In vitro developmental ability of ovine oocytes following intracytoplasmic injection with freeze-dried spermatozoa

Effects of triton X-100 pretreatment of lyophilized and frozen-thawed ram sperm on preimplantation embryo developmental competence

In this study, it was aimed to determine the effect of destruction of lyophilized and frozen-thawed ram sperm plasma and acrosomal membrane on development of embryos produced by intracytoplasmic sperm injection (ICSI). Semen samples were divided into two groups for lyophilization (L) and freezing (F). For the removal of the plasma membrane, L and F groups were incubated with Triton X-100 (LTX-100 and FTX-100, respectively). Integrities of the plasma membrane, acrosome and chromatin structure were evaluated. Oocytes were injected with these sperm groups. Although no plasma membrane and acrosome integrities of the L (0.0%) group were detected, the plasma membrane integrity of the F group (69.4%) was significantly higher than the FTX-100 group (23.6%) (p < 0.05). The acrosome integrity of the FTX-100 group (3.80%) was significantly lower than the F group (55.6%) (p < 0.05). The chromatin integrities of L and F groups were higher than the Triton X-100 treated groups (p < 0.05). ICSIs with L, LTX-100, F and FTX-100 sperm were produced similar cleavage and blastocyst rates. In conclusion, data presented here confirm that ram spermatozoa can effectively be lyophilized and injected into oocytes for initiation of embryonic development and Triton X-100 pretreatment is not necessary while using lyophilized and frozen semen.

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.

Past, present and future of ICSI in livestock species

During the past 2 decades, intracytoplasmic sperm injection (ICSI) has become a routine technique for clinical applications in humans. The widespread use among domestic species, however, has been limited to horses. In horses, ICSI is used to reproduce elite individuals and, as well as in humans, to mitigate or even circumvent reproductive barriers. Failures in superovulation and conventional in vitro fertilization (IVF) have been the main reason for the use of this technology in horses. In pigs, ICSI has been successfully used to produce transgenic animals. A series of factors have resulted in implementation of ICSI in pigs: need to use zygotes for numerous technologies, complexity of collecting zygotes surgically, and problems of polyspermy when there is utilization of IVF procedures. Nevertheless, there have been very few additional reports confirming positive results with the use of ICSI in pigs. The ICSI procedure could be important for use in cattle of high genetic value by maximizing semen utilization, as well as for utilization of spermatozoa from prepubertal bulls, by providing the opportunity to shorten the generation interval. When attempting to utilize ICSI in ruminants, there are some biological limitations that need to be overcome if this procedure is going to be efficacious for making genetic improvements in livestock in the future. In this review article, there is an overview and projection of the methodologies and applications that are envisioned for ICSI utilization in these species in the future.

Desiccated cat spermatozoa retain DNA integrity and developmental potential after prolonged storage and shipping at non-cryogenic temperatures

PURPOSE

To evaluate the DNA integrity and developmental potential of microwave-dehydrated cat spermatozoa after storage at - 20 °C for different time periods and/or overnight shipping on dry ice.

METHODS

Epididymal spermatozoa from domestic cats were microwave-dehydrated on coverslips after trehalose exposure. Dried samples were either assessed immediately, stored for various duration at - 20 °C, or shipped internationally on dry ice before continued storage. Dry-stored spermatozoa were rehydrated before assessing DNA integrity (TUNEL assays) or developmental potential (injection into in vitro matured oocytes followed by in vitro embryo culture for up to 7 days).

RESULTS

Percentages of dried-rehydrated spermatozoa with intact DNA was not significantly affected (P > 0.05) by desiccation and short-term storage (range, 78.9 to 80.0%) but decreased (P < 0.05) with storage over 5 months (range, 71.0 to 75.2%) compared to fresh controls (92.6 ± 2.2%). After oocyte injection with fresh or dried-rehydrated spermatozoa (regardless of storage time), percentages of activation, pronuclear formation, and embryo development were similar (P > 0.05). Importantly, spermatozoa shipped internationally also retained the ability to support embryo development up to the morula stage.

CONCLUSION

Results demonstrated the possibility to sustain DNA integrity and developmental potential of spermatozoa by dry-preservation, even after long-term storage and long-distance shipment at non-cryogenic temperatures. While further studies are warranted, present results demonstrate that dry preservation can be a reliable approach for simple and cost-effective sperm biobanking or shipment.

