Survival of small and large littermate blastocysts in swine after synchronous and asynchronous transfer procedures

Achievements and future perspectives of embryo transfer technology in pigs

Commercial embryo transfer (ET) has unprecedented productive and economic implications for the pig sector. However, pig ET has been considered utopian for decades mainly because of the requirements of surgical techniques for embryo collection and embryo deposition into recipients, alongside challenges to preserve embryos. This situation has drastically changed in the last decade since the current technology allows non-surgical ET and short- and long-term embryo preservation. Here, we provide a brief review of the improvements in porcine ET achieved by our laboratory in the past 20 years. This review includes several aspects of non-surgical ET technology and different issues affecting ET programmes and embryo preservation systems. The future perspectives of ET technology are also considered. We will refer only to embryos produced in vivo since they are the only type of embryos with possible short-term use in pig production.

Metabolic compounds within the porcine uterine environment are unique to the type of conceptus present during the early stages of blastocyst elongation

The objective of this study was to identify metabolites within the porcine uterine milieu during the early stages of blastocyst elongation. At Days 9, 10, or 11 of gestation, reproductive tracts of White cross-bred gilts (n = 38) were collected immediately following harvest and flushed with Roswell Park Memorial Institute-1640 medium. Conceptus morphologies were assessed from each pregnancy and corresponding uterine flushings were assigned to one of five treatment groups based on these morphologies: (a) uniform spherical (n = 8); (b) heterogeneous spherical and ovoid (n = 8); (c) uniform ovoid (n = 8); (d) heterogeneous ovoid and tubular (n = 8); and (e) uniform tubular (n = 6). Uterine flushings from these pregnancies were submitted for nontargeted profiling by gas chromatography-mass spectrometry (GC-MS) and ultra performance liquid chromatography (UPLC)-MS techniques. Unsupervised multivariate principal component analysis (PCA) was performed using pcaMethods and univariate analysis of variance was performed in R with false discovery rate (FDR) adjustment. PCA analysis of the GC-MS and UPLC-MS data identified 153 and 104 metabolites, respectively. After FDR adjustment of the GC-MS and UPLC-MS data, 38 and 59 metabolites, respectively, differed (p < .05) in uterine flushings from pregnancies across the five conceptus stages. Some metabolites were greater (p  < .05) in abundance for uterine flushings containing earlier stage conceptuses (i.e., spherical), such as uric acid, tryptophan, and tyrosine. In contrast, some metabolites were greater (p < .05) in abundance for uterine flushings containing later stage conceptuses (i.e., tubular), such as creatinine, serine, and urea. These data illustrate several putative metabolites that change within the uterine milieu during early porcine blastocyst elongation.

The effect of artificial insemination prior to transfer of a limited number of vitrified and warmed porcine embryos by open pulled straw (OPS) method on their survival ability for farrowing

Embryo transfer (ET) of 20 porcine expanded blastocysts (ExBs) vitrified and warmed (VW) by open pulled straw (OPS) to a recipient allows stable piglet production. The efficiency of artificial insemination (AI) prior to ET of 10 VW ExBs for piglet production was investigated. For one trial, 10-15 VW ExBs from single donor were assigned, 10 were used for ET and the remains were assessed for their in vitro viability. In the non-AI/ET group, 10 were transferred to each of five recipients. As AI/ET group, 10 were transferred to each of five recipients after AI. In AI/non-ET group, only AI was performed to seven gilts. In the non-AI/ET group, the pregnancy rate was 40%, but none of them farrowed. In the AI/ET group, all recipients produced piglets. Four (80.0%) delivered piglets from transferred VW ExBs. The survival rate of VW ExBs to term was 20.0% (10/50). In the AI/non-ET group, six of the seven gilts farrowed. There was no difference in in vitro viability between the non-AI/ET and AI/ ET groups (62.5% and 68.3%, respectively). AI prior to ET can be an appropriate way to maintain pregnancy and assist the development of a low number of VW ExBs to term.

