Differentiation of spermatogenic cells during in-vitro culture of testicular biopsy samples from patients with obstructive azoospermia: effect of recombinant follicle stimulating hormone

Use of assisted reproductive technologies (ARTs) to shorten the generational interval in ruminants: current status and perspectives

The challenges posed by climate change and increasing world population are stimulating renewed efforts for improving the sustainability of animal production. To meet such challenges, the contribution of genomic selection approaches, in combination with assisted reproductive technologies (ARTs), to spreading and preserving animal genetics is essential. The largest increase in genetic gain can be achieved by shortening the generation interval. This review provides an overview of the current status and progress of advanced ARTs that could be applied to reduce the generation time in both female and male of domestic ruminants. In females, the use of juvenile in vitro embryo transfer (JIVET) enables to generate offspring after the transfer of in vitro produced embryos derived from oocytes of prepubertal genetically superior donors reducing the generational interval and acceleration genetic gain. The current challenge is increasing in vitro embryo production (IVEP) from prepubertal derived oocytes which is still low and variable. The two main factors limiting IVEP success are the intrinsic quality of prepubertal oocytes and the culture systems for in vitro maturation (IVM). In males, advancements in ARTs are providing new strategies to in vitro propagate spermatogonia and differentiate them into mature sperm or even to recapitulate the whole process of spermatogenesis from embryonic stem cells. Moreover, the successful use of immature cells, such as round spermatids, for intracytoplasmic injection (ROSI) and IVEP could allow to complete the entire process in few months. However, these approaches have been successfully applied to human and mouse whereas only a few studies have been published in ruminants and results are still controversial. This is also dependent on the efficiency of ROSI that is limited by the current isolation and selection protocols of round spermatids. In conclusion, the current efforts for improving these reproductive methodologies could lead toward a significant reduction of the generational interval in livestock animals that could have a considerable impact on agriculture sustainability.

Molecular mechanisms of cellular dysfunction in testes from men with non-obstructive azoospermia

Male factor infertility affects 50% of infertile couples worldwide; the most severe form, non-obstructive azoospermia (NOA), affects 10-15% of infertile males. Treatment for individuals with NOA is limited to microsurgical sperm extraction paired with in vitro fertilization intracytoplasmic sperm injection. Unfortunately, spermatozoa are only retrieved in ~50% of patients, resulting in live birth rates of 21-46%. Regenerative therapies could provide a solution; however, understanding the cell-type-specific mechanisms of cellular dysfunction is a fundamental necessity to develop precision medicine strategies that could overcome these abnormalities and promote regeneration of spermatogenesis. A number of mechanisms of cellular dysfunction have been elucidated in NOA testicular cells. These mechanisms include abnormalities in both somatic cells and germ cells in NOA testes, such as somatic cell immaturity, aberrant growth factor signalling, increased inflammation, increased apoptosis and abnormal extracellular matrix regulation. Future cell-type-specific investigations in identifying modulators of cellular transcription and translation will be key to understanding upstream dysregulation, and these studies will require development of in vitro models to functionally interrogate spermatogenic niche dysfunction in both somatic and germ cells.

3D bioprinting for organ and organoid models and disease modeling

INTRODUCTION

3D printing, a versatile additive manufacturing technique, has diverse applications ranging from transportation, rapid prototyping, clean energy, and medical devices.

AREAS COVERED

The authors focus on how 3D printing technology can enhance the drug discovery process through automating tissue production that enables high-throughput screening of potential drug candidates. They also discuss how the 3D bioprinting process works and what considerations to address when using this technology to generate cell laden constructs for drug screening as well as the outputs from such assays necessary for determining the efficacy of potential drug candidates. They focus on how bioprinting how has been used to generate cardiac, neural, and testis tissue models, focusing on bio-printed 3D organoids.

EXPERT OPINION

The next generation of 3D bioprinted organ model holds great promises for the field of medicine. In terms of drug discovery, the incorporation of smart cell culture systems and biosensors into 3D bioprinted models could provide highly detailed and functional organ models for drug screening. By addressing current challenges of vascularization, electrophysiological control, and scalability, researchers can obtain more reliable and accurate data for drug development, reducing the risk of drug failures during clinical trials.

Human in vitro spermatogenesis as a regenerative therapy - where do we stand?

Spermatogenesis involves precise temporal and spatial gene expression and cell signalling to reach a coordinated balance between self-renewal and differentiation of spermatogonial stem cells through various germ cell states including mitosis, and meiosis I and II, which result in the generation of haploid cells with a unique genetic identity. Subsequently, these round spermatids undergo a series of morphological changes to shed excess cytoplast, develop a midpiece and tail, and undergo DNA repackaging to eventually form millions of spermatozoa. The goal of recreating this process in vitro has been pursued since the 1920s as a tool to treat male factor infertility in patients with azoospermia. Continued advances in reproductive bioengineering led to successful generation of mature, functional sperm in mice and, in the past 3 years, in humans. Multiple approaches to study human in vitro spermatogenesis have been proposed, but technical and ethical obstacles have limited the ability to complete spermiogenesis, and further work is needed to establish a robust culture system for clinical application.

Actions and Roles of FSH in Germinative Cells

Follicle stimulating hormone (FSH) is produced by the pituitary gland in a coordinated hypothalamic-pituitary-gonadal (HPG) axis event, plays important roles in reproduction and germ cell development during different phases of reproductive development (fetal, neonatal, puberty, and adult life), and is consequently essential for fertility. FSH is a heterodimeric glycoprotein hormone of two dissociable subunits, α and β. The FSH β-subunit (FSHβ) function starts upon coupling to its specific receptor: follicle-stimulating hormone receptor (FSHR). FSHRs are localized mainly on the surface of target cells on the testis and ovary (granulosa and Sertoli cells) and have recently been found in testicular stem cells and extra-gonadal tissue. Several reproduction disorders are associated with absent or low FSH secretion, with mutation of the FSH β-subunit or the FSH receptor, and/or its signaling pathways. However, the influence of FSH on germ cells is still poorly understood; some studies have suggested that this hormone also plays a determinant role in the self-renewal of germinative cells and acts to increase undifferentiated spermatogonia proliferation. In addition, in vitro, together with other factors, it assists the process of differentiation of primordial germ cells (PGCLCs) into gametes (oocyte-like and SSCLCs). In this review, we describe relevant research on the influence of FSH on spermatogenesis and folliculogenesis, mainly in the germ cell of humans and other species. The possible roles of FSH in germ cell generation in vitro are also presented.

Recellularization of testicular feminization testis in C57bl6 as a natural bioreactor for creation of cellularized seminiferous tubules: an experimental study

We determined histological aspects of implanted human decellularized testicular matrix (DTM) in C57BL6 as a primitive step for further testis tissue engineering. A total of 4 immature human testicles were obtained after bilateral orchiectomy from patients with testicular feminization syndrome. The optimal decellularization protocol was determined and the efficacy of decellularization was evaluated in two of the testicles. The remaining scaffolds were cut in 3 × 3 mm³ pieces and implanted between the tight muscles in 32 C57BL6. Biopsies were taken at 2, 4, 8, and 24 weeks postoperatively and stained with PLZF, protamine, and tekt1 markers. Histological examination of DTMs confirmed complete absence of nuclear remnants and preservation of the extracellular matrix. Successful cell seeding was observed in all follow-ups confirmed by H&E and IHC staining that increased continuously during the whole study. Interestingly, spermatogonial stem-like cells were observed on decellularized implants that were well differentiated during the follow-ups. Natural bioreactors may provide a good cell source for testes tissue regeneration. This technique may provide testis bioscaffold as a three-dimensional platform and further successful cell seeding to produce a functional testis. This novel technique may be beneficial for patients who require testicular supplementation.