Utilization of Rosmarinic and Ascorbic Acids for Maturation Culture Media in Order to Increase Sow Oocyte Quality Prior to IVF

The beneficial effect of antioxidant supplementation in maturation culture media of sow oocytes was evaluated by the expression quantification of apoptotic genes and the genes that ensure stability of germ cells during fertilization. The oocytes were cultivated for 44 h in conventional medium (C) or in medium supplemented with 105 µM rosmarinic acid (R) and 0.5 mM ascorbic acid (A) and classified into three quality classes by morphological observation from which the total RNA was isolated. The gene expression of Ptx3 and the apoptotic regulator p53, Bax and BCL-2 were evaluated by quantitative PCR technique. The decreased expression of the Bax gene in the A and R groups, compared to the control, indicates a protective role of antioxidants in the cells. Cell homeostasis was maintained, as reflected in the ratio of Bax/Bcl-2 in class I COCs (cumulus-oocyte complex) regardless of the experimental group, indicating minimum cellular stress. The expression of p53 genes was higher in all class III COC, but in A1 and R1 the expression was lower than in C1, and a similar Ptx-3 gene decreased significantly in groups A1, A2, A3 and R1 compared with control groups. Antioxidant supplementation showed beneficial effects on all morphological classes of pig COCs.

Freeze Drying as a Method of Long-Term Conservation of Mammalian Semen – A Review

With the development of biotechnological methods that allow the manipulation and free exchange of genetic material, the methods for collecting and storing such material need to be improved. To date, freezing in liquid nitrogen has allowed the storage of cells and entire plant and animal tissues for practically unlimited times. However, alternatives are still being sought to eliminate the constant need to maintain samples at a low temperature. Lyophilization or freeze drying is an alternative to standard freezing procedures. The storage of samples (lyophilisates) does not require specialised equipment but only refines the preservation method itself. In the case of cells capable of movement e.g., sperm, they lose the ability to reach the oocyte in vivo and for in vitro fertilization (IVF) because of the lyophilization process. However, freeze-dried sperm may be used for in vitro fertilization by intracytoplasmic sperm injection (ICSI), based on the results obtained in cleavage, embryo development and the production of live born offspring after embryo transfer. Studies on the lyophilization of sperm have been performed on many animal species, both in the laboratory and in livestock. This conservation method is considered to create biobanks for genetically valuable and endangered species with the simultaneous application of ICSI. This review article aimed to present the issues of the freeze-drying process of mammalian semen and help find solutions that will improve this technique of the long-term preservation of biological material.

The ART of bringing extinction to a freeze - History and future of species conservation, exemplified by rhinos

The ongoing mass extinction of animal species at an unprecedented rate is largely caused by human activities. Progressive habitat destruction and fragmentation is resulting in accelerated loss of biodiversity on a global scale. Over decades, captive breeding programs of non-domestic species were characterized by efforts to optimize species-specific husbandry, to increase studbook-based animal exchange, and to improve enclosure designs. To counter the ongoing dramatic loss of biodiversity, new approaches are warranted. Recently, new ideas, particularly the application of assisted reproduction technologies (ART), have been incorporated into classical zoo breeding programs. These technologies include semen and oocyte collection, artificial insemination, and in-vitro embryo generation. More futuristic ideas of advanced ART (aART) implement recent advances in biotechnology and stem-cell related approaches such as cloning, inner cell mass transfer (ICM), and the stem-cell-associated techniques (SCAT) for the generation of gametes and ultimately embryos of highly endangered species, such as the northern white rhinoceros (Ceratotherium simum cottoni) of which only two female individuals are left. Both, ART and aART greatly depend on and benefit from the rapidly evolving cryopreservation techniques and biobanking not only of genetic, but also of viable cellular materials suitable for the generation of induced pluripotent stem cells (iPSC). The availability of cryopreserved materials bridges gaps in time and space, thereby optimizing the available genetic variability and enhancing the chance to restore viable populations.

