Yoni Baert

What is the best cryopreservation protocol for human testicular tissue banking

STUDY QUESTION Is there a better alternative to the conventional cryopreservation protocols for human testicular tissue banking? SUMMARY ANSWER Uncontrolled slow freezing (USF) using 1.5 M dimethylsulphoxide (DMSO) and 0.15 M sucrose as cryoprotectants appears to be a user-friendly and efficient method for the cryopreservation of human testicular tissue. WHAT IS KNOWN ALREADY Currently, time-consuming controlled slow freezing (CSF) protocols that need expensive equipment are commonly used for human testicular tissue banking. USF and vitrification are cryopreservation techniques that were successfully applied in several animal models but need further exploration with human tissue. STUDY DESIGN, SIZE, DURATION Fragments (n = 160) of testicular tissue from 14 patients undergoing vasectomy reversal were assigned to a fresh control group or one of the following cryopreservation procedures: CSF using DMSO at a concentration of 0.7 or 1.5 M in the presence (+S) or absence of sucrose (-S), USF using either 0.7 or 1.5 M DMSO combined with sucrose, solid-surface vitrification (SSV) or direct cover vitrification (DCV). MATERIALS, SETTING, METHODS Light microscopic evaluations were performed to study apoptosis, germ cell proliferation ability, spermatogonial survival, coherence of the seminiferous epithelium and integrity of the interstitial compartment after cryopreservation. Ultrastructural alterations were studied by scoring cryodamage to four relevant testicular cell types. MAIN RESULTS AND THE ROLE OF CHANCE The USF 1.5 M DMSO + S protocol proved not solely to prevent cell death and to preserve seminiferous epithelial coherence, interstitial compartment integrity, SG and their potential to divide but also protected the testicular cell ultrastructure. A significant reduction in the number of SG per tubule from 21.4 ± 5.6 in control tissue to 4.9 ± 2.1, 8.2 ± 5.4, 11.6 ± 5.1, 8.8 ± 3.9, 12.6 ± 4.4 and 11.7 ± 5.7 was observed after cryopreservation combined with at least one other form of cryoinjury when using CSF 0.7 M DMSO -S, CSF 0.7 M DMSO + S, CSF 1.5 M DMSO + S, USF 0.7 M DMSO + S, SSV and direct cover vitrification (DCV), respectively (P < 0.001). LIMITATIONS, REASONS FOR CAUTION Supplementary research is required to investigate the effect on tissue functionality and to confirm this studys findings using prepubertal tissue. WIDER IMPLICATIONS OF THE FINDINGS An optimal cryopreservation protocol enhances the chances for successful fertility restoration. USF, being an easy and cost-effective alternative to CSF, would be preferable for laboratories in developing countries or whenever tissue is to be procured from a diseased child at a site distant from the banking facility.

Orthotopic grafting of cryopreserved prepubertal testicular tissue: in search of a simple yet effective cryopreservation protocol.

OBJECTIVE To investigate whether solid-surface vitrification (SSV) is an effective cryopreservation strategy regarding the integrity and function of prepubertal mouse testicular tissue. DESIGN Prospective experimental study. SETTING Academic research unit. ANIMAL(S) Mice. INTERVENTION(S) Testicular tissue from 5- to 10-day-old GFP(+) mice was cryopreserved with the use of a conventional uncontrolled slow freezing (USF) technique and SSV before intratesticular grafting in busulfan-treated GFP(-) mice. MAIN OUTCOME MEASURE(S) Ultrastructural cryoinjury to spermatogonial stem cells (SSCs) and somatic cells was assessed by electron microscopy. Tubular structure was evaluated by histology, and graft survival and spermatogenic recovery by immunohistochemistry. RESULT(S) The tubular morphology and the proportion of ultrastructural cryodamage were similar between vitrified and slow-frozen testicular fragments. Allografting of tissue after both USF and SSV resulted in a recovery of spermatogenesis similar to fresh samples. CONCLUSION(S) SSV resulted in success rates similar to USF in maintaining testicular cell ultrastructure, tubular morphology, and tissue function. These data provide further evidence that vitrification, being an inexpensive and simple technique, can be considered as an alternative for cryopreservation of prepubertal testicular tissue.

