Future perspectives in reconstructive surgery using tissue engineering

What's in the Pipeline about Bladder Reconstructive Surgery? Some Remarks on the State of the Art

The fusion of engineering with cell biology and advances in biomaterials may lead to de novo construction of implantable organs. Engineering of neobladder from autologous urothelial and smooth muscle cells cultured on biocompatible, either synthetic or naturally-derived substrates, is now feasible in preclinical studies and may have clinical applicability in the near future. The development of a bioartificial bladder would warrant the prevention of both the metabolic and neoplastic shortcomings of the intestinal neobladder. Two tissue-engineering techniques for bladder reconstruction have been tested on animals: 1) the in vivo technique involves the use of naturally-derived biomaterials for functional native bladder regeneration 2) the in vitro technique involves the establishment of autologous urothelial and smooth muscle cell culture from the host's urinary tract, after which the cells are seeded on the biodegradable matrix-scaffold to create a composite graft that is implanted into the same host for complete histotectonic regeneration. Waiting for the creation of a complete tissue-engineered bladder with a trigone-shaped base, we suggest, in surgical oncology after radical cystectomy, the realization of conduit or continent pouch using tissue-engineered material.

Co-culturing porcine normal urothelial cells, urinary bladder fibroblasts and smooth muscle cells for tissue engineering research

New strategies for culturing and co-culturing of the main types of urinary bladder cells are essential for successful establishment of biomimetic in vitro models, which could be applied for research into, and management of, diverse urological disorders. Porcine normal urothelial cells are available in nearly unlimited amounts and have many properties equivalent to human urothelial cells. In the present study, we established normal differentiated porcine urothelial cells in co-cultures with porcine urinary bladder normal fibroblasts and/or smooth muscle cells. The optimal culture medium for establishment of differentiated urothelial cells, demonstrated by positive immunofluorescence of uroplakins, cytokeratins (CK 7, CK 20), zonula occludens 1 (ZO-1), claudin 4, claudin 8, and E-cadherin, was the medium composed of equal parts of Advanced Dulbecco's modified Eagle's medium (A-DMEM) and MCDB 153 medium with physiological calcium concentration of 2.5 mM and without fetal bovine serum, named UroM (+Ca²⁺  - S). This medium was also proven to be suitable for culturing of bladder fibroblasts and smooth muscle cells and co-culturing of urothelial cells with these mesenchymal cells. Urothelial cell differentiation was optimal in UroM (+Ca²⁺  - S) medium in all co-culture conditions and when compared to all conditioned-media combinations. To summarize, these strategies for culturing and co-culturing of urinary bladder urothelial cells with mesenchymal cells could be used as new in vitro models for future basic and applicable research of the urinary bladder and thus potentially also for translational tissue engineering studies.

Biocompatibility of different nanostructured TiO2 scaffolds and their potential for urologic applications

Despite great efforts in tissue engineering of the ureter, urinary bladder, and urethra, further research is needed in order to improve the patient's quality of life and minimize the economic burden of different lower urinary tract disorders. The nanostructured titanium dioxide (TiO₂) scaffolds have a wide range of clinical applications and are already widely used in orthopedic or dental medicine. The current study was conducted to synthesize TiO₂ nanotubes by the anodization method and TiO₂ nanowires and nanospheres by the chemical vapor deposition method. These scaffolds were characterized with scanning electron microscopy (SEM) and X-ray diffraction (XRD) methods. In order to test the urologic applicability of generated TiO₂ scaffolds, we seeded the normal porcine urothelial (NPU) cells on TiO₂ nanotubes, TiO₂ nanowires, TiO₂ nanospheres, and on the standard porous membrane. The viability and growth of the cells were monitored everyday, and after 3 weeks of culturing, the analysis with scanning electron microscope (SEM) was performed. Our results showed that the NPU cells were attached on all scaffolds; they were viable and formed a multilayered epithelium, i.e., urothelium. The apical plasma membrane of the majority of superficial NPU cells, grown on all three different TiO₂ scaffolds and on the porous membrane, exhibited microvilli; thus, indicating that they were at a similar differentiation stage. The maximal caliper diameter measurements of superficial NPU cells revealed significant alterations, with the largest cells being observed on nanowires and the smallest ones on the porous membrane. Our findings indicate that different nanostructured TiO₂ scaffolds, especially nanowires, have a great potential for tissue engineering and should be further investigated for various urologic applications.

