LAPAROSCOPIC AUGMENTATION CYSTOPLASTY WITH DIFFERENT BIODEGRADABLE GRAFTS IN AN ANIMAL MODEL

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.

Application of biomaterials and tissue engineering in bladder regeneration

The primary functions of the bladder are storing urine under low and stable pressure and micturition. Various forms of trauma, tumors, and iatrogenic injuries can cause the loss of or reduce bladder function or capacity. If such damage is not treated in time, it will eventually lead to kidney damage and can even be life-threatening in severe cases. The emergence of tissue engineering technology has led to the development of more possibilities for bladder repair and reconstruction, in which the selection of scaffolds is crucial. In recent years, a growing number of tissue-engineered bladder scaffolds have been constructed. Therefore, this paper will discuss the development of tissue-engineered bladder scaffolds and will further analyze the limitations of and challenges encountered in bladder reconstruction.

Use of conditioned media (CM) and xeno-free serum substitute on human adipose-derived stem cells (ADSCs) differentiation into urothelial-like cells

Background

Congenital abnormalities, cancers as well as injuries can cause irreversible damage to the urinary tract, which eventually requires tissue reconstruction. Smooth muscle cells, endothelial cells, and urothelial cells are the major cell types required for the reconstruction of lower urinary tract. Adult stem cells represent an accessible source of unlimited repertoire of untransformed cells.

Aim

Fetal bovine serum (FBS) is the most vital supplement in the culture media used for cellular proliferation and differentiation. However, due to the increasing interest in manufacturing xeno-free stem cell-based cellular products, optimizing the composition of the culture media and the serum-type used is of paramount importance. In this study, the effects of FBS and pooled human platelet (pHPL) lysate were assessed on the capacity of human adipose-derived stem cells (ADSCs) to differentiate into urothelial-like cells. Also, we aimed to compare the ability of both conditioned media (CM) and unconditioned urothelial cell media (UCM) to induce urothelial differentiation of ADCS in vitro.

Methods

ADSCs were isolated from human lipoaspirates and characterized by flow cytometry for their ability to express the most common mesenchymal stem cell (MSCs) markers. The differentiation potential was also assessed by differentiating them into osteogenic and adipogenic cell lineages. To evaluate the capacity of ADSCs to differentiate towards the urothelial-like lineage, cells were cultured with either CM or UCM, supplemented with either 5% pHPL, 2.5% pHPL or 10% FBS. After 14 days of induction, cells were utilized for gene expression and immunofluorescence analysis.

Results

ADSCs cultured in CM and supplemented with FBS exhibited the highest upregulation levels of the urothelial cell markers; cytokeratin-18 (CK-18), cytokeratin-19 (CK-19), and Uroplakin-2 (UPK-2), with a 6.7, 4.2- and a 2-folds increase in gene expression, respectively. Meanwhile, the use of CM supplemented with either 5% pHPL or 2.5% pHPL, and UCM supplemented with either 5% pHPL or 2.5% pHPL showed low expression levels of CK-18 and CK-19 and no upregulation of UPK-2 level was observed. In contrast, the use of UCM with FBS has increased the levels of CK-18 and CK-19, however to a lesser extent compared to CM. At the cellular level, CK-18 and UPK-2 were only detected in CM/FBS supplemented group. Growth factor analysis revealed an increase in the expression levels of EGF, VEGF and PDGF in all of the differentiated groups.

Conclusion

Efficient ADSCs urothelial differentiation is dependent on the use of conditioned media. The presence of high concentrations of proliferation-inducing growth factors present in the pHPL reduces the efficiency of ADSCs differentiation towards the urothelial lineage. Additionally, the increase in EGF, VEGF and PDGF during the differentiation implicates them in the mechanism of urothelial cell differentiation.

Insulin-like growth factor 1 sustained-release collagen on urethral catheter prevents stricture after urethral injury in a rabbit model

OBJECTIVES

To evaluate the preventive effect of an insulin-like growth factor 1 sustained-release collagen urethral catheter on urethral stricture after urethral injury in a rabbit model.

