Protocol for isolation of spermatids from mouse testes

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.

Isolation of stage-specific spermatogenic cells by dynamic histone incorporation and removal in spermatogenesis

Due to the lack of an efficient in vitro spermatogenesis system, studies on mammalian spermatogenesis require the isolation of specific germ cell populations for further analyses. BSA gradient and elutriation have been used for several decades to purify testicular germ cells; more recently, flow cytometric cell sorting has become popular. Although each method has its advantages and disadvantages and is used depending on the purpose of the experiment, reliance on flow cytometric cell sorting is expected to be more prevalent because fewer cells can be managed. However, the currently used flow cytometric cell sorting method for testicular germ cells relies on karyotypic differences via DNA staining. Thus, it remains challenging to separate post-meiotic haploid cells (spermatids) according to their differentiation stage despite significant variations in morphology and chromatin state. In this study, we developed a method for finely separating testicular germ cells using VC mice carrying fluorescently tagged histones. This method enables the separation of spermatogonia, spermatocytes, and spermatids based on the intensity of histone fluorescence and cell size. Combined with a DNA staining dye, this method separates spermatids after elongation according to each spermiogenic stage. Although the necessity for a specific transgenic mouse line is less versatile, this method is expected to be helpful for the isolation of testicular germ cell populations because it is highly reproducible and independent of complex cell sorter settings and staining conditions.

An Improved Method for Purification of the Residual Bodies from the Seminiferous Tubules of Mice

Human fertility is declining in Western countries, and it is becoming increasingly clear that male infertility plays a pivotal role in the overall fertility decline. To understand the process that drives successful male germ cell maturation, the study of spermatogenesis of model organisms, such as mice, is essential. Residual bodies (RBs) play an important role in the last stages of spermatogenesis. They are formed at the time when post-meiotic spermatids undergo sequential differentiation steps so that the acrosome and flagellum are developed, the nucleus is markedly condensed, and the cytoplasm is lost. The masses of lost cytoplasm become RBs. Our recent work has shown that RB dynamics are highly sensitive to even small fertility defects. It was also noted that the transcriptome and proteome of RBs changes in response to spermatogenic defects. Thus, RBs represent an excellent and highly sensitive entity for studying male fertility. Previously published protocols for RB purification had some major limitations: they produced an RB fraction that was heavily contaminated with spermatozoa and erythrocytes or required tens of grams of starting material. In addition, most of the available protocols were developed for purification of RBs from rat testes. Here, we present a protocol that allows the isolation of 2.5-3 × 106 RBs from mouse testes with a purity of 98% from only 1 g of starting material. The purified material can be used for various downstream applications to study male fertility, such as transcriptome and proteome analyses, super-resolution microscopy, and electron and cryo-electron microscopy, amongst many others. © 2023 The Authors. Current Protocols published by Wiley Periodicals LLC. Basic Protocol: An improved method for purification of the residual bodies from the seminiferous tubules of mice.

Optimized protocol for isolation of germ cells from mouse testis by centrifugal elutriation

Germline development is challenging to study due to the diversity of cell types in mammalian testis. Here, we present an optimized protocol, namely centrifugal elutriation, that allows the simultaneous isolation of mouse germ cells at different stages with high purity within ∼2 h. This approach exploits the JE-5.0 centrifugal elutriation system that fractionates cells based on differential sedimentation gravity. We herein provide the optimized parameters and procedures for isolation of elongating spermatids, round spermatids, and pachytene spermatocytes from adult mouse testes.

For complete details on the use and execution of this protocol, please refer to Bao et al. (2018).

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Optimized protocol for efficient preparation of testicular single-cell suspension

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Rapid purification of three germ cell populations with high viability from mouse testes

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Easily scaled up and down depending on downstream applications

Publisher’s note: Undertaking any experimental protocol requires adherence to local institutional guidelines for laboratory safety and ethics.