Freezing of boar spermatozoa: fertilizing capacity with concentrated semen and a new thawing procedure

Effect of prostatic fluid on the quality of fresh and frozen-thawed canine epididymal spermatozoa

Canine epididymal spermatozoa have a low freeze-tolerance ability compared with ejaculated spermatozoa, which could arise from the absence of prostatic fluid (PF). Therefore, the purpose of this work was to elucidate the influence of PF on the quality of canine epididymal sperm before and after freezing. Caudae epididymides were retrieved from eight dogs after routine castration. Spermatozoa were released by slicing the tissue and were extended in either Tris solution or PF before freezing. Frozen sperm samples were thawed at 70 °C for 8 seconds in a waterbath. Sperm concentration, motility using computer-assisted sperm analysis, morphology, plasma membrane, acrosome and chromatin integrity were assessed in the fresh sperm samples (after 20 minutes incubation) and at 0 and 4 hours after thawing. Progressive motility, distance straight line, distance average path, average path velocity, curvilinear velocity, straight line velocity, straightness, linearity, wobble, and beat cross frequency were significantly increased after extraction into PF. There was a higher proportion of spermatozoa with DNA damage in the PF treatment group at 4 hours after thawing than in the Tris treatment group (15.8% vs. 6.7%, P < 0.05). These results suggest that the addition of PF to canine spermatozoa activates sperm motility in fresh spermatozoa but has a negative effect on chromatin integrity after freezing-thawing.

Successful non-surgical deep uterine transfer of porcine morulae after 24 hour culture in a chemically defined medium

Excellent fertility and prolificacy have been reported after non-surgical deep uterine transfers of fresh in vivo-derived porcine embryos. Unfortunately, when this technology is used with vitrified embryos, the reproductive performance of recipients is low. For this reason and because the embryos must be stored until they are transferred to the recipient farms, we evaluated the potential application of non-surgical deep uterine transfers with in vivo-derived morulae cultured for 24 h in liquid stage. In Experiment 1, two temperatures (25 °C and 37 °C) and two media (one fully defined and one semi-defined) were assessed. Morulae cultured in culture medium supplemented with bovine serum albumin and fetal calf serum at 38.5 °C in 5% CO2 in air were used as controls. Irrespective of medium, the embryo viability after 24 h of culture was negatively affected (P<0.05) at 25 °C but not at 37 °C compared with the controls. Embryo development was delayed in all experimental groups compared with the control group (P<0.001). Most of the embryos (95.7%) cultured at 37 °C achieved the full or expanded blastocyst stage, and unlike the controls, none of them hatched at the end of culture. In Experiment 2, 785 morulae were cultured in the defined medium at 37 °C for 24 h, and the resulting blastocysts were transferred to the recipients (n = 24). Uncultured embryos collected at the blastocyst stage (n = 750) were directly transferred to the recipients and used as controls (n = 25). No differences in farrowing rates (91.7% and 92.0%) or litter sizes (9.0 ± 0.6 and 9.4 ± 0.8) were observed between the groups. This study demonstrated, for the first time, that high reproductive performance can be achieved after non-surgical deep uterine transfers with short-term cultured morulae in a defined medium, which opens new possibilities for the sanitary, safe national and international trade of porcine embryos and the commercial use of embryo transfer in pigs.

An earlier uterine environment favors the in vivo development of fresh pig morulae and blastocysts transferred by a nonsurgical deep-uterine method

This study aimed to evaluate the effect of recipient-donor estrous cycle synchrony on recipient reproductive performance after nonsurgical deep-uterine (NsDU) embryo transfer (ET). The transfers (N=132) were conducted in recipients sows that started estrus 24 h before (–24 h; N=9) or 0 h (synchronous; N=31), 24 h (+24 h; N=74) or 48 h (+48 h; N=18) after the donors. A total of 30 day 5 morulae or day 6 blastocysts (day 0=onset of estrus) were transferred per recipient. The highest farrowing rates (FRs) were achieved when estrus appeared in recipients 24 h later than that in the donors (81.1%), regardless of the embryonic stage used for the transfers. The FR notably decreased (P<0.05) when recipients were –24 h asynchronous (0%), synchronous (61.3%) or +48 h asynchronous (50%) relative to the donors. No differences in litter size (LS) and piglet birth weights were observed among the synchronous and +24 h or +48 h asynchronous groups. While a +24 h asynchronous recipient was suitable for transfers performed with either morulae (FR, 74.3%; LS, 9.2 ± 0.6 piglets) or blastocysts (FR, 84.6%; LS, 9.8 ± 0.6 piglets), a + 48 h asynchronous recipient was adequate for blastocysts (FR, 87.5%; LS, 10.4 ± 0.7 piglets) but not for morulae (FR, 30.0%; LS, 7.3 ± 2.3 piglets). In conclusion, this study confirms the effectiveness of the NsDU-ET technology and shows that porcine embryos tolerate better a less advanced uterine environment if they are nonsurgically transferred deep into the uterine horn.

The battle of the sexes starts in the oviduct: modulation of oviductal transcriptome by X and Y-bearing spermatozoa

BACKGROUND

Sex allocation of offspring in mammals is usually considered as a matter of chance, being dependent on whether an X- or a Y-chromosome-bearing spermatozoon reaches the oocyte first. Here we investigated the alternative possibility, namely that the oviducts can recognise X- and Y- spermatozoa, and may thus be able to bias the offspring sex ratio.

