Systems for therapeutic angiogenesis in tissue engineering

The goals in tissue engineering include the replacement of damaged, injured, or missing body tissues with biologically compatible substitutes. To overcome initial tissue-mass loss, improved vascularization of the regenerated tissue is essential. Two pathways of tissue neovascularization are known: vasculogenesis, the in situ assembly of capillaries from undifferentiated endothelial cells (EC), and angiogenesis, the sprouting of capillaries from preexisting blood vessels. Recent advances in our understanding of the process of bloodvessel growth have provided significant tools for the neovascularization of bioengineered tissues. Several growth factors serve as stimuli for EC proliferation and migration as well as the formation of new blood vessels. They convey their effects via specific receptors expressed on the surface of EC. Vascular epithelial growth factor (VEGF) is a major regulator of neovascularization. VEGF plays a major role in the early development of blood-cell progenitors. Basic fibroblast growth factor (bFGF) was identified as the first angiogenic factor. It is a potent inducer of EC proliferation and blood-vessel growth in vitro and in vivo. VEGF and bFGF have been injected into undervascularized ischemic tissues, resulting in new blood-vessel formation and tissue perfusion. Gene-therapy approaches using VEGF cDNA injection into ischemic tissues have augmented the formation of collateral vessels. Angiogenic factors such as VEGF and bFGF have also been incorporated into bioengineered tissues and have facilitated blood-vessel growth. Other approaches such as prevascularization of the matrix prior to cell seeding and incorporation of EC into the bioengineered tissues have produced encouraging results. This article reviews the process of blood-vessel growth and tissue vascularization, placing emphasis on strategies that can be employed for efficient vascularization of engineered tissues in vitro and in vivo.

Renal therapy using tissue-engineered constructs and gene delivery

Currently available renal replacement therapies are not optimal for most patients. In addition to the inherent shortage of transplant organs, significant complications are associated with renal transplantation and immunosuppressive therapy. Dialysis neglects the resorptive, homeostatic, metabolic, and endocrinologic functions of the kidney and only partially replaces its filtration properties, resulting in morbidity and mortality. Application of tissue-engineering techniques may improve many aspects of renal function replacement. Identification of the growth factors capable of directing tissue development and of the technique to be used for their delivery would aid in the engineering of human tissue. The combination of tissue-engineering strategies with gene therapy might allow the transfection of diseased tissues with designated cDNA to eliminate inherent or acquired defects. Devices that have been targeted at replacing a single aspect of renal function, in addition to three-dimensional renal units that are capable of excreting urine-like solutes, have been used experimentally. Combination of these strategies may allow the formation of tissue-engineered kidneys in the future.

Tissue engineering of artificial 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 expertise in growth factor biology, a cell culture facility designed for human application, and personnel who have mastered the techniques of cell harvest, culture, and expansion. Polymer scaffold design and manufacturing resources are essential for the successful application of this technology. In order to apply these engineering techniques to humans, further studies need to be performed with many of the tissues described. The first human application of cell-based tissue engineering technology for urologic applications took place at our institution, with the injection of autologous cells for the correction of vesicoureteral reflux in children. The same technology has been expanded to treat adult patients with urinary incontinence. Trials of urethral tissue replacement with processed collagen matrices are in progress, and bladder replacement using tissue engineering techniques are currently being arranged. Recent progress suggests that engineered urologic tissues may have clinical applicability in the future.

Heparin-binding EGF-like growth factor expression increases selectively in bladder smooth muscle in response to lower urinary tract obstruction

Heparin-binding epidermal growth factor-like growth factor (HB-EGF), an activating ligand for the epidermal growth factor receptor (ErbB1) tyrosine kinase and at least one isoform of the ErbB4 receptor tyrosine kinase, is synthesized by the smooth muscle of the human bladder wall. In this study we tested the hypothesis that HB-EGF plays a role in the bladder-wall thickening that occurs in response to obstructive syndromes affecting the lower urinary tract, possibly by acting as an autocrine smooth muscle cell (SMC) growth factor. HB-EGF was mitogenic for primary culture human bladder SMC, and cell growth in serum-containing medium was inhibited more than 70% by [Glu52]-diphtheria toxin/CRM197, a specific HB-EGF inhibitor, consistent with a physiologic role for HB-EGF as an autocrine bladder SMC mitogen. Human and mouse bladder SMC in vivo and cultured human bladder SMC expressed the primary HB-EGF receptor, ErbB1, but not mRNA for the secondary HB-EGF receptor, ErbB4, thereby identifying ErbB1 as the cognate HB-EGF receptor in the bladder wall. Reverse transcription-polymerase chain reaction analysis also demonstrated ErbB2 and ErbB3 expression in human bladder muscle tissue, suggesting the possibility of receptor cross-talk after ErbB1 activation. Urethral ligation in mice resulted in an increase in steady-state HB-EGF mRNA expression up to 24 hours in whole bladder tissue in comparison with ErbB1 and glyceraldehyde 3-phosphate dehydrogenase mRNA levels, which did not change in a demonstrable pattern. HB-EGF protein increased coordinately with HB-EGF mRNA levels. Dissection of bladder tissue into muscle and mucosal layers demonstrated that the increase in HB-EGF mRNA occurred predominantly in the muscle layer, with peak levels (13-fold higher than sham controls) occurring 12 hours after obstruction. These data support a physiologic role for HB-EGF as a mediator of hypertrophic bladder tissue growth.

Pediatric retroperitoneoscopic nephrectomy using 2 mm. instrumentation

PURPOSE

We describe several modifications of the retroperitoneoscopic approach to nephrectomy for benign renal disease, including the use of 2 mm. instrumentation and prone patient positioning.

MATERIALS AND METHODS

A total of 14 children underwent retroperitoneoscopic nephrectomy in the prone position. An inflatable dissecting device was inserted into the retroperitoneum after a small muscle splitting incision was made at the lateral border of the sacrospinalis muscle approximately 1 cm. below the costovertebral angle. After inflation the dissecting device was replaced with a 5 mm. cannula and pneumoretroperitoneum was maintained with carbon dioxide insufflation. Two 2 mm. trocars were then placed under endoscopic guidance. Dissection was performed using 2 mm. instrumentation and the specimen was retrieved through the largest port site.

RESULTS

Nephrectomy was performed in 9 girls and 5 boys 3 months to 9.8 years old. The preoperative diagnosis included chronic pyelonephritis with minimal renal function, reflux with a nonfunctioning kidney, multicystic dysplastic kidney, an upper pole dysplastic moiety with an associated ureterocele and a dysplastic kidney with a vaginal ectopic ureter. Mean operative time for retroperitoneoscopic nephrectomy was 142 minutes with an estimated blood loss of less than 15 ml. Contralateral ureteral reimplantation was performed after retroperitoneoscopic dissection in 5 patients. Overall average hospital stay was 2 days and there were no complications.

CONCLUSIONS

Several modifications of the retroperitoneal approach, including the use of prone patient positioning and 2 mm. instrumentation for visualization and dissection, may improve the safety and efficacy of this technique in children.

Engineering tissues and organs

Genitourinary tissues can be engineered in-vitro and in-vivo for reconstruction using selective cell transplantation in combination with acellular matrices. This technology involves an interdisciplinary approach combining techniques of cell biology and materials sciences towards the development of functional tissues or organs. Tissues and organs in urology, such as the bladder, clitoris, corpus cavermosum, kidney, testis, ureter and urethra have been created in the laboratory, with varying degrees of functionality. Cells have also been recently used in patients as bulking agents for the treatment of vesicoureteral reflux and urinary incontinence. As the science of tissue engineering evolves, one can expect a wider application of this technology to the armamentarium of urologic surgery.

Progressive dilation for bladder tissue expansion

PURPOSE

The use of gastrointestinal tissue for augmentation cystoplasty is associated with numerous complications. We previously reported the development of a system in which ureters were progressively dilated and used for ureterocystoplasty. We have now applied a similar system for the progressive expansion of native bladder tissue. We investigated whether the expanded bladder tissue retained normal functional and phenotypic characteristics.

