Tissue engineered stents created from chondrocytes

PURPOSE

Trauma, operations or instrumentation of the urethra or ureter may lead to stricture disease. The use of a natural urethral stent made of autologous tissue would be advantageous due to its biocompatibility. In this study we investigated the feasibility of engineering cartilage stents in vitro and in vivo.

MATERIALS AND METHODS

We fabricated 40 cylinders 10 mm. long with an inner and outer diameter of 5 and 9 mm., respectively, from polyglycolic acid mesh coated with 50:50 polylactic-co-glycolic acid. Chondrocytes isolated from bovine shoulders were seeded onto the tubular polymer scaffolds at a seeding density of 60 x 106 cells per ml. Scanning electron microscopy was performed to determine the even distribution of chondrocytes throughout the polymer scaffolds. We implanted 20 cylinders under the skin of nude mice and 20 were cultured in stirred bio-reactors. Cytological characteristics, collagen content and mechanical durability were evaluated 4 and 10 weeks after cell seeding.

RESULTS

Gross examination of the engineered stents showed the solid, glistening appearance of cartilaginous tissue. Cytological analyses with hematoxylin and eosin, trichrome, alcian blue and safranin O confirmed cartilage, and the deposition of collagen and glycosaminoglycan in each group. Increased deposition of collagen and glycosaminoglycan was observed in the stents created in vivo. Biomechanical testing demonstrated that the cartilaginous cylinders in each group were readily elastic and withstood high degrees of pressure.

CONCLUSIONS

This study demonstrates the feasibility of creating cartilaginous stents in vitro and in vivo using chondrocyte seeded polymer matrices. This technology may be useful clinically for stricture disease in the genitourinary tract.

A noninvasive test for vesico-ureteric reflux in children

OBJECTIVE

To report the development and testing of a device for the noninvasive diagnosis of vesico-ureteric reflux (VUR) which avoids the need for urethral catheterization (currently required to reliably determine the presence of VUR), and which thus avoids the anxiety of parents and patients that causes many families to refuse such evaluation.

PATIENTS AND METHODS

Fifty-four children (49 girls and five boys, mean age 7.2 years, range 4-14) previously evaluated as having VUR volunteered to participate; no child was symptomatic at the time of the study. Refluxing units were known to be present by voiding cysto-urethrography (within 1 year, mean 7 months) in 45 and absent in 16. The device developed acquires electronically processed acoustic signals from the child during an observed urination. The signals are then analysed 'off-line' to determine the presence or absence of VUR. The initial preparation for the test included: (i) a full bladder [at least 0.80 x ((2 + age) x 30 mL)] measured by ultrasonography; and (ii) localization of the pelvi-ureteric junction by ultrasonography to accurately place the device's sensors on the child's back. The children were then positioned at a commode after placing the sensors; the recording was started and continued until voiding occurred. The children were tested with the recording and analysis team unaware of the presence and/or degree of VUR. The first 47 studies were single-kidney examinations and the remaining seven included simultaneous monitoring of both kidneys.

RESULTS

Sixty-one renal units were assessed and interpretable signals were obtained from 54 (89%). There were seven episodes of 'system failure' when no interpretable data were obtained. One unit with no VUR had a 'reflux' signal; in four kidneys, spontaneous (two) and postsurgical (two) resolution of reflux was predicted by the testing and subsequently verified by cyclic radionuclide cystography.

CONCLUSIONS

This noninvasive diagnostic technique detected VUR in 35 of 37 refluxing units and verified no reflux in 16 of 17 units without VUR. Further refinements may allow this technology to be used in all children with suspected VUR.

