Three-Dimensional Culture of Mouse Spermatogonial Stem Cells Using A Decellularised Testicular Scaffold

Tissue engineering studies in male infertility disorder

Infertility is an important issue among couples worldwide which is caused by a variety of complex diseases. Male infertility is a problem in 7% of all men. In vitro spermatogenesis (IVS) is the experimental approach that has been developed for mimicking seminiferous tubules-like functional structures in vitro. Currently, various researchers are interested in finding and developing a microenvironmental condition or a bioartificial testis applied for fertility restoration via gamete production in vitro. The tissue engineering (TE) has developed new approaches to treat male fertility preservation through development of functional male germ cells. This makes TE a possible future strategy for restoration of male fertility. Although 3D culture systems supply the perception of the effect of cellular interactions in the process of spermatogenesis, formation of a native gradient of autocrine/paracrine factors in 3D culture systems have not been considered. These results collectively suggest that maintaining the microenvironment of testicular cells even in the form of a 3D-culture system is crucial in achieving spermatogenesis ex vivo. It is also possible to engineer the testicular structures using biomaterials to provide a supporting scaffold for somatic and stem cells. The insemination of these cells with GFs is possible for temporally and spatially adjusted release to mimic the microenvironment of the in situ seminiferous epithelium. This review focuses on recent studies and advances in the application of TE strategies to cell-tissue culture on synthetic or natural scaffolds supplemented with growth factors.

Biomaterials for Testicular Bioengineering: How far have we come and where do we have to go?

Traditional therapeutic interventions aim to restore male fertile potential or preserve sperm viability in severe cases, such as semen cryopreservation, testicular tissue, germ cell transplantation and testicular graft. However, these techniques demonstrate several methodological, clinical, and biological limitations, that impact in their results. In this scenario, reproductive medicine has sought biotechnological alternatives applied for infertility treatment, or to improve gamete preservation and thus increase reproductive rates in vitro and in vivo. One of the main approaches employed is the biomimetic testicular tissue reconstruction, which uses tissue-engineering principles and methodologies. This strategy pursues to mimic the testicular microenvironment, simulating physiological conditions. Such approach allows male gametes maintenance in culture or produce viable grafts that can be transplanted and restore reproductive functions. In this context, the application of several biomaterials have been proposed to be used in artificial biological systems. From synthetic polymers to decellularized matrixes, each biomaterial has advantages and disadvantages regarding its application in cell culture and tissue reconstruction. Therefore, the present review aims to list the progress that has been made and the continued challenges facing testicular regenerative medicine and the preservation of male reproductive capacity, based on the development of tissue bioengineering approaches for testicular tissue microenvironment reconstruction.

Mini Bioreactor Can Support In Vitro Spermatogenesis of Mouse Testicular Tissue

Objective

It was in the early 20^th century when the quest for in vitro spermatogenesis started. In vitro spermatogenesis is critical for male cancer patients undergoing gonadotoxic treatment. Dynamic culture system creates in vivo-like conditions. In this study, it was intended to evaluate the progression of spermatogenesis after testicular tissue culture in mini-perfusion bioreactor.

Materials and Methods

In this experimental study, 12 six-day postpartum neonatal mouse testes were removed and fragmented, placed on an agarose gel in parallel to bioreactor culture, and incubated for 8 weeks. Histological, molecular and immunohistochemical evaluations were carried out after 8 weeks.

Results

Histological analysis suggested successful maintenance of spermatogenesis in tissues grown in the bioreactor but not on agarose gel, possibly because the central region did not receive sufficient oxygen and nutrients, which led to necrotic or degenerative changes. Molecular analysis indicated that Plzf, Tekt1 and Tnp1 were expressed and that their expression did not differ significantly between the bioreactor and agarose gel. Immunohistochemical evaluation of testis fragments showed that PLZF, SCP3 and ACRBP proteins were expressed in spermatogonial cells, spermatocytes and spermatozoa. PLZF expression after 8 weeks was significantly lower (P<0.05) in tissues incubated on agarose gel than in the bioreactor, but there was no significant difference between SCP3 and ACRBP expression among the bioreactor and agarose gel culture systems.

Conclusion

This three-dimensional (3D) dynamic culture system can provide somewhat similar conditions to the physiological environment of the testis. Our findings suggest that the perfusion bioreactor supports induction of spermatogenesis for generation of haploid cells. Further studies will be needed to address the fertility of the sperm generated in the bioreactor system..

Effect of NMDA receptor agonist and antagonist on spermatogonial stem cells proliferation in 2- and 3- dimensional culture systems

BACKGROUND

The main purpose of this study was to investigate the effect of D-serine (DS) and Dizocilpine (MK-801) on the proliferation of spermatogonial stem cells (SSCs) in two-dimensional (2D) and three-dimensional (3D) culture systems.