METHODS

We made urethral catheters coated either with insulin-like growth factor 1 impregnated collagen or with only collagen, and we divided 19 male Japanese white rabbits into three groups according to the kind of catheter inserted immediately after the rabbit's urethra was injured by electrocoagulation. Group 1 (n = 7) had a catheter coated with insulin-like growth factor 1 impregnated collagen inserted; group 2 (n = 7) had a catheter coated with only collagen inserted; and group 3 (n = 5) had an uncoated catheter inserted. A total of 14 days later, the injured urethras were evaluated by urethrography and urethroscopy, and were also histologically examined.

RESULTS

Urethrography showed that the ratio of the urethral lumen diameter in injured urethra to that in normal urethra was the largest in group 1 (P < 0.0001). In addition, five of the seven rabbits in group 1 (71.4%) had a urethral lumen large enough for passage of a urethroscope, a fraction larger than the corresponding fractions in groups 2 (57.1%) and 3 (20%). On histological analysis, the injured area not covered with regenerated urethral epithelium tended to be smaller in group 1 than the other two groups, but the mean difference was not significant (P = 0.19).

CONCLUSIONS

An insulin-like growth factor 1 sustained-release collagen urethral catheter significantly improves wound healing and prevents urethral stricture after urethral injury.

Silk Fibroin Scaffolds for Urologic Tissue Engineering

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

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.

Growth factor and small molecule influence on urological tissue regeneration utilizing cell seeded scaffolds

Regenerative medicine strategies combine various attributes from multiple disciplines including stem cell biology, chemistry, materials science and medicine. The junction at which these disciplines intersect provides a means to address unmet medical needs in an assortment of pathologies with the goal of creating sustainable, functional replacement tissues. Tissue damage caused by trauma for example, requires rapid responses in order to mitigate further tissue deterioration. Cell/scaffold composites have been utilized to initiate and stabilize regenerative responses in vivo with the hope that functional tissue can be attained. Along with the gross reconfiguration of regenerating tissues, small molecules and growth factors also play a pivotal role in tissue regeneration. Several regenerative studies targeting a variety of urological tissues demonstrate the utility of these small molecules or growth factors in an in vivo setting.

Organ bioengineering for the newborn

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

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.

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.

Bladder reconstruction using bovine pericardium in a case of enterovesical fistula

The use of graft materials in bladder mucosa has been examined in animal models, but debate exists over which materials are effective. Intestine has been used as a substitute in augmentation cystoplasty for patients with neuropathic bladder, but serious adverse effects of the operation have occurred in some instances. We report a case of a successful repair of an enterovesical fistula by use of bovine pericardium. The patient has remained well for 2.5 years. We suggest that bovine pericardium may be a suitable option as a bladder substitute.

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.

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.

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.

Regeneration of Uterine Horn Using Porcine Small Intestinal Submucosa Grafts in Rabbits

Tubal factor infertility may be reversed using porcine small-intestinal submucosa (SIS). The method uses as a model the New Zealand White rabbit uerine horn. In surgery, SIS grafts were prepared from porcine jejunum; the uterine horn segment was resected and a graft was placed; then the contralateral adnexa was resected. Fecundability was tested with natural mating. Three out of six rabbits became pregnant. Gross and microscopic examination confirmed regeneration of all tissue layers. Thus, this study determined that SIS facilitates successful regeneration of uterine horn morphology in a manner similar to that observed in other tissues and species.

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.

In-Vitro Gliding Resistance of Lapra-Ty Clip on Polypropylene and Glycolide Sutures

BACKGROUND AND PURPOSE

The LapraTy clip (LTc) is a useful tool for supplementing knot-tying during reconstructive laparoscopic surgery. However, data regarding its safety and efficacy are scarce. We critically assessed the in-vitro performance of the LTc over different sizes of two suture materials commonly used during reconstructive procedures.

MATERIALS AND METHODS

The gliding resistance (GR) of one or two LTcs was tested on various sizes of both Polysorb and Prolene sutures. The GR of each suture was then compared with its breaking strength. Forces were measured using a Vernier Force Sensor.