Kidney regeneration: Where we are and future perspectives

In 2012, about 16487 people received kidney transplants in the United States, whereas 95022 candidates were on the waiting list by the end of the year. Despite advances in renal transplant immunology, approximately 40% of recipients will die or lose graft within 10 years. The limitations of current therapies for renal failure have led researchers to explore the development of modalities that could improve, restore, or replace the renal function. The aim of this paper is to describe a reasonable approach for kidney regeneration and review the current literature regarding cell sources and mechanisms to develop a bioengineering kidney. Due to kidneys peculiar anatomy, extracellular matrix based scaffolds are rational starting point for their regeneration. The perfusion of detergents through the kidney vasculature is an efficient method for delivering decellularizing agents to cells and for removing of cellular material from the tissue. Many efforts have focused on the search of a reliable cell source to provide enrichment for achieving stable renal cell systems. For an efficient bioengineered kidney, these cells must be attached to the organ and then maturated into the bioractors, which simulates the human body environment. A functional bioengineered kidney is still a big challenge for scientists. In the last ten years we have got many improvements on the field of solid organ regeneration; however, we are still far away from the main target. Currently, regenerative centers worldwide have been striving to find feasible strategies to develop bioengineered kidneys. Cell-scaffold technology gives hope to end-stage renal disease patients who struggle with morbidity and mortality due to extended periods on dialysis or immunosupression. The potential of bioengineered organ is to provide a reliable source of organs, which can be refunctionalized and transplanted.

Evolution and trends in reconstructive facial surgery: an update

Surgical correction of congenital and acquired facial deformities has transcended the primitive era of using non biologic materials to current attempts at own face growing through biotechnology. A summative account of this trend is still lacking in the literature. The objective of this article is to present an update on current knowledge in the strides to achieve functionally and aesthetically perfect facial reconstruction. It highlights the impact of advancements in 3D imaging, stereolithographic biomodelling, microvascular surgical tissue transplantation and tissue biotechnology in the surgical efforts to solve the problems of facial disfigurement whether congenital or acquired.

Facial reconstruction by biosurgery: cell transplantation versus cell homing

The face distinguishes one human being from another. When the face is disfigured because of trauma, tumor removal, congenital anomalies, or chronic diseases, the patient has a strong desire for functional and esthetic restoration. Current practice of facial reconstruction using autologous grafts, synthetic fillers, and prostheses is frequently below the surgeon's and patient's expectations. Facial reconstruction is yet to take advantage of recent advances in seemingly unrelated fields of stem cell biology, chemical engineering, biomaterials, and tissue engineering. "Biosurgery," a new concept that we propose, will incorporate novel principles and strategies of bioactive cues, biopolymers, and/or cells to restore facial defects. Small facial defects can likely be reconstructed by cell homing and without cell transplantation. A critical advantage of cell homing is that agilely recruited endogenous cells have the potential to harness the host's innate capacity for regeneration, thus accelerating the rate of regulatory and commercialization processes for product development. Large facial defects, however, may not be restorable without cell delivery per our understanding at this time. New breakthrough in biosurgery will likely originate from integrated strategies of cell biology, cytokine biology, chemical engineering, biomaterials, and tissue engineering. Regardless of cell homing or cell delivery approaches, biosurgery not only will minimize surgical trauma and repetitive procedures, but also produce long-lasting results. At the same time, caution must be exercised against the development of products that lack scientific basis or dogmatic combination of cells, biomaterials, and biomolecules. Together, scientifically derived biosurgery will undoubtedly develop into new technologies that offer increasingly natural reconstruction and/or augmentation of the face.

The use of seromuscular tapered ileal tube in ureteral replacement: an experimental model

PURPOSE

To assess the capability of urothelium to proliferate, creep and line the inner surface of the interposed seromuscular tapered ileal tube.

MATERIALS AND METHODS

Under general anesthesia, 15 female dogs underwent resection of 5 cm of the mid ureter and replaced with tapered seromuscular ileal tube stented for 6 weeks. The animals were sacrificed, and cross section of the ileal ureters were examined histologically for the lining cells.

RESULTS

Multilayer of transitional epithelium was seen covering all the inner surface of the interposed seromuscular tube at the end of 6 weeks. Excessive inflammatory cell infiltration was a prominent finding in the submucosal layer.

CONCLUSION

Transitional epithelium has the capability to proliferate, grow and cover the inner surface of the interposed seromuscular ileal tube. Urothelium lining avoid the metabolic complications of the intestinal mucosa.

[Bioartificial urothelium generated from bladder washings. A future therapeutic option for reconstructive surgery]

Reconstructive surgery of lower urinary tract disorders can be limited by a shortage of adequate autologous tissue. Tissue engineering is an option for surgical reconstruction with evolved biological substitutes. Urethral repair with bioartificial urothelial implants can be an innovative method for sustained urothelial regeneration in situ. The needed urothelial cells are commonly isolated from native urothelium requiring surgery.The aim of this study was to establish primary human urothelial cell cultures from bladder washings in serum-free media and to generate urothelial tissue without seeding of matrices in a feeder cell-free system. It could be demonstrated that under these conditions bioartificial urothelium can be developed successfully from bladder washings. Its multilayered cellular structure and the initial differentiation in vitro, similar to native-grown urothelial tissue, are promising with regard to intended clinical application. Current work focuses on establishing cell culture techniques according to legal regulations, terminal differentiation of the urothelial constructs in vitro, and techniques to surgically implant lab-grown bioartificial urothelium.