RESULTS

By introducing X- or Y-sperm populations into the two separate oviducts of single female pigs using bilateral laparoscopic insemination we found that the spermatozoa did indeed elicit sex-specific transcriptomic responses. Microarray analysis revealed that 501 were consistently altered (P-value < 0.05) in the oviduct in the presence of Y-chromosome-bearing spermatozoa compared to the presence of X-chromosome-bearing spermatozoa. From these 501 transcripts, 271 transcripts (54.1%) were down-regulated and 230 transcripts (45.9%) were up-regulated when the Y- chromosome-bearing spermatozoa was present in the oviduct. Our data showed that local immune responses specific to each sperm type were elicited within the oviduct. In addition, either type of spermatozoa elicits sex-specific signal transduction signalling by oviductal cells.

CONCLUSIONS

Our data suggest that the oviduct functions as a biological sensor that screens the spermatozoon, and then responds by modifying the oviductal environment. We hypothesize that there might exist a gender biasing mechanism controlled by the female.

Transgenic pigs with pancreas-specific expression of green fluorescent protein

The development and regeneration of the pancreas is of considerable interest because of the role of these processes in pancreatic diseases, such as diabetes. Here, we sought to develop a large animal model in which the pancreatic cell lineage could be tracked. The pancreatic and duodenal homeobox-1 (Pdx1) gene promoter was conjugated to Venus, a green fluorescent protein, and introduced into 370 in vitro-matured porcine oocytes by intracytoplasmic sperm injection-mediated gene transfer. These oocytes were transferred into four recipient gilts, all of which became pregnant. Three gilts were sacrificed at 47-65 days of gestation, and the fourth was allowed to farrow. Seven of 16 fetuses obtained were transgenic (Tg) and exhibited pancreas-specific green fluorescence. The fourth recipient gilt produced a litter of six piglets, two of which were Tg. The founder Tg offspring matured normally and produced healthy first-generation (G1) progeny. A postweaning autopsy of four 27-day-old G1 Tg piglets confirmed the pancreas-specific Venus expression. Immunostaining of the pancreatic tissue indicated the transgene was expressed in β-cells. Pancreatic islets from Tg pigs were transplanted under the renal capsules of NOD/SCID mice and expressed fluorescence up to one month after transplantation. Tg G1 pigs developed normally and had blood glucose levels within the normal range. Insulin levels before and after sexual maturity were within normal ranges, as were other blood biochemistry parameters, indicating that pancreatic function was normal. We conclude that Pdx1-Venus Tg pigs represent a large animal model suitable for research on pancreatic development/regeneration and diabetes.

Heat-shock protein A8 restores sperm membrane integrity by increasing plasma membrane fluidity

The constitutive 70  kDa heat-shock protein, HSPA8, has previously been shown to contribute to the long-term survival of spermatozoa inside the mammalian female reproductive tract. Here, we show that a recombinant form of HSPA8 rapidly promotes the viability of uncapacitated spermatozoa, the ability of spermatozoa to bind to oviductal epithelial cells, enhances IVF performance, and decreases sperm mitochondrial activity. Fluorescence recovery after photobleaching revealed that the repair of membrane damage is achieved by an almost instantaneous increase in sperm membrane fluidity. The ability of HSPA8 to influence membrane stability and fluidity, as well as its conserved nature among mammalian species, supports the idea that this protein protects sperm survival through membrane repair mechanisms. Free Persian abstract A Persian translation of the abstract is freely available online at http://www.reproduction-online.org/content/147/5/719/suppl/DC1.

The increase in phosphorylation levels of serine residues of protein HSP70 during holding time at 17°C is concomitant with a higher cryotolerance of boar spermatozoa

Boar-sperm cryopreservation is not usually performed immediately after semen collection, but rather a holding time (HT) of 4 h–30 h at 17°C is spent before starting this procedure. Taking this into account, the aim of this study was to go further in-depth into the mechanisms underlying the improving effects of HT at 17°C on boar-sperm cryotolerance by evaluating the effects of two different HTs (3 h and 24 h) on overall boar-sperm function and survival before and after cryopreservation. Given that phospho/dephosphorylation mechanisms are of utmost importance in the overall regulation of sperm function, the phosphorylation levels of serine residues (pSer) in 30 different sperm proteins after a 3 h- or 24 h-HT period were also assessed. We found that a HT of 24 h contributed to a higher sperm resistance to freeze-thawing procedures, whereas mini-array protein analyses showed that a HT of 24 h induced a significant (P<0.05) increase in pSer (from 100.0±1.8 arbitrary units in HT 3 h to 150.2±5.1 arbitrary units in HT 24 h) of HSP70 and, to a lesser extent, in protein kinases GSK3 and total TRK and in the cell-cycle regulatory protein CDC2/CDK1. In the case of HSP70, this increase was confirmed through immunoprecipation analyses. Principal component and multiple regression analyses indicated that a component explaining a percentage of variance higher than 50% in sperm cryotolerance was significantly correlated with pSer levels in HSP70. In addition, from all the parameters evaluated before freeze-thawing, only pSer levels in HSP70 resulted to be able to predict sperm cryotolerance. In conclusion, our results suggest that boar spermatozoa modulate its function during HT, at least partially, by changes in pSer levels of proteins like HSP70, and this is related to a higher cryotolerance.

Production of diabetic offspring using cryopreserved epididymal sperm by in vitro fertilization and intrafallopian insemination techniques in transgenic pigs

Somatic cell nuclear transfer (SCNT) is a useful technique for creating pig strains that model human diseases. However, production of numerous cloned disease model pigs by SCNT for large-scale experiments is impractical due to its complexity and inefficiency. In the present study, we aimed to establish an efficient procedure for proliferating the diabetes model pig carrying the mutant human hepatocyte nuclear factor-1α gene. A founder diabetes transgenic cloned pig was generated by SCNT and treated with insulin to allow for normal growth to maturity, at which point epididymal sperm could be collected for cryopreservation. In vitro fertilization and intrafallopian insemination using the cryopreserved epididymal sperm resulted in diabetes model transgenic offspring. These results suggest that artificial reproductive technology using cryopreserved epididymal sperm could be a practical option for proliferation of genetically modified disease model pigs.

