The effect of freeze-drying media and storage temperature on ultrastructure and DNA of freeze-dried buffalo bull spermatozoa

Damages and stress responses in sperm cells and other germplasms during dehydration and storage at nonfreezing temperatures for fertility preservation

Long-term preservation of sperm, oocytes, and gonadal tissues at ambient temperatures has the potential to lower the costs and simplify biobanking in human reproductive medicine, as well as for the management of animal populations. Over the past decades, different dehydration protocols and long-term storage solutions at nonfreezing temperatures have been explored, mainly for mammalian sperm cells. Oocytes and gonadal tissues are more challenging to dehydrate so little to no progress have been made. Currently, the detrimental effects of the drying process itself are better characterized than the impact of long-term storage at nonfreezing temperatures. While structural and functional properties of germ cells can be preserved after dehydration, a long list of damages and stresses in nuclei, organelles, and cytoplasmic membranes have been reported and sometimes mitigated. Characterizing those damages and better understanding the response of germ cells and tissues to the stress of dehydration is fundamental. It will contribute to the development of optimal protocols while proving the safety of alternative storage options for fertility preservation. The objective of this review is to (1) document the types of damages and stress responses, as well as their mitigation in cells dried with different techniques, and (2) propose new research directions.

A successful protocol for achieving anhydrobiosis of Gallus Gallus Domesticus spermatozoa while maintaining their fertility IN VIVO

Lyophilization of avian semen is a new method for gene pool preservation. The goal of this study was to develop a protocol for the lyophilization of rooster semen with preserved fertility. Red Rhode Island rooster ejaculates (n = 20) were assessed by volume, motility, and concentration of spermatozoa. They were pooled and diluted 1:1 with a medium LCM-T20 containing trehalose (9.5 mM), exposed at 5 °C for 40 min and centrifuged, and then the supernatant was removed. Media LCM-T with trehalose (1.75 M) was added and exposed for 10 min. The semen was frozen in a thin layer in glass vials. Samples were lyophilized for 2 h at -150 … -50 °C. The water content of the samples after lyophilization was 6.1 ± 0.5% (CV 20%). The sample was rehydrated with a medium LCM-GA5 containing hyaluronic acid (40mg/100 mL media). The total motility of the spermatozoa was 1.0 ± 0.3%. From artificial insemination of virgin hens (n = 12) with rehydrated semen, one fertilized egg was obtained from eight laid eggs. All samples of perivitelline membranes of the obtained eggs had points of interaction with the spermatozoa (7-37 pcs/cm²), which confirmed the presence of viable rehydrated spermatozoa in the genital tract of the hen. To create a dry biobank for poultry, the first protocol for lyophilization of rooster semen was developed to ensure sperm fertility in vivo.

Trehalose Attenuates Detrimental Effects of Freeze-Drying on Human Sperm Parameters

Freeze-drying is one of the sperm preservation methods leading to the long-term preservation of sperm genetic material. Our main goal of this study was to evaluate the effect of the trehalose freeze-drying method on sperm motility, viability, morphology, acrosome, and DNA integrity compared with a standard protocol without trehalose. Twenty-five normozoospermic samples were included in this prospective study. Direct swim-up was used for sperm preparation. An experiment was performed on freeze-dried samples containing trehalose (0.2 M), and the results were compared to that without trehalose. The sperm parameters, including count, motility, morphology, viability, acrosome reaction, DNA denaturation, and DNA fragmentation, were evaluated before and after freeze-drying in both groups. The spermatozoa were totally immotile after freeze-drying in both groups. Sperm viability, acrosome integrity, and nondenatured sperm DNA were significantly higher in the trehalose group in comparison with that of without trehalose group. Nonfragmented sperm DNA showed an increasing trend in the trehalose group compared to the group without trehalose. While freeze-drying significantly reduced normal morphology, the addition of trehalose did not affect this parameter. The results of this study showed that trehalose can attenuate the detrimental effects of freeze-drying on human sperm parameters.

Dehydration of llama sperm using different osmolarity media and temperatures for preservation

The objective of this study was to evaluate effects of dehydration on sperm DNA with the aim of eventually using this method for preserving llama spermatozoa. Two experiments were conducted: 1) sperm preservation at 5 °C for 60 days in different hyperosmotic solutions (500, 800, 1000 and 1200 mOsmol/l) (n = 6, replications = 2) and 2) sperm preservation at 5 and -20 °C for 60 days in the same hyperosmotic solutions, with supplementary antibiotics (n = 6, replications = 2). Sperm motility, membrane functional integrity, viability and morphology were evaluated at 0 and 48 h of the preservation period (Experiment 1) and at 30 min and 24 h (Experiment 2). Sperm DNA was evaluated at 0 or 30 min (Experiment 1 and 2, respectively) and on days 7, 14, 21, 30 and 60 of the preservation periods. Motility, membrane functional integrity and viability were less when sperm were dehydrated, while sperm cell morphology was not affected. There was a smaller percentage of sperm with condensed chromatin as duration of the preservation period increased when stored in the different hyperosmotic solutions. There was a markedly smaller (P < 0.05) percentage of sperm with intact DNA in all solutions as the duration of preservation increased, with there being greater values for intact DNA at -20 °C than sperm preserved at 5 °C. Llama sperm chromatin condensation was slightly affected by the process of dehydration. There was a markedly smaller percentage of sperm with intact DNA in the dehydrated semen samples.