Stem cell-based therapies for fertility preservation in males: Current status and future prospects

With the decline in male fertility in recent years, strategies for male fertility preservation have received increasing attention. In this study, by reviewing current treatments and recent publications, we describe research progress in and the future directions of stem cell-based therapies for male fertility preservation, focusing on the use of spermatogonial stem cells (SSCs), SSC niches, SSC-based testicular organoids, other stem cell types such as mesenchymal stem cells, and stem cell-derived extracellular vesicles. In conclusion, a more comprehensive understanding of the germ cell microenvironment, stem cell-derived extracellular vesicles, and testicular organoids will play an important role in achieving male fertility preservation.

Spermatogonial Stem Cells for In Vitro Spermatogenesis and In Vivo Restoration of Fertility

Spermatogonial stem cells (SSCs) are the only adult stem cells capable of passing genes onto the next generation. SSCs also have the potential to provide important knowledge about stem cells in general and to offer critical in vitro and in vivo applications in assisted reproductive technologies. After century-long research, proof-of-principle culture systems have been introduced to support the in vitro differentiation of SSCs from rodent models into haploid male germ cells. Despite recent progress in organotypic testicular tissue culture and two-dimensional or three-dimensional cell culture systems, to achieve complete in vitro spermatogenesis (IVS) using non-rodent species remains challenging. Successful in vitro production of human haploid male germ cells will foster hopes of preserving the fertility potential of prepubertal cancer patients who frequently face infertility due to the gonadotoxic side-effects of cancer treatment. Moreover, the development of optimal systems for IVS would allow designing experiments that are otherwise difficult or impossible to be performed directly in vivo, such as genetic manipulation of germ cells or correction of genetic disorders. This review outlines the recent progress in the use of SSCs for IVS and potential in vivo applications for the restoration of fertility.

Rebuilding the human testis in vitro

Increasing rates of male infertility have led to a greater need for relevant model systems to gain further insight into male fertility and its failings. Spermatogenesis and hormone production occur within distinct regions of the testis. Defined by specialized architecture and a diverse population of cell types, it is no surprise that disruption of this highly organized microenvironment can lead to infertility. To date, no robust in vitro system has facilitated full spermatogenesis resulting in the production of fertilization‐competent human spermatozoa. Here, we review a selection of current in vitro systems available for modelling the human testis microenvironment with focus on the progression of spermatogenesis and recapitulation of the testis microenvironment.

In vitro formation of the blood-testis barrier during long-term organotypic culture of human prepubertal tissue: comparison with a large cohort of pre/peripubertal boys

STUDY QUESTION

How does the formation of the blood-testis barrier (BTB), as reflected by the expression of connexin 43 and claudin 11 proteins during the pubertal transition period, take place in vitro compared to samples from a large cohort of pre/peripubertal boys?

SUMMARY ANSWER

The BTB connexin 43 and claudin 11 expression patterns appeared to be partially achieved in organotypic culture when compared to that in samples from 71 pre/peripubertal patients.

WHAT IS KNOWN ALREADY

Although alterations in the protein expression patterns of the BTB, whose main components are connexin 43 and claudin 11, are known to be associated with impaired spermatogenesis in mice and adult men, there is a lack of knowledge on its formation in pre-peripubertal human tissue both in vitro and in vivo. Moreover, despite Sertoli cell (SC) maturation during long-term organotypic culture of immature testicular tissue (ITT), initiation of spermatogenesis has not yet been achieved.

STUDY DESIGN, SIZE, DURATION

Histological sections from 71 pre-peripubertal patients were evaluated for the formation of the BTB acting as in vivo controls according to age, SC maturation, clinical signs of puberty and germ cell differentiation. Testicular tissue fragments retrieved from three prepubertal boys were cultured in a long-term organotypic system to analyze the BTB formation and expression pattern in correlation with SC maturation.

PARTICIPANTS/MATERIALS, SETTING, METHODS

Testicular histological sections from 71 patients aged 0-16 years who underwent a biopsy between 2005 and 2014 to preserve their fertility before gonadotoxic treatment were examined. Immunohistochemistry (IHC) results for connexin 43 and claudin 11 as BTB markers, using a semi-quantitative score for their expression, and for Anti-Mullerian hormone (AMH), as SC maturation marker, were analyzed. Germ cell differentiation was evaluated on Hematoxylin-Eosin sections. Tanner stages at the time of biopsy were recorded from medical files. A longitudinal analysis of connexin 43, claudin 11 and AMH expressions on immunohistological sections of organotypic cultured testicular tissue from three prepubertal boys who underwent a biopsy for fertility preservation was performed. Immunostaining was evaluated at culture Days 0, 1, 3, 10, 16, 27, 32, 53, 64 and 139 for two different types of culture media.

MAIN RESULTS AND THE ROLE OF CHANCE

Immunohistochemical control sections showed progressive maturation of SCs, as shown by the decrease in AMH expression, with increasing age (P ≤ 0.01) and the AMH expression was negatively correlated with the expression of connexin 43 and claudin 11 (P ≤ 0.01 for both proteins). Androgen receptor (AR) expression increased with age (P ≤ 0.01) and was significantly correlated with the expression of connexin 43 (P = 0.002) and claudin 11 (P = 0.03). A statistical correlation was also found between the reduction of AMH expression and both the advancement of Tanner stages (P ≤ 0.01) and the differentiation of germ cells (P ≤ 0.01). Furthermore, positive correlations between BTB formation (using connexin 43 and claudin 11 expression) and age (P ≤ 0.01 for both the proteins), higher Tanner stages (P ≤ 0.001 and P ≤ 0.01 for connexin 43 and claudin 11, respectively), and presence of more advanced germ cells (P ≤ 0.001 for both proteins) were observed. In the subanalysis on organotypic cultured ITT, where a significant decrease in AMH expression as a marker of SC maturation was already reported, we showed the onset of expression of connexin 43 at Day 16 (P ≤ 0.001) and a constant expression of claudin 11 from Days 0 to 139, for all three patients, without differences between the two types of culture media.

LARGE SCALE DATA

N/A.

LIMITATIONS REASONS FOR CAUTION

Accessibility of prepubertal human testicular tissue is a major limiting factor to the analysis of cultured tissue samples from a wide number of patients, as would be needed to assess the in vitro development of the BTB according to the age. The impossibility of performing longitudinal studies on in vivo BTB formation in the same patient prevents a comparison of the time needed to achieve effective BTB formation and protein expression patterns in vivo and in vitro.

WIDER IMPLICATIONS OF THE FINDINGS

To the best of our knowledge, this is the first report describing the expression of two BTB proteins in samples from a cohort of prepubertal and peripubertal boys, for the in vivo pattern, and in cultured ITT from a few prepubertal boys, for the in vitro evaluation. Since the formation of this barrier is essential for spermatogenesis and because little is known about its protein expression patterns and development in humans, a deeper understanding of the testicular microenvironment is essential to improve ITT in vitro culture conditions. The final aim is to restore fertility by acheiving in vitro differentiation of spermatogonial stem cells, using cryopreserved ITT collected before gonadotoxic therapies.

STUDY FUNDING AND COMPETING INTEREST(S)

Funding was received from Fonds National de la Recherche Scientifique de Belgique (Grant Télevie Nos. 7.4554.14F and 7.6511.16) and Fondation Salus Sanguinis. No conflict of interest has to be disclosed.