MATERIALS AND METHODS

Urodynamic studies were performed in 5 beagle dogs and the bladder was divided horizontally into a superior bladder neo-reservoir, and an intact smaller bladder inferiorly with both ureters left intact and draining. A silicone catheter was threaded into the newly formed, superiorly located neo-reservoir, and connected to an injection port which was secured subcutaneously. A saline antibiotic solution was injected daily into the palpable injection port 4 weeks after surgery, dilating the neo-reservoir through the silicone catheter. Baseline and weekly cystograms were performed. Urodynamic studies of the neo-reservoirs were done immediately before sacrifice. Animals were sacrificed 3 months after the initial intervention and the bladder was examined grossly and microscopically.

RESULTS

Within 30 days after progressive dilation, the neo-reservoir volume was expanded at least 10-fold according to radiography and cystometrograms. Urodynamic studies of the dilated neo-reservoirs showed normal compliance in all animals. Microscopic examination of the expanded neo-reservoir tissue revealed normal histology. A series of immunocytochemical studies demonstrated that the dilated bladder tissue maintained normal phenotypic characteristics.

CONCLUSIONS

The system of progressive dilation is effective in expanding bladder tissue which is able to retain normal phenotypic and functional characteristics.

A novel inert collagen matrix for hypospadias repair

PURPOSE

In select patients with hypospadias in whom genital skin is insufficient alternative tissues are needed for urethral reconstruction. Although skin and mucosal grafts may be used, they may increase hospitalization and morbidity. We explored the feasibility of using a bladder submucosal, collagen based inert matrix as a free graft substitute for urethral repair.

MATERIALS AND METHODS

Four patients with a history of hypospadias underwent repeat hypospadias repair using a collagen based inert matrix for urethral reconstruction. The inert collagen matrix was trimmed to size as needed for each patient. The neourethra was created by anastomosing the matrix in an onlay fashion to the urethral plate with continuous 6-zero polyglactin sutures. The created neourethra size ranged from 5 to 15 cm.

RESULTS

After a 22-month followup 3 of the 4 patients had a successful outcome in regard to cosmesis and function. One patient in whom a 15 cm. neourethra was created had a subglanular fistula.

CONCLUSIONS

The use of a collagen inert matrix appears to be beneficial in patients who have undergone previous hypospadias repair and who may lack sufficient genital skin for reconstruction.

Autologous engineered cartilage rods for penile reconstruction

PURPOSE

Conditions such as inadequate and ambiguous genitalia that are caused by rudimentary penis, severe hypospadias or traumatic injury require surgical intervention. Although silicone penile prostheses are an accepted treatment modality, biocompatibility issues may be a problem in select cases. We previously demonstrated that rods composed of cartilage could be created using chondrocytes seeded on biodegradable polymer scaffolds. We showed that the cartilage rods engineered ex situ were readily elastic and withstood high degrees of pressure. We investigated the feasibility of applying the engineered cartilage rods in situ in an animal model.

MATERIALS AND METHODS

Autologous chondrocytes harvested from rabbit ears were grown and expanded in culture. Cells were seeded onto biodegradable poly-L-lactic acid coated polyglycolic acid polymer rods at a concentration of 50 x 10(6) chondrocytes per cm3. A total of 18 chondrocyte polymer scaffolds were implanted into the corporal spaces in 10 rabbits. As controls, 1 corpus in each of 2 rabbits was not implanted. The animals were sacrificed 1, 2, 3 or 6 months after implantation. Histological analysis was performed using hematoxylin and eosin, aldehyde fuschin-alcian blue and toluidine blue staining.

RESULTS

All animals tolerated the implants for the duration of the study without any complications. Gross examination after retrieval at 1 month showed well formed, milky white cartilage structures within the corpora. All polymers were fully degraded by 2 months. There was no evidence of erosion or infection at any of the implant sites. Histological analysis using alcian blue and toluidine blue staining revealed mature and well formed chondrocytes in the retrieved implants.

CONCLUSIONS

Autologous chondrocytes seeded on preformed biodegradable polymer structures form cartilage structures within the rabbit corpus cavernosum. This technology appears to be useful for creating autologous penile prostheses.

Direct in vivo gene transfer to urological organs

PURPOSE

Patients with urological disorders may benefit from gene based therapy. We investigated the feasibility of delivering exogenous genes into urological tissues in vivo using direct in vivo electrotransfection.

MATERIALS AND METHODS

Gene transfer to rat kidneys, testes and bladders was accomplished via direct local injection of pGL3/luciferase and beta-galactosidase reporter gene constructs, followed by an electrical pulse ranging from 55 to 115 msec at 100 V. Direct injection of deoxyribonucleic acid without an electrical pulse served as the control. The transfected and nontransfected organs were retrieved and analyzed by luciferase activity assay, histochemical and immunocytochemical staining for beta-galactosidase, and reverse transcription polymerase chain reaction with primers specific for beta-galactosidase messenger ribonucleic acid.

RESULTS

There was significant luciferase activity 1, 3 and 5 days after direct in vivo electrotransfection in kidneys and testes, and after 3, 5, 7 and 10 days in bladders. Positive beta-galactosidase enzyme activity and beta-galactosidase immunoreactivity were observed in the transfected renal tubular cells, testicular interstitial and germ cells, and uroepithelial bladder layer. Reverse transcription-polymerase chain reaction products of the transfected organs were noted, indicating the successful transcription of messenger ribonucleic acid.

CONCLUSIONS

This study demonstrates that direct in vivo electrotransfection is a feasible method of transient gene delivery into intact urological organs. Its apparent safety and relative simplicity suggest that direct in vivo electrotransfection may be useful clinically.

The incidence of intersexuality in children with cryptorchidism and hypospadias: stratification based on gonadal palpability and meatal position

PURPOSE

The combined findings of cryptorchidism and hypospadias often indicate the existence of an intersex state. Testicular maldescent and incomplete tubularization of the urethral plate occur in a spectrum with the severity of the 2 processes likely dependent on the degree of pathophysiology in the androgenic hormonal axis. The incidence of intersexuality in children with undescended testes, hypospadias and otherwise nonambiguous male genitalia has been reported to be 27%. Although the likelihood of genotypic or gonadal ambiguity has previously been associated with meatal position in this population, to our knowledge our study is the first to evaluate the incidence of intersexuality relative to whether the undescended testis is palpable or nonpalpable.

MATERIALS AND METHODS

The database at our hospital was searched for all cases of undescended testes (2,105) and hypospadias (1,057) between 1982 and 1996. Radiographic, histological and karyotypic data were compiled for all patients presenting with both diagnoses. Gonadal palpability (palpable versus nonpalpable) and meatal position (anterior versus mid versus posterior) were recorded and correlated with the likelihood of identifying an intersex condition. Ten boys with a diagnosis of undescended testes subsequent to inguinal hernial repair were excluded from study. Patients with congenital adrenal hyperplasia or complete testicular feminization were also excluded from study due to the clearly female appearance of the external genitalia. Statistical significance was assessed using Fisher's exact test.

RESULTS

We identified 79 patients presenting with undescended testes, hypospadias and a phallus that was believed to be a possible penis. Intersex conditions were identified with nearly equal frequency in the 44 cases of unilateral (30%) and 35 of bilateral (32%) cryptorchidism. In the unilateral undescended testes group patients with a nonpalpable testis were at least 3-fold more likely to have an intersex condition than those with a palpable undescended testis (50 versus 15%, p = 0.02). In the bilateral group patients with 1 or more nonpalpable testes were also nearly 3-fold as likely to have an intersex condition than those with bilateral palpable undescended gonads (47 versus 16%, p = 0.07). Meatal position was graded as anterior in 33% of cases, mid in 25% and posterior in 41% with the more posterior location conferring a significantly greater likelihood of an intersex condition (anterior 2 of 26, mid 1 of 20 and posterior 21 of 33).

CONCLUSIONS

Gonadal palpability is an important predictor of an intersex state in unilateral and bilateral cases of cryptorchidism with hypospadias. Patients with an undescended testis that cannot be palpated are significantly more likely to have an intersex condition than those in whom the undescended testis may be palpated on physical examination. The severity of hypospadias likewise has a strong positive correlation with an intersex state.

Acellular collagen matrix as a possible "off the shelf" biomaterial for urethral repair

OBJECTIVES

To determine whether a naturally derived collagen-based tissue substitute developed for urethral reconstruction would be suitable for urethral repair in an animal model. Several urethral conditions often require nongenital tissues for reconstruction, such as skin grafts or mucosal grafts from the bladder or buccal regions. However, the use of these tissues for urethroplasty may be associated with additional procedures for graft retrieval, prolonged hospitalization, and morbidity.

