Reconstitution of human corpus cavernosum smooth muscle in vitro and in vivo

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.

A Preliminary Study of Constructing the Tissue-Engineered Corpus Cavernosum With Autologous Adipose Stem Cells In Vivo

Introduction

The autologous skin flap is still the mainstream method for penile reconstruction, but it is very difficult to reconstruct a functional corpus cavernosum. Tissue engineering provides a new idea aiming to restore the damaged or absent corpus cavernosum.

Aim

To assess the feasibility of constructing the tissue-engineered corpus cavernosum with autologous adipose stem cells in a rabbit model.

Methods

A total of 30 New Zealand male white rabbits. Among them, 20 rabbits were used to obtain the original corpus cavernosum which were used to prepare the acellular corporal scaffolds (ACSs). The others were used for acquiring autologous adipose stem cells (ADSCs) and constructing tissue-engineered corpus cavernosum in vivo.

Outcome

ACSs were obtained from rabbit penile tissues through an established decellularization procedure. Rabbit autologous ADSCs as seed cells were harvested and expanded. The ADSCs seeded and unseeded ACSs were implanted back into the intramuscular and subcutaneous site in vivo, and the tissue-engineered corpus cavernosum was harvested and analyzed with gross morphology, histological staining, and real-time PCR assay after 1, 3, and 6 months.

Results

ACSs were successfully prepared. The cell non-cytotoxicity and integrity of micro-architecture of ACSs was confirmed in vitro. The cell-seeded scaffold in the intramuscular group was considered as the better strategy for constructing the tissue-engineered corpus cavernosum compared with the other groups. Some α-SMA and CD31 positive cells were detected and identified by immunofluorescent staining and real-time PCR assay in the tissue-engineered corpus cavernosum.

Clinical Translation

This study provides a new method for constructing the tissue-engineered corpus cavernosum.

Strengths and Limitations

First, it is urgent to improve the transformation rate of the endothelial cells and smooth muscle cells from ADSCs. Second, the scaffold harvested in this study was not a complete matrix. Third, further study is needed to explore the potential mechanism of which scaffolds are more suitable for living in intramuscular rather than subcutaneous environment.

Conclusion

In this study, we used the autologous ADSCs as seed cells, the acellular corpus cavernosum as scaffolds, and implanted the grafts back into the rabbit model to preliminarily construct the tissue-engineered corpus cavernosum. This study would provide help for further development in tissue-engineered corpus cavernosum.

Cao Z, Liu L, Jiao H, et al. A Preliminary Study of Constructing the Tissue-Engineered Corpus Cavernosum With Autologous Adipose Stem Cells In Vivo. Sex Med 2022;10:100563.

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.

Cavernous Nerve Injury Resulted Erectile Dysfunction and Regeneration

Erectile dysfunction (ED) is an important cause of reduced quality of life for men and their partners. Recent studies have found that cavernous nerve injury (CNI) during prostate cancer surgery and other pelvic surgery results in medically induced CNIED in more than 80% of patients. The efficacy of first- and second-line treatment options for ED is poor. A great deal of research has been devoted to exploring new methods of neuroprotection and nerve regeneration to save erectile function in patients with CNIED, especially in patients with cavernous nerve injury after prostate cancer surgery. In addition, such as neuromodulatory proteins, proimmune ligands, gene therapy, stem cell therapy, and the current cutting-edge low-energy shock wave therapy have shown advantages in basic research and limited clinical studies. In the context of today's modern medicine, these new therapeutic techniques are expected to be new tools in the treatment of cavernous nerve injury erectile dysfunction. This article presents the main causes, mechanisms, and treatment of cavernous nerve injury erectile dysfunction and combines them with new treatment strategies.

Male subfertility and oxidative stress

To date 15% of couples are suffering from infertility with 45-50% of males being responsible. With an increase in paternal age as well as various environmental and lifestyle factors worsening these figures are expected to increase. As the so-called free radical theory of infertility suggests, free radicals or reactive oxygen species (ROS) play an essential role in this process. However, ROS also fulfill important functions for instance in sperm maturation. The aim of this review article is to discuss the role reactive oxygen species play in male fertility and how these are influenced by lifestyle, age or disease. We will further discuss how these ROS are measured and how they can be avoided during in-vitro fertilization.

Co-culture of smooth muscle cells and endothelial cells on three-dimensional bioprinted polycaprolactone scaffolds for cavernosal tissue engineering

PURPOSE

In vitro evaluation of polycaprolactone (PCL) scaffolds fabricated by a three-dimensional (3D) printing technique for tissue engineering applications in the corpus cavernosum.