Boar sperm tyrosine phosphorylation patterns in the presence of oviductal epithelial cells: in vitro, ex vivo, and in vivo models

Spermatozoa transport through the oviduct is a controlled process that regulates sperm capacitation. A crucial event involved in capacitation is protein tyrosine phosphorylation (TP). This study was undertaken to determine whether similarities exist in protein TP distribution between spermatozoa bound or unbound to oviductal epithelial cells (OEC) in three different conditions: i)in vitro, spermatozoa coincubated with OEC cultures; ii)ex vivo, spermatozoa deposited in porcine oviductal explants from slaughtered animals; iii)in vivo, in which sows were inseminated and the oviduct was recovered. The localization of phosphotyrosine protein was determined using indirect immunofluorescence. The distribution of protein TP was significantly (P<0.05) different between bound and unbound cell populations in all experiments. In sows inseminated close to ovulation, spermatozoa were found mainly in the utero–tubal junction, where spermatozoa exhibited higher proportion of flagellum phosphorylation. Spermatozoa not bound to OEC exhibited high levels of protein phosphorylation (phosphorylated equatorial subsegment and acrosome and/or phosphorylated flagellum) in theex vivoandin vivoexperiments (P<0.05). However, unbound spermatozoa coincubated with OEC inin vitroconditions tended to show intermediate levels of TP (equatorial subsegment with or without phosphorylated flagellum). In spermatozoa bound to OEC, protein TP was located in the equatorial subsegment or presented no phosphorylation (P<0.05). Although sperm capacitation conditionsin vivowere not reproduciblein vitroin our experimental conditions, sperm and OEC binding seemed to be a mechanism for selecting spermatozoa with a low level of TP inin vivo,ex vivo, andin vitroexperiments.

Sex determination of porcine embryos using a new developed duplex polymerase chain reaction procedure based on the amplification of repetitive sequences

Polymerase chain reaction (PCR)-based assays have become increasingly prevalent for sexing embryos. The aim of the present study was to develop a suitable duplex PCR procedure based on the amplification of porcine repetitive sequences for sexing porcine tissues, embryos and single cells. Primers were designed targeting the X12696 Y chromosome-specific repeat sequence (SUSYa and SUSYb; sex-related primer sets), the multicopy porcine-specific mitochondrial 12S rRNA gene (SUS12S; control primer set) and the X51555 1 chromosome repeat sequence (SUS1; control primer set). The specificity of the primer sets was established and the technique was optimised by testing combinations of two specific primer sets (SUSYa/SUS12S; SUSYb/SUS12S), different primer concentrations, two sources of DNA polymerase, different melting temperatures and different numbers of amplification cycles using genomic DNA from porcine ovarian and testicular tissue. The optimised SUSYa/SUS12S- and SUSYb/SUS12S-based duplex PCR procedures were applied to porcine in vitro-produced (IVP) blastocysts, cell-stage embryos and oocytes. The SUSYb/SUS12S primer-based procedure successfully sexed porcine single cells and IVP cell-stage embryos (100% efficiency), as well as blastocysts (96.6% accuracy; 96.7% efficiency). This is the first report to demonstrate the applicability of these repetitive sequences for this purpose. In conclusion, the SUSYb/SUS12S primer-based duplex PCR procedure is highly reliable and sensitive for sexing porcine IVP embryos.

The effect of Laminaria japonic polysaccharide on sperm characteristics and biochemical parameters in cryopreserved boar sperm

The aim of the present study was to evaluate the cryoprotective effect of Laminaria japonic polysaccharide (LJP) on boar sperm. Semen samples were collected from seven mature Yorkshire boars once a week by the gloved hand technique and frozen-thawed in the extender with LJP added. Extender with LJP added at concentrations of 0.25, 0.5, 1.0, 1.5 and 2.0mg/mL to the extender and its effects on the quality of frozen-thawed boar sperm were assessed. Results showed: (i) sperm motility and plasma membrane integrity were greater in the extender containing 0.5 and 1.0mg/mL LJP, as compared to other groups (P<0.05); (ii) extender added 1.0mg/mL LJP showed the greatest plasma membrane and acrosomal integrity percentages in comparison with other groups (P<0.05); (iii) mitochondrial activity was significantly higher at the concentration of 0.5 and 1.0mg/mL LJP than those of other groups (P<0.05); (iv) in terms of biochemical assessments, 0.5 and 1.0mg/mL LJP improved SOD (superoxide dismutase) and CAT (catalase) concentrations, compared to other groups (P<0.05). However, no significant difference was found in GSH-Px (glutathione peroxidase) concentration when supplemented with LJP. Interestingly, LJP exhibited a dose-related response and the lesser concentration represented greater protective effects. It is also important to note that 1.0mg/mL LJP provides for an enhanced cryoprotective effect in boar semen.