Stem cells and tissue engineering applications of the genitourinary tract

The field of regenerative medicine continues to make substantial advancements in therapeutic strategies addressing urologic diseases. Tissue engineering borrows principles from the fields of cell biology, materials science, transplantation and engineering in an effort to repair or replace damaged tissues. This review is intended to provide a current overview of the use of stem cells and tissue engineering technologies specifically in the treatment of genitourinary diseases. Current themes in the field include the use of adult stem cells seeded onto biocompatible resorbable matrices for implantation as tissue substitutes, which is conducive to host tissue in-growth. Injection therapy of adult stem cells for organ rehabilitation is also making strong headway toward the restoration of organ structure and function. With new data describing the molecular mechanisms for differentiation, work has begun on targeting tissues for regeneration by genetic modification methods. Promising laboratory discoveries portend the emergence of a new class of clinical therapies for regenerative medicine applications in the genitourinary tract.

Tissue engineering of the synovial joint: the role of cell density

The ultimate goal in the tissue engineering of the synovial joint is to fabricate biologically derived analogues that can replace severely degenerated or traumatized synovial joint components. A number of challenges must be addressed before reaching this ultimate goal. In this report, the relevance of cell seeding density in the synthesis of chondrogenic and osteogenic matrices from human mesenchymal stem cells is explored. Human mesenchymal stem cells (hMSCs) were differentiated into chondrogenic cells and osteogenic cells ex vivo and encapsulated in poly(ethylene glycol) diacrylate (PEGDA) hydrogel at densities of 5 x 106 cells/ml, 40 x 10(6) cells/ml, and 80 x 10(6) cells/ml, in addition to a cell-free poly(ethylene glycol) (PEG) control group (0 x 10(6) cells/ml). Cell-seeded or cell-free PEG constructs were separately incubated in vitro for 4 weeks or implanted in vivo in the dorsum of immunodeficient rats for 4 weeks. In-vitro data demonstrated that hMSC-derived chondrocytes or hMSC-derived osteoblasts maintained their lineages per Safranin O and von Kossa staining after incubation for 4 weeks. The general pattern of initial cell seeding densities of 5 x 10(6) cells/ml, 40 x 10(6) cells/ml, and 80 x 10(6) cells/ml were preserved following in-vitro cultivation. Similarly, in-vivo data revealed that hMSC-derived chondrocytes and hMSC-derived osteoblasts maintained their respective lineages and the pattern of cell-seeding densities. An attempt was made to fabricate a composite construct with PEGDA hydrogel and polycaprolactone (PCL) with designed internal porosity for an osteochondral graft. Various cell-seeding densities as delineated in this report can be realized in the composite PEG-PCL graft. The findings demonstrate that cell-seeding density is likely a key parameter to consider in tissue-engineering design. The source of cells can either be transplanted cells or internally recruited cells.

Bladder augmentation without integration of intact bowel segments: critical review and future perspectives

PURPOSE

We evaluated the long-term results of autoaugmentation in the pediatric age group and summarized technical adaptations, experimental options and future perspectives for treating these patients.

MATERIALS AND METHODS

A directed MEDLINE literature review was performed to assess different techniques and alternative options in autoaugmentation procedures. Of 150 studies 49 in the subgroup with the longest duration of followup to show the long-term outcome of the autoaugmentation procedures were chosen for this review. Information gained from these data was reviewed and new perspectives were summarized.

RESULTS

Enterocystoplasy is an effective mode of therapy with acceptable morbidity and satisfactory clinical results, although it is major intraperitoneal surgery with various complications and patients need prolonged convalescence to adapt to these surgical procedures. On the other hand, patient selection seems to be the most crucial step for the success of autoaugmentation procedures because the clinical outcome does not appear to be durable.

CONCLUSIONS

Achievement of better compliance after autoaugmentation procedures seems to be less pronounced and of shorter duration than that of conventional enterocystoplasty. On the other hand, the low morbidity and lack of side effects of bowel integration into the urinary tract are the definite advantages of this technique. It is the responsibility of the physician to determine the balance between the limited efficacy of the procedures vs the definite advantages. Although functionally improved parameters are obtained in tissue engineered autologous bladders, there is an absolute need for additional studies before this challenging technique could be applied widely.

Adipose tissue engineering from human adult stem cells: clinical implications in plastic and reconstructive surgery

BACKGROUND

Despite certain levels of clinical efficacy, current autografts and synthetic materials for soft-tissue reconstruction and/or augmentation suffer from donor-site morbidity, rupture, dislocation, and volume reduction. Human adult stem cells can self-replicate and differentiate into adipogenic cells in response to appropriate signaling cues. This study investigated the shape and dimension maintenance of engineered adipose tissue from adult human mesenchymal stem cells.