In vitro porcine blastocyst development in three-dimensional alginate hydrogels

Appropriate embryonic and fetal development significantly impact pregnancy success and, therefore, the efficiency of swine production. The pre-implantation period of porcine pregnancy is characterized by several developmental hallmarks, which are initiated by the dramatic morphological change that occurs as pig blastocysts elongate from spherical to filamentous blastocysts. Deficiencies in blastocyst elongation contribute to approximately 20% of embryonic loss, and have a direct influence on within-litter birth weight variation. Although factors identified within the uterine environment may play a role in blastocyst elongation, little is known about the exact mechanisms by which porcine (or other species') blastocysts initiate and progress through the elongation process. This is partly due to the difficulty of replicating elongation in vitro, which would allow for its study in a controlled environment and in real-time. We developed a three dimensional (3-D) culture system using alginate hydrogel matrices that can encapsulate pig blastocysts, maintain viability and blastocyst architecture, and facilitate reproducible morphological changes with corresponding expression of steroidogenic enzyme transcripts and estrogen production, consistent with the initiation of elongation in vivo. This review highlights key aspects of the pre-implantation period of porcine pregnancy and the difficulty of studying blastocyst elongation in vivo or by using in vitro systems. This review also provides insights on the utility of 3-D hydrogels to study blastocyst elongation continuously and in real-time as a complementary and confirmatory approach to in vivo analysis.

Ovulation rate and early embryonic survival rate in female rabbits of a synthetic line and a local Algerian population

<p>A higher litter size at birth has been reported in female rabbits from a Synthetic line than in those of the Local Algerian population. The aim of this work was to analyse whether this difference in litter size was due to a higher ovulation rate and/or embryonic survival rate in Synthetic line than in Local Algerian population. In total, 24 multiparous female rabbits from Synthetic line and 23 from Local population were used in this experiment. Litter size at birth was recorded up to the first 3 parities. Litter size was 20% higher in Synthetic line than Local population. At their 4th gestation, the females were euthanized at 72 h post coitum. Synthetic line females had 50% more ova and embryos than those of Local population (+4.42 ova and +3.92 embryos, respectively). Synthetic line displayed a lower percentage of normal embryos and a larger number of unfertilized oocytes than Local population (–2.81% and +0.64 oocytes, respectively), but differences were not relevant. Synthetic line showed a lesser embryonic stage of development at 72 h post coitum, showing a higher percentage of early morulae (31.50 vs. 8.50%) and a lower percentage of compact morulae (51.45 vs. 78.65%) than Local population. No relevant difference was found for early embryonic survival rate between Synthetic line and Local population. In conclusion, the difference in litter size was mainly due to a higher ovulation rate in the Synthetic line, allowing more embryos to develop in this line.</p>

Effect of increased ovulation rate on embryo and foetal survival as a model for selection by ovulation rate in rabbits

Selection for ovulation rate in prolific species has not improved litter size, due to an increase in prenatal mortality, with most mortality observed in the foetal period. The aim of this study was to investigate the magnitude and timing of embryo and early foetal survival in females with high ovulation rate using hormonal treatment as a model for selection by ovulation rate. Two groups of females (treated and untreated) were used. Treated females were injected with 50 IU equine chorionic gonadotropin 48 h before mating. Females were slaughtered at 18 d of gestation. Ovulation rate (OR), number of implanted embryos (IE), number of live foetuses at 12 and 18 d (LF₁₂ and LF₁₈, respectively) were recorded. In addition, embryo survival (ES=IE/OR), foetal survival at 18 d of gestation (FS_LF18=LF₁₈/IE), foetal survival between 12 and 18 d of gestation (FS_LF18/LF12=LF₁₈/LF₁₂) and prenatal survival (PS_LF18=LF₁₈/OR) were estimated. For each female, the mean and variability of the weight for live foetuses (LFWm and LFWv, respectively) and their placentas (LFPWm and LFPWv, respectively) were calculated. Treated females had a higher ovulation rate (+3.02 ova) than untreated females, with a probability of 0.99. An increase in the differences (D) between treated and untreated females was observed from implantation to 18 d of gestation (D=–0.33, –0.70 and –1.28 for IE, LF₁₂ and LF₁₈, respectively). These differences had a low accuracy and the probability that treated females would have a lower number of foetuses also increased throughout gestation (0.60, 0.70 and 0.86 for IE, LF₁₂ and LF₁₈, respectively). According to the previous results for OR and LF₁₈, treated females showed a lower survival rate from ovulation to 18 d of gestation (D=–0.12, P=0.98 for PS_LF18). Treated females also had lower embryo and foetal survival (D=–0.10 and P=0.94 for ES and D=–0.08 and P=0.93 for FS_LF18). Main differences in foetal survival appeared from 12 to 18 d of gestation (D=–0.09 and P=0.98 for FS_LF18/LF12). Unexpectedly, treated females showed similar foetus weight and higher foetal placenta weight than untreated females (D=0.25 g, P=0.98) and lower variability for these traits (D=–0.02 g, P=0.72 for LFWv and D=–0.05 g, P=0.83 for LFPWv). These results are not related to a lower number of IE or LF₁₈. Thus, the effect of increasing by three ova in rabbits leads to a lower embryo and early foetal survival. There seems to be no relationship between foetal mortality and foetus weight.