Influence of temperature, serum, and gonadotropin supplementation in short- and long-term organotypic culture of human immature testicular tissue

OBJECTIVE

To study how temperature, serum, and gonadotropin supplementation affect the organotypic culture of human immature testicular tissue (ITT) in vitro.

DESIGN

Experimental basic science study.

SETTING

Reproductive biology laboratory.

PATIENT(S)

ITT from 4 boys with cancer that had testicular tissue cryopreserved as part of their fertility preservation treatment.

INTERVENTION(S)

In vitro organotypic culture of ITT, exposed to different temperatures (37°C vs. 34°C), serum (fetal bovine serum [FBS] vs. Knockout Serum Replacement [KOS]), and gonadotropin supplementation (with and without FSH and LH).

MAIN OUTCOME MEASURE(S)

Characterization of the tissue was performed at days 0, 14, and 70 with the use of reverse-transcription quantitative polymerase chain reaction, terminal deoxynucleotide transferase-mediated dUTP nick-end labeling, histologic analysis by means of hematoxylin-eosin staining, and immunohistochemical staining. Hormonal secretion was determined at days 3, 14, 28, and 70 by means of immunofluorescent assay.

RESULT(S)

The 37°C conditions showed an accelerated loss of tubular morphology and higher intratubular apoptosis. KOS supplementation triggered the up-regulation of STAR, SOX9, DAZL, DDX4, PLZF, and UTF1, the percentage of SOX9+/androgen receptor (AR)-positive mature Sertoli cells at day 14, and testosterone secretion. Gonadotropin supplementation increased the numbers of both undifferentiated UTF1+ spermatogonia and premeiotic VASA+/SYCP3+ spermatogonia at day 14, and the number of SOX9+ Sertoli cells at day 70. The low SOX9+/AR+ colocalization, the disorganized pattern of ZO-1, and the progressive decrease of antimüllerian hormone secretion indicated inefficient Sertoli cell maturation in vitro.

CONCLUSION(S)

The 34°C condition in KOS showed the best results for the survival of both spermatogonia and Sertoli cells. FSH/LH supplementation also improved long-term survival of Sertoli cells and the maturation of spermatogonia up to meiotic initiation in short-term culture.

In vitro spermatogenesis: A century-long research journey, still half way around

BACKGROUND

Spermatogenesis is one of the most complicated cellular differentiation processes in a body. Researchers struggled to find and develop a micro-environmental condition that can support the process in vitro. Such endeavors can be traced back to a century ago and are yet continuing.

METHODS

Reports on in vitro spermatogenesis and related works were selected and classified into four categories based on the method used; organ culture, tubule culture, cell culture, and 3-dimensional cell culture methods. Each report was critically reviewed from the present point of view by authors who have been working on in vitro spermatogenesis with organ culture method over a decade.

RESULTS

The organ culture method has the longest history and is the most successful method, which produced fertile mouse sperm from spermatogonial stem cells. Formulation of the medium was a key factor, most importantly serum-derived substances. However, factors in the serum that induce and support spermatogenesis in the cultured tissue remain to be identified. In addition, the success of mouse spermatogenesis is yet to be applied to other animals. On looking into the history of cell culture method, it became clear that Sertoli cells as feeder cells play an important role. Even with Sertoli cells, however, spermatogenic development has been limited to small parts of spermatogenesis, a segmented period of meiotic prophase for instance. Recent developments of organoid or 3-dimensional culture techniques are promising but they still need further refinements.

CONCLUSION

The study of in vitro spermatogenesis progressed significantly over the last century. We need more work, however, to establish a culture system that can induce and maintain complete spermatogenesis of many if not all mammalian species.

Testicular organoids: a new model to study the testicular microenvironment in vitro?

BACKGROUND

In recent decades, a broad range of strategies have been applied to model the testicular microenvironment in vitro. These models have been utilized to study testicular physiology and development. However, a system that allows investigations into testicular organogenesis and its impact in the spermatogonial stem-cell (SSC) niche in vitro has not been developed yet. Recently, the creation of tissue-specific organ-like structures called organoids has resurged, helping researchers to answer scientific questions that previous in vitro models could not help to elucidate. So far, a small number of publications have concerned the generation of testicular organoids and their application in the field of reproductive medicine and biology.

OBJECTIVE AND RATIONALE

Here, we aim to elucidate whether testicular organoids might be useful in answering current scientific questions about the regulation and function of the SSC niche as well as germ cell proliferation and differentiation, and whether or not the existing in vitro models are already sufficient to address them. Moreover, we would like to discuss how an organoid system can be a better solution to address these prominent scientific problems in our field, by the creation of a rationale parallel to those in other areas where organoid systems have been successfully utilized.

SEARCH METHODS

We comprehensively reviewed publications regarding testicular organoids and the methods that most closely led to the formation of these organ-like structures in vitro by searching for the following terms in both PubMed and the Web of Science database: testicular organoid, seminiferous tubule 3D culture, Sertoli cell 3D culture, testicular cord formation in vitro, testicular morphogenesis in vitro, germ cell 3D culture, in vitro spermatogenesis, testicular de novo morphogenesis, seminiferous tubule de novo morphogenesis, seminiferous tubule-like structures, testicular in vitro model and male germ cell niche in vitro, with no restrictions to any publishing year. The inclusion criteria were based on the relation with the main topic (i.e. testicular organoids, testicular- and seminiferous-like structures as in vitro models), methodology applied (i.e. in vitro culture, culture dimensions (2D, 3D), testicular cell suspension or fragments) and outcome of interest (i.e. organization in vitro). Publications about grafting of testicular tissue, germ-cell transplantation and female germ-cell culture were excluded.

OUTCOMES

The application of organoid systems is making its first steps in the field of reproductive medicine and biology. A restricted number of publications have reported and characterized testicular organoids and even fewer have denominated such structures by this method. However, we detected that a clear improvement in testicular cell reorganization is recognized when 3D culture conditions are utilized instead of 2D conditions. Depending on the scientific question, testicular organoids might offer a more appropriate in vitro model to investigate testicular development and physiology because of the easy manipulation of cell suspensions (inclusion or exclusion of a specific cell population), the fast reorganization of these structures and the controlled in vitro conditions, to the same extent as with other organoid strategies reported in other fields.

WIDER IMPLICATIONS

By way of appropriate research questions, we might use testicular organoids to deepen our basic understanding of testicular development and the SSC niche, leading to new methodologies for male infertility treatment.

Fertility restoration with spermatogonial stem cells

PURPOSE OF REVIEW

This review evaluates the state of the art in terms of challenges and strategies used to restore fertility with spermatogonial stem cells retrieved from prepubertal boys affected by cancer. Although these boys do not yet produce spermatozoa, the only option to preserve their fertility is cryopreservation of spermatogonial stem cells in the form of testicular cell suspensions or whole tissue pieces. Different techniques have been described to achieve completion of spermatogenesis from human, spermatogonial stem cells but none is yet ready for clinical application. A crucial point to address is gaining a full understanding of spermatogonial stem cell niche pathophysiology, where germ cells undergo proliferation and differentiation. Various fertility restoration approaches will be presented depending on the presence of an intact niche, dissociated niche, or reconstituted niche.

RECENT FINDINGS

Testicular organoids open the way to providing further insights into the niche. They can recreate the three-dimensional architecture of the testicular microenvironment in vitro, allowing a large number of applications, from physiology to drug toxicity investigations.