RESULTS

The GR of one LTc was significantly lower than the breaking strength of all Polysorb and Prolene suture sizes with the exception of 7-0 Prolene, with which the suture broke before the LTc slipped off. When two LTcs were placed sequentially, the GR increased significantly compared with a single LTc and was equal to or greater than the breaking strength for Polysorb 3-0 to 5-0 and Prolene 3-0 to 6-0. The percentage of GR over breaking strength was inversely related to suture size and was significantly greater with Prolene than with the Polysorb suture of the same size.

CONCLUSIONS

Our results provide a better understanding of the resistive force an LTc offers before slipping and therefore failing. The results observed with Prolene sutures are encouraging and must be further investigated in an animal study to confirm the safety of the LTc when used during reconstructive procedures.

Using porcine acellular collagen matrix (Pelvicol®) in bladder augmentation: experimental study

PURPOSE

Evaluate the rabbit augmented bladder with Pelvicol.

MATERIALS AND METHODS

Twenty New Zealand rabbits were divided into 4 groups. Bladder augmentation was performed using a 10 x 10 mm sized porcine acellular collagen matrix. The material was placed on the dome of the bladder wall as a patch with 5-0 polyglycolic sutures. The bladder was resected on the 7th, 14th day, 30th and 90th days, and processed for histological analysis.

RESULTS

No stone formation was found in the first, second and fourth weeks. In the first week, there was inflammatory appearance and roughness in the reconstructed area when compared to other sites on the bladder wall. The material could not be seen in some bladders because of acute inflammatory reaction. The normal bladder epithelium was found on the part of the bladder wall that follows the surface of the eroded material. In the second week, edema was observed through the bladder wall. Perivesical fat tissue increased and it was not easy to distinguish it from the surrounding area. In the fourth week, the bladder wall was thickened and there was a sensation of hardness present. The inner and outer surface of the material was darker than in the other bladders. In the third month, there was no inflammatory reaction; however, there was micro calcification and irregular detrusor regeneration.

CONCLUSIONS

Pelvicol cannot be suitable material for bladder augmentation because of the resultant micro calcification, thickening of the bladder wall and irregular development of detrusor regeneration.

Modified running vesicourethral anastomosis after robotically assisted laparoscopic radical prostatectomy: Use of solitary Lapra-Ty to secure posterior approximation

OBJECTIVES

We describe a novel method of ensuring posterior approximation and preventing urinary leak during the running anastomosis of robotically assisted laparoscopic prostatectomy.

METHODS

Two 3-0 Monocryl RB-1 sutures are tied end-to-end. The undyed suture is placed first at the 5-o'clock position on the bladder side outside-in and then through the urethra at the same location inside-out. Proceeding clockwise, the suture is placed twice more through both the bladder and the urethra. With gentle manipulation, the suture is cinched down to provide secure posterior approximation; however, if tension is released from the suture coming from the urethra, the approximation may loosen and could result in a potential "gap" and site for anastomotic leakage. To prevent potential loosening, tension is maintained on the stitch as a single Lapra-Ty is placed at the base of the suture as it leaves the urethra. When the tension is released, the posterior approximation is tightly maintained and the remaining anastomosis is completed.

RESULTS

We have performed 110 robotically assisted laparoscopic prostatectomies. Six urinary leaks requiring prolonged catheterization were identified in our first 90 patients (6.7%). We have not experienced any urinary leakage or short-term complications in the subsequent 20 patients using this technique.

CONCLUSIONS

We describe a novel technique to ensure secure posterior approximation during the vesicourethral anastomosis after robotically assisted laparoscopic prostatectomy. A single Lapra-Ty clip placed early during the anastomosis prevents potential "gaps" in the approximation that may be the source of troublesome leakage.