The current state of the problem of in vitro gene pool preservation in poultry

This review presents the current progress in and approaches to in vitro conservation of reproductive cells of animals, including birds, such as cryopreservation and freeze-drying, as well as epigenetic conditions for restoring viable spermatozoa and female gametes after conservation. Cryopreservation is an effective way to preserve reproductive cells of various species of animals and birds. In vitro gene pool conservation is aimed primarily to the restoration of extinct breeds and populations and to the support of genetic diversity in populations prone to genetic drift. It is the combination of ex situ in vivo and ex situ in vitro methods that can form the basic principles of the strategy of animal genetic diversity preservation. Also, use of cryopreserved semen allows faster breeding in industrial poultry farming. Despite numerous advances in semen cryobiology, new methods that can more efficiently restore semen fertility after cryopreservation are being sought. The mechanisms underlying the effect of cryopreservation on the semen parameters of cocks are insufficiently understood. The review reflects the results of recent research in the field of cryopreservation of female and male germ cells, embryonic cells, the search for new ways in the field of genetic diversity in vitro (the development of new cryoprotective media and new conservation technologies: freeze-drying). Molecular aspects of cryopreservation and the mechanisms of cryopreservation influence on the epigenetic state of cells are highlighted. Data on the results of studies in the field of male reproductive cell lyophilization are presented. The freeze-drying of reproductive cells, as a technology for cheaper access to the genetic material of wild and domestic animals, compared to cryopreservation, attracts the attention of scientists in Japan, Israel, Egypt, Spain, and France. There is growing interest in the use of lyophilized semen in genetic engineering technologies. Methods of freeze-drying are developed taking into account the species of birds. Organizational and legal ways of solving the problems of in vitro conservation of genetic resources of farm animals, including birds, are proposed.

Desiccation and supra-zero temperature storage of cat germinal vesicles lead to less structural damage and similar epigenetic alterations compared to cryopreservation

Understanding cellular and molecular damages in oocytes during exposure to extreme conditions is essential to optimize long-term fertility preservation approaches. Using the domestic cat (Felis catus) model, we are developing drying techniques for oocytes' germinal vesicles (GVs) as a more economical alternative to cryopreservation. The objective of the study was to characterize the influence of desiccation on nuclear envelope conformation, chromatin configuration, and the relative fluorescent intensities of histone H3 trimethylation at lysine 4 (H3K4me3) and at lysine 9 (H3K9me3) compared to vitrification. Results showed that higher proportions of dried/rehydrated GVs maintained normal nuclear envelope conformation and chromatin configuration than vitrified/warmed counterparts. Both preservation methods had a similar influence on epigenetic patterns, lowering H3K4me3 intensity to under 40% while maintaining H3K9me3 levels. Further analysis revealed that the decrease of H3K4me3 intensity mainly occurred during microwave dehydration and subsequent rehydration, whereas sample processing (permeabilization and trehalose exposure) or storage did not significantly affect the epigenetic marker. Moreover, rehydration either directly or stepwise with trehalose solutions did not influence the outcome. This is the first report demonstrating that the incidence of GV damages is lower after desiccation/rehydration than vitrification/warming.

Freezing, Vitrification, and Freeze-Drying of Equine Spermatozoa: Impact on Mitochondrial Membrane Potential, Lipid Peroxidation, and DNA Integrity

Maintaining the integrity of equine sperm subjected to preservation protocols is essential for the successful development of assisted reproduction procedures. The aim of this study was to assess the mitochondrial membrane potential, lipid peroxidation, and DNA integrity of equine sperm subjected to freezing, vitrification, and freeze-drying. Eight ejaculates obtained from four Colombian Creole horses were subjected to programmable freezing, vitrification, and freeze-drying. After thawing or rehydration, sperm motility and kinetics were assessed through a CASA system. The mitochondrial membrane potential (ΔΨM), lipid peroxidation (LPO), and DNA fragmentation index (DFI) of the spermatozoa were assessed by flow cytometry using the DiOC6 (3), C11-Bodipy 581/591, and propidium iodide (PI) fluorescent dyes. The statistical analysis was conducted via generalized linear models, mean comparisons via the Duncan test, and a principal component analysis. A higher rate of spermatozoa with a high ΔΨM was found for freeze-drying (40.26 ± 7.79%) compared with freezing (21.82 ± 5.38%) and vitrification (5.32 ± 1.17%) (P < .05). Likewise, a higher rate of nonperoxidized viable spermatozoa (Bodipy-/PI-) was found for freeze-drying (35.98 ± 7.01%) in relation to frozen (10.34 ± 2.69%) and vitrified (7.07 ± 2.00%) sperm (P < .05). The DFI of vitrified spermatozoa (0.12 ± 0.04%) was higher when compared with the frozen (0.03 ± 0.01%) and freeze-dried (0.02 ± 0.01%) samples (P < .05). The researchers conclude that vitrification generates greater sperm alterations than freeze-drying and freezing, whereas freeze-drying produces lower LPO and higher ΔΨM for equine spermatozoa.