Preservation of Mammalian Sperm by Freeze-Drying

Long-term preservation of mammalian sperm at suprazero temperatures is desired to save storage and space costs, as well as to facilitate transport of preserved samples. This can be accomplished by the freeze-drying of sperm samples. Although freeze-drying results in immotile and membrane-compromised sperm, intracytoplasmic sperm injection (ICSI) can be used to introduce such an immotile sperm into an oocyte and thus start the fertilization process. So far, it has been shown that improved freeze-drying protocols preserve chromosomal integrity and oocyte-activating factor(s) in rodent and mammalian species at 4 °C for several years and at ambient temperature for up to 1 year depending on species, which permits shipping freeze-dried samples at ambient temperature. This chapter concisely reviews freeze-drying of mammalian sperm first and then presents a simple freeze-drying protocol.

Dry storage of mammalian spermatozoa and cells: state-of-the-art and possible future directions

This review provides a snapshot of the current state-of-the-art of drying cells and spermatozoa. The major successes and pitfalls of the most relevant literature are described separately for spermatozoa and cells. Overall, the data published so far indicate that we are closer to success in spermatozoa, whereas the situation is far more complex with cells. Critical for success is the presence of xeroprotectants inside the spermatozoa and, even more so, inside cells to protect subcellular compartments, primarily DNA. We highlight workable strategies to endow gametes and cells with the right combination of xeroprotectants, mostly sugars, and late embryogenesis abundant (LEA) or similar 'intrinsically disordered' proteins to help them withstand reversible desiccation. We focus on the biological aspects of water stress, and in particular cellular and DNA damage, but also touch on other still unexplored issues, such as the choice of both dehydration and rehydration methods or approaches, because, in our view, they play a primary role in reducing desiccation damage. We conclude by highlighting the need to exhaustively explore desiccation strategies other than lyophilisation, such as air drying, spin drying or spray drying, ideally with new prototypes, other than the food and pharmaceutical drying strategies currently used, tailored for the unique needs of cells and spermatozoa.

Rosmarinic acid improves boar sperm quality, antioxidant capacity and energy metabolism at 17°C via AMPK activation

Boar sperm are susceptible to oxidative damage caused by reactive oxygen species (ROS) during storage. Adenosine monophosphate (AMP)-activated protein kinase (AMPK) is an important therapeutic target, because it is a cellular metabolism energy sensor and key signalling kinase in spermatozoa. We evaluated the effects of rosmarinic acid (RA), an antioxidant, on boar sperm during liquid storage to determine whether it protects boar sperm via AMPK activation. Boar ejaculates were diluted with Modena extender with different concentrations of RA and stored at 17°C for 9 days. Sperm quality parameters, antioxidant capacity, energy metabolism, AMPK phosphorylation and fertility were analysed. Compared with the control, 40 μmol/L significantly improved sperm motility, plasma membrane integrity and acrosome integrity (p < .05). The effective storage time of boar sperm was up to 9 days. On the third and seventh days, the sperm with RA exhibited increased total antioxidant capacity (T-AOC), superoxide dismutase (SOD) activity, adenosine triphosphate (ATP) content, mitochondrial membrane potential (ΔΨm) and glyceraldehyde-3-phosphate dehydrogenase (GAPDH) activity, whereas malondialdehyde (MDA) content was significantly decreased (p < .05). Western blot showed that RA, as well as AICAR (AMPK activator), promoted AMPK phosphorylation, whereas Compound C (AMPK inhibitor) inhibited this effect. The sperm-zona pellucida binding experiment showed that 40 μmol/L RA increased the number of sperm attached to the zona pellucida (p < .05). These findings suggest meaningful methods for improved preservation of boar sperm in vitro and provide new insights into the mechanism by which RA protects sperm cells from oxidative damage via AMPK activation.

