Pronuclear formation and cleavage of mammalian eggs after microsurgical injection of freeze-dried sperm nuclei

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.

Current Approaches of Preservation of Cells During (freeze-) Drying

The widespread application of therapeutic cells requires a successful stabilization of cells for the duration of transport and storage. Cryopreservation is currently considered the gold standard for the storage of active cells; however, (freeze-) drying cells could enable higher shelf life stability at ambient temperatures and facilitate easier transport and storage. During (freeze-) drying, freezing, (primary and secondary) drying and also the reconstitution step pose the risk of potential cell damage. To prevent these damaging processes, a wide range of protecting excipients has emerged, which can be classified, according to their chemical affiliation, into sugars, macromolecules, polyols, antioxidants and chelating agents. As many excipients cannot easily permeate the cell membrane, researchers have established various techniques to introduce especially trehalose intracellularly, prior to drying. This review aims to summarize the main damaging mechanisms during (freeze-) drying and to introduce the most common excipients with further details on their stabilizing properties and process approaches for the intracellular loading of excipients. Additionally, we would like to briefly explain recently discovered advantages of drying microorganisms, sperm, platelets, red blood cells, and eukaryotic cells, paying particular attention to the drying technique and residual moisture content.

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.

Chromosomal integrity and DNA damage in freeze-dried spermatozoa

Freeze-drying technology may one day be used to preserve mammalian spermatozoa indefinitely without cryopreservation. Freeze-dried mouse spermatozoa stored below 4°C for up to 1 year have maintained the ability to fertilize oocytes and support normal development. The maximum storage period for spermatozoa increases at lower storage temperatures. Freeze-drying, per se, may reduce the integrity of chromosomes in freeze-dried mouse spermatozoa, but induction of chromosomal damage is suppressed if spermatozoa are incubated with divalent cation chelating agents prior to freeze-drying. Nevertheless, chromosomal damage does accumulate in spermatozoa stored at temperatures above 4°C. Currently, no established methods or strategies can prevent or reduce damage accumulation, and damage accumulation during storage is a serious obstacle to advances in freeze-drying technology. Chromosomal integrity of freeze-dried human spermatozoa have roughly background levels of chromosomal damage after storage at 4°C for 1 month, but whether these spermatozoa can produce healthy newborns is unknown. The safety of using freeze-dried human spermatozoa must be evaluated based on the risks of heritable chromosome and DNA damage that accumulates during storage.

Characterization of chromosomal damage accumulated in freeze-dried mouse spermatozoa preserved under ambient and heat stress conditions

Structural chromosome aberrations and DNA damage generated in freeze-dried mouse spermatozoa were investigated. Freeze-dried sperm samples were preserved at 4, 25 and 50°C for short duration (1 day to 2 months) and at 25°C for long duration (2 years). The spermatozoa were injected into mouse oocytes to analyse the chromosomes of the zygotes at the first cleavage metaphase. Chromosome break of the chromosome-type aberrations was the most common type of structural chromosome aberrations observed in all freeze-dried samples. The frequency of chromatid exchanges rapidly increased in freeze-dried spermatozoa preserved at 50°C for 1-5 days. The frequency of chromatid-type aberrations (break and exchange) gradually increased in freeze-dried spermatozoa preserved at 25°C for up to 2 months. Alkaline comet assay revealed significant migration of damaged DNA accumulated in freeze-dried spermatozoa preserved at 50°C for 3 days and 25°C for 2 years. However, no DNA damage was detected using the same sperm samples by neutral comet assay, which can detect mostly DNA double-strand breaks in cellular DNA. These results suggest that DNA single-strand breaks were accumulated in freeze-dried spermatozoa preserved under ambient or heat conditions, and then chromatid-type aberrations, especially the chromatid exchanges, were formed via post-replication repair system in zygotes.

Novel gamete storage

The aim of this review is to outline recent advances in gamete storage that are beneficial for rescuing endangered species or for the breeding of companion animals. Much more information is available on the technical resolutions and practical applications of sperm cryopreservation in various species than of female gametes, reproductive tissues or organs. Mammalian sperm cryopreservation often works relatively efficiently; however, the ability of female gametes to be cryopreserved and still be viable for fertilisation is also essential for rescuing endangered species. For a proper evaluation of gamete cryopreservation possibilities in a given species, it is essential to understand the basic mechanism affecting the survival of cryopreserved cells, the technical and physical limitations, the available techniques and the new avenues to resolve the specific problems in that species. This paper is aimed to provide some help for this process. The limited length of this paper resulted in the omission of information on many important areas, including most data on teleosts, amphibian and insect cryopreservation.