Exome sequencing reveals a nonsense mutation in TEX15 causing spermatogenic failure in a Turkish family

Infertility is a global healthcare problem, and despite long years of assisted reproductive activities, a significant number of cases remain idiopathic. Our currently restricted understanding of basic mechanisms driving human gametogenesis severely limits the improvement of clinical care for infertile patients. Using exome sequencing, we identified a nonsense mutation leading to a premature stop in the TEX15 locus (c.2130T>G, p.Y710*) in a consanguineous Turkish family comprising eight siblings in which three brothers were identified as infertile. TEX15 displays testis-specific expression, maps to chromosome 8, contains four exons and encodes a 2789-amino acid protein with uncertain function. The mutation, which should lead to early translational termination at the first exon of TEX15, co-segregated with the infertility phenotype, and our data strongly suggest that it is the cause of spermatogenic defects in the family. All three affected brothers presented a phenotype reminiscent of the one observed in KO mice. Indeed, previously reported results demonstrated that disruption of the orthologous gene in mice caused a drastic reduction in testis size and meiotic arrest in the first wave of spermatogenesis in males while female KO mice were fertile. The data from our study of one Turkish family suggested that the identified mutation correlates with a decrease in sperm count over time. A diagnostic test identifying the mutation in man could provide an indication of spermatogenic failure and prompt patients to undertake sperm cryopreservation at an early age.

Cryopreservation of testicular tissue or testicular cell suspensions: a pivotal step in fertility preservation.

BACKGROUND Germ cell depletion caused by chemical or physical toxicity, disease or genetic predisposition can occur at any age. Although semen cryopreservation is the first reflex for preserving male fertility, this cannot help out prepubertal boys. Yet, these boys do have spermatogonial stem cells (SSCs) that able to produce sperm at the start of puberty, which allows them to safeguard their fertility through testicular tissue (TT) cryopreservation. SSC transplantation (SSCT), TT grafting and recent advances in in vitro spermatogenesis have opened new possibilities to restore fertility in humans. However, these techniques are still at a research stage and their efficiency depends on the amount of SSCs available for fertility restoration. Therefore, maintaining the number of SSCs is a critical step in human fertility preservation. Standardizing a successful cryopreservation method for TT and testicular cell suspensions (TCSs) is most important before any clinical application of fertility restoration could be successful. OBJECTIVE AND RATIONALE This review gives an overview of existing cryopreservation protocols used in different animal models and humans. Cell recovery, cell viability, tissue integrity and functional assays are taken into account. Additionally, biosafety and current perspectives in male fertility preservation are discussed. SEARCH METHODS An extensive PubMED and MEDline database search was conducted. Relevant studies linked to the topic were identified by the search terms: cryopreservation, male fertility preservation, (immature)testicular tissue, testicular cell suspension, spermatogonial stem cell, gonadotoxicity, radiotherapy and chemotherapy. OUTCOMES The feasibility of fertility restoration techniques using frozen-thawed TT and TCS has been proven in animal models. Efficient protocols for cryopreserving human TT exist and are currently applied in the clinic. For TCSs, the highest post-thaw viability reported after vitrification is 55.6 ± 23.8%. Yet, functional proof of fertility restoration in the human is lacking. In addition, few to no data are available on the safety aspects inherent to offspring generation with gametes derived from frozen-thawed TT or TCSs. Moreover, clarification is needed on whether it is better to cryopreserve TT or TCS. WIDER IMPLICATIONS Fertility restoration techniques are very promising and expected to be implemented in the clinic in the near future. However, inter-center variability needs to be overcome and the gametes produced for reproduction purposes need to be subjected to safety studies. With the perspective of a future clinical application, there is a dire need to optimize and standardize cryopreservation and safety testing before using frozen-thawed TT of TCSs for fertility restoration.