METHODS

A ventral urethral defect was created in 10 male rabbits. The acellular collagen matrix, obtained and processed from porcine bladder submucosa, was trimmed and used to replace the urethral defect in an onlay fashion. Serial urethrography was performed pre- and postoperatively at 0.5, 1, 2, 3, and 6 months. The animals were sacrificed 0.5, 1, 2, 3, and 6 months after surgery. The retrieved implants were analyzed grossly, histologically, and with immunocytochemistry.

RESULTS

All animals survived until being sacrificed without any noticeable voiding dysfunction. Serial urethrograms confirmed the maintenance of a wide urethral caliber without any signs of strictures. Gross examination at retrieval showed normally appearing tissue without any evidence of fibrosis. Histologically, the implanted matrices contained host cell infiltration and generous angiogenesis by 2 weeks after surgery. The presence of a confluent transitional cell layer was confirmed by immunocytochemical analyses using pancytokeratin antibodies. Anti-alpha actin antibodies demonstrated the migration of unorganized muscle fiber bundles 2 months after implantation and organized muscle bundles 6 months after implantation.

CONCLUSIONS

The acellular collagen matrix appears to be a useful material for urethral repair in the rabbit. The matrix can be processed easily, has good characteristics for tissue handling and urethral function, and has the advantage of being an "off the shelf" material.

Reconstitution of human corporal smooth muscle and endothelial cells in vivo

PURPOSE

The availability of autologous erectile tissue composed of corporal smooth muscle and endothelial cells would be beneficial in patients undergoing penile reconstruction. We previously showed that cultured cavernous cells seeded on polymer scaffolds form corporal muscle when implanted in vivo. However, to reconstruct corporal tissue endothelial and corporal muscle cells are necessary. In this study we investigated the possibility of developing tissue composed of corporal cells in vivo by combining smooth muscle and endothelial cells.

MATERIALS AND METHODS

Human corporal smooth muscle and endothelial cells were seeded on biodegradable polyglycolic acid polymer scaffolds at concentrations of 20 x 10(6) and 10 x 10(6) cells per cm3, respectively. A total of 60 polymer scaffolds seeded with cells and 20 control polymers without cells were implanted in the subcutaneous space of 20 athymic mice. Mice were sacrificed 1, 3, 5, 7, 14, 21, 28 and 42 days, respectively, after implantation. Immunocytochemical and histochemical analyses were performed with antifactor VIII, antipancytokeratins and anti-alpha actin antibodies.

RESULTS

Histologically the retrieved polymers seeded with corporal smooth muscle and endothelial cells showed the formation of multilayered smooth muscle strips adjacent to endothelial cells 7 days after implantation. Increased organization of the smooth muscle tissue and accumulation of endothelium lining the luminal structures were evident by 14 days. A well organized tissue construct was noted 28 and 42 days after implantation. There was no evidence of tissue formation in controls. Immunocytochemical analysis using antifactor VIII to identify native vasculature only and antipancytokeratins to identify ECV 304 endothelial cells only distinguished the origin of the vascular structures in each construct. Anti-alpha-actin confirmed the smooth muscle phenotype.

CONCLUSIONS

Human corporal smooth muscle and endothelial cells seeded on biodegradable polymer scaffolds formed vascularized corpus cavernosum muscle when implanted in vivo. To our knowledge this is the first demonstration in tissue engineering in which capillary formation was facilitated by the addition of endothelial cells in composite tissue in vivo.

A novel inert collagen matrix for hypospadias repair

PURPOSE

In select patients with hypospadias in whom genital skin is insufficient alternative tissues are needed for urethral reconstruction. Although skin and mucosal grafts may be used, they may increase hospitalization and morbidity. We explored the feasibility of using a bladder submucosal, collagen based inert matrix as a free graft substitute for urethral repair.

MATERIALS AND METHODS

Four patients with a history of hypospadias underwent repeat hypospadias repair using a collagen based inert matrix for urethral reconstruction. The inert collagen matrix was trimmed to size as needed for each patient. The neourethra was created by anastomosing the matrix in an onlay fashion to the urethral plate with continuous 6-zero polyglactin sutures. The created neourethra size ranged from 5 to 15 cm.

RESULTS

After a 22-month followup 3 of the 4 patients had a successful outcome in regard to cosmesis and function. One patient in whom a 15 cm. neourethra was created had a subglanular fistula.

CONCLUSIONS

The use of a collagen inert matrix appears to be beneficial in patients who have undergone previous hypospadias repair and who may lack sufficient genital skin for reconstruction.

Direct in vivo gene transfer to urological organs

PURPOSE

Patients with urological disorders may benefit from gene based therapy. We investigated the feasibility of delivering exogenous genes into urological tissues in vivo using direct in vivo electrotransfection.

MATERIALS AND METHODS

Gene transfer to rat kidneys, testes and bladders was accomplished via direct local injection of pGL3/luciferase and beta-galactosidase reporter gene constructs, followed by an electrical pulse ranging from 55 to 115 msec at 100 V. Direct injection of deoxyribonucleic acid without an electrical pulse served as the control. The transfected and nontransfected organs were retrieved and analyzed by luciferase activity assay, histochemical and immunocytochemical staining for beta-galactosidase, and reverse transcription polymerase chain reaction with primers specific for beta-galactosidase messenger ribonucleic acid.

RESULTS

There was significant luciferase activity 1, 3 and 5 days after direct in vivo electrotransfection in kidneys and testes, and after 3, 5, 7 and 10 days in bladders. Positive beta-galactosidase enzyme activity and beta-galactosidase immunoreactivity were observed in the transfected renal tubular cells, testicular interstitial and germ cells, and uroepithelial bladder layer. Reverse transcription-polymerase chain reaction products of the transfected organs were noted, indicating the successful transcription of messenger ribonucleic acid.

CONCLUSIONS

This study demonstrates that direct in vivo electrotransfection is a feasible method of transient gene delivery into intact urological organs. Its apparent safety and relative simplicity suggest that direct in vivo electrotransfection may be useful clinically.

Autologous engineered cartilage rods for penile reconstruction

PURPOSE

Conditions such as inadequate and ambiguous genitalia that are caused by rudimentary penis, severe hypospadias or traumatic injury require surgical intervention. Although silicone penile prostheses are an accepted treatment modality, biocompatibility issues may be a problem in select cases. We previously demonstrated that rods composed of cartilage could be created using chondrocytes seeded on biodegradable polymer scaffolds. We showed that the cartilage rods engineered ex situ were readily elastic and withstood high degrees of pressure. We investigated the feasibility of applying the engineered cartilage rods in situ in an animal model.

MATERIALS AND METHODS

Autologous chondrocytes harvested from rabbit ears were grown and expanded in culture. Cells were seeded onto biodegradable poly-L-lactic acid coated polyglycolic acid polymer rods at a concentration of 50 x 10(6) chondrocytes per cm3. A total of 18 chondrocyte polymer scaffolds were implanted into the corporal spaces in 10 rabbits. As controls, 1 corpus in each of 2 rabbits was not implanted. The animals were sacrificed 1, 2, 3 or 6 months after implantation. Histological analysis was performed using hematoxylin and eosin, aldehyde fuschin-alcian blue and toluidine blue staining.

RESULTS

All animals tolerated the implants for the duration of the study without any complications. Gross examination after retrieval at 1 month showed well formed, milky white cartilage structures within the corpora. All polymers were fully degraded by 2 months. There was no evidence of erosion or infection at any of the implant sites. Histological analysis using alcian blue and toluidine blue staining revealed mature and well formed chondrocytes in the retrieved implants.

CONCLUSIONS

Autologous chondrocytes seeded on preformed biodegradable polymer structures form cartilage structures within the rabbit corpus cavernosum. This technology appears to be useful for creating autologous penile prostheses.

Normal urodynamics in patients with bladder exstrophy: are they achievable?

PURPOSE

Urodynamic study was performed in patients with exstrophy to determine the effect of bladder neck reconstruction and the ability to achieve normal urodynamics following surgery.

MATERIALS AND METHODS

A total of 30 exstrophy cases at different stages of reconstruction were retrospectively reviewed in terms of bladder capacity, compliance, stability and presence of detrusor contractions following urodynamic study.

