Laparoscopic mid sagittal hemicystectomy and bladder reconstruction with small intestinal submucosa and reimplantation of ureter into small intestinal submucosa: 1-year followup

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

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

Does the Mesenchymal Stem Cell Source Influence Smooth Muscle Regeneration in Tissue-Engineered Urinary Bladders?

A variety of tissue engineering techniques utilizing different cells and biomaterials are currently being explored to construct urinary bladder walls de novo, but so far no approach is clearly superior. The aim of this study was to determine whether mesenchymal stem cells (MSCs) isolated from different sources, (bone marrow [BM-MSCs] and adipose tissue [ADSCs]), differ in their potential to regenerate smooth muscles in tissue-engineered urinary bladders and to determine an optimal number of MSCs for urinary bladder smooth muscle regeneration. Forty-eight rats underwent hemicystectomy and bladder augmentation with approximately 0.8 cm² graft. In the first and second groups, urinary bladders were reconstructed with small intestinal submucosa (SIS) seeded with 10 × 10⁶ or 4 × 10⁶ ADSCs/cm², respectively. In the third and fourth groups, urinary bladders were augmented with SIS seeded with 10 × 10⁶ or 4 × 10⁶ BM-MSCs/cm², respectively. In the fifth group, urinary bladders were augmented with SIS without cells. The sixth group (control) was left intact. Smooth muscle regeneration was evaluated by real-time polymerase chain reaction (RT-PCR) and histological examinations. Histologically, there were no significant differences between urinary bladders augmented with ADSCs and BM-MSCs, but there was a marked increase in smooth muscle formation in bladders augmented with grafts seeded with MSCs in higher density (10 × 10⁶/cm²) compared to lower density (4 × 10⁶/cm²). Molecular analysis revealed that bladders reconstructed with ADSC-seeded grafts expressed higher levels of smooth muscle myosin heavy chain, caldesmon, and vinculin. Bladders augmented with unseeded SIS were fibrotic and devoid of smooth muscles. ADSCs and BM-MSCs have comparable smooth muscle regenerative potential, but the number of MSCs used for graft preparation significantly affects the smooth muscle content in tissue-engineered urinary bladders.

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.

Is the poly (L- lactide- co- caprolactone) nanofibrous membrane suitable for urinary bladder regeneration?

The purpose of this study was to compare: a new five-layered poly (L-lactide-co-caprolactone) (PLC) membrane and small intestinal submucosa (SIS) as a control in rat urinary bladder wall regeneration. The five-layered poly (L-lactide-co-caprolactone) membrane was prepared by an electrospinning process. Adipose tissue was harvested from five 8-week old male Wistar rats. Adipose derived stem cells (ADSCs) were seeded in a density of 3×10(6) cells/cm2 onto PLC membrane and SIS scaffolds, and cultured for 5-7 days in the stem cell culture medium. Twenty male Wistar rats were randomly divided into five equal groups. Augmentation cystoplasty was performed in a previously created dome defect. Groups: (I) PLC+ 3×10(6)ADSCs; (II) SIS+ 3×10(6)ADSCs; (III) PLC; (IV) SIS; (V) control. Cystography was performed after three months. The reconstructed urinary bladders were evaluated in H&E and Masson's trichrome staining. Regeneration of all components of the normal urinary bladder wall was observed in bladders augmented with cell-seeded SIS matrices. The urinary bladders augmented with SIS matrices without cells showed fibrosis and graft contraction. Bladder augmentation with the PLC membrane led to numerous undesirable events including: bladder wall perforation, fistula or diverticula formation, and incorporation of the reconstructed wall into the bladder lumen. The new five-layered poly (L-lactide-co-caprolactone) membrane possesses poorer potential for regenerating the urinary bladder wall compared with SIS scaffold.

Augmentation cystoplasty using decellularized vermiform appendix in rabbit model

PURPOSE

The aim of this study was to produce a decellularized rabbit vermiform appendix (sacculus rotundus) and investigate its feasibility in bladder augmentation or appendicovesicostomy. The superiority of sacculus rotundus over other tissues is its unique mechanical properties as well as its abundant collagen content.