METHODS

Human mesenchymal stem cells were isolated from bone marrow of a healthy donor and differentiated into adipogenic cells. Adipocytes derived from these cells were encapsulated in a poly(ethylene glycol)-based hydrogel shaped into a generic cylinder (n = 6 implants), with hydrogel encapsulating human mesenchymal stem cells (n = 6) and cell-free hydrogel (n = 6) as controls. Porous collagen sponges were also used to seed human mesenchymal stem cell-derived adipocytes (n = 6), human mesenchymal stem cells (n = 4), or without cells (n = 4). All poly(ethylene glycol) and collagen constructs were implanted subcutaneously in athymic mice for 4 weeks.

RESULTS

In vivo grafts demonstrated the formation of substantial adipose tissue encapsulating human mesenchymal stem cell-derived adipogenic cells in either poly(ethylene glycol)-based hydrogel or collagen sponge and a lack of adipose tissue formation in cell-free or human mesenchymal stem cell-derived grafts. Engineered adipose tissue in poly(ethylene glycol)-based hydrogel maintained approximately 100 percent of the original dimensions after 4-week in vivo implantation, significantly higher than the approximately 35 to 65 percent volume retention by collagen sponge.

CONCLUSIONS

These findings demonstrate that the predefined shape and dimensions of adipose tissue engineered from human mesenchymal stem cells can be maintained after in vivo implantation. These data further indicate the potential for autologous applications in reconstructive and plastic surgery procedures.

Different Types of Scaffolds for Reconstruction of the Urinary Tract by Tissue Engineering

INTRODUCTION

Tissue engineering is an important and expanding field in reconstructive surgery. The ideal biomaterial for urologic tissue engineering should be biodegradable and support autologous cell growth. We examined different scaffolds to select the ideal material for the reconstruction of the bladder wall by tissue engineering.

MATERIALS AND METHODS

We seeded mouse fibroblasts and human keratinocytes in a co-culture model on 13 different scaffolds. The cell-seeded scaffolds were fixed and processed for electron microscopy, hematoxylin and eosin stain, and immunohistochemistry. Cell density and epithelial cell layers were evaluated utilizing a computer-assisted optical measurement system.

RESULTS

Depending on the growth pattern, scaffolds were classified into the following three distinct scaffold types: carrier-type scaffolds with very small pore sizes and no ingrowth of the cells. This scaffold type induces a well-differentiated epithelium. Fleece-type scaffolds with fibers and huge pores. We found cellular growth inside the scaffold but no epithelium on top of it. Sponge-type scaffolds with pores between 20 and 40 microm. Cellular growth was observed inside the scaffold and well-differentiated epithelium on top of it.

CONCLUSION

To our knowledge, this is the first time three distinct scaffold types have been reported. All types supported the cell growth. The structure of the scaffolds affects the pattern of cell growth.

[Neurogenic bladder in children: basic principles in diagnosis and treatment]

The diagnosis of neurogenic bladder can be easy in myelomeningocele and much more difficult in occult dysraphia or medical etiologies. Careful clinical examinations and urodynamic investigations are mandatory for the diagnosis and the follow up of affected patients. Clinico-anatomical correlations are poor. If urinary leak is the first apparent symptom, preservation of the upper urinary tract is the main goal of the surgeon. If natural history of the neurogenic bladder is destruction of the detrusor and paralysis of the trigona, obstructive uropathy is the main physiological concern. Urinary leak must be integrated in the global context of the bladder function in order to determine urinary incontinence type. Ideal micturition is voluntary, must be complete, and needs the synergistic action of a reservoir with a good capacity, a normal compliance, and adequate sphincter outlet resistances. Continence is obtained by balancing these functions, and associating medical treatment and surgery is necessary. Bladder intermittent catheterization is the clue to obtain in most of the cases complete evacuation of the bladder and protection of the upper urinary tract. Increasing bladder capacity is achieved more often by augmentation cystoplasty (colon, ileus, stomach and ureter can be used). Autoplasty at the beginning, artificial tissue engineering will be the future. Augmentation of the bladder outlet resistances need surgical reconstruction (young dees, Pipi-salles procedures...) or uretral and bladder neck suspensions, artificial urinary sphincters, endoscopic injections of bulking agents. All these techniques can be proposed and combined according to the patient's gender, age and social environment. Continent cystostomy allows obtaining continence in difficult cases and after unsuccessful surgery of the bladder neck. Other techniques are under evaluation and sacral neuromodulation give at the moment some promising results. Managing neurogenic bladder must not be considered only in urological terms: orthopedic troubles, digestive and sexual disorders must not be forgotten in order to obtain at least an "acceptable social life".

[In vitro three-dimensional reconstruction of human bladder mucosa]

OBJECTIVE

The purpose of this study is to apply the in vitro keratinocyte culture techniques and the tissue engineering principles to human urothelium, to reconstruct an in vitro three-dimensional human bladder mucosa, suitable for grafting.

MATERIAL AND METHODS

Biopsy specimens of human bladder mucosa were obtained from patients undergoing suprapubic prostatectomy, in vitro cultured and finally, an immunohistochemical study was made.