The relationship between feed efficiency traits and fertility in young beef bulls

Awda, B. J., Miller, S. P., Montanholi, Y. R., Vander Voort, G., Caldwell, T., Buhr, M. M. and Swanson, K. C. 2013. The relationship between feed efficiency traits and fertility in young beef bulls. Can. J. Anim. Sci. 93: 185–192. Great efforts have been taken in recent years for improving feed efficiency in beef cattle. Despite there being several studies on biological factors associated with this trait, little is known about the potential relationships between fertility and feed efficiency in beef cattle. The objective of this study was to examine the relationship between feed efficiency traits and bull fertility traits [sperm motility, viability and scrotal circumference (SC)]. From a total of 328 crossbred beef bulls that were subjected to a performance test (112 d in each of 6 yr), SC was measured and semen collected from 110 bulls using the electroejaculation method (average age±SE=417±2.5 d). Sperm were extended, cooled, and frozen in liquid nitrogen. Two residual feed intake (RFI) measures were considered with different prediction models for dry matter intake (DMI), RFIKoch included size and growth rate and RFIbkft included the additional adjustment for backfat thickness (BKFT). Sperm viability, motility and progressive motility of the 10 bulls with the greatest RFIKoch (Hi-RFIKoch) were greater than those of the 10 bulls with the lowest RFIKoch (Lo-RFIKoch; P<0.05, 0.01, and 0.05, respectively). Sperm motility (P<0.01), progressive motility and SC (P<0.05) of the 10 bulls with the greatest RFIbkft (Hi-RFIbkft) were greater than those of the 10 bulls with the lowest RFIbkft (Lo-RFIbkft). In summary, these data indicate that young beef bulls with greater feed efficiency have decreased sperm motility, sperm viability and SC, which is an undesirable effect of selection for improved feed efficiency that needs to be addressed through multiple trait selection.

Role of insulin-like growth factor-I and follicular fluid from ovarian follicles with different diameters on porcine oocyte maturation and fertilization in vitro

The objective of this study was to determine the effects of insulin-like growth factor-I (IGF-I) (0, 60, 120, 180, and 240 ng/mL) and follicular fluid (FF) derived from 2 to 5 and 6 to 10 mm diameter follicles (SpFFs and LpFFs, respectively) added during in vitro maturation (IVM) of porcine oocytes on nuclear maturation and IVF. Cumulus-oocyte complexes (COCs) were matured in NCSU-37 medium supplemented with SpFFs or LpFFs and various IGF-I concentrations. The COCs were cultured for 44 hours, and then fertilized in vitro. Maturation and IVF results were recorded 18 hours after insemination. The IVM (%) was higher (P < 0.05) in the COCs matured in LpFFs than with SpFFs when 0 (90.0 ± 6.9 vs. 76.3 ± 10.7) or 60 ng/mL IGF-I (92.0 ± 8.1 vs. 81.8 ± 10.2) was added. In SpFFs media, there was a quadratic relationship (P < 0.01) between IGF-I concentration and IVM (peak results at IGF-I = 129 ng/mL). However, when the COCs were matured with LpFFs, there was a decreasing linear effect between IGF-I concentration and IVM. At all concentrations of IGF-I, the percentage of degenerated oocytes was higher in COCs matured in SpFFs than in LpFFs. Penetration (%) did not differ (P > 0.05) between COCs matured with SpFFs or LpFFs when 60 (66.8 ± 9.4 vs. 72.7 ± 11.3) or 180 ng/mL of IGF-I (75.7 ± 10.4 vs. 73.8 ± 13.2) were used. Monospermy (%) was similar between SpFFs and LpFFs only with addition of 120 ng/mL IGF-I. The IVF performance (%) did not differ between COCs matured with SpFFs or LpFFs when IGF-I concentrations of 120 (28.5 ± 8.8 vs. 38.5 ± 8.3) and 180 ng/mL (24.3 ± 10.2 vs. 30.12 ± 8.2) were used. There was no effect of IGF-I concentration or of FF type on the number of penetrated sperm per oocyte and on male pronuclear formation. For COCs matured with SpFFs, there was a quadratic relationship between IGF-I concentration and penetration, monospermy, and IVF performance (peak results at IGF-I = 179, 122, and 135 ng/mL, respectively). Thus, on the basis of the observed quadratic relationships, we inferred that when using SpFFs, the addition of IGF-I (122-179 ng/mL) to the IVM medium produced results similar to those obtained with LpFFs without adding IGF-I. In conclusion, the addition of IGF-I to the IVM medium supplemented with SpFFs increased maturation and improved IVF results. Alternatively, IGF-I had no effect on IVM or IVF when used with LpFFs.

The cryobiology of spermatozoa

The impact of successful cryopreservation of spermatozoa can be found in many fields, including agriculture, laboratory animal medicine, and human assisted reproduction, providing a cost-effective and efficient method to preserve genetic material for decades. The success of any cryobiologic protocol depends critically on understanding the fundamentals that underlie the process. In this review, we summarize the biophysical fundamentals critical to much of the research in sperm cryobiology, provide a synopsis of the development of sperm cryobiology as a discipline, and present the current state and directions for future research in sperm cryobiology in the three major areas outlined above-agriculture, laboratory animal medicine, and human clinical assisted reproduction. There is much room for new research, both empiric and fundamental, in all areas, including refinement of mathematical models, optimization of cryoprotective agent addition and removal procedures for spermatozoa from many species, development of effective, efficient, and facile cryopreservation protocols and freezing containers for agricultural sperm cryopreservation, and tailoring cryopreservation protocols for individual human samples.