MATERIALS AND METHODS

The acellular matrix of vermiform appendix underwent different laboratory investigations prior to transplantation. We divided 12 rabbits into 3 groups: group I underwent bladder augmentation cystoplasty by detubularized acellular matrix. Group II underwent implantation of the tapered (tubularized) acellular matrix just beneath the seromuscular part of the bladder without connection to the bladder urothelium. Group III underwent the same procedure as group II plus reimplantation of tapered and tubularized acellular matrix (simulating an appendicovesicostomy). The distal end of the transplanted graft was connected to the bladder mucosal opening and was intubated by a 5Fr double blind ended feeding tube catheter. Biopsies were taken 3, 12, and 36months post-operatively for further histological and immunohistochemical analyses.

RESULTS

The results of the examinations performed prior to transplantation, revealed a decellularized structure resembling the native tissue with intact extracellular matrix, normal pits and appropriate gaps that will be suitable for further cell seeding. Histopathology examination of the biopsies after transplantations confirmed successful cell seeding with urothelial lining in groups I and III, while the inner lumen in group II showed no urothelial lining.

CONCLUSION

The results suggest that we can prospect to perform bladder reconstruction by the application of this method without complications of previously reported augmentation cystoplasty. In the current study we used the bladder as a natural bioreactor for autologous recellularization which may pave the road for clinical application in acellular matrix augmentation cystoplasty.

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.

New developments in ureteral stent design, materials and coatings

Ureteral stents are used in a variety of urological diseases and procedures. The majority of patients with indwelling ureteral stents experience bothersome symptoms and are at increased risk for urinary tract infection. Stent encrustation and the associated complications can also result in significant patient morbidity. The development of new stent designs using novel biomaterials, stent coatings and drug-eluting technologies are being applied to reduce the disadvantageous features of ureteral stents.

Increased porosity of electrospun hybrid scaffolds improved bladder tissue regeneration

The object of this study was to investigate the role of scaffold porosity on tissue ingrowth using hybrid scaffolds consisting of bladder acellular matrix and electrospun poly (lactide-co-glycolide) (PLGA) microfibers that mimic the morphological characteristics of the bladder wall in vitro and in vivo. We compared single-spun (SS) PLGA scaffolds with more porous cospun (CS) scaffolds (PLGA and polyethylene glycol). Scaffolds were characterized by scanning electron microscopy. Bladder smooth muscle cells (SMCs) were seeded, and proliferation and histological assays were performed. Sixteen rats were subjected to augmentation cystoplasty with seeded SS or CS scaffolds, morphological, and histological studies were performed 2 and 4 weeks after implantation. The porosities of SS and CS scaffolds were 73.1 ± 2.9% and 80.9 ± 1.5%, respectively. The in vitro evaluation revealed significantly deeper cell migration into CS scaffolds. The in vivo evaluation showed significant shrinkage of SS scaffolds (p = 0.019). The histological analysis revealed a bladder wall-like structure with urothelial lining and SMC infiltration in both groups. The microvessel density was significantly increased in the CS scaffolds (p < 0.001). Increasing the porosity of electrospun hybrid scaffolds is an effective strategy to enhance cell proliferation and distribution in vitro and tissue ingrowth in vivo.

Neurogenic bladder

Congenital anomalies such as meningomyelocele and diseases/damage of the central, peripheral, or autonomic nervous systems may produce neurogenic bladder dysfunction, which untreated can result in progressive renal damage, adverse physical effects including decubiti and urinary tract infections, and psychological and social sequelae related to urinary incontinence. A comprehensive bladder-retraining program that incorporates appropriate education, training, medication, and surgical interventions can mitigate the adverse consequences of neurogenic bladder dysfunction and improve both quantity and quality of life. The goals of bladder retraining for neurogenic bladder dysfunction are prevention of urinary incontinence, urinary tract infections, detrusor overdistension, and progressive upper urinary tract damage due to chronic, excessive detrusor pressures. Understanding the physiology and pathophysiology of micturition is essential to select appropriate pharmacologic and surgical interventions to achieve these goals. Future perspectives on potential pharmacological, surgical, and regenerative medicine options for treating neurogenic bladder dysfunction are also presented.