Derivation and characterization of a cytocompatible scaffold from human testis

STUDY QUESTION Is it possible to derive a scaffold from human testis for the purpose of tissue engineering and regenerative medicine? SUMMARY ANSWER We developed a method to produce a cytocompatible decellularized testicular matrix (DTM) while maintaining the native tissue-specific characteristics and components. WHAT IS KNOWN ALREADY The potential benefits of tissue-specific scaffolds consisting of naturally-derived extracellular matrix (ECM) have been demonstrated using a wide variety of animal and human tissue sources. However, so far, testis scaffolds have never been considered for constructive remodelling purposes. STUDY DESIGN, SIZE, DURATION Human cadaveric testicular tissue was exposed for 24 or 48 h to 1% Triton X-100 and/or 1% sodium dodecyl sulphate (SDS). Acellular samples were used for further scaffold characterization purposes. PARTICIPANTS/MATERIALS, SETTING, METHODS The extent of decellularization was evaluated by histology. Confirmation of cell removal in DTM was done by a DNA quantification technique. Retention of testicular tissue-specific characteristics was evaluated by mass spectrometry, immunohistochemistry, Alcian blue staining and scanning electron microscopy. Soluble toxicity and testicular cell attachment was assessed to check the cytocompatibility of DTM scaffolds. MAIN RESULTS AND THE ROLE OF CHANCE Histological analysis showed that DTM could be obtained by mechanical agitation in 1% SDS for 24 h. The resulting DTM was found to be clear of cells while retaining the typical three-dimensional structure and the major components of the native tissue scaffold, including collagen type I and IV, fibronectin, laminin and glycosaminoglycans. In addition, using proteomic analysis, we revealed numerous additional ECM proteins in DTM, indicating its complex nature. The mass spectrometry data were deposited to the ProteomeXchange with identifier PXD001524. Importantly, we demonstrated that DTM scaffolds are not cytotoxic, as evidenced by MTT assay not showing an aberrant fibroblast proliferation activity after indirect exposure, and support testicular cell attachment and infiltration. LIMITATIONS, REASONS FOR CAUTION The functionality of human testicular cells in DTM needs to be investigated. WIDER IMPLICATIONS OF THE FINDINGS Our results suggest that the insights into the molecular composition of the testicular ECM provide new clues for the unravelling of its important yet poorly understood role in regulating testicular function, and DTM-based bioscaffolds are promising components for the development of human in vitro spermatogenesis as a treatment for various types of male fertility disorders.

Cryopreservation of testicular tissue before long-term testicular cell culture does not alter in vitro cell dynamics

OBJECTIVE To assess whether testicular cell dynamics are altered during long-term culture after testicular tissue cryopreservation. DESIGN Experimental basic science study. SETTING Reproductive biology laboratory. PATIENT(S) Testicular tissue with normal spermatogenesis was obtained from six donors. INTERVENTION(S) None. MAIN OUTCOME MEASURE(S) Detection and comparison of testicular cells from fresh and frozen tissues during long-term culture. RESULT(S) Human testicular cells derived from fresh (n = 3) and cryopreserved (n = 3) tissues were cultured for 2 months and analyzed with quantitative reverse-transcription polymerase chain reaction and immunofluorescence. Spermatogonia including spermatogonial stem cells (SSCs) were reliably detected by combining VASA, a germ cell marker, with UCHL1, a marker expressed by spermatogonia. The established markers STAR, ACTA2, and SOX9 were used to analyze the presence of Leydig cells, peritubular myoid cells, and Sertoli cells, respectively. No obvious differences were found between the cultures initiated from fresh or cryopreserved tissues. Single or small groups of SSCs (VASA(+)/UCHL1(+)) were detected in considerable amounts up to 1 month of culture, but infrequently after 2 months. SSCs were found attached to the feeder monolayer, which expressed markers for Sertoli cells, Leydig cells, and peritubular myoid cells. In addition, VASA(-)/UCHL1(+) cells, most likely originating from the interstitium, also contributed to this monolayer. Apart from Sertoli cells, all somatic cell types could be detected throughout the culture period. CONCLUSION(S) Testicular tissue can be cryopreserved before long-term culture without modifying its outcome, which encourages implementation of testicular tissue banking for fertility preservation. However, because of the limited numbers of SSCs available after 2 months, further exploration and optimization of the culture system is needed.