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.

Embryonic diapause in humans: time to consider?

BACKGROUND

When a competent blastocyst stage embryo finds itself in an unreceptive uterus, it delays development. In around one hundred species representing various orders, this delay is known to be reversible, but this phenomenon - termed embryonic diapause (ED) - is not considered a general characteristic of all mammals.

PRESENTATION OF THE HYPOTHESIS

Recently, however, we demonstrated that a non-diapausing species, the sheep, is capable of ED, suggesting the hypothesis that this is in fact an ancestral trait common to all mammals, including humans.

TESTING THE HYPOTHESIS

In spite of the obvious difficulties in testing this idea, we propose a combination of indirect observations on human fertility patients, and direct study of the embryos of non-human primates.

IMPLICATIONS OF THE HYPOTHESIS

Support for our hypothesis would require revision of obstetric interventions routinely performed when a human pregnancy extends beyond the due date.

Embryonic diapause is conserved across mammals

Embryonic diapause (ED) is a temporary arrest of embryo development and is characterized by delayed implantation in the uterus. ED occurs in blastocysts of less than 2% of mammalian species, including the mouse (Mus musculus). If ED were an evolutionarily conserved phenomenon, then it should be inducible in blastocysts of normally non-diapausing mammals, such as domestic species. To prove this hypothesis, we examined whether blastocysts from domestic sheep (Ovis aries) could enter into diapause following their transfer into mouse uteri in which diapause conditions were induced. Sheep blastocysts entered into diapause, as demonstrated by growth arrest, viability maintenance and their ED-specific pattern of gene expression. Seven days after transfer, diapausing ovine blastocysts were able to resume growth in vitro and, after transfer to surrogate ewe recipients, to develop into normal lambs. The finding that non-diapausing ovine embryos can enter into diapause implies that this phenomenon is phylogenetically conserved and not secondarily acquired by embryos of diapausing species. Our study questions the current model of independent evolution of ED in different mammalian orders.

Production of piglets from in vitro-produced embryos following non-surgical transfer

The objective of this study was to enhance procedures for producing piglets derived from in vitro-produced (IVP) pig embryos by non-surgical embryo transfer (ET). The effects of insertion length for the catheter, asynchrony between the age of donor IVP blastocysts and the recipient estrous cycle, and volume of transfer medium were investigated. The IVP blastocysts at 5 days after in vitro fertilization were placed into porcine zygote medium (PZM)-5 supplemented with 10% (v/v) fetal bovine serum (PZM+FBS) in a 0.25 mL plastic straw (21-40 blastocysts per straw) and then transferred into one uterine horn of recipients using the Takumi(®) catheter for deep intrauterine insertion. Successful production of piglets derived from IVP embryos was achieved following non-surgical ET when the catheter was inserted at more than 30 cm anterior to the spiral guide spirette. The efficiency of piglet production (percentage number of piglet(s) born based on the number of embryos transferred) was greater (P<0.05) in recipients whose estrous cycle was asynchronous to that of donors with a 1-day delay (8.3%) than in those with a 2-day (1.5%) or 3-day (0.9%) delay, while pregnancy and farrowing rates (10-40%) did not differ among treatments. When blastocysts were transferred into recipients with 1.0 or 2.5 mL PZM+FBS, there were no significant differences in farrowing rate (30-40%) or average litter size (4.5-6.7) between treatments. The results of the present study indicate that the insertion length of the deep intrauterine catheter and the degree of asynchrony between donor embryos and recipient estrous cycle influenced on pregnancy and birth outcome following non-surgical transfer of IVP blastocysts.

