Autologous engineered cartilage rods for penile reconstruction

New Solutions for Old Problems: How Reproductive Tissue Engineering Has Been Revolutionizing Reproductive Medicine

Acquired disorders and congenital defects of the male and female reproductive systems can have profound impacts on patients, causing sexual and endocrine dysfunction and infertility, as well as psychosocial consequences that affect their self-esteem, identity, sexuality, and relationships. Reproductive tissue engineering (REPROTEN) is a promising approach to restore fertility and improve the quality of life of patients with reproductive disorders by developing, replacing, or regenerating cells, tissues, and organs from the reproductive and urinary systems. In this review, we explore the latest advancements in REPROTEN techniques and their applications for addressing degenerative conditions in male and female reproductive organs. We discuss current research and clinical outcomes and highlight the potential of 3D constructs utilizing biomaterials such as scaffolds, cells, and biologically active molecules. Our review offers a comprehensive guide for researchers and clinicians, providing insights into how to reestablish reproductive tissue structure and function using innovative surgical approaches and biomaterials. We highlight the benefits of REPROTEN for patients, including preservation of fertility and hormonal production, reconstruction of uterine and cervical structures, and restoration of sexual and urinary functions. Despite significant progress, REPROTEN still faces ethical and technical challenges that need to be addressed. Our review underscores the importance of continued research in this field to advance the development of effective and safe REPROTEN approaches for patients with reproductive disorders.

Biomaterial strategies for the application of reproductive tissue engineering

Human reproductive organs are of vital importance to the life of an individual and the reproduction of human populations. So far, traditional methods have a limited effect in recovering the function and fertility of reproductive organs and tissues. Thus, aim to replace and facilitate the regrowth of damaged or diseased tissue, various biomaterials are developed to offer hope to overcome these difficulties and help gain further research progress in reproductive tissue engineering. In this review, we focus on the biomaterials and their four main applications in reproductive tissue engineering: in vitro generation and culture of reproductive cells; development of reproductive organoids and models; in vivo transplantation of reproductive cells or tissues; and regeneration of reproductive tissue. In reproductive tissue engineering, designing biomaterials for different applications with different mechanical properties, structure, function, and microenvironment is challenging and important, and deserves more attention.

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Various biomaterials have been developed and used in reproductive tissue engineering.

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3D culture systems can lead to better cell-cell interactions for in vitro production of reproductive cells.

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Reproductive organoids and models are formed by biomaterials to simulate the environment of natural reproductive organs.

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Biomaterials should promote vascular regeneration and resist inflammation for in-situ reproductive tissue regeneration.

Salvage of a Near-Total Penile Amputation following Urinary Fistulization and Carbapenemase-Producing Klebsiella pneumoniae Infection with a Composite ALT Flap and Vascularized Fascia Lata

Reconstruction of complex penile defects is always challenging, as some defects are not possible to reconstruct with skin or mucosa grafts, and even local flaps may be precluded in complex wounds. We present a case of a 63-year-old otherwise healthy man, who underwent transurethral resection of the prostate for benign prostatic hyperplasia. After the procedure, he developed panurethral necrosis with consequent stricture. Three urethroplasties for reconstruction of the bulbar and distal urethra using buccal mucosa grafts, a preputial flap, and penile skin were performed by urology team in different institutions, but serious urinary fistulization and carbapenemase-producing Klebsiella pneumoniae (KPC) infection translated in a chronic wound, urethra necrosis, and near-total penile amputation. A composite anterolateral thigh flap and vascularized fascia lata were used with success together with a perineal urethroplasty in different stages, improving the ischemic wound condition. The extended segment of fascia lata was used for Buck's fascia replacement and circumferential reinforcement to cover the erectile bodies of the penis. The postoperative period was uneventful and after 12 months, there were no signs of recurrence or wound dehiscence. He was able and easily adapted to void in a seated position through the perineal urethrostomy that was made. To the best of our knowledge, this procedure has not been reported previously as a salvage procedure in a fistulizated and KPC infected penis, but it may be considered to avoid penile amputation in chronic infected and intractable wounds.

Tracheal cartilage growth promotion by intra-tracheal administration of basic FGF

PURPOSE

This study aimed to investigate whether intra-tracheal administration of basic fibroblast growth factor (b-FGF) promotes the growth of tracheal cartilage.