GH overexpression decreases spermatic parameters and reproductive success in two-years-old transgenic zebrafish males

Growth hormone (GH) transgenesis has been postulated as a biotechnological tool for improving growth performance in fish aquaculture. However, GH is implied in several other physiological processes, and transgenesis-induced GH excess could lead to unpredictable collateral effects, especially on reproductive traits. Here, we have used two-years-old transgenic zebrafish males to evaluate the effects of GH-transgenesis on spermatic parameters and reproductive success. Transgenic spermatozoa were analyzed in terms of motility, motility period, membrane integrity, mitochondrial functionality, DNA integrity, fertility and hatching rate. We have also performed histological analyses in gonad, in order to verify the presence of characteristic cell types from mature testes. The results obtained have shown that, even in transgenic testes present in all cells in normal mature gonads, a significant general decrease was observed in all spermatic and reproductive parameters analyzed. These outcomes raise concerns about the viability of GH-transgenesis appliance to aquaculture and the environmental risks at the light of Trojan gene hypothesis.

Cryobanking of farm animal gametes and embryos as a means of conserving livestock genetics

In the last few decades, farm animal genetic diversity has rapidly declined, mainly due to changing market demands and intensification of agriculture. But, since the removal of single species can affect the functioning of global ecosystems, it is in the interest of international community to conserve the livestock genetics and to maintain biodiversity. Increasing awareness on the reduction of breed diversity has prompted global efforts for conservation of farm animal breeds. The goals of conservation are to keep genetic variation as gene combinations in a reversible form and to keep specific genes of interest. For this purpose two types of strategies are usually proposed: in situ and ex situ conservation. In situ conservation is the breed maintaining within the livestock production system, in its environment through the enhancement of its production characteristics. Ex situ in vivo conservation is the safeguard of live animals in zoos, wildlife parks, experimental farms or other specialized centres. Ex situ in vitro conservation is the preservation of genetic material in haploid form (semen and oocytes), diploid (embryos) or DNA sequences. In the last few years, ex situ in vitro conservation programs of livestock genetic resources have focused interest on cryopreservation of gametes, embryos and somatic cells as well as testis and ovarian tissues, effectively lengthening the genetic lifespan of individuals in a breeding program even after the death. However, although significant progress has been made in semen, oocytes and embryo cryopreservation of several domestic species, a standardized procedure has not been established yet. The aim of the present review is to describe the cryobanking purposes, the collection goals, the type of genetic material to store and the reproductive biotechnologies utilized for the cryopreservation of farm animal gametes and embryos.

How is plasminogen/plasmin system contributing to regulate sperm entry into the oocyte?

Plasminogen is present in the oviduct, on the zona pellucida (ZP) and on oolemma, and reduces the number of sperm penetrating the oocyte during in vitro fertilization in pig and cow. It is unknown how this reduction occurs. We tested whether plasminogen (1) changed the ZP resistance to enzymatic digestion thus making the passage of the spermatozoa across it difficult; (2) reduced the sperm functionality, assessed by sperm viability, motility, spontaneous acrosome reaction and membrane lipid disorder; or (3) affected the sperm-ZP binding before or after sperm-ZP interaction. The mechanism by which plasminogen/plasmin system contributes to regulate sperm entry into the oocyte is not inducing a ZP hardening or a decrease in sperm functionality but detaching more than 50% of sperm bound to the ZP. It is suggested that the fertilizing spermatozoon activates plasminogen into plasmin at the oocyte surface and that plasmin removes additional spermatozoa attached to the ZP.

Does Seminal Plasma PSP-I/PSP-II Spermadhesin Modulate the Ability of Boar Spermatozoa to Penetrate Homologous Oocytes In Vitro?

Low concentration (0.15 mg per million of spermatozoa) of seminal plasma-derived PSP-I/PSP-II spermadhesin heterodimer is able to preserve the viability of highly extended boar spermatozoa. Whether spermatozoa also keep their fertilizing capacity is not yet known. The present study evaluated the effect of exposing freshly extended and frozen-thawed boar spermatozoa (10 million/mL) to PSP-I/PSP-II (1.5 mg/mL) for 30 or 120 minutes on sperm characteristics and the outcome of in vitro penetration of immature (IM) and in vitro matured (IVM) homologous oocytes, aiming to identify this spermadhesin as a suitable modulator for sperm-handling protocols. Although exposure to the heterodimer improved sperm viability and motility without increasing the levels of sperm acrosome exocytosis in both freshly extended and frozen-thawed spermatozoa, this pretreatment did not affect sperm penetration rates or sperm numbers per oocyte when pretreated fresh spermatozoa were coincubated with IM or IVM oocytes compared with controls. When cryopreserved spermatozoa were tested, however, on IVM oocytes, already a 30-minute preincubation exposure to PSP-I/PSP-II showed a significant blocking effect on penetration rate (from 90% to 32%, P < .05) and on mean sperm numbers per oocyte (2.9 to 1.6, P < .05). To disclose the nature of this paradox, frozen-thawed spermatozoa were cleansed (by centrifugation in saline bovine serum albumin or through Percoll density gradient separation) and the procedure repeated. Oocyte penetration (but not number of spermatozoa per oocyte) increased (P < .05) when spermatozoa were cleansed with Percoll compared with either washed or unwashed controls (53% vs 13% vs 31%, respectively). In addition, the percentages of polyspermic oocytes remained lower than control (38.5% vs 68.7%, respectively; P < .05). In conclusion, the results confirm that exposure of fresh or frozen-thawed boar spermatozoa to a low dose of seminal PSP-I/PSP-II spermadhesin preserves sperm viability and motility in vitro. Although there was no obvious influence of the heterodimer on the capability of freshly extended boar spermatozoa to penetrate homologous oocytes (either IM or IVM), PSP-I/PSP-II exerted a deleterious effect when frozen-thawed spermatozoa were used to penetrate IVM oocytes. Such an effect of cryopreservation seems to a certain extent reversible, since cleansing of the sperm surface decreased, at least partially, this blocking effect, increasing both penetration and the monospermic rates.