MATERIALS AND METHODS

PCL scaffolds were fabricated by use of a 3 D bioprinting system. The 3D-printed scaffolds had interconnected structures for cell ingrowth. Human aortic smooth muscle cells (haSMCs) were seeded on the scaffold and cultured for 5 days, and then human umbilical vein endothelial cells (HUVECs) were also added on the scaffolds and co-cultured with haSMCs for up to 7 days. The ability of these scaffolds to support the growth of HUVECs and haSMCs was investigated in vitro. 3 D strand-deposited scaffolds were characterized by scanning electron microscopy (SEM) images and porosity measurement.

RESULTS

SEM images showed the surface of the PCL scaffolds to be well covered by HUVECs and haSMCs. Immunofluorescent staining of α-flk1 and α-smooth muscle actin on the HUVECs and haSMCs seeded scaffolds confirmed that the cells remained viable and proliferated throughout the time course of the culture.

CONCLUSION

3 D bioprinting of a PCL scaffold is feasible for co-culturing of HUVECs and haSMCs. This was a preliminary study to investigate the possibility of fabrication of tissue-engineered corpus cavernosum.

Functional reconstruction of injured corpus cavernosa using 3D-printed hydrogel scaffolds seeded with HIF-1α-expressing stem cells

Injury of corpus cavernosa results in erectile dysfunction, but its treatment has been very difficult. Here we construct heparin-coated 3D-printed hydrogel scaffolds seeded with hypoxia inducible factor-1α (HIF-1α)-mutated muscle-derived stem cells (MDSCs) to develop bioengineered vascularized corpora. HIF-1α-mutated MDSCs significantly secrete various angiogenic factors in MDSCs regardless of hypoxia or normoxia. The biodegradable scaffolds, along with MDSCs, are implanted into corpus cavernosa defects in a rabbit model to show good histocompatibility with no immunological rejection, support vascularized tissue ingrowth, and promote neovascularisation to repair the defects. Evaluation of morphology, intracavernosal pressure, elasticity and shrinkage of repaired cavernous tissue prove that the bioengineered corpora scaffolds repair the defects and recover penile erectile and ejaculation function successfully. The function recovery restores the reproductive capability of the injured male rabbits. Our work demonstrates that the 3D-printed hydrogels with angiogenic cells hold great promise for penile reconstruction to restore reproductive capability of males.

Injury of corpus cavernosa results in erectile dysfunction, and repair leading to restoration of function is difficult. Here the authors construct 3D printed hydrogel constructs seeded with HIF-1α-expressing muscle derived stem cells to restore corpus function in a rabbit model.

The promise of regenerative medicine in the treatment of urogenital disorders

Polymers and scaffolds are the most significant tools in regenerative medicine. Urogenital disorders are an important group of diseases that greatly affect the patient's life expectancy and quality. Reconstruction of urogenital defects is one of the current challenges in regenerative medicine. Regenerative medicine, as well as tissue engineering, may offer suitable approaches, while the tools needed are appropriate materials and cells. Autologous urothelial cells obtained from biopsy, bone marrow-derived stem cells, adipose stem cells and urine-derived stem cells that expressed mesenchymal cell markers are the cells that mainly used. In addition, two main types of biomaterials mainly exist; synthetic polymers and composite scaffolds that are biodegradable polymers with controllable properties and naturally derived biomaterials such as extracellular matrix components and acellular tissue matrices. In this review, we present and evaluate the most appropriate and suitable scaffolds (naturally derived and synthetic polymers) and cells applied in urogenital reconstruction.