RESULTS

Bladder capacity increased from a third predicted volume for age to half after reconstruction. Approximately 80% of patients had compliant and stable bladders before bladder neck reconstruction. Following bladder neck reconstruction approximately half of the patients maintained normal compliance with a smaller number maintaining normal stability. A quarter of patients maintained normal filling dynamics following bladder neck reconstruction, and 19% maintained normal filling and voiding dynamics after reconstruction.

CONCLUSIONS

The majority of closed exstrophy bladders have normal filling dynamics before bladder neck reconstruction. Compliance and stability are impaired following bladder neck reconstruction. Approximately 25% of patients with exstrophy may maintain normal detrusor function following reconstruction. However, less invasive alternatives to the Young-Dees-Leadbetter bladder neck reconstruction should be sought.

Current and future modalities for functional renal replacement

Approximately 310,000 Americans suffer from end-stage renal disease, with more than 70,000 new cases reported each year. Advances in immunosuppressive therapy for transplanted patients, in addition to the refined care of patients who are dependent on dialysis, have led to an improved survival for patients with renal failure. Structural, molecular, and pharmacologic developments continue to enhance the efficacy and safety of dialysis in the future. In addition, progressive improvements in the past 2 decades in organ transplantation, a greater insight into the immunobiology of graft rejection, and better surgical and medical management have resulted in improved outcomes. Although renal xenotransplantation is still in its early stages of development, additional research is leading this technology forward. Recent successes in harvesting and expanding renal cells in vitro and the development of biologically active synthetic materials allow for the creation of three-dimensional functioning renal units, which, in the future, may be applied ex vivo or in vivo for partial or full replacement of kidney function.

De novo reconstitution of a functional mammalian urinary bladder by tissue engineering

Human organ replacement is limited by a donor shortage, problems with tissue compatibility, and rejection. Creation of an organ with autologous tissue would be advantageous. In this study, transplantable urinary bladder neo-organs were reproducibly created in vitro from urothelial and smooth muscle cells grown in culture from canine native bladder biopsies and seeded onto preformed bladder-shaped polymers. The native bladders were subsequently excised from canine donors and replaced with the tissue-engineered neo-organs. In functional evaluations for up to 11 months, the bladder neo-organs demonstrated a normal capacity to retain urine, normal elastic properties, and histologic architecture. This study demonstrates, for the first time, that successful reconstitution of an autonomous hollow organ is possible using tissue-engineering methods.

New advances in injectable therapies for the treatment of incontinence and vesicoureteral reflux

Clinical experience over the last two decades has demonstrated that the endoscopic correction of primary vesicoureteral reflux and urinary incontinence caused by intrinsic sphincteric dysfunction is both possible and effective. The ideal material for use in these regards has yet to be developed. As a result, there has been a continuing research effort directed towards the development of new injectable substances. Nonautologous substances, such as Teflon, collagen, and Deflux, and autologous substances such as fat, chondrocytes and muscle, have been used either clinically or are under investigation. Although the ideal substance has yet to be determined, many of the substances currently under development appear promising. The use of a particular substance may best be determined by the clinical circumstance involving each individual patient.

Future perspectives in reconstructive surgery using tissue engineering

Whenever there is a lack of native urologic tissue, reconstruction usually is performed with native nonurologic tissues, such as gastrointestinal segments, skin, or mucosa from multiple body sites. The use of native nonurologic tissues in the genitourinary tract is associated with adverse effects. Tissue engineering efforts currently are underway for almost every type of tissue and organ within the urinary system including bladder, ureter, urethra, and genitalia. Most of the efforts expended to engineer genitourinary tissues have 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, and polymer design are essential for the successful application of this technology. The first human application of cell-based tissue engineering technology for urologic applications recently occurred with the injection of autologous cells for the correction of vesicoureteral reflux in children and urinary incontinence in adults. Trials involving bladder replacement using tissue engineering techniques currently are being arranged. Recent progress suggests that engineered urologic tissues may have clinical applicability.

Reservoir calculi: a comparison of reservoirs constructed from stomach and other enteric segments

PURPOSE

The intestinal augmented bladder has an increased propensity to form urinary calculi. Predisposing risk factors include chronic bacteriuria, urinary stasis and mucus production. Gastric reservoirs have negligible mucus production and the ability to acidify the urine. We determined whether they also have a decreased incidence of stones.

MATERIALS AND METHODS

We retrospectively reviewed the records of all patients undergoing augmentation cyptoplasty (215) or creation of a freestanding reservoir (44) between May 1976 and March 1996. Of these cases 83 were augmented with stomach and 179 were constructed from other intestinal segments, (that is ileal, ileocecal, sigmoid and/or a combination of these). Presenting diagnosis, patient age, gender, additional surgical procedures, interval to stone formation and calculous composition were recorded. Patients were excluded from study when there was less than 1 year of followup, as were those with renal or pre-augmentation bladder calculi.

RESULTS

Stones formed in 32 of 207 patients (15%) after an average interval of 3.6 years (range 0.5 to 8.6). The majority of stones were composed of struvite (magnesium ammonium phosphate). Reservoirs containing gastric segments were significantly less likely to form calculi than those augmented with other intestinal segments (2 of 70 versus 30 of 137, p <0.0001 Fisher's exact test). Seven additional patients with pre-augmentation bladder stones who subsequently underwent gastrocystoplasty remain stone-free at an average followup of 3.0 years.

CONCLUSIONS

Calculous formation is rare in reservoirs that incorporate a gastric segment. In patients with gastric augmentation stones appear only to develop when the patient is on histamine blockade or has a propensity to form stones that only favor an acidic environment, such as uric acid.

Comparison of sonicated albumin enhanced sonography to fluoroscopic and radionuclide voiding cystography for detecting vesicoureteral reflux

PURPOSE

We compared sonicated albumin enhanced sonography to fluoroscopic and radionuclide voiding cystography for detecting vesicoureteral reflux.

MATERIALS AND METHODS

After obtaining informed consent we enrolled in our study 20 patients with known or suspected vesicoureteral reflux and no contraindications to intravesical sonicated albumin. All patients underwent albumin enhanced sonography, following which 10 patients each underwent radionuclide and fluoroscopic voiding cystography. Reflux was graded by the observing radiologist and urologist.

RESULTS

In 10 patients albumin enhanced sonography demonstrated reflux in 6 of the 7 (83%) ureters in which radionuclide cystography identified reflux. In 2 patients ultrasound studies were inadequate due to excessive movement during the procedure, and the patients were classified as unevaluable. In the remaining 10 patients 12 of 20 ureters (60%) were equal in the absence or presence of and degree of reflux on enhanced sonography and voiding cystourethrography. In 6 ureters voiding cystourethrography detected reflux more readily or revealed a higher grade of reflux. Two ureters had a higher reflux grade on enhanced sonography. No adverse effects were associated with intravesical sonicated albumin.

CONCLUSIONS

In experienced hands sonicated albumin enhanced sonography is safe for evaluating vesicoureteral reflux. It provides the simultaneous evaluation of renal contours, parenchyma and size in addition to bladder visualization. This new technique may prove to be useful as a followup study in patients with previously documented reflux or as a primary study for sibling screening.

Cartilage rods as a potential material for penile reconstruction

PURPOSE

Sex assignment is made in patients with ambiguous genitalia, genital trauma or iatrogenic injury after a thorough diagnostic evaluation and careful consultation with the family. In numerous instances a decision is made to rear the child as the female gender due to inadequate genitalia regardless of karyotype. Although a silicone penile prosthesis is accepted treatment in adults who require penile reconstruction, it has not been generally used in the pediatric population, mainly due to associated long-term problems. We determine the feasibility of creating natural penile prostheses of cartilage which, if biocompatible and elastic, may be used in patients who require genital reconstruction.

MATERIALS AND METHODS

Cartilage was harvested from the articular surface of calf shoulders. Chondrocytes were isolated, grown and expanded in vitro. Cells were seeded onto preformed cylindrical polyglycolic acid polymer rods 1 cm. in diameter and 3 cm. long at a concentration of 50 x 10(6) chondrocytes per cm.3. A total of 40 polymer scaffolds were implanted in the subcutaneous space of 20 athymic mice. In each mouse 2 implantation sites consisted of a polymer scaffold seeded with chondrocytes and a control (polymer alone). Mice were sacrificed 1, 2, 4 and 6 months after implantation, respectively. Stress relaxation studies to measure biomechanical properties, including compression, tension and bending, were performed on the retrieved structures. Histological analyses were done with hematoxylin and eosin, aldehyde fuchsin-alcian blue and toluidine blue staining.