Collagenous matrices as release carriers of exogenous growth factors

We have investigated the use of natural and synthetic collagenous matrices as carriers of exogenous growth factors. A bladder acellular matrix (BAM) was processed from rat bladder and compared with sponge matrix of porcine type 1 collagen. The lyophilized matrices were rehydrated by the aqueous solutions of basic fibroblast growth factor (bFGF), hepatocyte growth factor (HGF), platelet derived growth factor-BB (PDGF-BB), vascular endothelial growth factor (VEGF), insulin like growth factor-1 (IGF-1) and heparin binding epidermal growth factor-like growth factor (HB-EGF), to obtain the matrix incorporating each growth factor. The rehydration method enabled the growth factor protein to distribute into the matrix homogeneously. In vivo release test in the mouse subcutis revealed that, the property of BAM for growth factor release was similar to that of collagen sponge. Among the growth factors examined, bFGF release was the most sustained, followed by HGF and PDGF-BB. bFGF released from the two matrices showed similar in vivo angiogenic activity at the mouse subcutis in a dose-dependent manner. These findings demonstrate that the collagenous matrices function as release carriers of growth factors. This feature is promising to create a scaffold, which has a nature to control the tissue regeneration actively.

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

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

Bladder augmentation with an omental pedicled gastric seromuscular flap without the necessity of gastric resection

Bladder augmentation using gastrointestinal segments requires gastric or intestinal resection. This has several risks. In a rat model, we aimed to test the efficacy of a new procedure in which a gastric seromuscular (GSM) flap is separated from the gastric mucosa without the necessity of gastric resection, and this GSM flap, based on an omentum pedicle, is transferred to the bladder. A GSM flap based on an omental leaf was dissected from the gastric mucosa and rotated 180 degrees counter-clockwise, after ligation of the vessels relating to the omentum, until the mid-duodenum. After urodynamic analysis for control levels of bladder capacity and pressure, the GSM flap was anastomosed to the bladder with a continuous suture. Because four rats died due to bladder calculi, only 21 of 25 rats were killed at 1 month (n = 10) and 4 months (n = 11) for histopathological and urodynamic evaluations of the augmented bladder. Bladder capacity increased significantly in the augmented bladders compared to preaugmentation (P < 0.001). There was no significant difference between end-filling pressures of the augmented bladders and preaugmentation. Histopathological findings demonstrated that the muscular surface of the flap was completely re-epithelialized in all rats. Squamous metaplasia was detected in 30% (3/10) of the 1 month group rats, and in 55% (6/11) of 4 month rats (P > 0.05). Gross calculi formation appeared in 20% (2/10) of the 1 month group rats, and in 34% (4/11) of 4 month rats (P > 0.05). Our data show that the use of the GSM flap in the bladder of a rat resulted in the complete re-epithelialization of the flap and sufficient bladder capacity. Despite significant complications such as death, metaplasia and calculi, this technique may be considered as an alternative experimental model to traditional full-thickness patching, which needs gastric or intestinal resection.

Tissue engineering for the replacement of organ function in the genitourinary system

Acquired and congenital abnormalities may lead to genitourinary organ damage or loss, requiring eventual reconstruction. Tissue engineering follows the principles of cell transplantation, materials science, and engineering toward the development of biological substitutes that would restore and maintain normal function. Tissue engineering may involve matrices alone, wherein the body's natural ability to regenerate is used to orient or direct new tissue growth, or the use of matrices with cells. Both synthetic and natural biodegradable materials have been used, either alone or as cell delivery vehicles. Tissue engineering has been applied experimentally for the reconstitution of several urologic tissues and organs, including bladder, ureter, urethra, kidney, testis, and genitalia. Fetal applications have also been explored. Recently, several tissue engineering technologies have been used clinically including the use of cells as bulking agents for the treatment of vesicoureteral reflux and incontinence and urethral replacement. Recent progress suggests that engineered genitourinary tissues may have clinical applicability in the future.