Regenerative medicine strategies for treating neurogenic bladder

Neurogenic bladder is a general term encompassing various neurologic dysfunctions of the bladder and the external urethral sphincter. These can be caused by damage or disease. Therapeutic management options can be conservative, minimally invasive, or surgical. The current standard for surgical management is bladder augmentation using intestinal segments. However, because intestinal tissue possesses different functional characteristics than bladder tissue, numerous complications can ensue, including excess mucus production, urinary stone formation, and malignancy. As a result, investigators have sought after alternative solutions. Tissue engineering is a scientific field that uses combinations of cells and biomaterials to encourage regeneration of new, healthy tissue and offers an alternative approach for the replacement of lost or deficient organs, including the bladder. Promising results using tissue-engineered bladder have already been obtained in children with neurogenic bladder caused by myelomeningocele. Human clinical trials, governed by the Food and Drug Administration, are ongoing in the United States in both children and adults to further evaluate the safety and efficacy of this technology. This review will introduce the principles of tissue engineering and discuss how it can be used to treat refractory cases of neurogenic bladder.

Tissue engineering of human bladder

There are a number of conditions of the bladder that can lead to loss of function. Many of these require reconstructive procedures. However, current techniques may lead to a number of complications. Replacement of bladder tissues with functionally equivalent ones created in the laboratory could improve the outcome of reconstructive surgery. A review of the literature was conducted using PubMed to identify studies that provide evidence that tissue engineering techniques may be useful in the development of alternatives to current methods of bladder reconstruction. A number of animal studies and several clinical experiences show that it is possible to reconstruct the bladder using tissues and neo-organs produced in the laboratory. Materials that could be used to create functionally equivalent urologic tissues in the laboratory, especially non-autologous cells that have the potential to reject have many technical limitations. Current research suggests that the use of biomaterial-based, bladder-shaped scaffolds seeded with autologous urothelial and smooth muscle cells is currently the best option for bladder tissue engineering. Further research to develop novel biomaterials and cell sources, as well as information gained from developmental biology, signal transduction studies and studies of the wound healing response would be beneficial.

Microstructure and cytocompatibility of collagen matrices for urological tissue engineering

OBJECTIVES

• To analyse the in vitro cytocompatibility of several engineered collagen-based biomaterials for tissue engineering of the urinary tract. • Tissue-engineered implants for the reconstruction of the urinary tract are of major interest for urological researchers as well as clinicians. Although several materials have been investigated, the ideal replacement has still to be identified.

MATERIALS AND METHODS

• Several collagen matrices were tested. • Electron microscopy was used to visualize the microstructure of the tested matrices. • Examination of cell attachment and growth of primary porcine urothelial and smooth muscle cells were performed and cell phenotypes were analysed using immunohistochemical stains. • Urea permeability was investigated using Ussing chamber experiments.

RESULTS

• The best cytocompatibility for both urinary tract-specific cell types was obtained with OptiMaix(®) (Matricel GmbH, Herzogenrath, Germany) materials. • Cell-specific phenotypes were maintained during culture as shown by immunohistochemical staining. • Furthermore, simultaneous cultivation of both cell types for 7 and 14 days significantly reduced urea permeability.

CONCLUSION

• These results show the potential of OptiMaix materials in tissue engineering approaches of urinary tract tissues.

Tissue engineering and regenerative medicine research perspectives for pediatric surgery

Tissue engineering and regenerative medicine research is being aggressively pursued in attempts to develop biological substitutes to replace lost tissue or organs. Remarkable degrees of success have been achieved in the generation of a variety of tissues and organs as a result of concerted contributions by multidisciplinary groups in the field of biotechnology. Engineering of an organ is a complex process which is initiated by appropriate sourcing of cells and their controlled proliferation to achieve critical numbers for seeding on biodegradable scaffolds in order to create cell-scaffold constructs, which are thereafter maintained in bioreactors to generate tissues identical to those required for replacement. Extensive efforts in understanding the characteristics of cells and their interaction with specifically tailored scaffolds holds the key to their attachment, controlled proliferation and differentiation, intercommunication, and organization to form tissues. The demand for tissue-engineered organs is enormous and this technology holds the promise to supply customized organs to overcome the severe shortages that are currently faced by the pediatric patient, especially due to organ-size mismatch. The contemporary state of tissue-engineering technology presented in this review summarizes the advances in the various areas of regenerative medicine and addresses issues that are associated with its future implementation in the pediatric surgical patient.

Hair stem cells for bladder regeneration in rats: preliminary results

BACKGROUND

A variety of tissue engineering techniques are currently under development or investigation for bladder augmentation, but so far no approach is clearly superior. The aim of this study was to compare the suitability for cystoplasty augmentation in rats of in vivo implanted acellular bladder matrices (BAM) previously seeded with hair follicle stem cells and that of matrices implanted without the cells.