RESULTS

Gross examination revealed well formed, milk-white rod-shaped solid cartilaginous structures the same size as the initial implant. Compression, tension and bending studies demonstrated that the cartilaginous structures were readily elastic and withstood high degrees of pressure. Histochemical analyses showed mature, well formed chondrocytes in all implants. There was no evidence of cartilage formation in the controls.

CONCLUSIONS

Chondrocytes seeded on preformed biodegradable polymer structures form cartilage rods. The use of an entirely autologous system composed of biodegradable polymers and chondrocytes precludes an immunological reaction. This technology appears to be useful for the creation of a biocompatible malleable penile prosthesis, which may be useful in children with ambiguous genitalia and patients undergoing penile reconstruction.

Current findings in diagnostic laparoscopic evaluation of the nonpalpable testis

PURPOSE

We delineate the current findings and contribution of diagnostic laparoscopic evaluation in the management of nonpalpable testis.

MATERIALS AND METHODS

We reviewed all cases in which laparoscopy was considered the management associated with a nonpalpable testis in a 4-year period. Since our previous series, we have performed a careful examination for the testis after induction of anesthesia but before committing to laparoscopy. We recorded testis position and quality, character of the vas deferens and spermatic vessels, type of management and contribution of laparoscopy. We also reviewed contemporary published series and collated the findings of studies performed elsewhere.

RESULTS

We identified 263 nonpalpable testes in 225 patients between September 1992 and 1996. In 40 patients 46 testes (18%) were found during physical examination under anesthesia. Of the remaining cases considered appropriate for laparoscopy 215 with complete records were further analyzed. Only 12.6% could be considered missed on examination due to a viable testis distal to the inguinal ring. Of the testes 45.7% would have been found during inguinal exploration alone. In 9.8% of the patients there were intra-abdominal vanishing testes, while 4.2% had indeterminate cord structures on inguinal exploration that would have prompted abdominal extension without a laparoscopic demonstration that the vas and vessels entered the canal. A conventional inguinal incision would have provided optimal exposure for operative management in 34% of the testes. For testes distal to the internal ring when the vas and vessels were distinctly atretic we never identified a viable testis, while a normal appearing vas and vessel were associated with a 45% chance of a salvageable testis. Laparoscopy was informative regarding testis position in all cases in which it was performed.

CONCLUSIONS

In 13.2% of the cases laparoscopic findings precluded unnecessary abdominal exploration. The typical surgical incision for inguinal exploration would have left the surgeon compromised in 66% of the cases compared to the approach optimized as a result of laparoscopic testicular localization. Of the patients 34% arguably did not benefit from laparoscopy versus inguinal exploration. A simple examination under anesthesia significantly decreases the number of uninformative laparoscopic evaluations, and it is well worth the cost of a few minutes of operative time.

Sildenafil inhibits phosphodiesterase type 5 in human clitoral corpus cavernosum smooth muscle

Phosphodiesterases play an important physiological role by regulating the intracellular levels of cyclic nucleotides. In this study, we investigated the kinetic parameters of inhibition of phosphodiesterase (PDE) type 5 (EC 3.1.4.35, 3',5'-cyclic GMP phosphodiesterase) by a novel, high-affinity, selective PDE type 5 inhibitor, sildenafil, in intact cells and in soluble extracts of human clitoral corpus cavernosum smooth muscle cells. Sildenafil inhibited cGMP hydrolysis in the crude extract (Ki = 7.2 +/- 2.7) and in partially purified preparations (Ki = 9 nM) in a competitive manner, as determined by Dixon plots. Sildenafil was a more effective PDE type 5 inhibitor than zaprinast (Ki = 400.0 +/- 76.4 nM, crude extracts; 250 nM, partially purified). Stimulation of intracellular cGMP synthesis by the nitric oxide donor sodium nitroprusside resulted in a 3.3- and 2.9-fold increase in cGMP concentration in the presence of sildenafil or zaprinast, respectively, compared to sodium nitroprusside treatment alone in intact cells at physiological temperatures. These observations suggest that human clitoral corpus cavernosum smooth muscle tone may be regulated by the synthesis and release of nitric oxide and that this pathway is dependent on PDE type 5 activity.

Urachal anomalies: defining the best diagnostic modality

OBJECTIVES

Urachal abnormalities are uncommon and the literature is primarily comprised of case reports. Conclusions regarding the presentation and diagnosis of these abnormalities may be elucidated by reviewing a large experience.

METHODS

The records of 45 patients with urachal abnormalities in the pediatric age group were reviewed from 1970 to 1997. This included 24 boys and 21 girls with an age range from 1 day to 20 years (average 4.0 years). The presenting complaint was periumbilical discharge in 19 patients (42%), umbilical cyst or mass in 15 (33%), abdominal or periumbilical pain in 10 (22%), and dysuria in 1 (2%). The diagnosis consisted of a urachal sinus in 22 children (49%), a urachal cyst in 16 (36%), and a patent urachus in 7 (15%). Various radiographic studies were used to establish the diagnosis.

RESULTS

Patients with a urachal sinus had 16 voiding cystourethrograms performed (only 1 diagnostic), 9 sinograms (all diagnostic), 8 ultrasounds (4 diagnostic), and 1 excretory urogram (normal). Those with a urachal cyst had 8 voiding cystourethrograms (1 diagnostic), 5 excretory urograms (all normal), 4 ultrasounds (all diagnostic), and 1 computed tomography scan (diagnostic). Children with a patent urachus had 2 excretory urograms (both diagnostic), 1 voiding cystourethrogram (diagnostic), and 2 ultrasounds (normal). One baby with a patent urachus was diagnosed prenatally during ultrasound screening. The diagnosis was made by history and physical examination alone in 5 children and at the time of surgery in 1. Treatment consisted of surgical excision of the urachal abnormality with a cuff of bladder in 22 children, surgical excision without a bladder cuff in 22, incision and drainage of a urachal cyst (1%), and laparoscopic excision of a patent urachus with a bladder cuff in another (1%). There were three wound infections postoperatively. None developed any long-term sequelae.

CONCLUSIONS

The diagnosis of urachal abnormalities can be made with certainty if a good physical examination and the appropriate radiographic test are performed. A patient who presents with periumbilical drainage should have a sinogram performed, which should be diagnostic for both a urachal sinus and a patent urachus. Any child who presents with a periumbilical mass should have an ultrasound performed, which should be diagnostic for a urachal cyst.

Acute scrotal symptoms in boys with an indeterminate clinical presentation: comparison of color Doppler sonography and scintigraphy

PURPOSE

To compare the performance of color Doppler ultrasonography (US) and scintigraphy in assessing testicular perfusion in boys with clinically equivocal presentations.

MATERIALS AND METHODS

Forty-one boys with clinically equivocal testicular perfusion underwent color Doppler US and scintigraphy. Studies were retrospectively classified as consistent with torsion, consistent with nontorsion, or indeterminate. Sensitivity and specificity were determined with alternate positivity criteria (indeterminate studies first considered positive and then negative for torsion).

RESULTS

Color Doppler US demonstrated nine of 11 cases of torsion and 23 of 30 cases of nontorsion, with one false-positive and eight indeterminate studies. Scintigraphy demonstrated 10 of 11 cases of torsion and 29 of 30 cases of nontorsion, with two indeterminate studies (both in patients with inguinal testis). When indeterminate studies were considered positive for torsion, specificity was 77% for color Doppler US versus 97% for scintigraphy (P = .05). There were no other statistically significant differences between the sensitivities and specificities.

CONCLUSION

Color Doppler US and scintigraphy demonstrate no statistically significant difference in ability to demonstrate testicular torsion in boys with acute scrotal symptoms and indeterminate clinical presentations. Owing to its greater specificity, scintigraphy may help prevent unnecessary surgery when color Doppler US shows equivocal flow.