METHODS

Trachea of 4-week old mice were intubated and 2.5 μg b-FGF administered (Group 4) for periods from 1 to 5 days. Cervical tracheal outer diameter and tracheal ring length were compared in Group 1 (no intervention), Group 2 (tracheal intubation), Group 3 (intra-tracheal administration of distilled water) and Group 4, at 8 weeks of age. Outer diameter and tracheal ring length in Group 4 were also compared with that in Group 1 at 12 and 16 weeks of age.

RESULTS

At 8 weeks of age, tracheal ring length with b-FGF administration for more than 4 days in Group 4 was significantly increased over that following 1-day administration. At 8 weeks of age, mean outer diameter and the mean tracheal ring length in Group 4 were significantly greater than in the other groups. Mean outer diameter and mean tracheal ring length were significantly greater in Group 4 than in Group 1 at 12 and 16 weeks of age.

CONCLUSION

This study has shown that intra-tracheal administration of b-FGF enlarges the tracheal lumen.

Study of Mechanical Properties of Engineered Cartilage in an in Vivo Culture for Design of a Biodegradable Scaffold

Introduction

An engineered trachea with an absorbable scaffold should be used to augment the repair of a stenotic tracheal section in infants and children because this type of engineered airway structure can grow as the child grows. Our strategy for relief of tracheal stenosis is tracheoplasty by engineered cartilage implantation in accordance with the concept of costal cartilage grafting to enlarge the lumen. This study investigated the mechanical properties of regenerative cartilage with a biodegradable scaffold, Neoveil®, to aid in design of a composite scaffold that maintained semi-rigid properties until cartilage could be generated.

Materials and methods

New Zealand White rabbit (n=3) chondrocytes were isolated from auricular cartilage with collagenase type 2 digestion. Then 10×106/cm3 chondrocytes in atelocollagen solution were seeded onto polyglycolic acid (PGA) mesh. A total of 36 constructs, 12 from each rabbit, were implanted into athymic mice (3 constructs/mouse). Constructs were retrieved after 8 weeks and evaluated by measurements of mechanical and biochemical properties as well as histological examination. Thirty-six PGA mesh sheets of the same size but without cells were implanted in control mice.

Results

After 6 weeks of implantation, staining of sections with Safranin O revealed cartilage accumulation. Glycosaminoglycan was gradually produced from chondrocytes in the engineered constructs, correlating with the duration of implantation. Mechanical parameters had the same values as those for rabbit tracheal cartilage 8 weeks after implantation.

Conclusions

Biodegradable Neoveil® had good biocompatibility and was able to support extracellular matrix formation in engineered cartilage in an animal model.

Construction of engineered corpus cavernosum with primary mesenchymal stem cells in vitro

Various methods have been used to reconstruct the penis. The objective of this study was to investigate the feasibility of constructing engineered corpus cavernosum with primary mesenchymal stem cells (MSCs) in a rabbit model in vitro. Acellular corporal matrices (ACMs) were obtained from adult rabbit penile tissues through an established decellularization procedure. MSCs were separated, purified, and then seeded on ACMs to construct engineered corpus cavernosum. The seeded ACMs were subsequently cultured in an incubator for 14 days. Histological analyses showed that MSCs seeded on the ACMs had proliferated and were well distributed. Detection of CD31, vWF, smooth muscle actin (SMA), and myosin protein as well as vWF and myosin mRNA revealed that the MSCs had differentiated into endothelial cells and smooth muscle cells. In addition, cell morphology of the engineered corpus cavernosum was directly observed by transmission electron microscopy. This study demonstrated that engineered corpus cavernosum could be successfully constructed using primary MSCs in vitro. This technology represents another step towards developing engineered corpus cavernosum in vitro.

Innovative trends and perspectives for erectile dysfunction treatment: A systematic review

Objective

To review contemporary knowledge concerning the innovative trends and perspectives in the treatment of erectile dysfunction (ED).