MATERIALS AND METHODS

The rat hair follicle stem cell line was positive for CD34, p63, and Ki-67. 1 x 10(6) cells from 34 to 40 passages seeded onto nine BAM scaffolds were cultured for one week. Nine other scaffolds were left unseeded. Scaffolds were grafted into a surgically created defect within the anterior bladder wall: nine rats with acellular matrices and nine with cell-seeded BAM. Rats observed for six months were killed in monthly intervals. We performed gross examination, X-ray cystography, and hematoxylin-eosin, cytokine (CK)-7, CK-20, myoglobin, and desmin staining of the excised bladders.

RESULTS

Minimal adhesions were observed and urinary leakage was noted in one case. Two animals died in the acellular group. Rats developed stone disease in bladders reconstructed with acellular BAM. Bladder capacity was similar, but the shape was regular and characteristically oval only in bladders grafted with cell-seeded BAM. Muscle layers in the apical parts of the reconstructed bladder walls were extremely thin in the cases of acellular grafts and thicker in bladders reconstructed with cell-seeded grafts. Muscle layer regeneration was better in the cell-seeded group. Urothelium regenerated in all animals.

CONCLUSIONS

We have shown that hair follicle stem cells may be used for rat bladder wall regeneration.

Constructive remodeling of biologic scaffolds is dependent on early exposure to physiologic bladder filling in a canine partial cystectomy model

Biologic scaffolds composed of extracellular matrix (ECM) have been used to facilitate the constructive remodeling of several tissue types. Previous studies suggest that the ECM scaffold remodeling process is dependent on microenvironmental factors, including tissue-specific biomechanical loading. The objective of the present study was to evaluate the effects of long-term catheterization (LTC), with its associated inhibition of bladder filling and physiologic biomechanical loading, on ECM scaffold remodeling following partial cystectomy in a canine model. Reconstruction of the partial cystectomy site was performed using ECM scaffolds prepared from porcine small intestinal submucosa (SIS) or porcine urinary bladder matrix (UBM). Animals were randomly assigned to either a long-term catheterization (LTC) group (n=5, catheterized 28 d) or a short-term catheterization group (STC, n=5, catheterized 24 h), and scaffold remodeling was assessed by histologic methods at 4 and 12 wk postoperatively. By 4 wk, animals in the STC group showed a well-developed and highly differentiated urothelium, a robust vascularization network, abundant smooth muscle actin (SMA), and smooth muscle myosin heavy chain (smMHC) expressing spindle-shaped cells, and many neuronal processes associated with newly formed arterioles. In contrast, at 4 wk the scaffolds in LTC animals were not epithelialized, and did not express neuronal markers. The scaffolds in the LTC group developed a dense granulation tissue containing SMA+, smMHC-, spindle-shaped cells that were morphologically and phenotypically consistent with myofibroblasts, but not smooth muscle cells. By 12 wk postoperatively, the ECM scaffolds in the STC animals showed a constructive remodeling response, with a differentiated urothelium and islands of smooth muscle cells within the remodeled scaffold. In contrast, at 12 wk the scaffolds in LTC animals had a remodeling response more consistent with fibrosis even though catheters had been removed 8 wk earlier. These findings show that early exposure of site-appropriate mechanical loading (i.e., bladder filling) mediates a constructive remodeling response after ECM repair in a canine partial cystectomy model.

Regenerative medicine strategies for treatment of neurogenic bladder

Neurogenic bladder is a general term encompassing various neurologic dysfunctions in the bladder and external urethral sphincter caused by damage or disease. Therapeutic management options fall into the categories of conservative, minimally invasive or surgical. The current standard for surgical management is bladder augmentation using intestinal segments. However, because intestinal tissue possesses different functional characteristics to bladder tissue, numerous complications can ensue. Regenerative medicine uses combinations of cells and/or biomaterials to encourage regeneration of healthy tissue and offers an alternative approach for the replacement of lost or deficient organs, including the bladder. Promising results using the principles of regenerative medicine have already been obtained in children with neurogenic bladder caused by myelomeningocele. Human clinical trials, governed by the US FDA, are ongoing in the USA in both children and adults to further evaluate the safety and efficacy of this technology for regenerating bladders. More studies are in progress and additional advances in this field can be anticipated.