In vitro biocompatibility assessment of naturally derived and synthetic biomaterials using normal human urothelial cells

The reconstruction of urinary tissues often employs various types of biomaterials, and adequate material biocompatibility is essential for the successful reconstruction of urinary tissues. In this study we utilized a primary normal human urothelial cell culture system to evaluate the in vitro biocompatibility of a number of naturally derived biomaterials [i.e., bladder submucosa, small intestinal submucosa, collagen, and alginate] and polymeric biomaterials [i.e., poly(glycolic acid), poly(L-lactic acid), poly(lactic-co-glycolic acid), and silicone] that are either experimentally or clinically used in urinary reconstructive surgery. To determine the cytotoxic and bioactive effects of these biomaterials, the cell viability, metabolic activity, apoptotic properties, and DNA-synthesis activity were measured with four types of assays [Neutral Red, 3-(4,5-dimethylthiazol-2-yl)-2,5diphenyl tetrazolium bromide, apoptotic activity, and tritiated thymidine incorporation assays] using extract and direct contact methods. Most of the biomaterials tested did not induce significant cytotoxic effects and exhibited normal metabolic function and cell growth in vitro. This normal primary human urothelial cell culture model is suitable for in vitro biocompatibility assessments and is able to provide information on the cell-biomaterial interactions and the ability of biomaterials to support bioactive cell functions.

Tissue engineering in urology

Congenital abnormalities, cancer, trauma, infection, inflammation, iatrogenic injuries, and other conditions 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 (polyglycolic acid polymer scaffolds alone and with co-polymers of poly-1-lactic acid and poly-DL-lactide-coglycolide) and natural biodegradable materials (processed collagen derived from allogeneic donor bladder submucosa and intestinal submucosa) 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, urethral replacement, and bladder reconstruction. Recent progress suggests that engineered urologic tissues may have clinical applicability in the future.

Tubularized incised plate urethroplasty: expanded use in primary and repeat surgery for hypospadias

PURPOSE

We evaluated the impact of tubularized incised plate urethroplasty on primary and repeat hypospadias repair.

MATERIALS AND METHODS

We retrospectively reviewed the medical records of all boys who underwent hypospadias repair at our institution during a recent 3-year period. The level of the hypospadias defect, technique of repair, primary repair versus reoperation, age at surgery and complications were recorded.

RESULTS

A total of 520 hypospadias repairs were done from May 1996 through June 1999. We began to perform tubularized incised plate urethroplasty in November 1996. During the ensuing consecutive 32 months 181 primary and 25 repeat hypospadias repairs were done using this technique. Mean patient age at surgery was 22 months (range 3 months to 30 years). During the 6 months immediately before we began to use this method the Mathieu flip-flap procedure was the most commonly performed technique, accounting for 38% of all hypospadias repairs. In contrast, during the last 6 months reviewed tubularized incised plate urethroplasty accounted for 63% of all repairs, including 41 of 65 primary operations (63%) and 4 of 6 reoperations (67%), while no Mathieu procedures were performed. Postoperative followup was 6 to 38 months for tubularized incised plate repair. Overall meatal stenosis and a urethrocutaneous fistula developed in 1 and 14 boys, respectively (7% complication rate).

CONCLUSIONS

Tubularized incised plate urethroplasty has become the preferred technique of primary and repeat hypospadias repair at our institution. The technique has few complications as well as proved success and versatility that continues to expand its applicability and popularity.

Continuous release of endostatin from microencapsulated engineered cells for tumor therapy

Research studies suggest that tumor-related angiogenesis contributes to the phenotype of malignant gliomas. We assessed the effect of local delivery of the angiogenesis inhibitor endostatin on human glioma cell line (U-87MG) xenografts. Baby hamster kidney (BHK) cells were stably transfected with a human endostatin (hES) expression vector and were encapsulated in alginate-poly L-lysine (PLL) microcapsules for long-term delivery of hES. The release of biologically active endostatin was confirmed using assays of bovine capillary endothelial (BCE) proliferation and of tube formation. Human endostatin released from the microcapsules brought about a 67. 2% inhibition of BCE proliferation. Furthermore, secreted hES was able to inhibit tube formation in KDR/PAE cells (porcine aortic endothelial cells stably transfected with KDR, a tyrosine kinase) treated with conditioned U-87MG medium. A single local injection of encapsulated endostatin-secreting cells in a nude mouse model resulted in a 72.3% reduction in subcutaneous U87 xenografts' weight 21 days post treatment. This inhibition was achieved by only 150.8 ng/ml human endostatin secreted from 2 x 10(5) encapsulated cells. Encapsulated endostatin-secreting cells are effective for the treatment of human glioblastoma xenografts. Continuous local delivery of endostatin may offer an effective therapeutic approach to the treatment of a variety of tumor types.