METHODS AND RESULTS

The SSCs of male NMRI mice were isolated by enzymatic digestion and cultured for two weeks. Then, the identity of SSCs was validated by anti-Plzf and anti-GFR-α1 antibodies via immunocytochemistry (ICC). The proliferation capacity of SSCs was evaluated by their culture on a layer of the decellularized testicular matrix (DTM) prepared from mouse testis, as well as two-dimensional (2D) with different mediums. After two weeks of the initiation of proliferation culture on 3D and 2D medium, the pre-meiotic at the mRNA and protein levels were evaluated via qRT-PCR and flow cytometry methods, respectively. The results showed that the proliferation rate of SSCs in 3D culture with 50 mM glutamic acid and 20 mM D-serine was significantly different from other groups after 14 days treatment. mRNA expression levels of promyelocytic leukemia zinc finger (Plzf) in 3D cultures supplemented by 20 mM D-serine and 50 mM glutamic acid were considerably higher than the 3D control group (p < 0.001). The flow cytometry analysis revealed that the amount of Plzf in the 2D-culture groups of SSCs with 20 mM MK-801 was considerably lower compared to the 2D-culture control group (p < 0.001).

CONCLUSIONS

This study indicated that decellularized testicular matrix supplemented with D-serine and glutamic acid could be considered a promising vehicle to support cells and provide an appropriate niche for the proliferation of SSCs.

Formation of organoid-like structures in the decellularized rat testis

Objectives

In testis, the extracellular matrix (ECM) in addition to the supportive role for cells in the seminiferous epithelium, is also essential for the accurate functioning of these cells. Thus, using a decellularized testicular ECM (DTECM), as a scaffold for three-dimensional (3D) culture of testicular cells can mimic native ECM for studying in vitro spermatogenesis.

Materials and Methods

The rat testis was decellularized via perfusion of 0.5% sodium dodecyl sulfate (SDS) for 48 hr, followed by 1% Triton X-100 for 6 hr, and then 1% DNase I for 1 hr. The efficiency of decellularization was evaluated by histology, immunohistochemistry (IHC), scanning electron microscopy (SEM), and MTT test. The prepared scaffolds were recellularized with testicular cells and cultured and assessed with hematoxylin-eosin (H&E) staining after two weeks.

Results

Based on the H&E image, no trace of cell components could be observed in DTECM. IHC images demonstrated collagen types I and IV, laminin, and fibronectin were preserved. Masson's trichrome and alcian blue staining revealed that collagen and glycosaminoglycans (GAGs) were retained, and the SEM image indicated that 3D testicular architecture remained after the decellularization process. Based on the results of the MTT test, DTECM was cytocompatible, and H&E images represented that DTECM supports testicular cell arrangements in seminiferous tubule-like structures (STLSs) and organoid-like structures (OLSs).

Conclusion

The results showed that the applied protocol successfully decellularized the testis tissue of the rat. Therefore, these scaffolds may provide an appropriate vehicle for in vitro reconstruction of the seminiferous tubule.

Decellularization of Male Reproductive Tissue

Decellularized testicular matrix (DTM) enables researchers to focus on the specific composition of the testicular extracellular matrix (ECM) and elucidate its role in spermatogenesis. Furthermore, it provides the natural architectural arrangement that could guide the reorganization of dissociated testicular cells in vitro. This is a key consideration as the presence of an authentic nutritive and endocrine support has been proven to be essential for in vitro spermatogenesis, at least in the mouse (Oliver and Stukenborg in Andrology 8:825-834, 2020; Richer et al. in Andrology 12741, 2019). Hence, scaffolds of DTM could be harnessed for the development of a human in vitro spermatogenesis culture system, which is a missing link in male fertility preservation and could be a possible treatment for nonobstructive azoospermia (Gassei and Orwig in Steril 105:256-266, 2016).

Generation of a Highly Biomimetic Organoid, Including Vasculature, Resembling the Native Immature Testis Tissue

The creation of a testis organoid (artificial testis tissue) with sufficient resemblance to the complex form and function of the innate testis remains challenging, especially using non-rodent donor cells. Here, we report the generation of an organoid culture system with striking biomimicry of the native immature testis tissue, including vasculature. Using piglet testis cells as starting material, we optimized conditions for the formation of cell spheroids, followed by long-term culture in an air–liquid interface system. Both fresh and frozen-thawed cells were fully capable of self-reassembly into stable testis organoids consisting of tubular and interstitial compartments, with all major cell types and structural details expected in normal testis tissue. Surprisingly, our organoids also developed vascular structures; a phenomenon that has not been reported in any other culture system. In addition, germ cells do not decline over time, and Leydig cells release testosterone, hence providing a robust, tunable system for diverse basic and applied applications.