SUMMARY

In addition to the full elucidation of the niche microenvironment, achieving fertility restoration from cryopreserved human spermatogonial stem cells implies overcoming other important challenges. Testicular organoids might prove to be essential tools to progress in this field.

In Vitro Spermatogenesis: How Far from Clinical Application?

Male infertility affects 7 % of the male population, and 10 % of infertile men are azoospermic. In these instances, using microsurgical testicular sperm extraction (m-TESE) and intra-cytoplasmic sperm injection (ICSI) helps a significant number of patients. However, in vitro differentiation of diploid germ cells to mature haploid germ cell has the potential to benefit many others, including pediatric cancer survivors who have previously cryopreserved their immature testicular tissue prior to starting gonadotoxic cancer treatment as well as men with spermatogenic arrest. This systematic review evaluates and summarizes half a century of researchers' efforts towards achieving in vitro spermatogenesis in mammalian species. A myriad of experimental assays and approaches has been developed using whole testis tissue or separated single cells from testis in two- or three-dimensional cell culture systems (2D versus 3D). Recent advances in the mammalian in vitro spermatogenesis, particularly in murine and nonhuman primate systems, hold promise towards translating the availability of in vitro spermatogenesis models in the human clinical setting in the near future.

Does Fluoride Affect Serum Testosterone and Androgen Binding Protein with Age-Specificity? A Population-Based Cross-Sectional Study in Chinese Male Farmers

Many studies have demonstrated that exposure to excess fluoride was associated with a variety of diseases. Little is known about the variation of testosterone (T) levels caused by fluoride exposure. The aim of this study is to explore the association of fluoride exposure and age with serum T and androgen-binding protein (ABP) levels in male farmers. A cross-sectional study was conducted in a county of Henan Province, China, including high fluoride exposure from drinking water villages and control villages. Male farmers aged 18-55 years old who lived in these villages were recruited by cluster sampling and divided into a higher fluoride exposure group (HFG) and a lower fluoride exposure group (LFG) according to the level of urinary fluoride. Levels of T and ABP in serum were measured using chemiluminescence immunoassay (CLIA) and enzyme-linked immunosorbent assay (ELISA) respectively. Markedly lower T levels were observed in male farmers from the HFG than in those from the LFG (t = 2.496, P < 0.05). Furthermore, younger farmers, 18-29 and 30-39 years old, may be the most likely to have lower T levels when exposed to fluoride (P < 0.05). No significant differences were observed in serum ABP levels in all male farmers between the two groups with different fluoride exposure. These results supported that excess fluoride exposure decreased serum T levels of male farmers with age-specificity.

More attention should be paid to the treatment of male infertility with drugs--testosterone: to use it or not?

Testosterone replacement is strictly contraindicated for the treatment of male infertility’ was the advanced view from the ‘2013 European Association of Urology (EAU) guidelines on male infertility’, and this view brings extensive concern and questions. Although sufficient numbers of well-performed and controlled clinical trials that provide evidence supporting drug treatment of male infertility are not available at present, the opportunity to prove that these drugs are effective should not be prevented, and rigorous examination of drug therapy should be encouraged and strengthened. Therefore, I believe the above conclusion in the EAU guidelines is poorly conceived.

Fact or fiction: In vitro spermatogenesis

Many previous studies have aimed at spermatogenesis of male murine germ cells in vitro, but no efficient system has been established yet that covers the entire process of mammalian spermatogenesis in a culture dish permanently. In this review, we report on the requirements of spermatogenesis and the current state of different culture methods using testicular tissue fragments, single cell suspensions or three-dimensional culture environments.

Assuring safety without animal testing: the case for the human testis in vitro

From 15 to 17 June 2011, a dedicated workshop was held on the subject of in vitro models for mammalian spermatogenesis and their applications in toxicological hazard and risk assessment. The workshop was sponsored by the Dutch ASAT initiative (Assuring Safety without Animal Testing), which aims at promoting innovative approaches toward toxicological hazard and risk assessment on the basis of human and in vitro data, and replacement of animal studies. Participants addressed the state of the art regarding human and animal evidence for compound mediated testicular toxicity, reviewed existing alternative assay models, and brainstormed about future approaches, specifically considering tissue engineering. The workshop recognized the specific complexity of testicular function exemplified by dedicated cell types with distinct functionalities, as well as different cell compartments in terms of microenvironment and extracellular matrix components. This complexity hampers quick results in the realm of alternative models. Nevertheless, progress has been achieved in recent years, and innovative approaches in tissue engineering may open new avenues for mimicking testicular function in vitro. Although feasible, significant investment is deemed essential to be able to bring new ideas into practice in the laboratory. For the advancement of in vitro testicular toxicity testing, one of the most sensitive end points in regulatory reproductive toxicity testing, such an investment is highly desirable.

Concise review: Spermatogenesis in an artificial three-dimensional system

Culture of spermatogonial stem cells has been performed under a variety of conditions. Most featured two-dimensional systems, with different types of sera, conditioned media, feeder layers, and growth factors. Some have used three-dimensional (3D) matrices produced from gelatin, collagen, or other material. In spite of their increasingly sophisticated composition, however, complete spermatogenesis in vitro has not yet been achieved. In the seminiferous tubules, spermatogenesis occurs in an environment where cells are embedded in a 3D structure with specific niches regulating each stage of germ cell maturation mediated by hormones and paracrine/autocrine factors. We have recently reported achievement of complete in vitro spermatogenesis of mouse testicular germ cells in a 3D culture system featuring a soft agar matrix. This review discusses the advantages of the 3D culture system for studying the spermatogenic process in its entirety. Also discussed are the steps necessary to expand the applicability of the 3D culture system to human germ cell development and determine the functionality of culture-produced spermatozoa for generating offspring.

Intracytoplasmic spermatid injection and in vitro maturation: fact or fiction?

Intracytoplasmic injection with testicular spermatozoa has become a routine treatment in fertility clinics. Spermatozoa can be recovered in half of patients with nonobstructive azoospermia. The use of immature germ cells for intracytoplasmic injection has been proposed for cases in which no spermatozoa can be retrieved. However, there are low pregnancy rates following intracytoplasmic injection using round spermatids from men with no elongated spermatids or spermatozoa in their testes. The in vitro culture of immature germ cells to more mature stages has been proposed as a means to improve this poor outcome. Several years after the introduction of intracytoplasmic injection with elongating and round spermatids, uncertainty remains as to whether this approach can be considered a safe treatment option. This review outlines the clinical and scientific data regarding intracytoplasmic injection using immature germ cells and in vitro matured germ cells.

Biotechnological approaches to the treatment of aspermatogenic men

Aspermatogenesis is a severe impairment of spermatogenesis in which germ cells are completely lacking or present in an immature form, which results in sterility in approximately 25% of patients. Because assisted reproduction techniques require mature germ cells, biotechnology is a valuable tool for rescuing fertility while maintaining biological fatherhood. However, this process involves, for instance, the differentiation of preexisting immature germ cells or the production/derivation of sperm from somatic cells. This review critically addresses four potential techniques: sperm derivation in vitro, germ stem cell transplantation, xenologous systems, and haploidization. Sperm derivation in vitro is already feasible in fish and mammals through organ culture or 3D systems, and it is very useful in conditions of germ cell arrest or in type II Sertoli-cell-only syndrome. Patients afflicted by type I Sertoli-cell-only syndrome could also benefit from gamete derivation from induced pluripotent stem cells of somatic origin, and human haploid-like cells have already been obtained by using this novel methodology. In the absence of alternative strategies to generate sperm in vitro, in germ cells transplantation fertility is restored by placing donor cells in the recipient germ-cell-free seminiferous epithelium, which has proven effective in conditions of spermatogonial arrest. Grafting also provides an approach for ex-vivo generation of mature sperm, particularly using prepubertal testis tissue. Although less feasible, haploidization is an option for creating gametes based on biological cloning technology. In conclusion, the aforementioned promising techniques remain largely experimental and still require extensive research, which should address, among other concerns, ethical and biosafety issues, such as gamete epigenetic status, ploidy, and chromatin integrity.