Effects of Centrifugation Before Freezing on Boar Sperm Cryosurvival

Current protocols for boar sperm cryopreservation require the centrifugation of semen in order to separate sperm cells from the seminal plasma. This study evaluated the influence of different centrifugation regimes on both sperm recovery and yield (percentage of viable sperm with an intact acrosome relative to the initial sperm population) after centrifugation (experiment 1) as well as the influence of different centrifugation regimes on boar sperm cryosurvival (experiment 2). In both experiments, sperm-rich fractions from 3 boars were diluted, pooled, and cooled to 17 degrees C before centrifugation. In experiment 1, the g-forces tested were 400, 800, 1600, and 2400 x g for 3 or 5 minutes, using the standard regime (800 x g for 10 minutes) as a reference. Sperm recovery (Bürker Chamber) and yield (triple fluorescent stain of PI/R123/FITC-PNA [DNA-specific fluorochrome propidium iodide/mitochondria-specific fluorochrome rhodamine-123/acrosome-specific fluorochrome fluorescein isothiocyanate-labeled peanut (Arachis hypogaea) agglutinin]) were calculated. The highest recovery and yield (P <.05) values were achieved using 2400 x g for 5 or 3 minutes and 1600 x g for 5 minutes, which showed no differences (P >.05) from the reference in terms of sperm yield. In experiment 2, cooled semen was centrifuged using 3 different regimes: C1 (2400 x g for 3 minutes), C2 (1600 x g for 5 minutes), and C3 (800 x g for 10 minutes). Pellets were diluted in lactose-egg yolk (LEY)-glycerol-Equex STM (1 x 10(9) cells/mL) and frozen in 0.5-mL straws. After thawing, sperm quality was assessed after 30 and 150 minutes of incubation (37 degrees C). Centrifugation regimes C1 and C2 showed significantly (P <.05) higher postthaw sperm motility (assessed with a computer-assisted semen analysis system), viability (evaluated as for experiment 1), and percentage of uncapacitated sperm (assessed with a chlortetracycline assay) than did C3. In addition, C1 had the highest (P <.05) oocyte penetrating ability (assessed with the homologous in vitro penetration test performed with immature oocytes). Malondialdehyde production, assessed with the thiobarbituric acid reactive species test, was unaffected (P >.05) by the centrifugation regime used. We conclude that high g-force (2400 x g) and short centrifugation time (3 minutes) do not affect sperm recovery and yield and that, moreover, they have a positive effect on the cryosurvival of boar sperm. Therefore, we recommend the use of short-term centrifugation with a relatively high g-force (2400 x g for 3 minutes) in boar sperm cryopreservation protocol.

Effects of lipid polarisation on survival of in vivo-derived porcine zygotes vitrified by the superfine open pulled-straw method

This study aimed to evaluate the post-warming in vitro viability of intact porcine zygotes vitrified using the superfine open pulled-straw (SOPS) method and to investigate whether cryotolerance is increased by lipid polarisation before vitrification. In vivo-derived zygotes (n = 317) were either untreated before SOPS vitrification or subjected to one of the following pre-treatments: (1) centrifugation (20 min, 15 000g) or (2) equilibration in high-osmolality medium (6 min, 400 mOsm kg–1) followed by centrifugation. Vitrified–warmed and non-vitrified fresh zygotes were cultured in vitro for 120 h. There were no differences in the blastocyst formation rates between the vitrification groups (from 35.4 ± 5.3% to 48.2 ± 5.6%), but fresh zygotes exhibited higher (P < 0.001) blastocyst formation rates (87.5 ± 5.3%) than did vitrified–warmed zygotes. The total blastocyst cell number was similar among all groups (from 34.9 ± 2.8 to 44.1 ± 2.8). In conclusion, SOPS vitrification is a promising method for the cryopreservation of untreated in vivo-derived porcine zygotes. Neither lipid polarisation by centrifugation nor exposure to a high-osmolality medium followed by centrifugation affected the post-warming in vitro viability of zygotes. Our study also demonstrated that the donor is an important factor in determining the success of vitrification for in vivo-derived porcine zygotes.

Seminal plasma proteins as modulators of the sperm function and their application in sperm biotechnologies

Seminal plasma (SP) is known to play an important role in mammalian fertilization. However, the variability found in its composition among species, males and even fractions of the same ejaculate has made difficult to completely understand its effect in sperm function. Proteins are one of the major SP components that modulate sperm functionality. During the last years, intensive work has been performed to characterize the role of these proteins. They have been found to influence sperm capacitation, formation of the oviductal sperm reservoir and sperm-oocyte interaction. Sperm biotechnologies, such as sperm cryopreservation and flow cytometric sex-sorting, that involve a substantial dilution of the SP are detrimental to sperm quality. Attempts to improve the outcome of these biotechnologies include the restoration of SP, which has produced contradictory results. To overcome this variability, different research groups have proposed the application of isolated SP proteins. Herein, we will review the current knowledge in the role of the major SP proteins as modulators of sperm functionality. Furthermore, we will discuss the possible applications of the SP proteins in sperm cryopreservation and flow cytometric sex-sorting.