RESULTS

A three-dimensional in vitro tissue was obtained, composed of a bio-artificial submucosa (fibrin gel and fibroblast) where the uroepithelial cells were seeding. We used a biodegradable polyglycolic acid mesh to facilitate the tissue manipulation and implantation. An immature epithelium was obtained with a weak immunostaining to cytokeratins. The immunohistochemical study could not demonstrate the development of basement membrane.

CONCLUSIONS

In vitro keratinocyte culture techniques could be applied to other epithelial tissues like the urothelium. We obtained a three-dimensional in vitro tissue suitable for grafting in a relatively short time, which needs the matrix interactions in order to mature.

Bladder wall replacement by tissue engineering and autologous keratinocytes in minipigs

OBJECTIVE

To develop a tissue-engineered bladder wall replacement with autologous cells and a biodegradable scaffold, as whenever there is a lack of native urological tissue the bladder is reconstructed with different bowel segments, which has inevitable complications.

MATERIAL AND METHODS

Skin biopsies were taken from six minipigs, and primary fibroblast and keratinocyte cell cultures established. A partial resection of the urinary bladder was reconstructed by a cell-seeded scaffold covered with completely differentiated epithelium and supported by a mucosa-free pedicled ileum graft. Each pig was assessed urodynamically and by cystography before operation and every month until explantation; the pigs were killed at 1, 2 and 3 months after augmentation. Control groups (of six pigs each) with bladder augmentation with complete or denuded ileum were used. The bladders were assessed histologically and by distensibility measurements

RESULTS

The differentiated keratinocyte epithelium was still present on the reconstructed bladder wall after 3 months. The overall shrinkage rate was 6.5%. The engineered bladder wall had lower distensibility than the native one. The inflammatory reaction present initially had disappeared after 3 months.

CONCLUSIONS

The implanted, tissue-engineered substitution of the bladder wall is not only a bridging graft, but also a complete reconstruction. With this model, extended bladder wall substitution seems feasible and should be investigated in further studies.

New Perspectives of Penile Enhancement Surgery: Tissue Engineering with Biodegradable Scaffolds

OBJECTIVE

To evaluate in a multicenter, prospective study preliminary aesthetic and functional results of autologous ex-vivo tissue engineering for penile girth enhancement.

METHODS

From July 1999 to January 2004, 204 men of mean age 26.77 (range 19-54 years) underwent this procedure. Indications for penile girth enhancement were penile dysmorphic disorder and previous failed surgery for penile girth enhancement. Fibroblast cells harvested from 1 cc of biopsied scrotal dermal tissue were expanded in culture until the total cell number of at least 2x10(7) was reached. Suspended cells in culture medium were then seeded on pretreated tube-shaped PLGA scaffolds and incubated for 24 hours. After penile degloving, scaffolds were shape adjusted and transplanted between dartos and Buck's fascia when the skin was compliant or under the neurovascular bundle when the skin was not compliant.

RESULTS

A total of 84 randomly selected patients were followed 1 to 5 years postoperatively (median 24 months). The gain in girth ranged from 1.9 to 4.1cm (mean 3.15 cm). Postoperative complications occurred as infection in three, penile skin pressure necrosis in two and seroma formation in five patients and were all treated conservatively. Surgical intervention was appraised by patients on a scale from 1 to 5 as follows: the best mark (5) was given by 44.05%, very good (4) by 36.90%, good (3) by 19.05% and only one patient gave the mark 2 judging general penile appearance as dissatisfactory; mean score was 4.25.

CONCLUSION

Autologous tissue engineering by using biodegradable scaffolds as a carrier is a new and safe therapeutic approach for penile girth enhancement. The outcome of this study points out the necessity for its expanded clinical applicability in the future.

Engineered adipose tissue from human mesenchymal stem cells maintains predefined shape and dimension: implications in soft tissue augmentation and reconstruction

Soft tissue augmentation is a widespread practice in plastic and reconstructive surgery. The objective of the present study was to engineer adipose tissue constructs with predefined shape and dimensions, potentially utilizable in soft tissue augmentation and reconstruction, by encapsulating adult stem cell-derived adipogenic cells in a biocompatible hydrogel system. Bone marrow-derived adult human mesenchymal stem cells (hMSCs) were preconditioned by 1 week of exposure to adipogenic- inducing supplement followed by photoencapsulation in poly(ethylene glycol) diacrylate (PEGDA) hydrogel in predefined shape and dimensions. In two parallel experiments, the resulting hMSC-derived adipogenic cell-polymer constructs were either incubated in vitro in adipogenic medium or implanted in vivo in the dorsum of immunodeficient mice for 4 weeks. Tissue-engineered adipogenic constructs demonstrated positive reaction to oil red O staining both in vitro and in vivo, and expressed PPAR-gamma2 adipogenic gene marker in vivo. By contrast, control PEGDA hydrogel constructs encapsulating undifferentiated hMSCs failed to demonstrate the adipogenic gene marker and were negative for oil red O staining. Recovered in vitro and in vivo constructs maintained their predefined physical shape and dimensions. These data demonstrate that adipose tissue engineered from human mesenchymal stem cells can retain predefined shape and dimensions for soft tissue augmentation and reconstruction.