3D bioprinting of tissues and organs for regenerative medicine

3D bioprinting is a pioneering technology that enables fabrication of biomimetic, multiscale, multi-cellular tissues with highly complex tissue microenvironment, intricate cytoarchitecture, structure-function hierarchy, and tissue-specific compositional and mechanical heterogeneity. Given the huge demand for organ transplantation, coupled with limited organ donors, bioprinting is a potential technology that could solve this crisis of organ shortage by fabrication of fully-functional whole organs. Though organ bioprinting is a far-fetched goal, there has been a considerable and commendable progress in the field of bioprinting that could be used as transplantable tissues in regenerative medicine. This paper presents a first-time review of 3D bioprinting in regenerative medicine, where the current status and contemporary issues of 3D bioprinting pertaining to the eleven organ systems of the human body including skeletal, muscular, nervous, lymphatic, endocrine, reproductive, integumentary, respiratory, digestive, urinary, and circulatory systems were critically reviewed. The implications of 3D bioprinting in drug discovery, development, and delivery systems are also briefly discussed, in terms of in vitro drug testing models, and personalized medicine. While there is a substantial progress in the field of bioprinting in the recent past, there is still a long way to go to fully realize the translational potential of this technology. Computational studies for study of tissue growth or tissue fusion post-printing, improving the scalability of this technology to fabricate human-scale tissues, development of hybrid systems with integration of different bioprinting modalities, formulation of new bioinks with tuneable mechanical and rheological properties, mechanobiological studies on cell-bioink interaction, 4D bioprinting with smart (stimuli-responsive) hydrogels, and addressing the ethical, social, and regulatory issues concerning bioprinting are potential futuristic focus areas that would aid in successful clinical translation of this technology.

TGFβ-1 and epithelial-mesenchymal interactions promote smooth muscle gene expression in bone marrow stromal cells: Possible application in therapies for urological defects

Purpose

For regenerative and cellular therapies of the urinary tract system, autologous bladder smooth muscle cells (SMCs) have several limitations, including constricted in vitro proliferation capacity and, more importantly, inability to be used in malignant conditions. The use of in vitro (pre-)differentiated multipotential adult progenitor cells may help to overcome the shortcomings associated with primary cells.

Methods

By mimicking environmental conditions of the bladder wall, we investigated in vitro effects of growth factor applications and epithelial-mesenchymal interactions on smooth muscle gene expression and on the morphological appearance of adherent bone marrow stromal cells (BMSCs).

Results

Transcription growth factor beta-1 (TGFβ-1) upregulated the transcription of myogenic gene desmin and smooth muscle actin-γ2 in cultured BMSCs. Stimulatory effects were significantly increased by coculture with urothelial cells. Prolonged stimulation times and epigenetic modifications further enhanced transcription levels, indicating a dose-response relationship. Immunocytochemical staining of in vitro-differentiated BMSCs revealed expression of myogenic protein α-smooth muscle actin and desmin, and changes in morphological appearance from a fusiform convex shape to a laminar flattened shape with filamentous inclusions similar to the appearance of bladder SMCs. In contrast to the TGFβ-1 action, application of vascular endothelial growth factor (VEGF) did not affect the cells.

Conclusions

The combined application of TGFβ-1 and epithelial-mesenchymal interactions promoted in vitro outgrowth of cells with a smooth muscle-like phenotype from a selected adherent murine bone marrow-derived cell population.

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.

An experimental study: evaluating the tissue structure of penis with 2D-ShearWave™ Elastography

The aim of this study was to investigate the feasibility of two-dimensional-ShearWave™ Elastography (2D-SWE) on evaluating the change of tissue structure of penis. Twenty healthy male Sprague Dawley rats were divided into penis-developed group (PDG, 52 weeks) and penis-underdeveloped group (PUDG, 5 weeks). The ultrafast ultrasound device-Aixplorer® (SuperSonic Imagine) was used for 2D-SWE imaging of the penis, the measurement index was shear wave stiffness (SWS, kPa). All rat penises were cut off immediately after ultrasonic examination. After paraffin embedding, slicing and hematoxylin-eosin staining, the tissue structure of the penis was observed under light microscope. SWS of all rat penises were measured successfully. The results showed that SWS of PDG was significantly lower than PUDG (P=0.008). At the same time, the pathological results found that there were significant differences in the tissue structures (sinusoids, smooth muscle cells and fibrocytes) of the penises between the two groups. These results suggest that there are significant differences in SWS between different tissue structures of penis. 2D-SWE is expected to be used on the etiological diagnosis of erectile dysfunction by serving as a new noninvasive method of evaluating the change of tissue structure of penis.

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.

A new method of measuring the stiffness of corpus cavernosum penis with ShearWave™ Elastography

OBJECTIVE

To evaluate the feasibility of measuring the stiffness of corpus cavernosum penis (CCP) with ShearWave™ Elastography (SWE; SuperSonic Imagine, Aix-en-Provence, France).