Bioengineered tissues for urogenital repair in children

The most common congenital abnormalities involve the genitourinary system. These include hypospadias, in which the urethral opening develops in an improper position, and bladder exstrophy, in which the bladder develops on the outer surface of the abdomen. Children with these conditions will require immediate and multiple reconstructive surgeries. Currently, reconstruction may be performed with native nonurologic tissues (skin, gastrointestinal segments, or mucosa), homologous tissues from a donor (cadaver or living donor kidney), heterologous tissues or substances (bovine collagen), or artificial materials (silicone, polyurethane, teflon). However, these materials often lead to complications after reconstruction, either because the implanted tissue is rejected, or because inherently different functional parameters cause a mismatch in the system. For example, replacement of bladder tissue with gastrointestinal segments can be problematic due to the opposite ways in which these two tissues handle solutes-urologic tissue normally excretes material, and gastrointestinal tissue generally absorbs the same materials. This mismatched state can lead to metabolic complications as well as infection and other issues. The replacement of lost or deficient urologic tissues with functionally equivalent ones would improve the outcome of reconstructive surgery in the genitourinary system. This goal may soon be attainable with the use of tissue engineering techniques.

Challenges in a larger bladder replacement with cell-seeded and unseeded small intestinal submucosa grafts in a subtotal cystectomy model

OBJECTIVE

To evaluate small intestinal submucosa (SIS), unseeded or seeded, as a possible augmentation material in a canine model of subtotal cystectomy.

MATERIALS AND METHODS

In all, 22 male dogs had a 90% partial cystectomy and were then divided into three groups. At 1 month after the initial cystectomy, dogs in group 1 (unseeded, six) and group 2 (seeded, six) received a bladder augmentation with a corresponding SIS graft. The dogs in group 3 (ten) received no further surgery and were considered the surgical control group. All dogs were evaluated before and after surgery with blood chemistry, urine culture, intravenous urography, cystograms and cystometrograms. After surgery (at 1, 5 and 9 months), the bladders were examined using routine histology and immunohistochemistry.

RESULTS

All 22 dogs survived the subtotal cystectomy, and 18 survived their intended survival period. One dog, in group 2 (seeded), was killed at 1 month after augmentation due to bladder perforation caused by a large piece of incompletely absorbed SIS. Three other dogs (group 1, two; and group 2, one) were killed within 2 months after augmentation due to bladder obstruction by stones. Group 1 and group 2 SIS grafts had moderate to heavy adhesion, graft shrinkage, and some had bone and calcification at the graft site. Histologically, there was limited bladder regeneration in both groups. Interestingly, dogs in group 3 at 1 month after cystectomy (when group 1 and 2 received their augmentations) had severely shrunken bladders and histologically had severe inflammation, fibroblast infiltration and muscle hypertrophy. These results verify the subtotal cystectomy model.

CONCLUSIONS

The use of seeded or unseeded SIS in a subtotal cystectomy model does not induce the same quality and quantity of bladder regeneration that is seen in the 40% non-inflammatory cystectomy model. This study provides important insights into the process of regeneration in a severely damaged bladder. The results led us to re-evaluate the critical elements required for a complete bladder replacement using tissue-engineering techniques.

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.

Technology insight: Novel ureteral stent materials and designs

Ureteral stents are an important tool for aiding upper urinary tract drainage, but can cause significant patient morbidity. Common problems include stent-induced pain, hematuria, dysuria, infection, and encrustation. From a urologist's perspective, stents must be easy to maneuver in the urinary tract, radiopaque, and affordable. Since the development of the modern day stent in 1978, stents have evolved to include softer biomaterials that are more resistant to encrustation and infection. An ideal biomaterial is one that is not affected by its environment and does not elicit reactive changes in surrounding tissues. To date, the ideal biomaterial or stent does not exist. This review discusses developments that address the issues of infection, biofilm formation, encrustation, and patient comfort. Stent materials including polyurethane, silicone, biodegradable substances and new combination polymers are reviewed, in addition to novel stent coatings such as heparin, hydrogel, and silver nitrate. Ureteral stent technologies currently lag behind vascular stents, particularly drug-eluting stents, but new developments will continue to improve these essential urological tools.

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.