Tissue engineering in urologic surgery

The use of nonurologic tissues in the genitourinary tract is common (owing to a lack of a better alternative) despite the known possible adverse effects. Selective cell transplantation is providing a means to engineer genitourinary tissues that may be used for reconstruction. This novel technology involves an interdisciplinary approach, combining techniques of cell biology and materials sciences towards the development of functional tissues or organs. Tissues associated with urology, such as clitoral, cavernosal, urethral, vesical, ureteral, and renal have been created in the laboratory, with varying degrees of function. Cells have also been recently used in patients as bulking agents for the treatment of vesicoureteral reflux and urinary incontinence. As the science of tissue engineering evolves, one can expect a wider application of this technology to the armamentarium of urologic surgery.

Bladder augmentation using allogenic bladder submucosa seeded with cells

OBJECTIVES

The search for a suitable material to reconstruct the genitourinary tract has been a challenging task. Bowel has been widely used for urinary tract reconstruction, despite its subsequent complications. We investigated the possibility of using allogenic bladder submucosa, a tissue consisting of nonimmunogenic acellular collagen, either with or without cells, as a material for bladder augmentation.

METHODS

Partial cystectomies were performed in 10 beagle dogs. Both urothelial and smooth muscle cells were harvested and expanded separately in 5 animals. The allogenic bladder submucosa obtained from sacrificed dogs was seeded with muscle cells on one side and urothelial cells on the opposite side. All beagles underwent cruciate cystotomies on the bladder dome. Augmentation cystoplasty was performed with the allogenic bladder submucosa seeded with cells in 5 animals and with the allogenic bladder submucosa without cells in 5. The augmented bladders were retrieved 2 and 3 months after augmentation.

RESULTS

Bladders augmented with the allogenic bladder submucosa seeded with cells showed a 99% increase in capacity compared with bladders augmented with the cell-free allogenic bladder submucosa, which showed only a 30% increase in capacity. All dogs showed a normal bladder compliance, as evidenced by urodynamic studies. Histologically, all retrieved bladders contained a normal cellular organization consisting of a urothelial lined lumen surrounded by submucosal tissue and smooth muscle. Immunocytochemical analyses confirmed the urothelial and muscle cell phenotype and showed the presence of nerve fibers.

CONCLUSIONS

These results show that allogenic bladder submucosa seeded with cells appears to be an excellent option as a biomaterial for bladder augmentation.

Videofetoscopically assisted fetal tissue engineering: skin replacement

BACKGROUND/PURPOSE

Treatment of several congenital anomalies is frequently hindered by lack of enough tissue for surgical reconstruction in the neonatal period. The purposes of this study were (1) introduction of a novel concept in perinatal surgery, involving minimally invasive harvest of fetal tissue, which is then processed through tissue engineering techniques in vitro while pregnancy is allowed to continue, so that, at delivery, the newborn can benefit from having autologous, expanded tissue promptly available for surgical implantation at birth; (2) analysis of the progress of an engineered fetal skin graft with time, after implantation in the neonate; and (3) study of the effects of current tissue engineering techniques on fetal keratinocytes and fetal dermal fibroblasts.

METHODS

Ten 90- to 95-day-gestation fetal lambs underwent surgical creation of two large paramedian excisional skin defects on the posterior body wall. Subsequently, fetal skin specimens no larger than 1.5 x 1.5 cm were videofetoscopically harvested. Fetal keratinocytes and dermal fibroblasts were then separately cultivated and expanded in vitro for 45 to 50 days, resulting in a total of approximately 250 to 300 million cells. Seven to 10 days before fetal delivery, all cells were seeded in two layers on a 16 to 20-cm2, 3-mm thick biodegradable polyglycolic acid polymer matrix. One to 4 days after delivery, the autologous engineered skin was implanted over one of two previously created skin defects. The second skin defect region received an absorbable polymer scaffold without cells as a control. If necessary, the original skin wounds were further amplified before implantation. Each animal provided at least one time-point for histological analysis of both types of repair through excisional biopsies performed at weekly intervals, up to 8 weeks postimplantation. Normal skin specimens were also used as controls.

RESULTS

Fetal and neonatal survival rates were 100%. Based on previous postnatal skin engineering studies, fetal dermal fibroblasts multiplied significantly faster in vitro (approximately fivefold) than expected. Fetal keratinocytes multiplied at expected postnatal rates. The engineered grafts induced faster epithelization of the wound (partial at 1 week and complete between 2 and 3 weeks postoperatively) than did the acellular ones (partial at 3 weeks and complete between 3 and 4 weeks postoperatively). Analysis of skin architecture showed a higher level of epidermal organization and less dermal scarring in the wounds that received the engineered, cell-implanted polymer scaffold.

CONCLUSIONS

(1) Videofetoscopically assisted fetal tissue engineering is a viable method for obtaining expanded autologous tissue for prompt surgical reconstruction at birth. (2) Fetal skin can be expanded and engineered in vitro at faster rates than expected postnatally, with current tissue engineering techniques. (3) Engineered autologous fetal skin induces a faster and more organized healing of neonatal skin defects than that observed with second intention. This concept may prove useful for the treatment of certain human neonatal conditions such as giant neoplasias, ectopia cordis, and other body wall defects.

Constant elevation in renal pelvic pressure induces an increase in urinary N-acetyl-beta-D-glucosaminidase in a nonobstructive porcine model

PURPOSE

To clarify the physiological significance of renal pelvic pressure elevations encountered in the evaluation of hydronephrotic kidney we examined the effects of different levels of renal pelvic pressure on the induction of renal injury.

MATERIALS AND METHODS

A nonobstructive porcine model was created in which the urine drained against a constant predetermined pressure gradient. Renal pelvic pressure of 10, 20 and 40 cm. was created in 2, 2 and 4 animals, respectively. During 18 to 23 hours serial urinary N-acetyl-beta-D-glucosaminidase levels were determined as an indicator of renal tubular injury. Tissue specimens were examined histologically and renal arterial blood flow was monitored.

RESULTS

Urinary N-acetyl-beta-D-glucosaminidase levels in the kidneys subjected to 10 cm. water remained essentially unchanged. However, at 20 and 40 cm. water statistically significant increases were observed. Similarly, renal arterial blood flow was unchanged at 10 cm. water but it became significantly lower than in controls at 20 and 40 cm. water. Histological evaluation revealed mild to moderate tubular dilatation in the kidneys subjected to 20 and 40 cm. water.

CONCLUSIONS

Excessively high collecting system pressure induced renal cellular injury, as reflected by an increase in urinary N-acetyl-beta-D-glucosaminidase levels. While renal pelvic pressure up to 10 cm. water appeared to be innocuous, renal cellular injury was evident within as little as 1 hour at renal pelvic pressures 20 cm. water or greater. The degree of N-acetyl-beta-D-glucosaminidase in the urine also correlated with a decrease in renal arterial blood flow.

Videofetoscopically assisted fetal tissue engineering: bladder augmentation

BACKGROUND/PURPOSE

Treatment of several congenital anomalies is frequently hindered by lack of enough tissue for surgical reconstruction in the neonatal period. Minimally invasive harvest of fetal tissue, which is then processed through tissue engineering techniques in vitro while pregnancy is allowed to continue so that at delivery a newborn with a prenatally diagnosed congenital anomaly can benefit from having autologous, expanded tissue promptly available for surgical reconstruction at birth. This concept was applied to a bladder defect.

METHODS

Bladder exstrophy was surgically created in ten 90- to 95-day gestation fetal lambs, which were divided in two groups. In group I, a small fetal bladder specimen was harvested through a minimally invasive technique (videofetoscopy). Urothelial and smooth muscle cells were then separately cultivated and expanded in vitro for 55 to 60 days, resulting in a total of approximately 200 million cells. Seven to 10 days before delivery, the cells were seeded in two layers in a 16- to 20-cm2, 3-mm thick biodegradable polyglycolic acid polymer matrix. One to 4 days after delivery, autologous engineered tissue was used for surgical augmentation of the exstrophic bladder. In group II, no harvest was performed, and the bladder exstrophy was primarily closed after delivery. In both groups, a catheter was left inside the bladder for 3 weeks, at which time a cystogram was performed and the catheter then removed. In all animals, at 60 days, another cystogram was performed and urodynamic studies of the bladder were performed. The bladder was then removed for histological analysis.