[Experimental study about viability of autologous free graft in vitro cultivated urinary epithelium]

OBJECTIVE

The purpose of this study is to apply the in vitro keratinocyte culture techniques and the tissue engineering principles to urothelium, to obtain a three-dimensional autologous tissue suitable for grafting. We also showed the viability of free graft cultured urothelium in an experimental model.

MATERIAL AND METHODS

An animal experimental model was designed to apply the techniques of cellular culture and tissue engineering. Biopsy specimens of bladder mucosa were obtained, in vitro cultured and posteriorly implanted in each animal. We established three groups based on different follow-up periods (7, 14 and 30 days), and made a final histomorphological study to demonstrate the viability of the graft at the end of its respective follow-up period.

RESULTS

A three-dimensional in vitro tissue was obtained, composed of a bio-artificial submucosa (fibrin gel and fibroblast) where the uroepithelial cells were seeding; a biodegradable polyglycolic acid mesh was used to facilitate the tissue manipulation and implantation. In the morphological study all the implants appeared viable, but the grafts with longer implantations periods were better conformed, showing a tisular structure with multiple cellular layers.

CONCLUSIONS

In vitro keratinocyte culture techniques could be applied to other epithelial tissues as the urothelium. We obtained a three-dimensional in vitro tissue suitable for grafting in a relatively short time. The histological study demonstrated that free autologous urothelial graft is totally viable, opening future clinics applications.

Tissue engineering applications of therapeutic cloning

Few treatment options are available for patients suffering from diseased and injured organs because of a severe shortage of donor organs available for transplantation. Therapeutic cloning, where the nucleus from a donor cell is transferred into an enucleated oocyte in order to extract pluripotent embryonic stem cells, offers a potentially limitless source of cells for replacement therapy. Scientists in the field of tissue engineering apply the principles of cell transplantation, material science, and engineering to construct biological substitutes that will restore and maintain normal function in diseased and injured tissues. The present chapter reviews recent advances that have occurred in therapeutic cloning and tissue engineering and describes applications of these new technologies that may offer novel therapies for patients with end-stage organ failure.

NONSECRETORY INTESTINOCYSTOPLASTY: A 10-YEAR EXPERIENCE

PURPOSE

We present long-term results on the use of demucosalized intestine for reconstructive surgery of the bladder.

MATERIALS AND METHODS

A total of 129 bladder augmentations with demucosalized intestine were performed in 123 patients (55% males and 45% females) 3 months to 53 years old during the last 10 years. Of the patients 82 presented with neurogenic bladder, 40 with bladder exstrophy, 3 each with tuberculosis and posterior urethral valves, and 1 with female hypospadias. Sigmoid was used in 104 cases and ileum in 25. In 105 cases a silicone balloon was left inside the augmented bladder for 2 weeks. In the remaining cases bladder mucosa was preserved and no mold was used. A silicone inflatable bladder neck cuff was implanted at the same time as augmentation in 32 patients.

RESULTS

Followup ranged from 3 to 135 months (median 51.0). There was a 329% increase in bladder capacity and compliance increased 7-fold. There were 13 (10.1%) cases considered failures, which were treated with reaugmentation using demucosalized ileum (6), different forms of augmentation (5) and no reaugmentation (2). There was no mucus formation, bladder perforation or neoplasia.

CONCLUSIONS

Based on our study we conclude that demucosalized intestine is a safe alternative for bladder augmentation and can be used for the same indications as total bowel segments.

Tissue-engineered buccal mucosa for substitution urethroplasty

OBJECTIVE

To develop tissue-engineered buccal mucosa (TEBM) for use in substitution urethroplasty, as urethral reconstruction is limited by the amount and type of tissue that is available for grafting, and BM has become the favoured tissue for use as a urethral substitute in the last decade.

MATERIALS AND METHODS

After enzymatic treatment of a small (0.5 cm) BM biopsy the epidermis and dermis were mechanically separated. Oral keratinocytes were isolated from the epidermis and oral fibroblasts from the dermis. These cells were expanded and applied to sterilized de-epidermized dermis (DED) to obtain a full-thickness TE oral mucosa. Horizontal migration of keratinocytes on the DED was assessed using a tetrazolium-blue (MTT) assay. The TEBM was assessed histologically after mechanical stressing in vitro using catheterization and meshing.

RESULTS

Histologically the TEBM closely resembled the native oral mucosa after culturing at an air-liquid interface for 2 weeks. The MTT assay showed good horizontal migration of keratinocytes on the DED. Serial histology revealed a gradually increasing thickness of the epidermis and remodelling of the dermis by the fibroblasts from day 1 to day 14. Despite subjecting the TEBM to mechanical stress the integrity of the epidermal-dermal junction was maintained.

CONCLUSIONS

We report the successful culture of full-thickness TEBM for substitution urethroplasty, which is robust and suitable for clinical use.