Boar sperm quality and oxidative status as affected by rosmarinic acid at 17 °C

Peroxidation damage induces sublethal injury to boar sperm during preservation. Rosmarinic acid (RA) has already been verified to efficiently protect cells from oxidant-induced injury and to produce significant effect on cryopreservation of semen. Through our experiments, we aim at investigating whether RA has a positive effect on the preservation of pig semen at room temperature. The semen collected from sexually mature Large White boars were preserved at 17 °C in Beltsville thawing solution (BTS) supplied. The boar sperm were exposed to 0, 25, 50, 75, 100, 125 and 150 μM RA in vitro and the sperm functions were examined. The sperm motility, the acrosome and plasma membrane integrity, the catalase activity (CAT), the total antioxidative capacity (T-AOC) activity and the malondialdehyde content (MDA) were examined at 0, 1, 3 and 5 days. The BTS diluent containing RA improved the sperm quality during the process of liquid preservation compared with the control treatment. After 5 days of liquid preservation, the addition of RA at 100 μM produced an optimal effect on the survival time as well as on the maintenance of motility, acrosome and plasma membrane integrity; T-AOC activity; CAT activity; and the MDA content. Besides, our results in the reproductive experiments showed that the addition of RA at 100 μM to the BTS diluent increased the pregnancy rate. These results suggest that the proper concentration of RA in boar semen extenders possibly improves the artificial insemination efficiency by reducing the sperm damage and the subsequent dysfunction during liquid preservation in swine production systems.

Dry biobanking as a conservation tool in the Anthropocene

Species are going extinct at an alarming rate, termed by some as the sixth mass extinction event in the history of Earth. Many are the causes for this but in the end, all converge to one entity - humans. Since we are the cause, we also hold the key to making the change. Any change, however, will take time, and for some species this could be too long. While working on possible solutions, we also have the responsibility to buy time for those species on the verge of extinction. Genome resource banks, in the form of cryobanks, where samples are maintained under liquid nitrogen, are already in existence but they come with a host of drawbacks. Biomimicry - innovation inspired by Nature, has been a huge source for ideas. Searching methods that Nature utilizes to preserve biological systems for extended periods of time, we realize that drying rather than freezing is the method of choice. We thus argue here in favor of preserving at least part of the samples from critically endangered species in dry biobanks, a much safer, cost-effective, biobanking approach.

Effect of chelating and antioxidant agents on morphology and DNA methylation in freeze-drying rabbit (Oryctolagus cuniculus) spermatozoa

Freeze-drying (FD) has been exhaustively tried in several mammalian species as an alternative technique to sperm cryopreservation, but few studies have been done in rabbits (Oryctolagus cuniculus). The main objective of this study was to compare the protective effect of various antioxidants added to EDTA medium on structural and functional components of FD rabbit spermatozoa and on their status of global DNA methylation. FD media used were composed of basic FD medium (10 mM Tris-HCl buffer and 50 mM NaCl) supplemented with either 50 mM EDTA alone (EDTA) or added with 105 µM of rosmarinic acid (RA, EDTA-RA) or 10 µM of melatonin (MLT, EDTA-MLT). The effect of each medium on the preservation of FD spermatozoon structure was evaluated with light and scanning electron microscopy (SEM). Global DNA methylation was quantified in all FD sperm samples as well as in fresh spermatozoa. Morphologically, fracture points were evidenced in the neck, mid and principal piece of the spermatozoon tail. No differences in spermatozoon fracture points were evidenced among FD treatments: intact spermatozoa were the largest (p < .01) category, whereas the most frequent (p < .01) injury was the neck fracture, resulting in tailless heads. At SEM, the head of spermatozoa showed a well-conserved shape and intact membrane in all treatments. DNA methylation status was the same in all FD treatments. In conclusion, supplementation of EDTA, EDTA-RA and EDTA-MLT during FD preserved rabbit sperm morphological integrity and methylation status as well. Therefore, the difficulty of getting viable offspring using FD semen is likely unrelated to the impact of the lyophilization process on DNA methylation and morphology of lyophilized spermatozoa.

Production of mouse fetuses using spermatozoa exposed temporarily to high temperature or continuously to room temperature after freeze-drying in Na+-free/K+-rich EGTA buffer