Methods

Medline was reviewed for English-language journal articles between January 2000 and March 2016, using the terms ‘erectile dysfunction treatments’, ‘new trends’ and ‘perspectives’. In all, 114 original articles and 16 review articles were found to be relevant. Of the 76 cited papers that met the inclusion criteria, 51 papers had level of evidence of 1a–2b, whilst 25 had level of evidence of 3–4. Criteria included all pertinent review articles, randomised controlled trials with tight methodological design, cohort studies, and retrospective analyses. We also manually reviewed references from selected articles.

Results

Several interesting studies have addressed novel phosphodiesterase type 5 inhibitors (PDE5Is), orodispersible tablets, their recent chronic use, and combination with other agents. A few controlled studies have addressed herbal medicine as a sole or additional treatment for ED. Experimental studies and exciting review papers have addressed stem cells as novel players in the field of ED treatment. Other recent articles have revised the current status of low-intensity extracorporeal shockwave therapy in the field of ED. A few articles without long-term data have addressed new technologies that included: external penile support devices, penile vibrators, tissue engineering, nanotechnology, and endovascular tools for ED treatment.

Conclusions

The current treatment of ED is still far from ideal. We expect to see new drugs and technologies that may revolutionise ED treatment, especially in complex cases.

New advances in erectile technology

New discoveries and technological advances in medicine are rapid. The role of technology in the treatment of erectile dysfunction (ED) will be widened and more options will be available in the years to come. These erectile technologies include external penile support devices, penile vibrators, low intensity extracorporeal shockwave, tissue engineering, nanotechnology and endovascular technology. Even for matured treatment modalities for ED, such as vacuum erectile devices and penile implants, there is new scientific information and novel technology available to improve their usage and to stimulate new ideas. We anticipate that erectile technologies may revolutionize ED treatment and in the very near future ED may become a curable condition.

Tissue engineering of reproductive tissues and organs

Regenerative medicine and tissue engineering technology may soon offer new hope for patients with serious injuries and end-stage reproductive organ failure. Scientists are now applying the principles of cell transplantation, material science, and bioengineering to construct biological substitutes that can restore and maintain normal function in diseased and injured reproductive tissues. In addition, the stem cell field is advancing, and new discoveries in this field will lead to new therapeutic strategies. For example, newly discovered types of stem cells have been retrieved from uterine tissues such as amniotic fluid and placental stem cells. The process of therapeutic cloning and the creation of induced pluripotent cells provide still other potential sources of stem cells for cell-based tissue engineering applications. Although stem cells are still in the research phase, some therapies arising from tissue engineering endeavors that make use of autologous adult cells have already entered the clinic. This article discusses these tissue engineering strategies for various organs in the male and female reproductive tract.

Tissue engineering of the penis

Congenital disorders, cancer, trauma, or other conditions of the genitourinary tract can lead to significant organ damage or loss of function, necessitating eventual reconstruction or replacement of the damaged structures. However, current reconstructive techniques are limited by issues of tissue availability and compatibility. Physicians and scientists have begun to explore tissue engineering and regenerative medicine strategies for repair and reconstruction of the genitourinary tract. Tissue engineering allows the development of biological substitutes which could potentially restore normal function. Tissue engineering efforts designed to treat or replace most organs are currently being undertaken. Most of these efforts have occurred within the past decade. However, before these engineering techniques can be applied to humans, further studies are needed to ensure the safety and efficacy of these new materials. Recent progress suggests that engineered urologic tissues and cell therapy may soon have clinical applicability.

Tissue engineering: current strategies and future directions

Novel therapies resulting from regenerative medicine and tissue engineering technology may offer new hope for patients with injuries, end-stage organ failure, or other clinical issues. Currently, patients with diseased and injured organs are often treated with transplanted organs. However, there is a shortage of donor organs that is worsening yearly as the population ages and as the number of new cases of organ failure increases. Scientists in the field of regenerative medicine and tissue engineering are now applying the principles of cell transplantation, material science, and bioengineering to construct biological substitutes that can restore and maintain normal function in diseased and injured tissues. In addition, the stem cell field is a rapidly advancing part of regenerative medicine, and new discoveries in this field create new options for this type of therapy. For example, new types of stem cells, such as amniotic fluid and placental stem cells that can circumvent the ethical issues associated with embryonic stem cells, have been discovered. The process of therapeutic cloning and the creation of induced pluripotent cells provide still other potential sources of stem cells for cell-based tissue engineering applications. Although stem cells are still in the research phase, some therapies arising from tissue engineering endeavors that make use of autologous, adult cells have already entered the clinical setting, indicating that regenerative medicine holds much promise for the future.