Therapeutic cloning applications for organ transplantation

A severe shortage of donor organs available for transplantation in the United States leaves patients suffering from diseased and injured organs with few treatment options. Scientists in the field of tissue engineering apply the principles of cell transplantation, material science, and engineering to construct biological substitutes that will restore and maintain normal function in diseased and injured tissues. Therapeutic cloning, where the nucleus from a donor cell is transferred into an enucleated oocyte in order to extract pluripotent embryonic stem cells, offers a potentially limitless source of cells for tissue engineering applications. The present chapter reviews recent advances that have occurred in therapeutic cloning and tissue engineering and describes applications of these new technologies that may offer novel therapies for patients with end-stage organ failure.

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

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

Therapeutic Cloning and Tissue Engineering

A severe shortage of donor organs available for transplantation in the United States leaves patients suffering from diseased and injured organs with few treatment options. Scientists in the field of tissue engineering apply the principles of cell transplantation, material science, and engineering to construct biological substitutes that will restore and maintain normal function in diseased and injured tissues. Therapeutic cloning, where the nucleus from a donor cell is transferred into an enucleated oocyte in order to extract pluripotent embryonic stem cells, offers a potentially limitless source of cells for tissue engineering applications. The present chapter reviews recent advances that have occurred in therapeutic cloning and tissue engineering and describes applications of these new technologies that may offer novel therapies for patients with end-stage organ failure.

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

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

Acrylic acid grafting and collagen immobilization on poly(ethylene terephthalate) surfaces for adherence and growth of human bladder smooth muscle cells

In tissue engineering, degradable or non-degradable polymer matrices can act as cell-carrier-scaffolds. Cell adhesion and growth on these scaffolds can be promoted by immobilizing extracellular matrix proteins. Therefore, in this study, polymer poly(ethylene terephthalate) (PET) films were surface modified by graft polymerization of acrylic acid, to subsequently allow collagen (types I and III) immobilization and human smooth muscle cell expansion. The surfaces of PET were activated by plasma, followed by acrylic acid graft polymerization, resulting in covalently bound brushes, containing an average of either 0.22+/-0.1 or 5.93+/-0.87 microg/cm2 of poly(acrylic acid) (PAA). Subsequent electrostatic adsorption of collagen gave a surface concentration of 4.96 and 17.2 microg/cm2, respectively, as determined using radiolabelled 125I collagen. Both PET films grafted with 0.22 microg/cm2 of PAA with or without adsorbed collagen were apt for smooth muscle cell adhesion and proliferation. However, films grafted with 5.93 microg/cm2 were not. PAA-grafted PET films, onto which serum proteins of the culture medium adsorbed spontaneously, proved to be better matrices than films on which collagen has been immobilized. It, therefore, can be speculated that other serum proteins are more important than collagen for the human smooth muscle cell adhesion and growth on surface-modified polymer matrices.

Generation of histocompatible tissues using nuclear transplantation

Nuclear transplantation (therapeutic cloning) could theoretically provide a limitless source of cells for regenerative therapy. Although the cloned cells would carry the nuclear genome of the patient, the presence of mitochondria inherited from the recipient oocyte raises questions about the histocompatibility of the resulting cells. In this study, we created bioengineered tissues from cardiac, skeletal muscle, and renal cells cloned from adult bovine fibroblasts. Long-term viability was demonstrated after transplantation of the grafts into the nuclear donor animals. Reverse transcription-PCR (RT-PCR) and western blot analysis confirmed that the cloned tissues expressed tissue-specific mRNA and proteins while expressing a different mitochondrial DNA (mtDNA) haplotype. In addition to creating skeletal muscle and cardiac "patches", nuclear transplantation was used to generate functioning renal units that produced urinelike fluid and demonstrated unidirectional secretion and concentration of urea nitrogen and creatinine. Examination of the explanted renal devices revealed formation of organized glomeruli- and tubule-like structures. Delayed-type hypersensitivity (DTH) testing in vivo and Elispot analysis in vitro suggested that there was no rejection response to the cloned renal cells. The ability to generate histocompatible cells using cloning techniques addresses one of the major challenges in transplantation medicine.

Future trends in bladder reconstructive surgery

The incorporation of bowel into the urinary tract is associated with significant long-term complications. Therefore, considerable efforts are being made to avoid the use of enteric epithelium in bladder reconstruction. The simplest of these entail the use of native urothelium that is already available, with techniques such as auto-augmentation, auto-augmentation de-epithelialized enterocystoplasty, and ureterocystoplasty. Unfortunately, in many patients, the bladder is too small, or dilated ureters are not available, and these techniques cannot be applied. Recently, experimental techniques are examining the use of tissue expansion to the ureter and bladder to increase the volume of tissue available. Tissue engineering techniques are being applied to bladder regeneration, and considerable advances have already been made leading to in vivo animal experimentation, the results of which are very encouraging. The details of these most recent advances will be discussed in detail in this report.

