Development of sperm vitrification protocols for two endangered salmonid species: the Adriatic grayling, Thymallus thymallus, and the marble trout, Salmo marmoratus

Cryopreservation: A Comprehensive Overview, Challenges, and Future Perspectives

Cryopreservation is the most prevalent method of long-term cell preservation. Effective cell cryopreservation depends on freezing, adequate storage, and correct thawing techniques. Recent advances in cryopreservation techniques minimize the cellular damage which occurs while processing samples. This article focuses on the fundamentals of cryopreservation techniques and how they can be implemented in a variety of clinical settings. The article presents a brief description of each of the standard cryopreservation procedures, such as slow freezing and vitrification. Alongside that, the membrane permeating and nonpermeating cryoprotectants are briefly discussed, along with current advancements in the field of cryopreservation and variables influencing the cryopreservation process. The diminution of cryoinjury incurred by the cell via the resuscitation process will also be highlighted. In the end application of cryopreservation techniques in many fields, with a special emphasis on stem cell preservation techniques and current advancements presented. Furthermore, the challenges while implementing cryopreservation and the futuristic scope of the fields are illustrated herein. The content of this review sheds light on various ways to enhance the output of the cell preservation process and minimize cryoinjury while improving cell revival.

Characteristics and Cryopreservation of Semen of Sex-Reversed Females of Salmonid Fish

Sex reversal has been used as a breeding strategy by salmonid fish to produce genetically and phenotypically single sex populations. Production of all-female fish has great importance for the creation of monosex female triploids of salmonid fish, which are valued for their sterility, lack of female maturation, and larger commercial size. Among salmonids, the majority of rainbow trout (Oncorhynchus mykiss) production is based on all-female production with a high proportion of all-female triploid production in Europe. The main aim of this review is to present the recent knowledge regarding sex-reversed females (SRFs) of salmonid fish. We discuss the methods of sex reversal as well as their effects on the morphology and histology of the reproductive tract. We focus on the characteristics of SRF semen as well as the factors determining semen quality. The lower quality of SRF sperm compared to that of normal males has resulted in the need for the artificial maturation of semen. Most importantly, methods of semen storage-both short-term and long-term (cryopreservation)-that can improve hatchery operations are presented with the special emphasis on recent progress in development of efficient cryopreservation procedures and use of cryopreserved semen in hatchery practice. Moreover, we also address the emerging knowledge concerning the proteomic investigations of salmonid sperm, focusing primarily on the proteomic comparison of normal male and SRF testicular semen and presenting changes in SRF rainbow trout sperm proteome after in vitro incubation in artificial seminal plasma.

Cryopreservation of human induced pluripotent stem cells by using a new CryoLogic vitrification method

Human induced pluripotent stem cells (hiPSCs) have the properties of differentiation potential and unlimited self-renewal. Developing efficient and highly safe methods to preserve hiPSCs is important due to they have demonstrated tremendous promise in disease etiology, drug discovery, and regenerative medicine applications. Traditionally, open systems for cell cryopreservation, such as conventional slow freezing and vitrification methods, were widespread application in the storage and transportation of hiPSCs. However, these two methods have such problems of low recovery rate and the risk of cross-contamination. Recently, closed systems for cell cryopreservation, such as CryoLogic Vitrification Method (CVM), were introduced to store and transport embryos. In this study, we developed a new friendly CVM by loading a small piece of hiPSCs colonies in the vitrification solution to the hook of Fiberplug to increase the cooling rate. To warm them, the CVM Fiberplug was immersed directly in a 37 °C warming solution for 1 min, and hiPSCs were then transferred to mTeSR1 medium. The result revealed that the new CVM had a high recovery rate and maintained the stemness and differentiation potential of hiPSCs. Our new CVM not only provide a safe way for hiPSCs preservation but also has a high survival rate in the storage of hiPSCs.

Breakthroughs and new horizons in reproductive biology of rare and endangered animal species

Because of higher extinction rates due to human and natural factors, more basic and applied research in reproductive biology is required to preserve wild species and design proper strategies leading to sustainable populations. The objective of the review is to highlight recent, inspiring breakthroughs in wildlife reproduction science that will set directions for future research and lead to more successes in conservation biology. Despite new tools and approaches allowing a better and faster understanding of key mechanisms, we still know little about reproduction in endangered species. Recently, the most striking advances have been obtained in nonmammalian species (fish, birds, amphibians, or corals) with the development of alternative solutions to preserve fertility or new information about parental nutritional influence on embryo development. A novel way has also been explored to consider the impact of environmental changes on reproduction-the allostatic load-in a vast array of species (from primates to fish). On the horizon, genomic tools are expected to considerably change the way we study wildlife reproduction and develop a concept of "precision conservation breeding." When basic studies in organismal physiology are conducted in parallel, new approaches using stem cells to create artificial gametes and gonads, innovations in germplasm storage, and more research on reproductive microbiomes will help to make a difference. Lastly, multiple challenges (for instance, poor integration of new tools in conservation programs, limited access to study animals, or few publication options) will have to be addressed if we want reproductive biology to positively impact conservation of biodiversity.

Cryopreservation and transplantation of common carp spermatogonia

Common carp (Cyprinus carpio) is one of the most cultured fish species over the world with many different breeds and plenty of published protocols for sperm cryopreservation. However, data regarding preservation of gonadal tissue and surrogate production is still missing. A protocol for freezing common carp spermatogonia was developed through varying different factors along a set of serial subsequent experiments. Among the six cryoprotectants tested, the best survival was achieved with dimethyl sulfoxide (Me₂SO). In the next experiment, a wide range of cooling rates (0.5–10°C/min) and different concentrations of Me₂SO were tested resulting in the highest survival achieved using 2 M Me₂SO and cooling rate of -1°C/min. When testing different tissue sizes and incubation times in the cryomedia, the highest viability was observed when incubating 100 mg tissue fragments for 30 min. Finally, sugar supplementation did not yield significant differences. When testing different equilibration (ES) and vitrification solutions (VS) used for needle-immersed vitrification, no significant differences were observed between the tested groups. Additionally, varied exposure time to VS did not improve the vitrification outcome where the viability was 4-fold lower than that of freezing. The functionality of cryopreserved cells was tested by interspecific transplantation into sterilized goldfish recipients. The exogenous origin of the germ cells in gonads of goldfish recipient was confirmed by molecular markers and incorporation rate was over 40% at 3 months post-transplantation. Results of this study can serve for long-term preservation of germplasm in carp which can be recovered in a surrogate recipient.