Clinical review: Present and future prospects of male fertility preservation for children and adolescents

CONTEXT

Rapid progress in fertility preservation strategies has led to the investigation of ways in which fertile gametes could be generated from cryopreserved immature testicular tissue. Childhood cancer patients remain the major group that can benefit from these techniques. Other potential candidates include patients undergoing gonadectomy and patients with Klinefelter's syndrome and cryptorchid testes. This review aims to present an overview of the current state of knowledge in experimental germ cell transplantation, testicular tissue transplantation, and germ cell culture as fertility preservation methods for males.

METHODOLOGY

We included English articles published in PubMed as well as personal files with the focus on studies including human or nonhuman material.

MAIN FINDINGS

Germ cell and testicular tissue transplantation demonstrate clinical options to mature germ cells from immature primate testicular tissue. The most promising approach involves autologous grafting of immature testicular tissue, whereas germ cell maturation in vitro provides the best strategies to overcome problems of cancer contamination in cryopreserved testicular tissue. Three-dimensional and organ culture systems offer the possibility to differentiate immature male germ cells up to the stage of elongated spermatids. Further characterization of early germ cell development in humans is needed to modify these systems for clinical use.

Quantitative analysis of cellular proliferation and differentiation of the human seminiferous epithelium in vitro

The aim of the present work was to quantitate the temporal and stage-specific effects of follicle-stimulating hormone (FSH) and testosterone on the proliferation and differentiation capacities of the human seminiferous epithelium. Seminiferous tubule fragments were kept in culture for 28 days and 5-bromo-2'-deoxyuridine incorporation was used to determine cell proliferation. Data demonstrated a gradual loss of germ cells during the culture period, no decrease in Sertoli cell numbers, and maintenance of the general architecture of the seminiferous tubules. Both FSH and testosterone increased germ cell survival, spermatogonia proliferation, and germ cell differentiation, especially during the first week of culture. At the end of the first week, differentiation of spermatocytes was observed, especially when 50 IU/L FSH and 1 µmol/L testosterone were used. In conclusion, using this methodology, it was possible to quantify germ cell proliferation and differentiation, in a reproducible way, with results compatible with the timing of human spermatogenesis in vivo.

Detection of human cytomegalovirus in motile spermatozoa and spermatogenic cells in testis organotypic culture

Background

The presence of human cytomegalovirus (HCMV) in male genital tract suggests its vertical transmission with spermatozoa and the development of a potentially dangerous fetal infection. The objective of the present study was to evaluate the possibility of intracellular HCMV localization in male germ cells and to examine the effect of the virus on human spermatogenesis.

Methods

Semen samples from 91 infertile and 47 fertile men were analyzed. HCMV was detected by real time PCR, rapid culture method and PCR in situ. Human testis organotypic culture and quantitative karyological analysis were used to investigate viral effects on spermatogenesis. Localization of HCMV in immature germ cells and spermatozoa was studied by immunostaining with monoclonal antibodies and ultrastructural analysis of infected organotypic culture.

Results

Viral DNA was detected in 12.3% samples of motile spermatozoa, while infectious activity only in 2.9% infertile and fertile men without statistically significant intergroup difference. According to PCR in situ, the mean percentage of infected cell in both groups was 1.5% (0.25%-15%), which can serve as a criterion for evaluating the risk of HCMV transmission. In HCMV-infected organotypic culture viral antigens were identified in spermatides on day 4, in spermatogonia and spermatocytes on day 8, and in spermatozoa on day 14. Empty and full capsides and virions were visualized in germ cells by electron microscopy. The number of cells before introduction in culture was taken for 100%. On day 14 infected culture contained 36.8% spermatogonia, 18.7% spermatocytes, 27.6% round spermatides and 42.5% elongated spermatides; in comparison with 82.2%, 51.5%, 70.4% and 65.7% in uninfected culture, respectively (all p < 0.05). There were no changes in the number and viability of spermatozoa.

Conclusions

HCMV was detected in male germ cells, both in sperm samples and in testis organotypic culture. The virus may infect immature germ cells which develop to mature HCMV-carrying spermatozoa. A considerable decrease in the number of immature germ cells indicates that HCMV produces a direct gametotoxic effect and can contribute to male infertility.

Evaluation of in vitro spermatogenesis using poly(D,L-lactic-co-glycolic acid) (PLGA)-based macroporous biodegradable scaffolds

Successful in vitro differentiation of spermatogenic cells into spermatids appears to offer extremely attractive potential for the treatment of impaired spermatogenesis and male infertility. Experimental evidence indicates that biocompatible polymers may improve in vitro reconstitution and regeneration of tissues of various origins. Here, we fabricated highly porous biodegradable poly(D,L-lactic-co-glycolic acid) or PLGA co-polymer scaffolds by combining the gas-foaming and salt-leaching methods, using ammonium bicarbonate as a porogen, which allowed us to generate polymer scaffolds with a high density of interconnected pores of 400-500 µm in average diameter, concomitant with a high malleability to mould a wide range of temporal tissue scaffolds requiring a specific shape and geometry. The PLGA scaffolds were biocompatible and biodegradable, as evidenced by the fact that they survived almost 3 month long subcutaneous xenografting into immunodeficient host mice and became easily destroyable after recovery. Immature rat testicular cells that were seeded onto the surface of the scaffold exhibited about 65% seeding efficiency and up to 75% viability after 18 days in culture. Furthermore, our scaffolds enhanced the proliferation and differentiation of spermatogenic germ cells to a greater extent than conventional in vitro culture methods, such as monolayer or organ culture. Taken together, an implication of the present findings is that the PLGA-based macroporous scaffold may provide a novel means by which spermatocytes could be induced to differentiate into presumptive spermatids.

Differentiation of human round spermatids into motile spermatozoa through in vitro coculture with Vero cells

Purpose

This study was undertaken to examine whether human early round spermatids will differentiate in an in vitro coculture with Vero cells.

Methods

A total of 1450 and 400 isolated early round spermatids mechanically collected from two non-obstructive and three obstructive azoospermic men with a normal karyotype were cocultured on Vero cell monolayers in minimum essential medium plus 10% fetal bovine serum, with or without 50 or 100 IU/L FSH and 1 or 10 μmol/L testosterone, at 32.5°C, in an environment of 5% CO₂ in air. Morphological changes of the spermatids were observed microscopically.

Results

After 7 days of coculture, almost half (40-50%) of the round spermatids from both non-obstructive and obstructive azoospermic men resumed spermiogenesis in vitro. Only cells from the latter patients gave rise to spermatozoa, a few of which had a motile flagellum. Low concentrations of FSH and testosterone increased the percentage of in vitro spermiogenesis.

Conclusions

Isolated round spermatids can resume spermiogenesis in vitro when cocultured on a Vero cell monolayer.