Fluorometric evaluation of cryopreserved bovine spermatozoa extended in egg yolk and milk

A comparison of fluorogenically quantifiable parameters of cryopreserved, bovine spermatozoa that had been processed in homogenized milk and egg yolk citrate-based extenders was made using flow cytometry. Semen from four bulls was processed in egg yolk-citrate or homogenized milk extenders, packaged in straws and frozen at -196 degrees C. Samples were thawed at 37 degrees C, subdivided into three portions and stained after 0, 1.5 and 3 h of incubation at 37 degrees C. Spermatozoa were stained using a combination of carboxyfluorescein diacetate (CFDA) and propidium iodide (PI) and analyzed by dual parameter flow cytometry. The sperm cells were quantified fluorometrically at each time interval for both green and red fluorescence. The proportion of spermatozoa retaining the fluorescent CFDA derivative was larger at each time interval for samples in egg yolk citrate than those in milk. Differences in the retention of spermatozoal viability were detected between identical samples of bovine spermatozoa extended in milk or egg yolk based media.

Non-surgical deep intrauterine transfer of superfine open pulled straw (SOPS)-vitrified porcine embryos: evaluation of critical steps of the procedure

Previous trials achieved extremely poor results when using the one-step warming method in a syringe in combination with non-surgical deep intrauterine transfer (NET) of superfine open pulled straw (SOPS)-vitrified embryos. This study aimed to assess the effect of the warming procedure on the in vitro and in vivo development of SOPS-vitrified embryos. The effect of the passage of the vitrified-warmed (VW) embryos through the NET catheter was also evaluated. Groups of 4 to 6 morulae and blastocysts, collected from weaned sows, were SOPS-vitrified in 1 μL of vitrification medium, warmed by the one-step warming method in a dish or in a 1-mL syringe and cultured in vitro for 48 h to evaluate the embryo survival (ES) and hatching rates (HR). Warming in syringe had a deleterious effect (P < 0.05) on the in vitro ES (60.5 ± 10.4%) and HR (39.6 ± 9.5%) of VW embryos in comparison with embryos warmed in a dish (85.4 ± 10.6% and 69.0 ± 8.4%, respectively). This decreased embryonic development was due to the increased time required between the removal of the straws from the liquid nitrogen and the contact of the embryos with the warming medium when the warming was performed in a syringe in comparison with that for the warming in a dish. After verifying that the passage of VW embryos through the NET catheter does not have a damaging effect on their further in vitro development, the negative effect of warming in a syringe was also confirmed after NET. Fifteen fresh and SOPS-vitrified embryos warmed in a syringe or in a dish were transferred to each recipient (n = 28) and recovered 24 h later to assess their developmental progression. All embryos from the syringe group were found to have degenerated at recovery. The in vivo ES and HR from the dish group (80.4 ± 3.4% and 14.2 ± 7.2%, respectively) were lower (P < 0.05) than those from the fresh group (94.0 ± 4.1% and 36.8 ± 7.8%, respectively). Combining the warming in a dish and the NET procedure, 35 VW embryos were transferred to each of 10 gilts. Five recipients farrowed an average of 10.4 ± 0.9 piglets. In conclusion, the method of one-step warming in a syringe has a negative effect on the in vitro and in vivo viability of SOPS-vitrified porcine embryos. In addition, NET of SOPS-vitrified embryos warmed by the one-step method in a dish showed promising reproductive performance of recipients. However, despite the great potential of this technology, further developments are required for large-scale commercial applications.

Emerging applications of sperm, embryo and somatic cell cryopreservation in maintenance, relocation and rederivation of swine genetics

Advances in porcine assisted reproductive technology (ART) make it possible to use cryopreserved sperm, embryos and somatic cells in the maintenance, relocation and regeneration of swine genetics. In this review, development of key application-limiting technology is discussed in each cell type, focusing on the efficiencies, ease of storage and transportation, and minimization of pathogen transmission. Methods to regenerate swine genetics and/or models using frozen sperm, embryos and somatic cells in combination with other porcine ARTs, such as in vitro fertilization (IVF), intracytoplasmic sperm injection (ICSI), and somatic cell nuclear transplantation (SCNT), are also discussed. The applications of these ARTs utilizing cryopreserved cells will greatly increase the efficiency as well as biosecurity for maintenance, relocation and rederivation of swine genetics/models.

Effect of different monosaccharides and disaccharides on boar sperm quality after cryopreservation

The aim of the present study was to evaluate the cryoprotectant effect of different non-permeating sugars for boar sperm. Pooled semen from three boars was used for the experiments. In the first experiment, the sperm quality of boar sperm cryopreserved with an egg-yolk based extender supplemented with different monosaccharides (glucose, galactose or fructose) was compared to a control cryopreserved in lactose-egg yolk extender. In the second experiment, the effect of five disaccharides (lactose, sucrose, lactulose, trehalose or melibiose) on boar sperm cryosurvival was studied. Several sperm quality parameters were assessed by flow cytometry in samples incubated for 30 and 150 min at 37°C after thawing: percentages of sperm with intact plasma membrane (SIPM), sperm presenting high plasma membrane fluidity (HPMF), sperm with intracellular reactive oxygen substances production (IROSP) and apoptotic sperm (AS). In addition, the percentages of total motile (TMS) and progressively motile sperm (PMS) were assessed at the same incubation times with a computer-assisted sperm analysis system. Freezing extenders supplemented with each of the monosaccharide presented smaller cryoprotective effect than the control extender supplemented with lactose (P<0.05). However, from the three monosaccharides tested, glucose provided the best sperm quality after freezing-thawing. With respect to the disaccharides studied, samples frozen with the extender supplemented with lactulose exhibited in general the lowest sperm quality, except for the percentage of capacitated sperm, which was highest (P<0.05) in the samples cryopreserved with the trehalose extender. Our results suggest that disaccharides have higher cryoprotective effect than monosaccharides, although the monosaccharide composition of the disaccharides is also important, since the best results were obtained with those disaccharides presenting glucose in their composition.