Future sexual medicine physiological treatment targets

INTRODUCTION

Sexual function in men and women incorporates physiologic processes and regulation of the central and peripheral nervous systems, the vascular system, and the endocrine system. There is need for state-of-the-art information as there is an evolving research understanding of the underlying molecular biological factors and mechanisms governing sexual physiologic functions.

AIM

To develop an evidence-based, state-of-the-art consensus report on the current knowledge of the major cellular and molecular targets of biologic systems responsible for sexual physiologic function.

METHODS

State-of-the-art knowledge representing the opinions of seven experts from four countries was developed in a consensus process over a 2-year period.

MAIN OUTCOME MEASURES

Expert opinion was based on the grading of evidence-based medical literature, widespread internal committee discussion, public presentation, and debate.

RESULTS

Scientific investigation in this field is needed to increase knowledge and foster development of the future line of treatments for all forms of biological-based sexual dysfunction. This article addresses the current knowledge of the major cellular and molecular targets of biological systems responsible for sexual physiologic function. Future treatment targets include growth factor therapy, gene therapy, stem and cell-based therapies, and regenerative medicine.

CONCLUSIONS

Scientific discovery is critically important for developing new and increasingly effective treatments in sexual medicine. Broad physiologic directions should be vigorously explored and considered for future management of sexual disorders.

Engineered cartilage covered ear implants for auricular cartilage reconstruction

Cartilage tissues are often required for auricular tissue reconstruction. Currently, alloplastic ear-shaped medical implants composed of silicon and polyethylene are being used clinically. However, the use of these implants is often associated with complications, including inflammation, infection, erosion, and dislodgement. To overcome these limitations, we propose a system in which tissue-engineered cartilage serves as a shell that entirely covers the alloplastic implants. This study investigated whether cartilage tissue, engineered with chondrocytes and a fibrin hydrogel, would provide adequate coverage of a commercially used medical implant. To demonstrate the in vivo stability of cell-fibrin constructs, we tested variations of fibrinogen and thrombin concentration as well as cell density. After implantation, the retrieved engineered cartilage tissue was evaluated by histo- and immunohistochemical, biochemical, and mechanical analyses. Histomorphological evaluations consistently showed cartilage formation over the medical implants with the maintenance of dimensional stability. An initial cell density was determined that is critical for the production of matrix components such as glycosaminoglycans (GAG), elastin, type II collagen, and for mechanical strength. This study shows that engineered cartilage tissues are able to serve as a shell that entirely covers the medical implant, which may minimize the morbidity associated with implant dislodgement.

Use of tissue engineering in treatment of the male genitourinary tract abnormalities

INTRODUCTION

A variety of congenital and acquired male genitourinary tract abnormalities can lead to organ damage or tissue loss that requires surgical reconstruction. Traditional reconstructive methods do not produce consistent satisfactory structural or functional replacement and may damage the genitourinary tract. Tissue engineering provides a promising alternative for the treatment of these disorders.

AIM

The aim of this article is to provide an update on clinical and experimental evidence concerning the application of tissue engineering to treatment of abnormalities in the male genitourinary tract system.

METHODS

A PubMed search was performed to retrieve relevant clinical and basic literature.

MAIN OUTCOME MEASURES

The topics discussed in this review include the experimental and clinical application of tissue engineering for reconstruction of the urethra, penis, testis, and prostate.

RESULTS

Tissue engineering techniques can provide a plentiful source of healthy tissue for reconstructive purposes. Acellular matrix scaffold and seed cells are two key elements in tissue engineering. Proper employment of seed cells and scaffold material may result in synergistic effects. Moreover, new tissue engineering technologies are being transferred from the laboratory to clinical practice.

CONCLUSIONS

Tissue engineering provides biological substitutes that can restore and maintain normal function in diseased and injured tissues, thus providing an effective technique for regeneration of the male genitourinary tract.