Characteristics of peri-implantation porcine concepti population and maternal milieu influence the transcriptome profile

Asynchrony of trophectoderm elongation, gestational days 11-12, is evident in porcine concepti, and rapid progression through this phase has been associated with conceptus competency. The goal of the current study was to determine the extent of transcriptomic responses of concepti to developmental delay and their physiological implications. Gestational day 11 concepti with the same morphology, ovoid and 7-8 mm, were isolated and designated as control or developmentally delayed if collected from a homogenous ovoid conceptus population or heterogeneous conceptus population (ovoid to filamentous), respectively. Total RNA prepared from four distinct control and four distinct developmentally delayed concepti, was analyzed using an Agilent high-density custom porcine microarray. Two hundred nine transcripts were found differentially expressed between normal and developmentally delayed concepti. Functional analysis of these genes indicated that a significant number of the genes regulate signal transduction/transcription, organismal development, metabolism, and cell adhesion and can be modulated by transforming growth factor β1 (TGFβ1). Ten genes were selected for real-time PCR validation of differential expression based on a known role in steroid synthesis, endometrium receptivity, and modulation of trophoblast differentiation/growth or interaction with TGFβ1. As in the microarray, all except one, achaete-scute complex homolog 2, were preferentially up-regulated in delayed concepti. Overall, findings suggested that despite similar morphology, the transcriptome of developmentally delayed concepti is distinct from control counterparts. Also highlighted were ways by which the conceptus' microenvironment might be affected and developmental factors that may be of interest to interrogate further to determine if, and how, they affect embryo competency/elongation.

Oestrous synchronization, ovarian superovulation and intraspecific transfers from a closed breeding colony of inbred SLA miniature pigs

The inbred SLA miniature pig is a unique animal model developed for organ transplantation studies and pre-clinical experimental purposes. Reported oestrous synchronization and superovulation treatments were examined in two SLA haplotypes (AA and DD) to allow collection of embryos for both practical embryo transfer and experimental technologies from a closed breeding colony. Pre-puberal miniature pigs were poor responders to oestrous synchronization treatments, while post-puberal sows were equivalent to commercial sows. Following superovulation, the ovulation number (corpora .hemorrhagica) was higher (p < 0.05) in the cycling sows when compared with non-cycling sows. Ovulations were equivalent to commercial pre-puberal gilts and non-cycling sows (p > 0.05). No difference in ovulation number between haplotypes was observed, which differs from the previous report (DD>AA). Collection of zygotes for pronuclear injection was the highest in the non-cycling post-puberal miniature pig group (p < 0.05), although significantly lower when compared with the commercial pig treatment groups (p < 0.05). The incidence of cystic endometrial hyperplasia in our colony was equivalent to rates observed in commercial pigs. Pronuclear visualization following centrifugation was the highest in the non-cycling miniature sow group and approximates to about 25% of ovulations and about half the rate observed in the commercial pigs (50%). Miniature pig embryos transferred between SLA haplotypes and transfer of DD embryos to commercial pigs resulted in live births at a higher efficiency than previously reported. This study demonstrates the feasibility of undertaking assisted reproductive technologies in a closed breeding colony of inbred SLA miniature pigs without compromise to the breeding programmes.

Factors influencing the success of embryo transfer in the pig

Progress in reproductive biotechnologies has led to an increased use of embryo transfer in both swine research and swine production. This review article describes the history and subsequent development of porcine embryo transfer. Special attention is given to aspects of the overall process of embryo transfer which are unique to pigs.