New horizons for in vitro spermatogenesis? An update on novel three-dimensional culture systems as tools for meiotic and post-meiotic differentiation of testicular germ cells

Culture and differentiation of male germ cells has been performed for various purposes in the past. To date, none of the studies aimed at in vitro spermatogenesis has resulted in a sufficient number of mature gametes. Numerous studies have revealed worthy pieces of information, building up a body of information on conditions that are required to maintain and mature male germ cells in vitro. In this review, we report on previously published and unpublished experiments addressing murine germ cell differentiation in three-dimensional (3D) in vitro culture systems. In a systematic set of experiments, we examined the influence of two different matrices (soft agar and methylcellulose) as well as the need for gonadotrophin support. For the first time, we demonstrate that pre-meiotic male germ cells [revealed by the absence of meiotic marker expression (e.g. Boule)] obtained from immature mice pass through meiosis in vitro. After several weeks of culture, we obtained morphologically normal spermatozoa embedded in the matrix substance. Complete maturation relied on support from somatic testicular cells and the presence of gonadotrophins but appeared independent from the matrix in a 3D culture environment. Further research efforts are required to reveal the applicability of this culture technique for human germ cells and the functionality of the spermatozoa for generating offspring.

Hormonal regulation of spermatogenesis and spermiogenesis

Normal testicular function is dependent upon hormones acting through endocrine and paracrine pathways both in vivo and in vitro. Sertoli cells provide factors necessary for the successful progression of spermatogonia into spermatozoa. Sertoli cells have receptors for follicle stimulating hormone (FSH) and testosterone which are the main hormonal regulators of spermatogenesis. Hormones such as testosterone, FSH and luteinizing hormone (LH) are known to influence the germ cell fate. Their removal induces germ cell apoptosis. Proteins of the Bcl-2 family provide one signaling pathway which appears to be essential for male germ cell homeostasis. In addition to paracrine signals, germ cells also depend upon signals derived from Sertoli by direct membrane contact. Somatostatin is a regulatory peptide playing a role in the regulation of the proliferation of the male gametes. Activin A, follistatin and FSH play a role in germ cell maturation during the period when gonocytes resume mitosis to form the spermatogonial stem cells and differentiating germ cell populations. In vitro cultures systems have provided evidence that spermatogonia in advance stage of differentiation have specific regulatory mechanisms that control their fate. This review article provides an overview of the literature concerning the hormonal pathways regulating spermatogenesis.

Isolated spermatogonia protrude active pseudopodia in vitro

When dispersed spermatogenic cells obtained by enzymatic digestion from prepuberal mice, adult male mice, nonazoospermic men and normospermic men were observed live using Normarski optics, it was found that, respectively, 47.4%, 1.4%, 5.1%, and 2.4% of them protruded active pseudopodia. These cells were 8 to 10 mum in diameter, had a high N/C ratio, and had one to two prominent nucleoli that were close to a distinct nuclear membrane. They showed low alkaline phosphatase activities and homogeneous nuclear immunoreactive patterns using gamma-H2AX, which suggests that they were spermatogonia.

Effect of 2,3,7,8-tetrachlorodibenzo-p-dioxin on testicular spermatogenesis-related panels and serum sex hormone levels in rats

OBJECTIVES

To determine the detrimental role of tetrachlorodibenzo-p-dioxin (TCDD) in testicular histology, spermatogenesis-related panels and proteome, and serum sex hormone levels.

MATERIALS AND METHODS

In all, 40 male rats were divided into equal groups: a normal control (NC) group that received vehicle and saline, and a TCDD-treated (TT) group injected intraperitoneally with TCDD (one dose, 50 microg/kg body weight). The rats were killed 4 weeks after TCDD exposure and testicular weight, histopathology, proteome and variables related to spermatogenesis, and serum sex hormone levels were investigated.

RESULTS

TCDD induced a significant decrease in testicular weight, Johnsen's score, seminiferous tubular size, percentage of tubules containing sperm, sperm counts, germ cell counts and Sertoli cell index. In addition, there was a significant decrease in serum testosterone level (P < 0.01) and a remarkable increase in oestradiol (P < 0.01), follicle-stimulating hormone (P < 0.05) and luteinizing hormone (P < 0.05) levels in the TT group. The expression of six testicular proteins including testis-specific heat shock protein (Hsp70), protein disulphide isomerase A3 precursor, 3-phosphoglycerate dehydrogenase, nonmuscle myosin heavy-chain type B-like protein, and superoxide dismutase 1 were significantly up-regulated (P < 0.05-0.01). Interestingly, fertility protein SP22 and phosphatidylethanolamine-binding protein were down-regulated but this was only significant for fertility protein SP22 (P < 0.05).

CONCLUSION

TCDD induces marked histological changes in the testis, impairs variables related to spermatogenesis, and increases serum oestradiol levels but decreases testosterone levels. In particular, TCDD disturbs testicular proteome profiles in rats.

In vitro culture of testicular germ cells: regulatory factors and limitations

Spermatogenesis is regulated mainly by endocrine factors and also by testicular paracrine/autocrine growth factors. These factors are produced by Sertoli cells, germ cells, peritubular cells and interstitial cells, mainly Leydig cells and macrophages. The interactions and the ratio between Sertoli and germ cells in the seminiferous tubules ensure successful spermatogenesis. In order to culture spermatogonial stem cells (SSCs) in vitro, researchers tried to overcome some of the obstacles -- such as the low number of stem cells in the testis, absence of specific markers to identify SSCs -- in addition to difficulties in keeping the SSCs alive in culture. Recently, some growth factors important for the proliferation and differentiation of SSCs were identified, such as glial cell line derived neurotrophic factor (GDNF), stem cell factor (SCF) and leukemia inhibitory factor (LIF); also, markers for SSCs at different stages were reported. Therefore, some groups succeeded in culturing SSCs (under limitations), or more differentiated cells and even were able to produce in vitro germ cells from embryonic stem cells. Thus, success in culturing SSCs is dependent on understanding the molecular mechanisms behind self-renewal and differentiation. Culture of SSCs should be a good tool for discovering new therapeutic avenue for some infertile men or for patients undergoing chemotherapy/radiotherapy (pre-puberty or post-puberty).

In vitro differentiation of germ cells from nonobstructive azoospermic patients using three-dimensional culture in a collagen gel matrix

OBJECTIVE

To assess the effectiveness of the three-dimensional culture of spermatogenic cells in a collagen gel matrix from nonobstructive azoospermic patients and examine the relation between the success rate of in vitro spermatogenesis and serum FSH level as a diagnostic prediction.

DESIGN

Prospective study using radioimmunoassay, immunocytochemistry, and flow cytometry with primary cultured cells.

SETTING

Gynecologic clinics and human reproduction research laboratory.

PATIENT(S)

Primary culture of spermatogenic cells established from 18 nonobstructive azoospermic patients who underwent histologic diagnoses.

INTERVENTION(S)

Primary culture of spermatogenic cells in a collagen-based gel matrix, subjected to immunological and flow cytometric analyses.

MAIN OUTCOME MEASURE(S)

In vitro culture of spermatogenic cells was established in an extracellular milieu that more closely resembled the in vivo condition. The number of chromosomes in newly generated cells during culture was determined by fluorescence-activated cell sorter (FACS) and immunocytochemical analysis. Effects of FSH on the differentiation of the spermatogenic cells were measured.

RESULT(S)

Results of histologic studies indicated that 8 of 18 patients showed the spermatocyte arrest. Immunocytochemical and FACS analysis indicated that after 12 days in culture, haploid cells comprised 11%-37% of the cultured cell population with a characteristic expression of a cellular marker for spermatids. The serum level of FSH appeared to be closely correlated with an increase in the number of haploid cells in culture.