Bioengineered corporal tissue for structural and functional restoration of the penis

Various reconstructive procedures have been attempted to restore a cosmetically acceptable phallus that would allow normal reproductive, sexual, and urinary function in patients requiring penile reconstruction. However, these procedures are limited by a shortage of native penile tissue. We previously demonstrated that a short segment of the penile corporal body can be replaced using naturally derived collagen matrices with autologous cells. In the current study, we examined the feasibility of engineering the entire pendular penile corporal bodies in a rabbit model. Neocorpora were engineered from cavernosal collagen matrices seeded with autologous cells using a multistep static/dynamic procedure, and these were implanted to replace the excised corpora. The bioengineered corpora demonstrated structural and functional parameters similar to native tissue and male rabbits receiving the bilateral implants were able to successfully impregnate females. This study demonstrates that neocorpora can be engineered for total pendular penile corporal body replacement. This technology has considerable potential for patients requiring penile reconstruction.

Human tracheal chondrocytes as a cell source for augmenting stenotic tracheal segments: the first feasibility study in an in vivo culture system

INTRODUCTION

Construction of engineered respiratory tract using tissue-engineered cartilage has not yet been reported. In order to generate artificial trachea using human chondrocytes obtained from tracheal cartilage, we investigated whether human tracheal chondrocytes can act as a cell source to fabricate engineered airway patches to augment stenotic parts of the trachea.

MATERIALS AND METHODS

After informed consent, chondrocytes were obtained from five patients who needed tracheal surgery. A small piece of resected tracheal cartilage was digested by collagenase type 2 for 3-4 h. This yielded chondrocytes, which were expanded in vitro and seeded onto biodegradable scaffolds; these were then implanted subcutaneously in athymic mice. The implanted constructs were retrieved 8 weeks later for histologic and biochemical analysis.

RESULTS

In monolayer cultures, chondrocytes proliferated well, showing a 100- to 1,000-fold increase in 1 month. Once expanded, the cells lost their original morphological and biologic characteristics, but the engrafted scaffold showed histologic and biochemical characteristics of cartilage. Viable chondrocytes and extracellular matrix were detected, and glycosaminoglycan (GAG) in vivo was present.

CONCLUSIONS

Here we show that a small piece of human tracheal cartilage can generate sufficient chondrocytes in vitro and form tracheal cartilage architecture in an in vivo environment.

Bioengineered tissues for urogenital repair in children

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

Engineering tissues, organs and cells

Patients suffering from diseased and injured organs may be treated with transplanted organs; however, there is a severe shortage of donor organs that is worsening yearly, given the ageing population. In the field of regenerative medicine and tissue engineering, scientists apply the principles of cell transplantation, materials science and bioengineering 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 stem cell field is also advancing rapidly, opening new options for therapy, including the use of amniotic and placental fetal stem cells. This review covers recent advances that have occurred in regenerative medicine and describes applications of these technologies using chemical compounds that may offer novel therapies for patients with end-stage organ failure.

Regenerative Medicine: Applications and Development in Urology

Purpose

Congenital abnormalities and acquired disorders can lead to organ damage and loss. Nowadays, transplantation represents the only effective treatment option. However, there is a marked decrease in the number of organ donors, which is even yearly worsening due to the population aging. The regenerative medicine represents a realistic option that allows to restore and maintain the normal functions of tissues and organs. This article reviews the principles of regenerative medicine and the recent advances with regard to its application to the genitourinary tract.

Recent findings

The field of regenerative medicine involves different areas of technology, such as tissue engineering, stem cells and cloning. Tissue engineering involves the field of cell transplantation, materials science and engineering in order to create functional replacement tissues. Stem cells and cloning permit the extraction of pluripotent, embryonic stem cells offering a potentially limitless source of cells for tissue engineering applications. Most current strategies for tissue engineering depend upon a sample of autologous cells from the patient's diseased organ. Biopsies from patients with extensive end-stage organ failure, however, may not yield enough normal cells. In these situations, stem cells are envisaged as being an alternative source. Stem cells can be derived from discarded human embryos (human embryonic stem cells), from fetal tissue or from adult sources (bone marrow, fat, skin). Therapeutic cloning offers a potentially limitless source of cells for tissue engineering applications. Regenerative medicine and tissue engineering scientists have increasingly applied the principles of cell transplantation, materials science and bioengineering to construct biological substitutes that will restore and maintain normal function in urological diseased and injured tissues such as kidney, ureter, bladder, urethra and penis.

