladder (approx 0.5 cm cranial to the ureteral orifices), the remaining bladder stump was closed with a colonic seromuscular patch. Eleven weeks later, cystoscopy revealed an intramural ureteral stricture, for which treatment included a mucosal apposition neoureterocystostomy. Thirteen months after the first surgery, the dog developed pyelonephritis, which was successfully treated. By 3 months after subtotal cystectomy, the dog's urinary bladder was almost normal in size. Frequency of urination decreased from 3 to 4 urinations/h immediately after surgery to once every 3 hours after 2 months; approximately 4 months after the subtotal cystectomy, urination frequency was considered close to normal.

CLINICAL RELEVANCE

Urinary bladder torsion is a surgical emergency in dogs. Ischemia of the urinary bladder wall may result from strangulation of the arterial and venous blood supply and from overdistension. Subtotal resection of the urinary bladder, preserving only the trigone area and the ureteral openings, and colonic seromuscular augmentation can be used to successfully treat urinary bladder torsion in dogs.

Overactive bladder

The overactive bladder is a common condition, which has significant effects on quality of life. The aetiology in most cases is unknown, and treatment outcomes have until recently been unsatisfactory. Management includes excluding pathology and implementing behavioural changes such as caffeine reduction, bladder and pelvic floor training, as well as antimuscarinic drug therapy. Compliance is often problematic, and this can be improved with some of the newer antimuscarinics with fewer side-effects, and a good therapist/patient relationship. In the majority of cases this 'treatment package' is successful, but in those where it is not, intravesical therapies have been introduced, e.g. neuromodulation, alternative drug therapies (e.g. vanilloids, botox) and surgery. With a better understanding of the aetiology and identification of risk factors better outcomes from treatment are likely.

Update on the role of anticholinergic drug therapy in the management of overactive bladder

OBJECTIVE

To review the published literature and describe the pathophysiology and management of overactive bladder (OAB), with emphasis on the comparative efficacy and adverse event profiles of anticholinergic agents approved for the management of OAB symptoms and evaluation of their place in therapy.

DATA SOURCES

A MEDLINE search of English language literature that addresses the pathophysiology and management of OAB symptoms. The references in identified articles were evaluated for additional relevant articles. Drug Topics' Red Book was referenced for cost comparisons, and package inserts were used for specific drug and dosing information.

STUDY SELECTION

Human studies that presented efficacy and safety data with respect to anticholinergic medications in the treatment of OAB were selected.

DATA EXTRACTION

Studies were abstracted to identify key characteristics with respect to efficacy and safety in OAB, in particular anticholinergic side effects, with the greatest weight given to studies that compared two or more anticholinergic medications.

DATA SYNTHESIS

Epidemiologic studies have shown that the unpredictable and bothersome symptoms associated with OAB occur in approximately 16% of the worldwide adult population. Conservative management of OAB should include a combination of pharmacologic and nonpharmacologic interventions that have been found to improve outcomes when used in appropriately selected patients. Although long recognized as the most effective pharmacotherapy for OAB, anticholinergic agents have been associated with poor tolerability attributable to anticholinergic adverse events. New medications, formulations, and drug delivery systems have been developed with the goal of achieving effective treatment with improved tolerability.

CONCLUSIONS

Among these agents, extended-release and transdermal formulations have improved tolerability while retaining at least comparable efficacy. More research is needed regarding other routes of administration and new drug entities that specifically target the pathologic mechanisms involved in OAB.

Induction of proliferation and differentiation of cultured urothelial cells on acellular biomaterials

OBJECTIVE

To determine the optimum conditions for the proliferation of urothelial cells, leading to the confluent coverage of large surfaces of biocompatible membranes, and for their terminal differentiation.

MATERIALS AND METHODS

Porcine and human urothelial cells were cultured on different matrices under different growth conditions. Proliferative activity and the viability of cells were evaluated using fluorescent markers for nuclei and cytoplasm. Growth and differentiation were assessed by histological, histochemical and immunohistochemical methods.

RESULTS

Under fibroblastic induction and supplementation of 5% fetal calf serum (FCS), urothelial cells showed more proliferation than in other conditions tested. Terminal differentiation of superficial cells was achieved by lowering the concentration of FCS to 1% at the air-liquid interface.

CONCLUSIONS

The mitogenic effects of the extracellular matrix content of biological membranes and fibroblastic inductive factors are synergistic with each other, and can compensate for a low FCS concentration and the absence of other additives. Lowering the FCS concentration to 1% inhibits the proliferation of urothelial cells and permits their terminal differentiation.