Exogenous administration of recombinant human FSH does not improve germ cell survival in human prepubertal xenografts

In a previous study, meiotic activity was observed in human intratesticular xenografts from peripubertal patients. However, full spermatogenesis could not be established. The present study aimed to evaluate whether the administration of recombinant human FSH could improve the spermatogonial survival and the establishment of full spermatogenesis in intratesticular human xenografts. Human testicular tissue was obtained from six boys (aged 2.5-12.5years). The testicular biopsy was fragmented and one fragment of 1.5-3.0mm(3) was transplanted to the testis of immunodeficient nude mice. Transplanted mice were assigned to different experimental groups to enable evaluation of the effects of FSH administration and freezing. The structural integrity of the seminiferous tubules, the spermatogonial survival and the presence of differentiated cells were evaluated by histology and immunohistochemistry. Freezing or administration of FSH did not influence tubule integrity and germ cell survival in human xenografts. Meiotic germ cells were observed in the xenografts. More tubules containing only Sertoli cells were observed in frozen-thawed grafts, and more tubules with meiotic cells were present in fresh grafts. There was no clear influence of FSH treatment on meiotic differentiation. Administration of FSH did not improve the establishment of full spermatogenesis after intratesticular tissue grafting.

A no-stop mutation in MAGEB4 is a possible cause of rare X-linked azoospermia and oligozoospermia in a consanguineous Turkish family

PurposeThe purpose of this study was to identify mutations that cause non-syndromic male infertility using whole exome sequencing of family cases.MethodsWe recruited a consanguineous Turkish family comprising nine siblings with male triplets; two of the triplets were infertile as well as one younger infertile brother. Whole exome sequencing (WES) performed on two azoospermic brothers identified a mutation in the melanoma antigen family B4 (MAGEB4) gene which was confirmed via Sanger sequencing and then screened for on control groups and unrelated infertile subjects. The effect of the mutation on messenger RNA (mRNA) and protein levels was tested after in vitro cell transfection. Structural features of MAGEB4 were predicted throughout the conserved MAGE domain.ResultsThe novel single-base substitution (c.1041A>T) in the X-linked MAGEB4 gene was identified as a no-stop mutation. The mutation is predicted to add 24 amino acids to the C-terminus of MAGEB4. Our functional studies were unable to detect any effect either on mRNA stability, intracellular localization of the protein, or the ability to homodimerize/heterodimerize with other MAGE proteins. We thus hypothesize that these additional amino acids may affect the proper protein interactions with MAGEB4 partners.ConclusionThe whole exome analysis of a consanguineous Turkish family revealed MAGEB4 as a possible new X-linked cause of inherited male infertility. This study provides the first clue to the physiological function of a MAGE protein.

Scaffold-Based and Scaffold-Free Testicular Organoids from Primary Human Testicular Cells

Organoid systems take advantage of the self-organizing capabilities of cells to create diverse multi-cellular tissue surrogates that constitute a powerful novel class of biological models. Clearly, the formation of a testicular organoid (TO) in which human spermatogenesis can proceed from a single-cell suspension would exert a tremendous impact on research and development, clinical treatment of infertility, and screening of potential drugs and toxic agents. Recently, we showed that primary adult and pubertal human testicular cells auto-assembled in TOs either with or without the support of a natural testis scaffold. These mini-tissues harboured both the spermatogonial stem cells and their important niche cells, which retained certain specific functions during long-term culture. As such, human TOs might advance the development of a system allowing human in vitro spermatogenesis. Here we describe the methodology to make scaffold-based and scaffold-free TOs.

Preparation of Scaffolds from Decellularized Testicular Matrix

Biological scaffolds composed of extracellular matrix (ECM) are typically derived by processes that involve decellularization of tissues or organs. Here we describe a simple and robust methodology for the preparation of decellularized testicular matrix (DTM) scaffolds with minimal damage to the native three-dimensional structure and tissue-specific ECM components. Such DTM scaffolds can help to gain a better insight into the molecular composition and function of testicular ECM and to develop new tissue engineering approaches to treat various types of male fertility disorders.