RESULTS

Fetal survival rate was 100%. One newborn died immediately after the implantation of the engineered bladder from an anesthetic accident. The other nine (four in group I and five in group II) survived. One of the animals from group I lost its bladder catheter prematurely and had a urinary leak detected only at the time of death. There were no other complications. The engineered bladders were more compliant (P < .05) and had greater capacity pressures greater than 20 mm Hg (P < .05) than those closed primarily. Histological analysis of the engineered tissue showed a multilayered urothelial lining on the luminal side and overlying layers of smooth muscle cells surrounded by connective tissue.

CONCLUSIONS

Videofetoscopically assisted fetal bladder engineering may be a viable alternative for prompt bladder reconstruction at birth. The architecture of autologous engineered fetal bladder tissue resembles that of native bladder. This concept may prove useful for the treatment of certain human neonatal conditions such as bladder and cloacal exstrophies.

Estimating normal bladder capacity in children

PURPOSE

An accurate estimation of normal bladder capacity can be helpful in evaluating the patient with genitourinary disease and in interpreting urodynamic data. Prior studies have provided initial estimates. We propose 2 new equations that are practical, easy to use and more accurate than those previously published.

MATERIALS AND METHODS

We retrospectively reviewed the records of more than 5,000 children undergoing radionuclide cystography at our institution. Radionuclide cystography was conducted by instilling (99m)technetium pertechnetate via gravity drip in awake children. Bladder capacity was believed to be achieved when rate of inflow diminished to a minimal rate, initiation of voiding occurred or significant discomfort was indicated. Patients with vesicoureteral reflux, infravesical obstruction, urinary tract infection, dysfunctional voiding or other lower urinary tract pathology were excluded from the study. Linear and nonlinear regression modeling established the relationship between age and bladder capacity.

RESULTS

A total of 2,066 children (598 boys and 1,468 girls) had normal radionuclide cystography and were included in the analysis. Analysis of variance demonstrated that increasing age was strongly predictive of bladder capacity (p <0.0001). Because a nonlinear model was the most accurate formula for all ages (4.5 x age(0.40) = capacity [ounces]), 2 practical linear equations were determined: 2 x age (years) + 2 = capacity (ounces) for children less than 2 years old, and age (years) divided by 2 + 6 = capacity (ounces) for those 2 years old or older. Although girls had larger capacities than boys, the rate of increase was not significantly different between them.

CONCLUSIONS

The relationship between normal bladder capacity and age in children follows a nonlinear curve. This nonlinear relationship can be approximated by 2 practical linear formulas that are easy to remember and are derived from a larger population than any prior study. These formulas provided accurate estimations of bladder capacity when prospectively applied to normal patients.

Endoscopic substances for the treatment of vesicoureteral reflux

The endoscopic treatment of reflux, like that of urinary incontinence, is effective. Several materials and endoscopic delivery systems are currently under evaluation for the treatment of reflux and incontinence. These include silicone microimplants, glass particles, collagen, dextranomer microspheres, a detachable balloon system, chondrocytes, and muscle cells. Although the endoscopic treatment is rendered in a similar fashion for both urinary incontinence and reflux, the acceptable safety and efficacy parameters of the bulking agents may differ, depending on the condition treated and the age of the patient. A review of the endoscopic bulking substances and systems currently available is presented.

A novel gene delivery system using urothelial tissue engineered neo-organs

PURPOSE

Presently gene delivery is most effectively achieved by ex vivo gene transfer, which includes removal of the target tissue, in vitro gene delivery to the target cells, possible selection to enhance the proportion of transfected cells and reintroduction of the gene modified cells. Reintroduction of transformed cells in vivo has been a challenging task. Based on the feasibility of tissue engineering techniques in which cells seeded on biodegradable polymer scaffolds form tissue when implanted in vivo, we explored the possibility of developing a neo-organ system for in vivo gene therapy.

MATERIALS AND METHODS

Normal human urothelial cells were harvested, expanded in vitro and seeded on biodegradable polymer scaffolds. The cell-polymer complex was then transfected with PGL3-luc, pCMV-luc and pCMV beta-gal promoter reporter gene constructs. The transfected cell-polymer scaffolds were then implanted in athymic mice and the engineered tissue was retrieved 0, 1, 3, 5 and 7 days after implantation.

RESULTS

The reporter gene assay demonstrated an expression of luciferase activity at days 1, 3, 5 and 7 with the peak at day 5. X-gal and beta-galactosidase antibody assays stained positive on the deoxyribonucleic acid treated transfection.

CONCLUSIONS

Successful gene transfer can be achieved using biodegradable polymer scaffolds as a urothelial cell delivery vehicle. The transfected cell-polymer scaffold forms an organ-like structure with functional expression of the transfected genes. This study demonstrates that urothelial tissue engineered gene transfer is safe and effective.

Detachable self-sealing membrane system for the endoscopic treatment of incontinence

PURPOSE

The endoscopic treatment of urinary incontinence is limited by the injectable substances currently available. The ideal injectable material should be able to conserve its volume, be nonmigratory and nonantigenic. Toward this goal we developed a system for the treatment of incontinence in which a catheter with an inflatable and detachable self-sealing silicone membrane fits through a standard cystoscopic needle. We present our experience with this system.

MATERIALS AND METHODS

A total of 20 female beagle dogs underwent cystoscopy and in 15 a self-sealing membrane was placed endoscopically in the submucosal region of the proximal urethra at the 3 and 9 o'clock positions. Each membrane was inflated through the delivery catheter with 0.2 cc povidone. Coaptation of the urethra due to the relative bulking effect of the inflated membrane was confirmed endoscopically in each animal. Five control animals received only an injection of saline. Four animals were sacrificed at 1, 3, 6, 12 and 18 months, respectively. At sacrifice gross and histological examinations were performed.

RESULTS

At retrieval up to 18 months after implantation the membrane remained inflated and at the same position at which it had been initially placed. There was no evidence of povidone volume loss or extravasation. Membranes were encapsulated by a fibrous capsule. Only a few inflammatory cells surrounded the capsule by month 1 and there were none by month 3. Histological examination of periurethral tissue and distant organs showed no evidence of particle migration.

CONCLUSIONS

The detachable self-sealing membrane system is easily implantable, nonmigratory, nonantigenic and able to conserve its volume. These studies indicate that this system may be effective for the endoscopic treatment of incontinence.

Continent urinary diversion: the Children's Hospital experience

PURPOSE

Continent urinary diversion has become increasingly important for treating childhood urinary tract pathology that cannot be managed by direct reconstructive techniques. We review our 9-year experience with continent diversion.

MATERIALS AND METHODS

Since 1986 continent diversions were created in 74 patients 3 to 38 years old (mean age 13.7). The underlying pathological condition was the exstrophy/epispadias complex in 34 patients, neurological disorders in 23, malignancy in 13 and other congenital anomalies in 4. Followup averaged 5.2 years after the last procedure. Nonbladder reservoirs in 39 patients (53%) were fashioned from ileocolic (17), colic (7), gastrocolic (6), sigmoid (3), gastrosigmoid (2), ileosigmoid (2), ileal (1) and gastroileac (1) segments. When possible, the native bladder was incorporated into the reconstructive strategy. A total of 26 patients underwent bladder augmentation with intestine or stomach, including ileal (11), gastric (8), sigmoid (3), gastroileac (2) and ileocolic (2) segments. Nine other patients did not require bladder augmentation. Continence mechanisms were a flap valve (Mitrofanoff principle) in 50 patients, nipple valve in 15 and ileal plication (Indiana pouch) in 9. When the Mitrofanoff principle was used with a native bladder reservoir in 30 cases, outlet resistance was altered by bladder neck division (15), fascial sling placement (6) or Young-Dees-Leadbetter bladder neck reconstruction (2). In the remaining 7 patients the bladder neck remained intact.

RESULTS

Excellent continence was obtained. The Mitrofanoff principle initially provided continence in 41 patients (82%). Six of the 9 incontinent patients were dry after a single revision. A total of 13 patients (87%) with nipple valves and 7 (78%) with Indiana pouches were dry, and the remaining 5 were cured after a single revision. Ultimately continence was achieved in 71 of the 74 patients (96%) after a maximum of 2 operations. Of the 48 complications in 29 patients the most common were difficulty in catheterizing (11), stones (11), infection (8) and upper tract deterioration (4).

CONCLUSIONS

Many options exist for reconstructing complex anomalies. Choices must be individualized based on patient anatomy. The dry state may be achieved in most cases without resorting to a bag on the abdomen.