Tissue engineering applications in the genitourinary tract system

The concept of cell transplantation using tissue engineering techniques has provided numerous possibilities in the area of urologic tissue reconstruction. Tissue engineering applications in the genitourinary tract system have been investigated in almost every tissue in order to improve, restore and replace existing tissue function. Although most reconstructive efforts still remain in the experimental stage, several technologies have been transferred to the bedside with satisfactory outcome. In this article, we describe tissue engineering approaches attempted in the genitourinary system for reconstruction.

Effect of chronic, low-pressure, sterile vesicoureteral reflux on renal growth and function in a porcine model: a radiologic and pathologic study

PURPOSE

To study the effects of chronic, low-pressure, sterile vesicoureteral reflux (VUR) on renal growth and function in a porcine model.

MATERIALS AND METHODS

Unilateral VUR was created in five pigs, with the contralateral kidney serving as a control. Preoperatively, and 1 year later, ultrasonography, technetium 99m-dimercaptosuccinic acid (DMSA) scintigraphy, contrast material-enhanced computed tomography (CT), and contrast-enhanced magnetic resonance (MR) imaging were performed. Morphologic abnormalities and relative uptake of (99m)Tc-DMSA were recorded. The postcontrast enhancement ratios for parenchymal regions of interest at CT and MR imaging were determined. Ruthenium 103-labeled microspheres were used to determine regional blood flow. After the pigs were sacrificed, the kidneys were excised, weighed, and analyzed pathologically.

RESULTS

Two of five refluxing kidneys had less than 45% function at scintigraphy. One of these two kidneys was small at postmortem examination. There were no other imaging or gross pathologic abnormalities. There was no significant difference in regional blood flow between the refluxing and nonrefluxing kidneys. In all of the operated on kidneys, histologic examination showed focal chronic inflammation and fibrosis.

CONCLUSION

Low-pressure sterile reflux into previously normal kidneys led to mild, focal, chronic interstitial inflammation and fibrosis after 1 year. Imaging findings were normal apart from a subtle decrease in tubular function in two refluxing kidneys.

Initial experience with the transurethral self-detachable balloon system for urinary incontinence in pediatric patients

PURPOSE

A new endoscopic technique to treat urinary incontinence in children using a self-detachable balloon device was studied.

MATERIALS AND METHODS

The study includes 11 patients with a mean age of 14.6 years and all of whom had intrinsic sphincter deficiency due to myelomeningocele in 9, spinal artery bleed in 1 and cloacal exstrophy in 1. All patients were on clean intermittent catheterization preoperatively and postoperatively. Endoscopic balloon treatment was performed on an outpatient basis. A mean of 5 balloons (range 2 to 8) were placed per patient. All patients underwent formal urodynamic study preoperatively and at 6 weeks and 6 months following balloon placement.

RESULTS

Of the 9 patients without prior bladder neck surgery 7 had improvement in urodynamic parameters, including urethral pressure profile in all 7 and functional bladder capacity in 6, 4 were markedly improved clinically and 2 were dry. Two patients with prior bladder neck surgery were clinically unchanged following balloon placement, although 1 had urodynamic improvement.

CONCLUSIONS

Our initial experience with the transurethral self-detachable balloon system as a minimally invasive outpatient procedure to treat urinary incontinence in children has been encouraging. To date this procedure appears most applicable to the patient who has not undergone surgery and has a neurogenic etiology for urinary incontinence.

Defunctionalized bladders: effects before and after refunctionalization in an animal model

PURPOSE

Bladder behavior after refunctionalization is usually unpredictable. We comparatively analyze various aspects of bladder defunctionalization and subsequent refunctionalization using an animal model.