22 week assessment of bladder acellular matrix as a bladder augmentation material in a porcine model

Previous studies on the reconstruction of porcine bladder using bladder acellular matrix allograft (BAMA) have indicated positive preliminary results with respect to graft shrinkage and cellular repopulation. The current study was conducted to investigate the feasibility of using BAMA in a similar model of bladder reconstruction out to longer time frames (22 weeks). At predetermined time points, the macroscopic, histological and mechanical properties of explanted native and BAMA tissues were evaluated and compared. Macroscopically, contracture of the BAMA was observed. The peripheral regions of the grafts experienced extensive cellular repopulation. Towards the centre however, all grafts were consistently devoid of organized smooth muscle bundles and a well-developed urothelium. An alteration in both the amount and organization of collagen was also observed within this region. Significant differences (p < 0.05) in the rupture strain and the elastic modulus of the BAMA compared to native bladder tissue appear to correlate with macroscopic graft contracture as well as the fibroproliferative tissue response of the matrix.

Validation of targets and drug candidates in an engineered three-dimensional cardiac tissue model

High-throughput target discovery confronts the biopharmaceutical industry with a plethora of target candidates. The validation of these candidates in disease-specific animal models often lacks the required throughput. Here, we discuss perspectives and limitations of a novel engineered three-dimensional cardiac tissue, which enables the influence of gene and drug intervention to be monitored on a cellular and molecular level under physiological conditions in sufficient throughput. The model is an extremely helpful filter to prioritize multiple development candidates before moving a project into large animal models with higher predictivity.

New surgical techniques in pediatric urology

More sophisticated endoscopic instruments, combined with a better understanding of bladder and urethral pathology, have significantly improved the therapeutic approaches for both posterior urethral valves and ureteroceles. New generation lithotripters have allowed for a safe and efficient method of treating urinary calculi in children, which was once thought too injurious a process with first-generation machines. The rapidly advancing field of laparoscopy, aided by the development of more optically refined and diminutive instruments, has allowed for its application in a wide variety of surgical interventions in pediatric urology. The tubularized incised plate urethroplasty has challenged more traditional approaches to hypospadias repair and is now considered by many pediatric urologists to be the best approach for midshaft and distal hypospadias. The one-stage approach to exstrophy repair may hold the answer to improved continence without a formal bladder neck reconstruction. Finally, the field of tissue engineering leads the way to new advances in autologous biological substitutes in the surgically-challenged patient where there is a shortage of local tissues at the surgeon's disposal.

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.

Fibrin glue as matrix for cultured autologous urothelial cells in urethral reconstruction

In the present study, we have established a technique to create an artificial urethra in a rat animal model by transplantation of in vitro-expanded urothelial cells onto an in vivo-prefabricated tube formation using tissue engineering methods. Urothelial cells from isogenic rats were harvested for culture. A silicon catheter was used to induce a connective tissue capsule-tube formation underneath the abdominal skin. Two weeks later, the cultivated urothelial cells were seeded onto the lumen of this tube using fibrin glue as delivery matrix. The histomorphological and immunohistochemical studies revealed a viable multilayered urothelium, lining the inner surface of the prior formed connective tissue tube-formation 4 weeks after grafting the cells. We have shown that cultured and in vitro-expanded urothelial cells can be successfully reimplanted onto a prefabricated tube-like structure using fibrin glue as a delivery matrix and native cell expansion vehicle. The results suggest that the creation of an artificial urethra may be achieved in vivo using tissue engineering methods, showing potential for urethral reconstruction and providing autologous urothelium for reconstructive surgery in the genitourinary tract.

Urinary diversion and reconstruction

Orthotopic bladder augmentation and substitution has been established as the standard procedure for urinary diversion in many institutions, with current studies reporting mainly on continence rates and procedure-associated complications, such as the risk of impairment of neobladder function by local tumor recurrences in the small pelvis. Similarly, in other types of continent diversion, such as continent cutaneous diversion and rectal reservoirs, current interest is primarily directed towards minimization of surgery-associated complications.

Biomaterials in functional reconstruction

Recent initiatives in the development of biomaterials for functional reconstruction involve the alloplasts, the biological and the bioengineered biomaterials. Anti-infective alloplastic biomaterials (Foley catheters coated with rifampicin/minocycline bonded to silicone or ciprofloxacin liposome-containing hydrogel) allow a reduction in the rate of bacterial contamination, but the risk of future bacterial resistance is a matter for concern. New generations of biologic collagen-based tissue-matrix grafts are derived from bladder (bladder acellular matrix graft and bladder submucosa collagen matrix), ureter or small intestine (subintestinal submucosa). There are high hopes that these materials may have applications in augmentation cystoplasty. Using tissue engineering (autologous cells expanded in vitro and grafted onto biodegradable matrix), biocompatible malleable penile prostheses have been obtained experimentally. Most of the results obtained with these new biomaterials are exclusively experimental, but they offer great hope for future functional reconstruction of the urinary tract.