Applications of emerging technologies to the study and conservation of threatened and endangered species

Sustaining viable populations of all wildlife species requires the maintenance of habitat, as well as an understanding of the behaviour and physiology of individual species. Despite substantial efforts, there are thousands of species threatened by extinction, often because of complex factors related to politics, social and environmental conditions and economic needs. When species become critically endangered, ex situ recovery programmes that include reproductive scientists are the usual first line of defence. Despite the potential of reproductive technologies for rapidly increasing numbers in such small populations, there are few examples of success. This is not the result of a failure on the part of the technologies per se, but rather is due to a lack of knowledge about the fundamental biology of the species in question, information essential for allowing reproductive technologies to be effective in the production of offspring. In addition, modern conservation concepts correctly emphasise the importance of maintaining heterozygosity to sustain genetic vigour, thereby limiting the practical usefulness of some procedures (such as nuclear transfer). However, because of the goal of maintaining all extant gene diversity and because, inevitably, many species are (or will become) 'critically endangered', it is necessary to explore every avenue for a potential contributory role. There are many 'emerging technologies' emanating from the study of livestock and laboratory animals. We predict that a subset of these may have application to the rescue of valuable genes from individual endangered species and eventually to the genetic management of entire populations or species. The present paper reviews the potential candidate techniques and their potential value (and limitations) to the study and conservation of rare wildlife species.

Fertilization and development in vitro of bovine oocytes following intracytoplasmic injection of heat-dried sperm heads

This study investigated the development of bovine oocytes following intracytoplasmic injection of sperm heads from spermatozoa dried by heating. When sperm suspension was heated in a dry oven at 50, 56, 90, and 120 degrees C, the mean amounts of residual water were about 0.3 g water/g dry weight within 8 h, 6 h, 1.5 h, and 20 min of heating, respectively. Oocyte activation, cleavage of oocytes, and development of cleaved embryos to the morula stage were better in oocytes injected with spermatozoa stored at 25 degrees C for 7-10 days following drying at 50 and 56 degrees C than at 90 and 120 degrees C; however, only a small proportion of oocytes developed to the blastocyst stage. When spermatozoa were dried at 50 degrees C for 16 h, activation, male pronucleus (MPN) formation, cleavage, and development to the morula stage were less good than when spermatozoa were dried for 8 and 10 h and no blastocysts were obtained. The development of oocytes was significantly better when spermatozoa were stored for 7-10 days at 4 degrees C than 25 degrees C after drying at 50 degrees C for 8 h. Longer storage (7 days-12 mo) of heat-dried spermatozoa at 4 degrees C did not affect MPN formation in activated oocytes, but blastocyst development was significantly lower when spermatozoa were stored for 3 mo or more. These results demonstrate that bovine oocytes can be fertilized with heat-dried spermatozoa and that the fertilized oocytes can develop at least to the blastocyst stage.

Activation, Pronuclear Formation, and Development In Vitro of Pig Oocytes Following Intracytoplasmic Injection of Freeze-Dried Spermatozoa1

The fertilization of pig oocytes following intracytoplasmic injection of freeze-dried spermatozoa was evaluated. Activation and male pronuclear (MPN) formation were better in oocytes injected with isolated freeze-dried sperm heads than whole freeze-dried spermatozoa, but cleaved embryos were generally difficult to develop to the morula or blastocyst stage. When spermatozoa were freeze-dried for 24 h, oocyte activation and MPN formation in activated oocytes after sperm head injection were inhibited. Embryo development to the blastocyst stage was only obtained after injecting sperm heads isolated from spermatozoa freeze-dried for 4 h and stored at 4 degrees C. The proportion of embryos that developed to the blastocyst stage was not increased by the treatment of injected oocytes with Ca ionophore (5-10 microM). Increasing the sperm storage time did not affect oocyte activation or MPN formation, but blastocyst development was observed only after 1 mo of storage. These results demonstrate that pig oocytes can be fertilized with appropriately freeze-dried spermatozoa and that the fertilized oocytes can develop to the blastocyst stage.

Activation of mouse oocytes following intracytoplasmic injection of chicken sperm extract

The cytosolic factor from the sperm of a wide variety of species has been reported to induce [Ca2+]i increase and/or activation in oocytes. Although many species have been studied, there is no data available on the chicken sperm factor responsible for activation of oocytes. This study was aimed to verify the activation of mouse oocyte by intracytoplasmic injection of chicken sperm extract (CSE). Survival rate of oocytes without rupture or lytic degeneration following injection was greater than 80% regardless of the presence or absence of CSE. Among the intact oocytes, activation rates following injection were 27.5% (11 of 40) in the sham operation group. Injection of CSE resulted in significantly higher activation rates in the 1/10 dilution group (57.8%, 26 of 45) compared with the sham operation group (p = 0.0045). Calculated amount of injected sperm extract of 1/10 dilution of CSE was equivalent of 12 chicken sperm. When the 1/10 diluted mouse sperm extract (MSE) was injected, survival rate of injected oocytes and activation rate of the survived oocytes was 82% (41 of 50) and 78% (32 of 41), respectively. Activation rate of MSE-injected oocytes was a little but significantly higher than that of CSE-injected oocytes (p < 0.037). In conclusion, it suggests that CSE can activate the mouse oocyte and that oocyte activating sperm factor(s) may be common between avian and mammal.