Conclusions

Regenerative medicine offers several applications in acquired and congenital genitourinary diseases. Tissue engineering, stem cells and, mostly, cloning have been applied in experimental studies with excellent results. Few preliminary human applications have been developed with promising results.

Formation of Cartilage In Vivo with Immobilized Autologous Rabbit Auricular Cultured Chondrocytes in Collagen Matrices

BACKGROUND

The availability of generated cartilage de novo is one of the needs of reconstructive surgery. In this study, the authors constructed a matrix formed by autologous immobilized chondrocytes using collagen gel as a scaffold. Furthermore, the ability of these matrices to engraft and generate new cartilage was examined.

METHODS

Biopsy specimens of elastic cartilage were surgically obtained from the ears of eight New Zealand White rabbits. After collagenase II digestion of cartilage, chondrocytes were isolated and propagated in culture medium. Chondrocytes were immobilized into bovine collagen lattices and implanted, replacing pieces of removed native cartilage. Five weeks after implantation, the rabbits were killed and the ears were examined macroscopically and analyzed by means of histochemical methods.

RESULTS

The results show the formation of new cartilage from implanted lattices with chondrocytes. Gross analysis of the ears shows similarities in appearance, consistency, texture, and histology between native and new cartilage. Fluorescence of the nucleus from bisbenzimide-labeled chondrocytes was detected in newly formed tissue, pointing out its in vitro culture origin. No signs of an inflammatory reaction attributable to implants were found in either the control or the chondrocyte lattices.

CONCLUSION

The authors suggest that this approach is of value for future clinical use.

Recent applications of regenerative medicine to urologic structures and related tissues

PURPOSE OF REVIEW

A severe shortage of donor tissues and organs exists, which is worsening yearly given the aging population. Currently, patients suffering from diseased and injured organs are treated with transplanted organs or cells. This paper reviews recent advances that have occurred in regenerative medicine and describes application of new technologies to treat diseased or damaged organs and tissues.

RECENT FINDINGS

Although most current strategies for tissue engineering depend upon a sample of autologous cells from the diseased organ of the patient, biopsies from patients with extensive end-stage organ failure may not yield enough normal cells. In these situations, stem cells are envisioned as being an alternative source. Stem cells can be derived from discarded human embryos (human embryonic stem cells), from fetal tissue, or from adult sources (bone marrow, fat, skin). Therapeutic cloning offers a potentially limitless source of cells for tissue engineering applications.

SUMMARY

Recently, scientists in the fields of regenerative medicine and tissue engineering have applied the principles of cell transplantation, material science, and bioengineering to construct biological substitutes that will restore and maintain normal function in diseased and injured tissues.

Recent developments in tissue engineering and regenerative medicine

PURPOSE OF REVIEW

Currently, patients suffering from diseased and injured organs are treated with transplanted organs or cells. There is, however, a severe shortage of donor tissues and organs that is worsening yearly given the aging population. This paper reviews recent advances that have occurred in regenerative medicine and describes applications of new technologies to treat diseased or damaged organs and tissues.

RECENT FINDINGS

Most current strategies for tissue engineering depend upon a sample of autologous cells from the diseased organ of the patient. Biopsies from patients with extensive end-stage organ failure, however, may not yield enough normal cells. In these situations, stem cells are envisioned as being an alternative source. Stem cells can be derived from discarded human embryos (human embryonic stem cells), from fetal tissue or from adult sources (bone marrow, fat, skin). Therapeutic cloning offers a potentially limitless source of cells for tissue engineering applications.

SUMMARY

Increasingly, scientists in the fields of regenerative medicine and tissue engineering have applied the principles of cell transplantation, material science and bioengineering to construct biological substitutes that will restore and maintain normal function in diseased and injured tissues.