METHODS

40 healthy volunteers with ages ranging from 19 to 81 years (mean, 36 years; standard deviation, 17 years) were selected in this study. The ultrafast ultrasound device Aixplorer(®) (SuperSonic Imagine) was used for the research and the probe selected was SuperLinear™ SL15-4 (SuperSonic Imagine). The shear wave stiffness (SWS) of CCP was measured using SWE images. The measurement indexes of SWS included (1) SWS of CCP measured in the transverse section (SWS-T), (2) SWS of CCP measured in the longitudinal section (SWS-L) and (3) mean of SWS-T and SWS-L (SWS-M). The interval between hormone test and SWE examination of each subject was less than 7 days. The paired t-test was used to analyse the differences between SWS-T and SWS-L. The Pearson correlation was used to analyse the correlation of SWS of CCP with age as well as with sex hormone levels.

RESULTS

There was no significant difference between SWS-T and SWS-L (p > 0.05). SWS (SWS-T, SWS-L, SWS-M) was negatively correlated with age and oestradiol value, and SWS (SWS-T, SWS-L, SWS-M) was positively correlated with testosterone value.

CONCLUSION

SWE could serve as a new non-invasive method of evaluating the stiffness of CCP.

ADVANCES IN KNOWLEDGE

It is the first time that we have discussed the feasibility of measuring the stiffness of CCP with SWE and analysed the correlation of SWS of CCP with age as well as with sex hormone levels.

Tissue engineering for human urethral reconstruction: systematic review of recent literature

BACKGROUND

Techniques to treat urethral stricture and hypospadias are restricted, as substitution of the unhealthy urethra with tissue from other origins (skin, bladder or buccal mucosa) has some limitations. Therefore, alternative sources of tissue for use in urethral reconstructions are considered, such as ex vivo engineered constructs.

PURPOSE

To review recent literature on tissue engineering for human urethral reconstruction.

METHODS

A search was made in the PubMed and Embase databases restricted to the last 25 years and the English language.

RESULTS

A total of 45 articles were selected describing the use of tissue engineering in urethral reconstruction. The results are discussed in four groups: autologous cell cultures, matrices/scaffolds, cell-seeded scaffolds, and clinical results of urethral reconstructions using these materials. Different progenitor cells were used, isolated from either urine or adipose tissue, but slightly better results were obtained with in vitro expansion of urothelial cells from bladder washings, tissue biopsies from the bladder (urothelium) or the oral cavity (buccal mucosa). Compared with a synthetic scaffold, a biological scaffold has the advantage of bioactive extracellular matrix proteins on its surface. When applied clinically, a non-seeded matrix only seems suited for use as an onlay graft. When a tubularized substitution is the aim, a cell-seeded construct seems more beneficial.

CONCLUSIONS

Considerable experience is available with tissue engineering of urethral tissue in vitro, produced with cells of different origin. Clinical and in vivo experiments show promising results.

The potential role of regenerative medicine in the man-agement of traumatic patients

Traumatic injury represents the most common cause of death in ages 1 to 44 years and a significant proportion of patients treated in hospital emergency wards each year. Unfortunately, for patients who survive their injuries, survival is not equal to complete recovery. Many traumatic injuries are difficult to treat with conventional therapy and result in permanent disability. In such situations, regenerative medicine has the potential to play an important role in recovery of function. Regenerative medicine is a field that seeks to maintain or restore function with the development of biological substitutes for diseased or damaged tissues. Several regenerative approaches are currently under investigation, with a few achieving clinical application. For example, engineered skin has gained FDA approval, and more than 20 tissue engineered skin substitutes are now commercially available. Other organ systems with promising animal models and small human series include the central and peripheral nervous systems, the musculoskeletal system, the respiratory and genitourinary tracts, and others. This paper will be a clinically oriented review of the regenerative approaches currently under investigation of special interest to those caring for traumatic patients.

Organ bioengineering for the newborn

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

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.

Emerging tools for erectile dysfunction: a role for regenerative medicine

Erectile dysfunction (ED) is the most common sexual disorder reported by men to their health-care providers and the most investigated male sexual dysfunction. Currently, the treatment of ED focuses on 'symptomatic relief' of ED and, therefore, tends to provide temporary relief rather than providing a cure or reversing the cause. The identification of a large population of "difficult-to-treat" patients has triggered researchers to identify novel treatment approaches, which focus on cure and restoration of the underlying cause of ED. Regenerative medicine has developed extensively in the past few decades and preclinical trials have emphasized the benefit of growth factor therapy, gene transfer, stem cells and tissue engineering for the restoration of erectile function. Development of clinical trials involving immunomodulation in postprostatectomy ED patients and the use of maxi-K channels for gene therapy are illustrative of the advances in the field. However, the search for novel treatment targets and a wealth of preclinical studies represent a dynamic and continuing field of enquiry.