Bovine blastocyst development from oocytes injected with freeze-dried spermatozoa

Pronuclear formation, and the chromosomal constitution and developmental capacity of bovine zygotes formed by intracytoplasmic sperm injection with freeze-dried (lyophilized) spermatozoa were evaluated. Frozen-thawed spermatozoa were selected, freeze-dried, and stored at 4 degrees C until use. After 22-24 h of in vitro maturation oocytes were denuded and injected singly with a lyophilized spermatozoon. Injected oocytes were activated by treatment with 10 microM ionomycin (5 min) alone and in combination with 1.9 mM 6-dimethylaminopurine (DMAP) for 4 h. Ionomycin plus DMAP activation treatment resulted in a significantly higher proportion of sperm-injected oocytes with two pronuclei than was found after activation with ionomycin alone (74% vs. 56%; P < 0.03). The rates of cleavage, morula, and blastocyst development of sperm-injected oocytes treated with ionomycin plus DMAP were higher than after activation with ionomycin alone (63.3%, 34.2%, and 29.6% vs. 44.7%, 18.7%, and 10.6%, respectively; P < 0.05). Seventy-three percent of blastocysts produced with lyophilized sperm were diploid. These results demonstrate that in vitro-matured bovine oocytes can be fertilized with freeze-dried sperm cells, and that resultant zygotes can develop into karyotypically normal blastocysts.

Long-term outcomes of elective human sperm cryostorage

BACKGROUND

Sperm cryopreservation allows men with threatened fertility to preserve their progenitive potential, but there is little data on long-term outcomes of elective sperm cryostorage programmes.

METHODS AND RESULTS

Over 22 years, 930 men sought semen cryostorage in a single academic hospital, of which 833 (90%) had spermatozoa cryostored. Among 692 (74%) men surviving their illness, sperm samples were discarded for 193 (21% of all applicants, 28% of survivors) and cryostored spermatozoa were used for 64 men (7% of all applicants, 9% of survivors) in 85 treatment cycles commencing at a median of 36 months post-storage (range 12-180 months) with nearly 90% of usage started within 10 years of storage and none after 15 years. Pregnancy was most efficiently produced by intracytoplasmic sperm injection (median three cycles) compared with conventional IVF (median eight cycles) or artificial insemination (median more than six cycles; P < 0.05). A total of 141 (15%) of men had died and of these, 120 (85% of those dying) had their spermatozoa discarded; requests to prolong cryostorage were received from relatives of 21 men (2% of all applicants, 15% of deceased) of which three cases had spermatozoa transferred for use with no pregnancies reported. Sperm concentration was lower for all cryostorage groups compared with healthy sperm donor controls (P < 0.05). Following orchidectomy, men with testicular cancer had sperm density approximately half that of all other groups of men seeking cryostorage (P < 0.05), the lowering attributable to removal of one testis rather than in defects in spermatogenesis.

CONCLUSION

Elective sperm cryopreservation is an effective, if sparsely used, form of fertility insurance for men whose fertility is threatened by medical treatment and is an essential part of any comprehensive cancer care programme.

Unprotected freezing of human spermatozoa exerts a detrimental effect on their oocyte activating capacity and chromosome integrity

The influence of unprotected freezing of mammalian spermatozoa on their oocyte activating capacity and chromosome integrity is unknown. However, this type of sperm treatment has been used in assisted reproduction by intracytoplasmic sperm injection in cattle and humans. The mouse oocyte injection test was used to analyse the influence of unprotected freezing of human spermatozoa on their reproductive characteristics. Mouse oocytes were microinjected with intact human spermatozoa or spermatozoa treated with two cycles of unprotected freeze-thawing. Oocytes surviving the injection were either cultured without further treatment or exposed to ethanol solution to induce parthenogenetic activation. Both injected and activated oocytes were used for sperm chromosome analysis. The results revealed a significant reduction in oocyte activating capacity and a tenfold increase in the incidence of structural chromosomal abnormalities in human spermatozoa treated by unprotected freezing. We conclude that unprotected freezing of human spermatozoa has a detrimental effect on their reproductive characteristics. Our data also provide a new perspective on the stability of mammalian spermatozoa to physical factors and demonstrate the importance of detailed analysis of the stability of sperm structures for successful development of new approaches in assisted reproduction.