CONCLUSION(S)

The present three-dimensional culture in a collagen gel matrix provides a suitable means by which spermatocytes could be induced to differentiate into presumptive spermatids in vitro. In addition, the plasma FSH level could be a good indicator for the success of differentiation of cultured spermatogenic cells obtained from patients with spermatogenic arrest.

Human testis in organotypic culture: application for basic or clinical research

BACKGROUND

Over recent decades, recurring efforts have been devoted to developing testicular cell or tissue cultures for basic and clinical research. However, there remains much confusion, particularly concerning the fate of human germ cells in culture.

OBJECTIVE

To reassess the status of human testicular cell types as well as the ability of germ cells to divide and differentiate in organotypic culture.

METHODS

Human testicular fragments were maintained for 2 weeks in culture. The viability and functionality of testicular cells were assessed using light and electronic microscopy, apoptotic cell labelling, 5-bromo-2'-deoxyuridine (BrdU) incorporation, immunohistochemistry and quantitative PCR against specific cell markers.

RESULTS

A gradual loss of meiotic and post-meiotic germ cells occurred throughout the culture period, irrespective of the presence of gonadotrophins. However, all germ cell types remained traceable for up to 16 days, some still dividing and differentiating at a rate compatible with the in vivo situation. Good maintenance of the general architecture of the explants associated with clearly quantifiable levels of several somatic cell markers was observed.

CONCLUSION

Although this culture model is clearly unsuitable for preparing germ cells for therapeutic purposes, it does represent a most valuable tool for testing the effects of biological and chemical agents on testicular tissue.

Efforts to create an artificial testis: culture systems of male germ cells under biochemical conditions resembling the seminiferous tubular biochemical environment

Induction of meiotic and post-meiotic alterations of male germ cells in vitro has been the target of several research efforts since 1960. However, to date, the establishment of an ideal culture system in which spermatogonial stem cells can be maintained and directed to proliferate and undergo meiosis and complete spermiogenesis does not exist. This is attributed to the difficulties concerning the isolation and purification of defined subpopulations of germ cells and the establishment of male germ cell lines. In addition, there is no adequate knowledge regarding the optimal biochemical conditions that promote the survival and differentiation of germ cells in long-term cultures. This review focuses on the methodologies that have been proved sufficient to achieve differentiation of cultured male germ cells. Furthermore, the factors regulating spermatogenesis and the technical prerequisites to achieve differentiation of cultured male germ cells are described. Finally, the role of in vitro cultures of immature diploid germ cells in the therapeutic management of men negative for haploid cells in their testes and the subsequent potential genetic and epigenetic risks are discussed.

In vitro maturation of fresh and frozen-thawed mouse round spermatids

Both initiation and maintenance of spermatogenesis are hormonally regulated by follicle stimulating hormone (rFSH) and testosterone. Co-culture systems also have important roles in the maintenance of spermatogenic cells. In this study, the effects of FSH and testosterone, co-culture system with Vero cells and co-culture supplemented with the hormones for maturation of frozen-thawed spermatids were determined. Testicular cells were suspended from the testis of National Medical Research Institute (NMRI) male mice and divided into two parts. The first aliquot of suspension was allocated for using as fresh and the rest was quickly cryopreserved. The frozen specimens were thawed and washed using Dulbecco modified Eagle's minimum essential medium (DMEM) medium. The fresh specimens were cultured in four groups: control (cultured on DMEM with 10% FBS), hormone (cultured on a medium supplemented with rFSH and testosterone), co-culture (cultured on Vero cells) and co-culture + hormone (cultured on Vero cells combined with rFSH and testosterone). The frozen-thawed specimens were cultured accordingly. The number of spermatids was recorded daily and the survival rates of each group were evaluated using Trypan blue test. The results showed that the number of the elongating spermatids was increased during the first day of the culture of fresh hormone, co-culture and co-culture + hormone groups. Viability rates of all kinds of the spermatid reduced during the 96 h of culturing. Our findings showed that the addition of hormone could support cell viability better than the co-culture. They also confirmed that the fresh round spermatid cells can progress into elongating and elongated spermatid only within the first 2 days of the culture in hormone, co-culture and co-culture + hormone groups. In the frozen-thawed specimens no extra significant increase in the number of cells was observed.

Intracytoplasmic injection of spermatozoa and spermatogenic cells: its biology and applications in humans and animals

Intracytoplasmic sperm injection (ICSI) has become the method of choice to overcome male infertility when all other forms of assisted fertilization have failed. Animals in which ICSI has produced normal offspring include many species. Success rate with normal spermatozoa is well above 50% in the mouse but ICSI success rates in other animals have been low, ranging from 0.3 to 16.5%. Mouse ICSI revealed that spermatozoa that cannot participate in normal fertilization can produce normal offspring by ICSI, provided their nuclei are genomically intact. Human ICSI using infertile spermatozoa has been highly successful perhaps because of the intrinsic instability of human sperm plasma membrane. The health of children born after ICSI and other assisted fertilization techniques is of major concern. Careful analyses suggest that higher incidences of congenital malformations and/or low birth weights after assisted fertilization are largely attributable to parental genetic background and increased incidence of multiple births, rather than to the techniques of assisted fertilization. Since the physiological and nutritional environments of developing embryos may cause persisting alteration in DNA methylation, extreme caution must be exercised in handling gametes and embryos in vitro. In the mouse, round spermatid injection (ROSI) has been routinely successful but its use in humans is controversial. Whether human ROSI and assisted fertilization involving younger spermatogenic cells are medically safe must be the subject of further investigations.

Overcoming maturation arrest by in vitro spermatogenesis: search for the optimal culture system

In some men with nonobstructive azoospermia caused by germ cell maturation arrest, spermatogenesis can be reactivated in vitro, either by culturing segments of explanted seminiferous tubules or by coculturing isolated germ cells on monolayers of somatic cell lines. Further studies are needed to compare the efficacy of these two culture systems in terms of restoration of fertilizing ability of in vitro-formed gametes and to evaluate the safety of the clinical use of these cells in assisted reproduction treatment.

The effect of pure FSH administration in non-obstructive azoospermic men on testicular sperm retrieval

BACKGROUND

In cases of azoospermia due to impaired spermatogenesis, spermatozoa can be retrieved by sperm extraction (TESE) from testicular biopsy.

OBJECTIVE

To evaluate the efficacy of pure follicle-stimulating hormone (pFSH) on sperm recovery, and measure the predictive value of testicular histology.

STUDY DESIGN

In all, 108 patients were studied. These included those with Sertoli cell-only (n=16), focal spermatogenesis (n=36), maturation arrest (n=19) and hypospermatogenesis (n=37) in previous explorative biopsies. All had normal serum FSH, LH and testosterone levels. In 63 cases, 75IU pFSH were administered, either i.m. or s.c., three times a week, for 3 months and the control group (n=45) no treatment was given.

RESULTS

The sperm retrieval rate was 64% (40/63 pts.) in pFSH treated men versus 33% (15/45 pts.) in controls (P<0.01). In Sertoli cell-only patients, the rate was 2/7 (28%) versus 4/9 (44%) in controls and treated men, respectively (P>0.05); and 3/8 (37%) versus 5/11 (45%) in maturation arrest (P>0.05); 6/14 (42%) versus 18/23 (78%) in hypospermatogenesis (P<0.05); and 4/16 (25%) versus 13/20 (65%) in focal spermatogenesis (P<0.01). Treatment with pFSH also improved the quantity of retrieved spermatozoa compared to control values (P<0.05).

CONCLUSION

pFSH treatment improves the success of TESE for non-obstructive azoospermic men with normal FSH levels.