Regenerative medicine strategies

Applications of regenerative medicine technology may offer novel therapies for patients with injuries, end-stage organ failure, or other clinical problems. Currently, patients suffering from diseased and injured organs can be treated with transplanted organs. However, there is a severe shortage of donor organs that is worsening yearly as the population ages and new cases of organ failure increase. 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 will restore and maintain normal function in diseased and injured tissues. The stem cell field is also advancing rapidly, opening new avenues for this type of therapy. For example, therapeutic cloning and cellular reprogramming may one day provide a potentially limitless source of cells for tissue engineering applications. While stem cells are still in the research phase, some therapies arising from tissue engineering endeavors have already entered the clinical setting successfully, indicating the promise regenerative medicine holds for the future.

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.

Future prospects in the treatment of erectile dysfunction: focus on avanafil

The treatment of erectile dysfunction (ED) has been revolutionized in the last 15 years with the introduction of type 5 phosphodiesterase (PDE5) inhibitors. Their efficacy, safety, and ease of administration have made them first-line treatment for ED. This article reviews the current therapies available for ED, and the new PDE5 inhibitors that are being investigated. Furthermore, it examines all the current ED treatment options that are in different phases of development (including oral and topical pharmacotherapy, gene therapy, and tissue engineering). A special emphasis is on avanafil, a new PDE5 inhibitor that has been studied extensively in Phase I and II clinical trials and has undergone several Phase III trials. Avanafil is a promising medication for ED due to its favorable pharmacokinetics, safety, and efficacy.

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.

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.

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.

Stem cells for regeneration of urological structures

OBJECTIVES

This review focuses on advances in regenerative therapies using stem cells in urology.

METHODS

A detailed literature search was performed using the PubMed database of the National Center of Biotechnology Information. Publications of experimental investigations and clinical trials using stem cells in reconstructive urology have been summarized and critically reviewed.

RESULTS

Tissue engineering and autologous cell therapy techniques have been developed to generate prostheses for different urological tissues and organ systems. During the last decade, increasing numbers of studies have described stem cells in the context of therapeutic tools. The ability of adult and embryonic stem cells as well as progenitors to improve bladder wall architecture, improve renal tubule formation, or promote restoration of spermatogenesis or recovery of continence has been investigated in several animal models. Although results have been encouraging, only a myoblast-based therapy of incontinence has reached clinical trials.

CONCLUSIONS

Several populations of adult stem cells and progenitor cells have been studied as useful cellular sources in the treatment and reconstruction of urological organs. However, considerable basic research still needs to be performed to ensure the controlled differentiation and long-term fate of stem cells following transplantation.

[Regenerative medicine in andrology: tissue engineering and gene therapy as potential treatment options for penile deformations and erectile dysfunction]

Tissue engineering and gene therapy are currently investigated in animal studies for reconstructing penile tissue or treating erectile dysfunction. This review aims to ecamine these experimental efforts from the last years and tries to give a brief introduction to the basic methodology of these new techniques from the field of regenerative medicine.

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.

Tissue Engineering in Urology: Between Basic Research and Clinical Applications

Tissue engineering follows the principles of cell and tissue culture, cloning and stem cell production, and materials science to develop biological substitutes, which could repair and maintain normal function. The biomaterials must be able to control the structure and function of engineered tissue by interacting with both transplanted and host cells. Either natural or synthetic biodegradable materials have been used as cell delivery scaffolds. The stem cell field is also advancing rapidly, opening new options for regenerative medicine. In the genitourinary system, tissue engineering has been applied experimentally for the reconstitution of pelvis, ureter, bladder, urethra, penile corpora cavernosa and testis. This literature review underlines recent advances that have occurred in tissue engineering and describes their clinical repercussions, particularly in offering novel therapies in urogenital pathology.

Isolation of Primary Endothelial and Stromal Cell Cultures of the Corpus Cavernosum Penis for Basic Research and Tissue Engineering

OBJECTIVES

Primary cell cultures derived from the corpus cavernosum are frequently used as in vitro models to define cellular mechanisms involved in erectile function. However, previous studies often lack detailed isolation protocols or a precise characterisation of the culture composition excluding especially contaminating fibroblasts. This study aimed at critically analysing and reproducing reported isolation methods, as well as establishing new procedures to receive highly pure and morphologically differentiated endothelial, smooth muscle and fibroblastic cells derived from the human penis.