Impact of Porcine Pancreas Decellularization Conditions on the Quality of Obtained dECM

Due to the limited number of organ donors, 3D printing of organs is a promising technique. Tissue engineering is increasingly using xenogeneic material for this purpose. This study was aimed at assessing the safety of decellularized porcine pancreas, together with the analysis of the risk of an undesirable immune response. We tested eight variants of the decellularization process. We determined the following impacts: rinsing agents (PBS/NH₃·H₂O), temperature conditions (4 °C/24 °C), and the grinding method of native material (ground/cut). To assess the quality of the extracellular matrix after the completed decellularization process, analyses of the following were performed: DNA concentration, fat content, microscopic evaluation, proteolysis, material cytotoxicity, and most importantly, the Triton X-100 content. Our analyses showed that we obtained a product with an extremely low detergent content with negligible residual DNA content. The obtained results confirmed the performed histological and immuno-fluorescence staining. Moreover, the TEM microscopic analysis proved that the correct collagen structure was preserved after the decellularization process. Based on the obtained results, we chose the most favorable variant in terms of quality and biology. The method we chose is an effective and safe method that gives a chance for the development of transplant and regenerative medicine.

Comparison of two methods for prolong storage of decellularized mouse whole testis for tissue engineering application: An experimental study

Background

Biological scaffolds are derived by the decellularization of tissues or organs. Various biological scaffolds, such as scaffolds for the liver, lung, esophagus, dermis, and human testicles, have been produced. Their application in tissue engineering has created the need for cryopreservation processes to store these scaffolds.

Objective

The aim was to compare the two methods for prolong storage testicular scaffolds.

Materials and Methods

In this experimental study, 20 male NMRI mice (8 wk) were sacrificed and their testes were removed and treated with 0.5% sodium dodecyl sulfate followed by Triton X-100 0.5%. The efficiency of decellularization was determined by histology and DNA quantification. Testicular scaffolds were stored in phosphate-buffered saline solution at 4°C or cryopreserved by programmed slow freezing followed by storage in liquid nitrogen. Masson's trichrome staining, Alcian blue staining and immunohistochemistry, collagen assay, and glycosaminoglycan assay were done prior to and after six months of storage under each condition.

Results

Hematoxylin-eosin staining showed no remnant cells after the completion of decellularization. DNA content analysis indicated that approximately 98% of the DNA was removed from the tissue (p = 0.02). Histological evaluation confirmed the preservation of extracellular matrix components in the fresh and frozen-thawed scaffolds. Extracellular matrix components were decreased by 4°C-stored scaffolds. Cytotoxicity tests with mouse embryonic fibroblast showed that the scaffolds were biocompatible and did not have a harmful effect on the proliferation of mouse embryonic fibroblast cells.

Conclusion

Our results demonstrated the superiority of the slow freezing method for prolong storage of testicular scaffolds.

Advanced bioengineering of male germ stem cells to preserve fertility

In modern life, several factors such as genetics, exposure to toxins, and aging have resulted in significant levels of male infertility, estimated to be approximately 18% worldwide. In response, substantial progress has been made to improve in vitro fertilization treatments (e.g. microsurgical testicular sperm extraction (m-TESE), intra-cytoplasmic sperm injection (ICSI), and round spermatid injection (ROSI)). Mimicking the structure of testicular natural extracellular matrices (ECM) outside of the body is one clear route toward complete in vitro spermatogenesis and male fertility preservation. Here, a new wave of technological innovations is underway applying regenerative medicine strategies to cell-tissue culture on natural or synthetic scaffolds supplemented with bioactive factors. The emergence of advanced bioengineered systems suggests new hope for male fertility preservation through development of functional male germ cells. To date, few studies aimed at in vitro spermatogenesis have resulted in relevant numbers of mature gametes. However, a substantial body of knowledge on conditions that are required to maintain and mature male germ cells in vitro is now in place. This review focuses on advanced bioengineering methods such as microfluidic systems, bio-fabricated scaffolds, and 3D organ culture applied to the germline for fertility preservation through in vitro spermatogenesis.

Detection of Type I and III collagen in porcine acellular matrix using HPLC-MS

Acellular matrix (ACM) has been widely used as a biomaterial. As the main component of ACM, collagen type and content show influence on the material properties. In this research, the collagen in ACM from different tissues of pig were determined by detection of marker peptides. The marker peptides of Type I and III collagen were identified from the digested collagen standards using ions trap mass spectrometry (LCQ). The relationship between the abundance of marker peptide and collagen concentration was established using triple quadrupole mass spectrometer (TSQ). The contents of Type I and III collagen in ACM from different tissues were determined. The method was further verified by hydroxyproline determination. The results showed that, the sum of Type I and III collagen contents in the ACM from small intestinal submucosa, dermis and Achilles tendon of pig were about 87.59, 81.41 and 61.13%, respectively, which were close to the total collagen contents in these tissues. The results proved that this method could quantitatively detect the collagen with different types in the ACM of various tissues.