Pharmacological concentrations of follicle-stimulating hormone and testosterone improve the efficacy of in vitro germ cell differentiation in men with maturation arrest

OBJECTIVE

To examine whether in vitro differentiation of germ cells from men with maturation arrest is improved by augmenting FSH and T concentrations above the values effective in samples from men with normal spermatogenesis.

DESIGN

Prospective, controlled in vitro study.

SETTING

Private assisted reproduction centers and a university department.

PATIENT(S)

Men with meiotic or postmeiotic maturation arrest.

INTERVENTION(S)

Testicular spermatid extraction, in vitro culture of testicular biopsy samples, intraoocyte injection of elongated spermatids, embryo culture and transfer.

MAIN OUTCOME MEASURE(S)

Progression of in vitro germ cell differentiation, fertilization, and pregnancy outcomes with in vitro cultured germ cells.

RESULT(S)

In some cases of meiotic and postmeiotic maturation arrest, more advanced germ cell stages were achieved by in vitro culture in the presence of 500 IU/L FSH as compared with 50 IU/L FSH. The beneficial effect of 500 IU/L FSH was further potentiated by a simultaneous increase of T concentration from 1 to 10 microM. Fertilizations with germ cells recovered after incubation with these pharmacological hormone concentrations gave rise to viable embryos and the births of five healthy babies.

CONCLUSION(S)

Pharmacological concentrations of FSH and T are beneficial for in vitro maturation of germ cells from some men with in vivo maturation arrest.

Assisted reproduction with in-vitro-cultured testicular spermatozoa in cases of severe germ cell apoptosis: a pilot study

BACKGROUND

Apoptosis-related cell damage is known to compromise success rates of assisted reproduction with ejaculated spermatozoa. This study was undertaken to determine whether the frequency of apoptosis-related cell damage and reproductive performance of testicular spermatozoa from men with non-obstructive azoospermia can be improved by in-vitro culture.

METHODS

Testicular tissue samples were cultured for 2 days in the presence of 50 IU/l FSH and 1 micromol/l testosterone. The frequency of spermatozoa showing DNA strand breakage and plasma membrane phosphatidylserine externalization was compared in before-culture and after-culture samples. The after-culture samples were used in assisted reproduction attempts.

RESULTS

In a group of 11 azoospermic patients with at least two previous intracytoplasmic sperm injection (ICSI) failures, the incidence of DNA strand breakage was high in living testicular spermatozoa from before-culture samples, but significantly lower in after-culture samples (96 versus 30%, P < 0.001). The same applied to the incidence of phosphatidylserine externalization in the motile sperm subpopulation from the before-culture and after-culture samples (83 versus 6%, P < 0.001). Seven ongoing clinical pregnancies (six with fresh embryos and one with cryopreserved embryos) were established.

CONCLUSIONS

Severe testicular sperm apoptosis may become a new indication for testicular tissue in-vitro culture before ICSI.

Developmental potential of elongating and elongated spermatids obtained after in-vitro maturation of isolated round spermatids

BACKGROUND

Round spermatid injections are associated with disappointing clinical outcomes, and although these cells have been shown to mature into late spermatids in vitro, the developmental potential of such gametes remains to be demonstrated.

METHODS

Round spermatids were isolated from 12 testicle samples of patients with obstructive azoospermia, hypoplasia, complete maturation arrest, and incomplete Sertoli cell-only syndrome. They were cultured for 7 days at 32 degrees C, 5% CO(2)in air, in microdrops of Vero cell-conditioned medium containing 10% synthetic serum substitute.

RESULTS

From the 238 round spermatids cultured, 25.2% attained the elongating and 5.5% the elongated spermatid stage (3-4 days per step). Relatively higher maturation rates were found in cases with obstructive azoospermia, but differences were significant only for elongated spermatids (9.3%). No differences were found in maturation rates between cases with non-obstructive azoospermia (4.3% of elongated spermatids). Experimental microinjections with elongating and elongated spermatids revealed a low fertilization rate (40.9%) but a normal blastocyst formation rate (60%).

CONCLUSIONS

Late spermatids resulting from in-vitro culture of round spermatids in conditioned medium, either in controls in cases with a spermiogenetic block, appeared able to successfully fertilize the human oocyte and elicit normal embryo development.

Genetic causes of male infertility: current concepts

Infertile men with severe spermatogenic defects and low or no sperm counts have a significantly higher rate of genetic abnormalities than fertile men. The fact that intracytoplasmic sperm injection can potentially bypass natural selection barriers to genetic disease transmission has brought a sobering but important impetus to recent research in the area of genetic infertility. Recent studies have focused on examining the prevalence of certain genetic defects in infertile men, analyzing the molecular basis of infertility in genetic disorders, and detecting new causes of genetic infertility. Several novel research findings deserve mention for their potential impact on genetic infertility. It has been demonstrated that elongated and round spermatids can be successfully injected into human oocytes and viable births obtained. Likewise, significant advances have been made in the arena of interspecies germ cell transplantation. Of some concern is the finding of a relationship between faulty DNA repair and infertility in men with severe testis failure. This review summarizes the recent genetic advances in these areas of male genetic infertility.

Present and future therapeutic strategies for idiopathic oligozoospermia

The effectiveness of medical treatment for idiopathic oligozoospermia (IO) has been at best doubtful until now and a logical consequence of this unsatisfactory situation has been the partial displacement of this approach by assisted reproduction techniques. This state of affairs has resulted from insufficient investigation, inappropriately designed clinical trials and consistent disregard for the principles of evidence-based medicine. Protocol-related shortcomings and wrong interpretation of the data available have also been some of the all too frequent problems encountered in this therapeutic approach. In this rather misty situation, it appears that, of the therapeutic agents used so far, follicle stimulating hormone (FSH) (mainly FSH-secretagogues) may exert some beneficial effects on a number of biological endpoints related to spermatogenesis and sperm maturation. The short and medium term prospects of medical treatment for IO rest mainly with improvement of investigative procedures to a higher degree of sophistication, with emphasis placed on identifying the causes rather than the results of dysfunction so that a better selection of candidates can be made. Moreover, the introduction of prognostic indices for evaluation of the beneficial effects of a therapeutic agent may be of paramount importance. Finally, a better assessment of the preparations available and, possibly, the introduction of new more specific agents may also be an important step forward in this field. This type of large-scale effort should not be left to individual investigators or special centres working independently, but it may come under the auspices of a central regulating agency so that undisputed results from large, multicentre and uniform studies might be obtained, if medical treatment is to remain a good option. In this context, it may also be emphasized that andrology's main task should always be to treat the male with the problem rather than his healthy female partner, whenever this is possible.

Diagnostic and therapeutic testis biopsy

Testicular biopsy has been traditionally used as a diagnostic tool in the management of infertility. With the advent of assisted reproductive technology, testicular biopsy is now used therapeutically to retrieve sperm for intracytoplasmic sperm injection (ICSI). The feasibility of testicular sperm extraction for ICSI is reviewed in this article. Although less invasive techniques such as testicular fine needle aspiration and percutaneous needle biopsy are efficacious, particularly in cases of obstructive azoospermia, studies in the current literature support that open testicular biopsy is a more reliable method to obtain testicular specimen. Different measures to reduce the complication rate of open testicular biopsy, including the application of microsurgical techniques, are addressed here. Other areas of recent development related to testicular biopsy that are reviewed include processing of testicular tissue, cryopreservation of retrieved spermatozoa, in vitro maturation of spermatozoa, and microinjection of immature spermatogenic precursor cells.