Tissue Engineering Using Adult Stem Cells

Patients with a variety of diseases may be treated with transplanted tissues and organs. However, there is a shortage of donor tissues and organs, which is worsening yearly because of the aging population. Scientists in the field of tissue engineering are applying the principles of cell transplantation, material science, and bioengineering to construct biological substitutes that will restore and maintain normal function in diseased and injured tissues. The stem cell field is also advancing rapidly, opening new options for cellular therapy and tissue engineering. The use of adult stem cells for tissue engineering applications is promising. This chapter discusses applications of these new technologies for the engineering of tissues and organs. The first part provides an overview of regenerative medicine and tissue engineering techniques; the second highlights different adult stem cell populations used for tissue regeneration.

Tissue engineering, stem cells and cloning: current concepts and changing trends

Organ damage or loss can occur from congenital disorders, cancer, trauma, infection, inflammation, iatrogenic injuries or other conditions and often necessitates reconstruction or replacement. Replacement may take the form of organ transplant. At present, there is a severe shortage of donor organs that is worsening with the aging of the population. Tissue engineering follows the principles of cell transplantation, materials science and engineering towards the development of biological substitutes that can restore and maintain normal tissue function. Therapeutic cloning involves the introduction of a nucleus from a donor cell into an enucleated oocyte to generate embryonic stem cell lines whose genetic material is identical to that of its source. These autologous stem cells have the potential to become almost any type of cell in the adult body, and thus would be useful in tissue and organ replacement applications. This paper reviews recent advances in stem cell research and regenerative medicine, and describes the clinical applications of these technologies as novel therapies for tissue or organ loss.

[Current status of tissue engineering in urology. Review of the literature]

In the eighties a new field of the medicine appears wich applies the principles of cellular cultivation to synthetic biodegradable polymers scaffolds with the purpose of creating autologous biological substitutes that could improve, maintain or restore the function of organs or damaged tissues. The Tissue Engineering constitutes a new discipline in full phase of development especially in USA, with multiple potential applications in several medical specialities. Our speciality can't remain indifferent to interest and encouraging future originated by this new science. In this work we have made a wide bibliographical revision in the Medline to know the antecedents, current state and the possible future applications of Tissue Engineering in Urology.

Technology Insight: applications of tissue engineering and biological substitutes in urology

Patients suffering from diseased or injured organs may be treated with transplanted organs. However, there is a severe shortage of donor organs, which is worsening yearly owing to the ageing population. Scientists in the field of regenerative medicine and tissue engineering apply the principles of cell transplantation, materials science, and bioengineering to construct biological substitutes that will restore and maintain normal function in diseased and injured tissues. This article reviews recent advances in regenerative medicine and describes applications of biological substitutes that may offer novel therapies for patients with end-stage organ failure.

Ingénierie tissulaire et thérapie cellulaire en urologie

Tissue engineering refers to the techniques that are aimed at regeneration of human tissues and organs. Two elements are necessary for these techniques: matrix and cells. Matrix is the scaffold where tissues may organise. Cells are either autologous cells stimulated to regenerate in vivo, aided by implantation of matrix ("guided tissue regeneration"), or autologous cells cultured outside the body (in vitro) and later returned as auto-transplants. All types of conventional tissue reconstructive surgery need tissue engineering. These techniques have been introduced recently into the clinical practice. One of the main limitations of reconstructive surgery in genitourinary tract is the lack of autologous tissue. Two autotransplants could be distinguished: coherent tissue structure or cell suspensions. The great number of studies published in this area emphasizes the importance of the future clinical implication in urology.

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

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

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

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

[Tissue engineering in urology. Basic principles and application]

Tissue engineering is a rather new field of science. Despite this fact, some experimental investigations have already been applied in clinical studies. Compared to other medical fields, tissue engineering in urology is well established. Tissue-engineered bulking agents and tissue-engineered bladder augments are being investigated in clinical trials. Even though the knowledge gained in recent years is promising, the results of cellular therapies need to be critically judged before being finally applied in patients. Genetic engineering and stem cell research (adult undifferentiated cells) have had major impact on the field of tissue engineering over the past 2 years. By using the technology of genetic engineering, biochemical and functional qualities of tissues may be modified. Adult stem cells may help to substitute lost tissue in an autologous fashion by isolating undifferentiated cells from the body and by differentiating them into a desired cell type. These cells may be used to form native functional tissue to replace a diseased organ or organ part.

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.

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.

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.

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.

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.

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.