Heparin-binding EGF-like growth factor is an autocrine growth factor for human urothelial cells and is synthesized by epithelial and smooth muscle cells in the human bladder

The epidermal growth factor receptor (HER1) has been implicated in regenerative growth and proliferative diseases of the human bladder epithelium (urothelium), however a cognate HER1 ligand that can act as a growth factor for normal human urothelial cells (HUC) has not been identified. Here we show that heparin-binding EGF-like growth factor (HB-EGF), an activating HER1 ligand, is an autocrine regulator of HUC growth. This conclusion is based on demonstration of HB-EGF synthesis and secretion by primary culture HUC, identification of HER1 as an activatable HB-EGF receptor on HUC surfaces, stimulation of HUC clonal growth by HB-EGF, inhibition of HB-EGF-stimulated growth by heparin and of log-phase growth by CRM 197, a specific inhibitor of HB-EGF/HER1 interaction, and identification of human urothelium as a site of HB-EGF precursor (proHB-EGF) synthesis in vivo. ProHB-EGF expression was also detected in the vascular and detrusor smooth muscle of the human bladder. These data suggest a physiologic role for HB-EGF in the regulation of urothelial proliferation and regeneration subsequent to mucosal injury. Expression of proHB-EGF is also a feature of differentiated vascular and detrusor smooth muscle in the bladder. Because proHB-EGF is known to be the high affinity diphtheria toxin (DT) receptor in human cells, synthesis of the HB-EGF precursor by human urothelium also suggests the possibility of using the DT-binding sites of proHB-EGF as an in vivo target for the intraluminal treatment of urothelial diseases.

Reconstructive options in genitourinary rhabdomyosarcoma

PURPOSE

We attempted to develop a rational and consistent scheme for surgical reconstruction in patients with genitourinary rhabdomyosarcoma.

MATERIALS AND METHODS

We reviewed the records of 35 patients with resectable genitourinary rhabdomyosarcoma treated from 1970 to 1993.

RESULTS

Primary sites included bladder in 11 cases, prostate in 13, vagina/uterus in 9 and pelvic tumors of uncertain origin in 2. A total of 33 patients underwent surgery, including partial and radical cystectomy in 17 (bowel conduit diversion in 10, continent urinary diversion in 6 and ureterosigmoidostomy in 1). Overall 30 of the 33 surgical patients are free of disease 4 months to 24 years after diagnosis.

CONCLUSIONS

A nonrefluxing colon conduit is appropriate at cystectomy. Continent diversion fashioned from the original conduit may be planned as the patient achieves a durable disease-free status.

Progressive ureteral dilation for subsequent ureterocystoplasty

PURPOSE

The complications associated with bladder augmentation using the gastrointestinal tract are well known. A bladder based ureteral flap is a viable alternative for augmentation. However, its use is limited to cases in which a dilated ureter is already present due to associated pathological conditions, such as reflux. We designed a system for performing progressive dilation in a normal ureter, which can subsequently be used for augmentation.

MATERIALS AND METHODS

Ten rabbits underwent unilateral ureteral ligation at the ureterovesical junction and ipsilateral nephrectomy. A silicone catheter was threaded into the proximal ipsilateral ureter and connected to an injection port, which was secured subcutaneously. Ten days to 2 weeks after surgery a saline-antibiotic solution was injected subcutaneously daily into the injection port. Cystography and cystometrography were performed with an accurate measurement of bladder capacity. Ureterography was done initially and then weekly by injecting contrast medium into the ureter. After ureteral dilation ureterocystoplasty was performed in each animal.

RESULTS

After 1 month of daily saline-antibiotic solution injections the ureteral units were dilated at least 10-fold, as measured by radiography. The dilated ureteral diameter exceeded that of adjacent colon in each instance. Augmentation cystoplasty was performed with the reconfigured dilated ureteral segment. Repeat cystography and cystometrography showed an average 260% increase in bladder capacity (range 190 to 380%).

CONCLUSIONS

Ureteral dilation can be accomplished using our system. At least a 10-fold increase in ureteral size is possible. The dilated ureteral segment can be used effectively for bladder augmentation, avoiding the use of bowel segments.

Ten-year experience with the artificial urinary sphincter in children

PURPOSE

To assess the efficacy of the artificial urinary sphincter survival and continence were first evaluated 5 years ago. We now evaluated the effects of the artificial urinary sphincter more than a decade after implantation.

MATERIALS AND METHODS

Before 1985 an artificial urinary sphincter was implanted in 22 male and 14 female consecutive patients 4 to 30 years old (median age 12). In addition, between 1985 and 1990, 18 other children underwent artificial urinary sphincter implantation. Results of both series were compared.

RESULTS

Of the 25 sphincters in the original series that were functioning after 5 years 1 was removed and 2 patients were lost to followup, resulting in 22 functioning implants (61% of the patients). Mean survival time of the prostheses was 12.1 years and average followup for functioning sphincters was 13.7 years. There was no statistically significant difference in artificial urinary sphincter survival between the original group at 5 years and the second group treated after 1985. Of the patients in both groups with sphincters in place 32 of 39 (82%) were dry. Augmentation cystoplasty was performed in 9 of 18 patients (50%) in the second series (5 preoperatively and 4 postoperatively) compared to 10 of 36 (28%) in the original series at 5 years (3 preoperatively and 7 postoperatively). Renal failure developed in 6 patients from both series.

CONCLUSIONS

The artificial urinary sphincter is a durable long-term solution for children with intractable incontinence. Long-term surveillance of the urinary tract is mandatory because of the potential for renal failure in patients who have bladder hypertonicity after placement of the device.

Human albumin solder supplemented with TGF-beta 1 accelerates healing following laser welded wound closure

BACKGROUND AND OBJECTIVE

We examined the possibility that human albumin solder can be used as a vehicle for site specific delivery of growth factors for the purpose of accelerating tissue repair following laser welded wound closure. Certain human recombinant growth factors have been shown to accelerate wound healing in model systems. Pilot in vitro studies have established that several growth factors, including TGF-beta 1, maintain bioactivity following exposure to temperatures achieved during laser tissue welding. Using a temperature controlled laser delivery system (TCL) to precisely maintain welding temperatures, it is now possible to avoid thermal denaturation of exogenous bioactive molecules such as growth factors.

STUDY DESIGN/MATERIALS AND METHODS

HB-EGF, bFGF, and TGF-beta 1 were tested in vitro for maintenance of bioactivity after exposure to 80 degrees C. In vivo experiments using porcine skin determined the efficacy of solders augmented with growth factors. Incisions were repaired using human albumin alone or supplemented with HB-EGF (2 micrograms), bFGF (10 micrograms), or TGF-beta 1 (1 microgram). Wounds were excised at 3, 5, and 7 days post-operatively. Tensile strength, total collagen content, and histology were performed.

RESULTS

At 3 days, tensile strength (TS) of TGF-beta 1 wounds were 36% (P < 0.05) and 20% (n.s.) stronger than laser alone and suture closures, respectively. By 5 days the TS of the TGF-beta 1 group increased by 50% (P < 0.05) and 59% (P < 0.02) over laser alone and suture groups, respectively. At 7 days the TGF-beta 1 group was 50% (P < 0.05) and 79% (P < 0.01) stronger than laser solder alone or suture, respectively. The HB-EGF and bFGF groups were equivalent to the laser solder group at all time points. Total collagen TGF-beta 1 Accelerates Healing Following Laser Welding content at 7 days increased in the TGF-beta 1 group by 7% (n.s.) over the suture group and 21% (P < 0.05) in the laser group.

CONCLUSION

Human albumin solder supplemented with TGF-beta 1 increases the early post-operative strength of laser welded wounds. This novel application of laser tissue soldering augmented with a growth factor has the potential to bring about immediate fluid tight seals while providing site specific delivery of biological modifiers. This may lead to an overall improvement in post-operative convalescence, wound infections, and hospital costs.

Hydrocele of the spermatic cord: embryology and ultrasonographic appearance

Five cases of hydrocele of the spermatic cord are presented. All five patients had a firm inguinal mass, and ultrasonography, performed to exclude adenopathy, incarcerated hernia, and paratesticular tumor, showed an avascular cystic mass superior to and separate from the testicle. A testicular hydrocele did not coexist. This typical appearance should lead to a confident diagnosis of this benign but rare anomaly. Elective surgery may prevent the development of an acquired indirect hernia.