Present study aimed to determine to what extent freeze-dried spermatozoa were able to withstand high-temperature conditions: transient increase in storage temperature and long-term exposure to room temperature. Mouse spermatozoa were freeze-dried in EGTA/Tris-HCl buffered solution alkalinized using KOH (K-ETBS, pH 7.7), and then stored for up to 7 months at 4 °C or 25 °C. After 2 months' storage, some of the 4°C-stored spermatozoa were exposed to 40 °C for 1 week or 1 month, then again stored at 4 °C for the remaining storage period. Following storage, rehydrated spermatozoa were injected into mouse oocytes. The resulting zygotes were assessed for chromosome damage, in vitro development up to the blastocyst stage, and post-implantation development to normal fetuses on day 18 of gestation. In storage at 4 °C, one-week exposure to 40 °C had no adverse effect on the chromosome integrity and developmental competence compared to non-exposure to 40 °C (continuous storage at 4 °C). In contrast, one-month exposure to 40 °C caused an increasing level of chromosome damage (36%, P < 0.05) and reduced frequencies of blastocysts (54%, P < 0.05) and normal fetuses (36%, P < 0.05) compared to the frequencies obtained by continuous storage at 4 °C (15%, 82% and 52%, respectively). Storage at 25 °C resulted in accumulation of chromosome damage (27%, P < 0.05), leading to decreased blastocyst formation (63%, P < 0.05). But, the frequency of normal fetus (44%) was not significantly different from that obtained by continuous storage at 4 °C. Consequently, mouse spermatozoa freeze-dried in K-ETBS withstood temporary exposure to 40 °C for 1 week. Chromosome damage accumulated in spermatozoa during storage at 25 °C.

Long-term preservation of freeze-dried rabbit sperm by adding rosmarinic acid and different chelating agents

Freeze-drying (FD) technique has been applied as an alternative technology to preserve gene resources to allow simple sperm preservation and shipment at 4 °C. Nevertheless, DNA sperm might be damaged by mechanical or oxidative stress throughout FD procedure. Therefore, suitable protection to maintain DNA integrity is required. The aim of this study was to determine the effect of rosmarinic acid (RA) as an antioxidant and two chelating agents (EGTA and EDTA) on the DNA integrity of freeze-dried rabbit sperm after storage of the samples at 4 °C and room temperature for 8 months. Rabbit sperm were freeze-dried in basic medium (10 mM Tris-HCl buffer and 50 mM NaCl) supplemented with 50 mM EGTA (1), 50 mM EGTA plus 105 μM RA (2), 50 mM EDTA (3) or 50 mM EDTA plus 105 μM RA (4). Semen samples were kept at 4 °C and room temperature during 8 months. After rehydration, DNA integrity was evaluated with Sperm Chromatin Dispersion test observing that DNA fragmentation was higher when semen samples were freeze-dried with EGTA (10.9%) than with EDTA (4.1%) (p < 0.01). Furthermore, RA acted better under adverse conditions and no significant differences were found in temperature storage. Summarizing, FD is a method that can allow simple gene resources preservation among 4 °C to 25 °C during 8 months and transportation without the need for liquid nitrogen or dry ice. EDTA chelating agent is the most suitable media for freeze-dried rabbit sperm and the addition of RA protects the DNA against the oxidative stress caused during FD procedure.

Freeze-dried spermatozoa: An alternative biobanking option for endangered species

In addition to the iconic wild species, such as the pandas and Siberian tigers, an ever-increasing number of domestic species are also threatened with extinction. Biobanking of spermatozoa could preserve genetic heritages of extinct species, and maintain biodiversity of existing species. Because lyophilized spermatozoa retain fertilizing capacity, the aim was to assess whether freeze-dried spermatozoa are an alternative option to save endangered sheep breeds. To achieve this objective, semen was collected from an Italian endangered sheep breed (Pagliarola), and a biobank of cryopreserved and freeze-dried spermatozoa was established, and evaluated using IVF (for frozen spermatozoa) and ICSI procedures (for frozen and freeze-dried spermatozoa). As expected, the fertilizing capacity of cryopreserved Pagliarola's spermatozoa was comparable to commercial semen stocks. To evaluate the activating capability of freeze-dried spermatozoa, 108 MII sheep oocytes were subjected to ICSI, and allocated to two groups: 56 oocytes were activated by incubation with ionomycin (ICSI-FDSa) and 52 were not activated (ICSI-FDSna). Pronuclear formation (2PN) was investigated at 14-16 h after ICSI in fixed presumptive zygotes. Only artificially activated oocytes developed into blastocysts after ICSI. In the present study, freeze-dried ram spermatozoa induced blastocyst development following ICSI at a relatively high proportion, providing evidence that sperm lyophilization is an alternative, low cost storage option for biodiversity preservation of domestic species.