METHODS

We evaluated numerous isolation and enrichment techniques using cavernosal tissue from 57 patients. Assessment factors displayed the purity, cell yield, practicability and reproducibility. The purity in cultured cells was analysed using immunocytochemistry and Western blots.

RESULTS

An enzymatic protocol was established for the isolation and cultivation of cavernosal endothelial cells with an impressive purity of 98.0+/-0.8%. In contrast, already published nearly pure smooth muscle cell cultures were not reproducible in our laboratory. Meaningful evidence for an overwhelming presence of fibroblasts in these widely accepted pure smooth muscle cell cultures is presented.

CONCLUSION

Endothelial cell cultures derived from human corpora cavernosa are reproducible and reliable to serve for cell culture-based investigations of the endothelial dysfunction. The discrepancy in the purity of smooth muscle cell cultures might reflect laboratory and tissue source factors, lacking an exclusion of fibroblasts in other studies or changes in stromal phenotype under culture conditions. Further research is necessary to clarify a possible plasticity between smooth muscle cells and (myo)fibroblasts and assess functional properties.

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 and regenerative medicine: concepts for clinical application

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 aging population. Scientists in the field of regenerative medicine and tissue engineering apply 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. 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. This paper reviews recent advances that have occurred in regenerative medicine and describes applications of these new technologies that may offer novel therapies for patients with end-stage organ failure.

Formation of corporal tissue architecture in vivo using human cavernosal muscle and endothelial cells seeded on collagen matrices

We explored the feasibility of developing corporal tissue, consisting of human cavernosal smooth muscle and endothelial cells in vivo, using three-dimensional acellular collagen matrices, which are similar in architecture to native corpora. Acellular collagen matrices were derived from processed donor rabbit corpora, using cell lysis techniques. Human corpus cavernosal muscle and endothelial cells were seeded on the acellular matrices. A total of 80 matrices, 20 without cells and 60 with cells, were implanted subcutaneously in athymic mice. An additional 36 matrices seeded with cells were maintained in culture for up to 4 weeks. Hydroxyproline quantification, Western blot analysis, RT-PCR, and scanning electron microscopy of the matrices, with and without cells, were performed at various time points. Animals were killed 3 days and 1, 2, 3, 4, 6, and 8 weeks after implantation. Immunocytochemical and histological analyses were performed to confirm the muscle and endothelial phenotype. Organ bath studies were performed in order to determine the degree of tissue contraction. Western blot analysis detected alpha-actin, myosin, and tropomyosin proteins from human corporal smooth muscle cells. Expression of muscarinic acetylcholine receptor (mAChR) subtype m4 mRNA was demonstrated by RT-PCR from corporal muscle cells before and 8 weeks after seeding. The implanted matrices showed neovascularity into the sinusoidal spaces by 1 week after implantation. Increasing organization of smooth muscle and endothelial cells lining the sinusoidal walls was observed at 2 weeks and continued with time. The matrices were covered with the appropriate cell architecture 4 weeks after implantation. The matrices showed a stable collagen concentration over 8 weeks, as determined by hydroxyproline quantification. Immunocytochemical studies using alpha-actin and factor VIII antibodies confirmed the presence of corporal smooth muscle and endothelial cells, both in vitro and in vivo, at all time points. There was no evidence of cellular organization in the control matrices. Organ bath studies showed that the cell-seeded corporal tissue matrices responded to electrical field stimulation, whereas the unseeded implants failed to respond. This study demonstrates that human cavernosal smooth muscle and endothelial cells seeded on three-dimensional acellular collagen matrices derived from donor corpora are able to form well-vascularized corporal tissues in vivo.

Tissue engineering in urology: where are we going?

Tissue engineering in urology is a broad term used to describe the development of alternative tissue sources for diseased or dysfunctional native urologic tissue. This article reviews the recently published techniques involving synthetic and natural biodegradable matrices alone, known as "unseeded" scaffolds, and the latest data on "seeded" scaffolds, which are impregnated with cultured cells from urologic organs. Recent discoveries in reporter gene labeling of urologic tissue are discussed as a new method to identify and track the fates of these transplanted cells in vivo. This article also investigates how these bioengineering techniques are applied to synthetic and natural scaffolds, such as polyglycolic acid and porcine small intestine submucosa, to increase bladder capacity, repair urethral strictures, and replace corporal plaques in Peyronie's disease. Furthermore, recently published reports that these materials have been seeded with chondrocytes to create corporal rods for penile prostheses and stents for ureteral and urethral stricture disease are discussed. With these latest developments as a foundation, the future directions of tissue engineering in urology are presented.