Tissue engineering, stem cells, and cloning for the regeneration of urologic organs

Tissue engineering efforts are currently being undertaken for every type of tissue and organ within the urinary system. Most of the effort expended to engineer genitourinary tissues has occurred within the last decade. Tissue engineering techniques require a cell culture facility designed for human application. Personnel who have mastered the techniques of cell harvest, culture, and expansion as well as polymer design are essential for the successful application of this technology. Various engineered genitourinary tissues are at different stages of development, with some already being used clinically, a few in preclinical trials, and some in the discovery stage. Recent progress suggests that engineered urologic tissues may have an expanded clinical applicability in the future.

Simplified laparoscopic radical cystectomy with orthotopic ileal neobladder creation in a porcine model

BACKGROUND AND PURPOSE

Laparoscopic radical cystectomy with orthotopic ileal neobladder creation is a technically challenging and lengthy surgical procedure. We present our experience with a simplified technique for laparoscopic cystectomy and neobladder creation in the porcine model.

MATERIALS AND METHODS

Ten female minipigs underwent a purely laparoscopic radical cystectomy with orthotopic ileal neobladder creation. Nine ureterointestinal anastomoses were performed using a simplified "dunk" technique, where the ureter was prolapsed 5 mm into the afferent limb and the periureteral tissue was secured to the bowel serosa with three superficial sutures. Six ureters were not stented, and three had indwelling stents inserted. In 11 ureters, the anastomosis was performed using a running mucosa-to-mucosa technique (three with stents, eight without stents). The Lapra-Ty suture clip (Ethicon Endosurgery, Cincinnati, OH) was used to secure the running sutures on the urethra, ureters, and neobladder. Animals were harvested at 3 to 8 weeks (mean 6.5 weeks) after surgery. Serology, static cystogram, intravenous urography, and gross and histopathologic evaluations were performed.

RESULTS

Of six unstented dunked ureterointestinal anastomoses, two (33%) were widely patent, two were strictured but patent, and two were completely obstructed. In the three stented ureters implanted using the dunk technique, one (33%) was widely patent, one was strictured, and one was completely obstructed. All ureterointestinal anastomoses performed with a mucosa-to-mucosa running anastomosis, whether stented (three ureters) or not stented (eight ureters), were widely patent. Lapra-Ty clip migration into the neobladder pouch caused urethral obstruction resulting in delayed bladder perforation in two animals.

CONCLUSIONS

Laparoscopic cystectomy and ileal neobladder creation is technically feasible. Attempts to simplify the ureterointestinal anastomosis require further evaluation and modification. Stent placement appears to be unnecessary in the laparoscopic ureterointestinal anastomosis. Laparoscopic creation of the ileal neobladder remains a technically challenging procedure.

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.

Morphologic study of small intestinal submucosa as a body wall repair device

BACKGROUND

The extracellular matrix (ECM) derived from porcine small intestinal submucosa (SIS) has been used as a constructive scaffold for tissue repair in both preclinical animal studies and human clinical trials. Quantitative characterization of the host tissue response to this xenogeneic scaffold material has been lacking.

MATERIALS AND METHODS

The morphologic response to a multilaminate form of the SIS-ECM was evaluated in a chronic, 2-year study of body wall repair in two separate species: the dog and the rat. Morphologic response to the SIS-ECM was compared to that for three other commonly used bioscaffold materials including Marlex mesh, Dexon, and Perigard. Quantitative measurements were made of tissue consistency, polymorphonuclear cell response, mononuclear cell response, tissue organization, and vascularity at five time points after surgical implantation: 1 week, 1, 3, and 6 months, and 2 years.

RESULTS

All bioscaffold materials functioned well as a repair device for large ventral abdominal wall defects created in these two animal models. The SIS-ECM bioscaffold showed a greater number of polymorphonuclear leukocytes at the 1-week time point and a greater degree of graft site tissue organization after 3 months compared to the other three scaffold materials. There was no evidence for local infection or other detrimental local pathology to any of the graft materials at any time point.

CONCLUSIONS

Like Marlex, Dexon, and Perigard, the SIS-ECM is an effective bioscaffold for long-term repair of body wall defects. Unlike the other scaffold materials, the resorbable SIS-ECM scaffold was replaced by well-organized host tissues including differentiated skeletal muscle.