MATERIALS AND METHODS

A total of 18 rabbits were divided equally into 3 groups. Animals in group 1 underwent 2 successive surgical procedures, including bladder division and reattachment. Bladder division was performed by hemisecting the bladder from dome to trigone into a functioning and nonfunctioning chamber. Bladder reattachment was achieved by reanastomosing both hemibladders. Group 2 animals underwent sham operations, and group 3 animals were age matched normal controls. Serial urodynamic studies and fluoroscopic cystograms were performed in all animals. Gross, histochemical (hematoxylin and eosin, Masson's trichrome and Sirius red) and immunocytochemical (alpha-actin, collagen I and III) analyses, collagen content determination and organ bath studies were performed.

RESULTS

The defunctionalized hemibladders demonstrated lower wet weight, capacity and compliance compared to the functional contralateral and normal control bladders. Refunctionalization of the bladders resulted in a progressive recovery of capacity and compliance with time. The bladder contractile response and connective tissue-to-muscle ratio were abnormal in the defunctionalized segments but normalized after bladder refunctionalization.

CONCLUSIONS

Defunctionalization results in remarkable alterations in bladder growth, capacity, compliance and distribution of connective tissue. However, these bladders demonstrate an innate capacity to recover from these alterations following refunctionalization.

Comparative assessment of pediatric testicular volume: orchidometer versus ultrasound

PURPOSE

Testicular volume measurements obtained with the Prader and Rochester orchidometers were compared to those obtained using scrotal ultrasound. The ability of each orchidometer versus ultrasound in detecting volume differential between 2 testes and the accuracy of orchidometer measurement by a less experienced examiner to that of a urologist were compared.

MATERIALS AND METHODS

A total of 65 males were examined by the attending urologist and urology nurse using the Prader and Rochester orchidometers, and scrotal ultrasound was subsequently performed by an attending radiologist. Statistical analysis of the results was performed to determine the correlation of orchidometer measurements between examiners, as well as with ultrasound, and sensitivity and specificity of orchidometer and ultrasound in detecting defined volume differentials between testes of 10%, 15%, 20% and 25%.

RESULTS

There was a strong linear relationship between testicular volume measurements using either orchidometer and ultrasound. To detect a defined volume differential as determined by ultrasound orchidometer sensitivity was weak, whereas orchidometer specificity was better. There was a strong correlation between orchidometer measurements of the urology nurse and attending urologist.

CONCLUSIONS

Although the orchidometer remains valuable in assessing size of the individual testis, it is too insensitive to volume differentials relative to ultrasound to be used routinely to determine growth impairment. For this reason observation of an adolescent with varicocele should include an annual ultrasound assessment of testicular volume.

Ketorolac suppresses postoperative bladder spasms after pediatric ureteral reimplantation

We evaluated the efficacy of ketorolac in suppressing postoperative bladder spasms after ureteroneocystostomy (ureteral reimplantation). Twenty-four pediatric patients undergoing intravesical ureteroneocystostomy were enrolled prospectively to receive either ketorolac or placebo via double-blinded randomization. Twelve patients in each group shared similar preoperative characteristics. All were maintained on an epidural infusion of bupivacaine (0.1%) with fentanyl (2 microg/mL) throughout the study. Patients were given either ketorolac (0.5 mg. kg(-1). dose(-1)) or placebo (equivalent volume saline) IV after surgery and every 6 h thereafter for 48 h. Parents were instructed to record bladder spasm episodes prospectively by using a standardized time-flow diary. Three patients (25%) in the ketorolac group experienced bladder spasms, compared with 10 patients (83%) in the placebo group (two-sided P < 0.05). The median severity score for the ketorolac group was 1.2 (mild = 1.0, severe = 3.0), compared with 2.6 for the placebo group (P = 0.003). We conclude that IV ketorolac reduces the frequency and severity of postoperative bladder spasms after intravesical ureteroneocystostomy.

IMPLICATIONS

We studied the efficacy of ketorolac, a prostaglandin synthesis inhibitor, in the treatment of bladder spasm after ureteroneocystostomy (antireflux operation). Patients were randomized in a double-blinded manner to receive either ketorolac or placebo after the surgery. We demonstrate that ketorolac reduces the frequency and severity of postoperative bladder spasm.