Porosity of porcine bladder acellular matrix: impact of ACM thickness

The objectives of this study are to examine the porosity of bladder acellular matrix (ACM) using deionized (DI) water as the model fluid and dextran as the indicator macromolecule, and to correlate the porosity to the ACM thickness. Porcine urinary bladders from pigs weighing 20-50 kg were sequentially extracted in detergent containing solutions, and to modify the ACM thickness, stretched bladders were acellularized in the same manner. Luminal and abluminal ACM specimens were subjected to fixed static DI water pressure (10 cm); and water passing through the specimens was collected at specific time interval. While for the macromolecule porosity testing, the diffusion rate and direction of 10,000 MW fluoroescein-labeled dextrans across the ACM specimens mounted in Ussing's chambers were measured. Both experiments were repeated on the thin stretched ACM. In both ACM types, the fluid porosity in both directions did not decrease with increased test duration (3 h); in addition, the abluminal surface was more porous to fluid than the luminal surface. On the other hand, when comparing thin to thick ACM, the porosity in either direction was higher in the thick ACM. Macromolecule porosity, as measured by absorbance, was higher for the abluminal thick ACM than the luminal side, but this characteristic was reversed in the thin ACM. Comparing thin to thick ACM, the luminal side in the thin ACM was more porous to dextran than in the thick ACM, but this characteristic was reversed for the abluminal side. The porcine bladder ACM possesses directional porosity and acellularizing stretched urinary bladders may increase structural density and alter fluid and macromolecule porosity.

Urothlelium Facilitates the Recruitment and Trans-Differentiation of Fibroblasts into Smooth Muscle in Acellular Matrix

PURPOSE

Tissue engineering has shown promise for patients requiring bladder reconstruction secondary to diverse diseases such as spina bifida and tuberculosis. In this study we addressed whether urothelium in conjunction with an acellular bladder matrix is necessary for the recruitment of host cells to repopulate the graft and whether the urothelium facilitates trans-differentiation of host fibroblastic cells into bladder smooth muscle type cells.

MATERIALS AND METHODS

Urothelium from embryonic mice and rats (E18) was microdissected from bladder stroma after enzymatic digestion with 10 mM ethylenediaminetetraacetic acid. Acellular bladder matrix was prepared from postnatal day 1 rat and mouse pups using a combination of membrane disruption and DNA digestion. Urothelium was placed inside the bladder matrix and then grown either underneath the renal capsule or subcutaneously in athymic mice for 2 to 24 weeks. Grafts were sectioned and immunocytochemistry was performed with antibodies for alpha-actin smooth muscle, uroplakin, cytokeratins and vimentin to assess for the development of detrusor muscle.

RESULTS

Embryonic bladder urothelium resulted in ingrowth of fibroblasts into acellular matrix in greater than 85% of 60 grafts consisting of acellular matrix and bladder urothelium. Moreover, there was apparent trans-differentiation of these fibroblasts into a smooth muscle phenotype. This smooth muscle development occurred in a graded, incremental fashion starting as early as 3 weeks and resulting in almost complete repopulation of the matrix at 6 months.

CONCLUSIONS

These data support the hypothesis that epithelial mesenchymal signaling is important for the differentiation of bladder smooth muscle. Smooth muscle development during augmentation with acellular matrix is facilitated by the placement of epithelia onto the surface of the matrix.

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.

Laparoscopic transverse hemicystectomy with ileocystoplasty in a porcine model

BACKGROUND AND PURPOSE

The ideal replacement for bladder tissue is yet to be described, although multiple alternatives have been studied. Currently, enterocystoplasty, despite its limitations, is considered the gold standard for bladder augmentation. This study evaluated the feasibility, safety, and morbidity of laparoscopic ileocystoplasty in a large-animal model.

MATERIALS AND METHODS

In eight minipigs, laparoscopy was performed using four ports. A segment of ileum was delivered through a 3-cm umbilical incision and detubularized and refashioned using standard open surgical technique. Laparoscopic hemicystectomy was then performed, followed by laparoscopic suturing of the ileal patch to the bladder. The bladder was drained with a Foley catheter, but no pelvic drain was placed. All animals were followed for for a minimum of 3 months. Preoperative and postoperative evaluation included measurement of bladder capacity, ultrasound imaging of the kidneys, blood counts, and serum electrolyte and creatinine measurements. Two of the animals were sacrificed at 3 months and one at 6 months, and the bladders were harvested.

RESULTS

Eight animals underwent ileocystoplasty without intraoperative or postoperative complications. The average operating and anastomosis time was 250 minutes and 96 minutes, respectively. All animals had normal preoperative blood values that remained normal during follow-up. Bladder capacity decreased initially to 71% of the baseline volume and then increased to 83% and 117% at 3 and 6 months. One of three animals sacrificed was noted to have a right midureteral stricture.

CONCLUSIONS

We developed a reliable laparoscopic technique for ileocystoplasty that may extend the advantages of laparoscopy, including better cosmesis and reduced risk of postoperative adhesions, to bladder augmentation.