The effects of group size on development and interferon-tau secretion by in-vitro fertilized and cultured bovine blastocysts

The effects of culturing bovine embryos in groups were investigated. In the first experiment, 1000 oocytes were matured, fertilized and then cultured in groups of 40 in 25 microl of medium. From half of these groups, blastocysts were removed and cultured separately, while in the other half blastocysts were allowed to remain in the group culture microdrop. Blastocysts developed equally well in both groups, although hatching was reduced in those blastocysts removed from the culture droplet. In the second experiment, 1000 zygotes were cultured from the 8-cell stage to the blastocyst stage either individually or in groups of 40. Culture in groups increased the formation of blastocysts, the percentage of hatching blastocysts, the number of cells within blastocysts and the production of interferon-tau. In the final experiment, 1000 zygotes were cultured in groups up to the blastocyst stage. Two-thirds of these blastocysts were then cultured in groups of three, while the remaining blastocysts were cultured individually. Co-culture did not affect hatching or cell number but significantly elevated interferon-tau secretion. These results demonstrate that group culture either before or after blastocyst formation can alter the expression of a specific gene important for the establishment of pregnancy.

Follicular development and ovulation in sows: effect of hCG and GnRH treatment

Follicular growth, chronology of ovulation and embryo morphology were compared in sows ovulating spontaneously and sows, in which the ovulation was attempted induced by hCG or GnRH. Indwelling catheters were placed on day 1 (weaning = day 0) in the ear veins of 18 sows, which were then randomly divided into 3 groups: a control group (N = 6), a group (N = 6) given 750 iu hCG (Physex) im 76h after weaning (hCG group) and a group (N = 6) given 500 micrograms GnRH (Fertagyl) im 76h (N = 3) or 100h after weaning (N = 3) (GnRH group). Follicular diameter and time of ovulation were monitored by ultrasonography every 4h from day 3 until ovulation or development of cysts by means of a sector scanner fitted with a 5.0/7.5 MHz multiangle probe. Heat detection was performed every 8h from day 3 until ovulation. On day 13, the sows were slaughtered, the number of corpora luteae (CL) was counted, and embryos were flushed from the uteri. The control group showed clear heat symptoms, and on day 3, the follicles were typically 3-7 mm and grew up to 7-10 mm over 2 days, where they remained for approximately 24h until ovulation took place 41h +/- 9h after first sign of standing heat. The hCG group exhibited no signs of heat, and the follicles only reached 5-8 mm in diameter at time of ovulation, which occurred 40h +/- 1h after hCG-injection. The GnRH group exhibited inconsistent signs of heat, and the follicles reached a maximum size of 7-12 mm in diameter where they remained for more than 24h. Only 2 sows in this group ovulated within 84-92h after the GnRH injection, and development of bursa cysts and cystic follicles was a common finding. The average number of CL was 18.2 +/- 5.7 per sow (N = 16, range: 3-27) with no significant difference between the groups. Total embryo recovery was 79 +/- 13% with no significant difference between groups. The embryo diversity calculated as standard deviation of the maximum diameter was higher in the hCG group as compared with the control group.(ABSTRACT TRUNCATED AT 400 WORDS)

Survival of early preimplantation porcine embryos after co-culture with cells producing an avian retrovirus

To determine the relative survival of porcine embryos after co-culture with cells producing an avian retrovirus, four-cell stage embryos were obtained from sows following synchronization with altrenogest and superovulation with gonadotropins. These embryos were randomly assigned to the following treatments: no manipulation (zona-intact); zona removed with acidified Tyrode's solution (zona-free); and zona removed followed by co-culture with D-17 canine cells producing an avian retrovirus vector derived from spleen necrosis virus (zona-free + co-culture). The survival rates of four-cell stage embryos to morulae or early blastocysts during a 48-h culture period were 93.3, 80.0 and 57.7% in zona-intact, zona-free and zona-free + co-culture groups, respectively. Following embryo transfer, the development of embryos to fetuses at six weeks of gestation was 37.5, 30.0 and 11.7% in zona-intact, zona-free and zona-free + co-culture groups. These results indicate that early preimplantation porcine embryos can develop to apparently normal fetuses following co-culture with cells producing a retrovirus, and the feasibility of this method for retrovirus-mediated gene transfer in pigs was demonstrated.