Bladder augmentation techniques in women

Augmentation cystoplasty is performed in women for a variety of indications, including neurogenic bladder dysfunction, inflammatory diseases, small fibrosed bladders, idiopathic urge incontinence and enuresis. The preoperative evaluation, surgical techniques and postoperative management are reviewed. Complications of stone formation, urinary tract infections, mucus production, metabolic disturbances, hematuria and dysuria syndrome, tumors and perforations are addressed. In addition, alternative techniques such as ureterocystoplasty, autoaugmentation, seromuscular cystoplasty and the future of augmentation of the bladder utilizing techniques of tissue engineering are discussed. The management of pregnancy in women who have previously undergone augmentation cystoplasty is also reviewed.

New methods of bladder augmentation

Gastrointestinal segments are commonly used for bladder replacement or repair. However, when gastrointestinal tissue is in contact with the urinary tract, several complications may ensue. Recent surgical approaches have relied on native urological tissue for reconstruction. These are based on sound surgical principles, allowing for the exclusion of tissue that is not urological. De-epithelialized bowel segments, either alone or over native urothelium, have also been used. An experimental system of progressive dilatation for ureters and bladders has been proposed. This appears promising, although it has yet to be attempted clinically. There has been a resurgence of interest in the use of acellular collagen-based matrices as scaffolds for bladder regeneration; experimental work is currently underway. Recently, functional bladder tissue has been engineered using selective cell transplantation. This technique uses autologous cells, so avoiding rejection. Tissue is obtained from the host, the cells then dissociated and expanded in vitro, re-attached to a matrix and implanted into the same host. Clinical trials are currently being arranged. Even though the use of bowel for bladder tissue replacement was first proposed over 100 years ago, it remains the gold standard, despite its associated problems. It is evident that urothelial-urothelial anastomoses are preferable functionally. Experience is currently being gained with the recent clinical and experimental approaches to augmentation cystoplasty. It is hoped that this will result in more technologies and methods for bladder augmentation.

Sibling vesicoureteral reflux in multiple gestation births

BACKGROUND

Vesicoureteral reflux (VUR) is the most commonly inherited disease of the genitourinary tract. Although the majority of evidence supports a genetic cause, the tendency for this condition to spontaneously improve over time has made it difficult to determine the actual mode of transmission. We report the incidence of VUR in siblings of multiple gestation births and for the first time compare the relative incidence of reflux between identical and fraternal twins.

METHODS

A database consisting of all radionuclide cystograms and voiding cystourethrograms performed between the years 1986 and 1996 was searched for multiple gestation births. The medical records of each patient were evaluated for age at presentation, zygosity, reflux grade, and time to resolution. Children with secondary causes of VUR (eg, posterior urethral valves) were excluded. Triplets were treated as 2 pairs of twins for statistical analysis.

RESULTS

Forty-six pairs met the inclusion criteria (31 dizygotic and 15 monozygotic). Overall, 23 (50%) of 46 siblings of index cases had demonstrable VUR. Comparison of VUR prevalence between identical and nonidentical twins was revealing with 80% (12/15) of identical twins and 35% (11/31) of fraternal twins having VUR. When only the youngest individuals in each group were considered, 100% (7/7) of the monozygotics and 50% (5/10) of the dizygotics demonstrated this trait.

CONCLUSIONS

High concordance for VUR in identical twin siblings supports a genetic basis for the transmission of this disease. Results obtained from fraternal twin siblings provides convincing evidence that this trait is transmitted in an autosomal dominant fashion.