Glycerol decreases the integrity of the perinuclear theca in boar sperm

We evaluated the effect of glycerol on the perinuclear theca (PT) of boar sperm. Samples from six ejaculates obtained from three different boars were incubated in the detergent Brij 36-T. Spermatozoa were treated with a glycerol concentration of either 2 or 4%, and incubated for 10 or 30 min; two other samples were treated with protease inhibitors (PI; leupeptin or an inhibitor commercial cocktail), mixed with 4% glycerol, and incubated for 30 min. A third glycerol-free group was used as the control. The samples were processed for electron microscopy evaluation. The PT remained intact in 78% of the control samples while, after addition of glycerol for 30 min, the proportion of spermatozoa with disrupted or absent PT increased (P < 0.05). PT was preserved in PI samples, but PT changes increased (P < 0.05). Differences due to treatment with glycerol (2 or 4%) at 10 or 30 min were not observed. These results show, to our knowledge for the first time, the adverse effect of glycerol on the integrity of the PT.

Identification of the inorganic pyrophosphate metabolizing, ATP substituting pathway in mammalian spermatozoa

Inorganic pyrophosphate (PPi) is generated by ATP hydrolysis in the cells and also present in extracellular matrix, cartilage and bodily fluids. Fueling an alternative pathway for energy production in cells, PPi is hydrolyzed by inorganic pyrophosphatase (PPA1) in a highly exergonic reaction that can under certain conditions substitute for ATP-derived energy. Recombinant PPA1 is used for energy-regeneration in the cell-free systems used to study the zymology of ATP-dependent ubiquitin-proteasome system, including the role of sperm-borne proteasomes in mammalian fertilization. Inspired by an observation of reduced in vitro fertilization (IVF) rates in the presence of external, recombinant PPA1, this study reveals, for the first time, the presence of PPi, PPA1 and PPi transporter, progressive ankylosis protein ANKH in mammalian spermatozoa. Addition of PPi during porcine IVF increased fertilization rates significantly and in a dose-dependent manner. Fluorometric assay detected high levels of PPi in porcine seminal plasma, oviductal fluid and spermatozoa. Immunofluorescence detected PPA1 in the postacrosomal sheath (PAS) and connecting piece of boar spermatozoa; ANKH was present in the sperm head PAS and equatorial segment. Both ANKH and PPA1 were also detected in human and mouse spermatozoa, and in porcine spermatids. Higher proteasomal-proteolytic activity, indispensable for fertilization, was measured in spermatozoa preserved with PPi. The identification of an alternative, PPi dependent pathway for ATP production in spermatozoa elevates our understanding of sperm physiology and sets the stage for the improvement of semen extenders, storage media and IVF media for animal biotechnology and human assisted reproductive therapies.

Single Layer Centrifugation Can Be Scaled-Up Further to Process up to 150 mL Semen

Single-Layer centrifugation has been used to improve the quality of sperm samples in several species. However, where stallion or boar semen is to be used for AI, larger volumes of semen have to be processed than for other species, thus limiting the effectiveness of the original technique. The objective of the present study was to scale up the SLC method for both stallion and boar semen. Stallion semen could be processed in 100 mL glass tubes without a loss of sperm quality, and similarly, boar semen could be processed in 200 mL and 500 mL tubes without losing sperm quality. The results of these preliminary studies are encouraging, and larger trials are underway to evaluate using these methods in the field.

Colloid centrifugation removes seminal plasma and cholesterol from boar spermatozoa

The objective of the present study was to investigate the effect of Single-Layer Centrifugation (SLC) on boar spermatozoa, namely the effect of removal of seminal plasma proteins and cholesterol from the surface of spermatozoa. The presence of porcine seminal plasma proteins I and II (PSP-I/PSP-II) before and after SLC was studied using immunofluorescence, whereas the removal of cholesterol was shown qualitatively by thin-layer chromatography (TLC). Finally, the integrity of the sperm plasma membrane was observed by electron microscopy. It was shown that the seminal plasma proteins PSP-I and -II were removed from spermatozoa during SLC but could be restored by adding seminal plasma to the SLC-selected sperm samples. Some cholesterol was also lost from the spermatozoa during SLC but the plasma membrane itself appeared to be morphologically intact. Further studies are underway to examine the relevance of these findings to boar sperm cryopreservation and sperm fertility.

Characterisation of an in vitro system to study maternal communication with spermatozoa

In vivo, gamete maturation, fertilisation and early embryonic development take place inside the oviduct. Several studies have indicated that local responses towards gametes and embryos are generated by the maternal reproductive tract. However, no defined in vitro model currently exists to allow detailed and systematic investigation of maternal communications with gametes and embryos. Therefore, we characterised an in vitro model based on the interaction of boar spermatozoa with an immortalised porcine oviduct epithelial cell line to evaluate different factors that may affect this model. The factors tested were sperm viability, source of spermatozoa, cell passage effect and the effect of reproductive and non-reproductive epithelial cells in the interaction with spermatozoa. After 24 h of co-incubation, RNA was extracted and used to synthesise cDNA for quantitative real-time PCR. Alteration in the expression of genes such as adrenomedullin, heat-shock 70-kDa protein 8 and prostaglandin E synthase was considered as the end point of this assay. The results showed that sperm viability and cell passage number had an effect on oviductal gene expression in response to spermatozoa. Oviductal cells showed significant alterations in gene expression when compared with non-reproductive epithelial cells. The simple in vitro system described here has potential application for further studies in our understanding of mechanisms involved in maternal interactions with spermatozoa.