Biomaterials for tissue engineering

Biomaterials play a critical role in the engineering of new functional genitourinary tissues for the replacement of lost or malfunctioning tissues. They provide a temporary scaffolding to guide new tissue growth and organization and may provide bioactive signals (e.g., cell-adhesion peptides and growth factors) required for the retention of tissue-specific gene expression. A variety of biomaterials, which can be classified into three types--naturally derived materials (e.g., collagen and alginate), acellular tissue matrices (e.g., bladder submucosa and small-intestinal submucosa), and synthetic polymers [e.g., polyglycolic acid, polylactic acid, and poly(lactic-co-glycolic acid)]--have proved to be useful in the reconstruction of a number of genitourinary tissues in animal models. Some of these materials are currently being used clinically for genitourinary applications. Ultimately, the development or selection of appropriate biomaterials may allow the engineering of multiple types of functional genitourinary tissues.

Tissue engineering of the bladder

When gastrointestinal tissue is used for bladder augmentation or replacement, multiple complications may ensue, such as infection, metabolic disturbances, urolithiasis, perforation, increased mucous production, and malignancy. Therefore, alternative methods are being sought for cystoplasty. There has been a resurgence of interest in the use of acellular collagen-based matrices as scaffolds for bladder regeneration. Experimental work involving several collagen matrices, such as allogenic bladder and intestinal tissues, is currently being conducted in several academic centers. Recently, functional bladder tissue has been engineered using selective cell transplantation. The approach that has been followed for bioengineering of bladder tissue involves the use of autologous cells, thus avoiding rejection, whereby a biopsy of tissue is obtained from the host, after which the cells are dissociated and expanded in vitro, reattached to a matrix, and implanted into the same host.

Tissue-engineering applications for phallic reconstruction

Pathologic penile conditions often require reconstructive surgery. Due to the limited amount of autologous tissues available for reconstruction, other tissue substitutes have been used. Phallic reconstruction using engineered autologous genital tissue, i.e., tissue derived from the patient's own cells, may be preferable. In this article we describe tissue-engineering approaches that may be applicable to genital reconstruction.

Experimental and clinical experience using tissue regeneration for urethral reconstruction

Various urethral conditions often require additional tissue for reconstruction. Although several innovative tissues have been proposed for possible use as free grafts for urethral repair, all have specific advantages and disadvantages. The use of these tissues may be associated with additional procedures for graft retrieval, prolonged hospitalization, and donor-site morbidity. For these reasons, alternate materials have been sought for urethral repair. Our laboratory has developed an acellular collagen matrix that has shown adequate urothelial-cell epithelialization and urethral-tissue regeneration both experimentally and clinically. After a 3-year follow-up period, all patients who have had their urethras reconstructed with the acellular matrix are doing well, showing no clinical change from their immediate postoperative results. Other acellular materials may soon be tried clinically. Long-term studies need to be conducted before any of these materials can be accepted for routine use in urethral reconstructive procedures.

Controlled release of therapeutic agents: slow delivery and cell encapsulation

Some of the most promising systems for the controlled release of bioactive agents, i.e., peptides or hormones, involve the encapsulation or entrapment of hormones or peptides in biocompatible polymeric devices that enable their continuous release over prolonged periods. In urology, two major pathologic conditions, androgen deficiency and prostate cancer, currently benefit from treatments based on controlled delivery. Leuprolide acetate depot (Lupron-depot) was one of the first controlled-delivery systems used for the treatment of prostate cancer. Clinical studies indicate that patients with prostate cancer who undergo therapy with leuprolide acetate depot can benefit from this treatment. Currently available androgen-replacement therapies include the oral administration of testosterone tablets or capsules, depot injections, sublingual treatment, and skin patches. However, side effects such as metabolic inactivation of testosterone on oral administration; fluctuations in levels of the hormone; and burning, rash, and skin necrosis during the use of skin patches may occur. These side effects may be avoided through the application of encapsulated Leydig cells, which produce testosterone. Studies in our laboratory have shown that Leydig cells encapsulated in alginate/poly-L-lysine/alginate microspheres are capable of secreting testosterone in culture and in vivo. Microencapsulated Leydig cells delivered intraperitoneally into castrated rats maintained a testosterone level of 0.51 ng/ml for more than 3 months without any human chorionic gonadotropin stimulation. Similar studies are also being conducted in our laboratory on encapsulation of ovarian cells for the secretion of progesterone and estrogen in culture and in vivo using microencapsulation techniques.