Placental abnormalities in equine pregnancies generated by SCNT from one donor horse

Swine clones: potential application for animal production and animal models

Somatic cell nuclear transfer (SCNT), or cloning, is used to reprogram cells and generate genetically identical embryos and animals. However, the cloning process is inefficient, limiting its application to producing valuable animals. In swine, cloning is mainly utilized to produce genetically modified animals. Indeed, recombinant DNA technologies have evolved considerably in recent years, with homologous recombination and gene editing technologies becoming more efficient and capable of recombining both alleles in a single cell. The selection of appropriate cells and their use as nuclear donors for SCNT is the most common method for generating edited and genetically modified animals for commercial and research purposes. This article reviews current applications of swine cloning and shares our personal experiences with the procedure in this species.

A comparative study across mule, equine and equine clone pregnancies regarding the determination of the day of birth

Monitoring equine parturition effectively is essential for preemptive intervention in periparturient issues and ensuring the overall well-being of both mares and foals. However, its implementation in breeding farms is challenging due to variable gestational lengths and nocturnal births. Predictive techniques have the potential to streamline the monitoring process, reduce labor intensity, and minimize costs. Research on foaling prediction in mares carrying mule or equine clone fetuses is scarce. Therefore, this study aimed to comparatively analyze foaling prediction parameters in mares pregnant with mule, equine, or equine clone fetus. The study included vulvar relaxation, sacroiliac ligament tension, pH, BRIX index, and concentrations of calcium, phosphorus, magnesium, sodium, and potassium in prepartum mammary secretions. Sixty pregnant mares were used for this study and grouped as follows: 25 mares with mule fetuses (MF), 20 with equine clone fetuses (CF), and 15 with equine control fetuses (EF). Results showed significant differences in vulvar relaxation and sacroiliac ligament tension only in MF group (p < 0.05) on the day of parturition compared to the other days evaluated, different from the other groups. Levels of pH notably decreased on parturition day (mean 5.7 ± 0.04, p < 0.0001), with lower values in MF (6.05 ± 0.02) and CF (6.08 ± 0.04) compared to EF (6.26 ± 0.04) (p < 0.03). The BRIX index showed variation across mares and was not a good parameter for foaling prediction. Electrolytes correlated positively with impending parturition, showing no significant differences among groups. The MF and CF groups exhibited a substantial increase (102.13 % and 110.66 %, respectively) in mean calcium concentrations on the day before foaling, unlike EF (38.29 %). In conclusion, the pH values were different in mammary secretions between mares carrying mule and clone fetuses, in contrast to equine control fetuses. Nevertheless, there was a trend of decreasing pH values closer to parturition in all groups. Conversely, the BRIX index serves as a valuable indicator of colostrum quality yet does not offer insights into the proximity of parturition. While electrolyte concentrations did not reveal significant differences among groups, it is worth noting that the evaluation of phosphorus emerges as a new parameter to explore in mares nearing parturition, since it obtained a pattern similar to calcium.

Could assisted reproductive techniques affect equine fetal membranes and neonatal outcome?

Embryo transfer (ET) and intracytoplasmic sperm injection (ICSI) are widely used in equine species, but their effects on fetal adnexa and neonates have not been investigated yet. The aim of this study was to retrospectively evaluate whether pregnancies obtained by ET or ICSI could be associated with the presence of macroscopic alterations of fetal membranes (FM) and umbilical cord (UC) and if the use of these techniques could influence neonatal outcome. Sixty-six light breed mares hospitalized at the Veterinary Teaching Hospital, University of Bologna, for attending delivery were included in the study. Mares were divided into Artificial Insemination (AI; 32/66 mares, 48 %), Embryo Transfer (ET; 12/66 mares, 18.2 %) and Intracytoplasmic Sperm Injection (ICSI; 22/66 mares, 33 %) groups. All the medical reports of mares and their foals were reviewed and data about mare, pregnancy, foaling, fetal membranes, umbilical cord and foal were recorded. The occurrence of dystocia resulted statistically different between AI group and ICSI group (p = 0.0066), and between AI group and ET group (p = 0.044). Macroscopic examination of FM revealed alterations in 30/66 mares (46 %): 8/32 in AI (25 %), 7/12 in ET (58 %) and 15/22 in ICSI (68 %) with significant lower incidence in AI compared to ET (p = 0.04) and ICSI (p = 0.002) groups. Alterations reported were chorionic villi hypoplasia, chorioallantois edema, allantois cysts, necrotic areas and greenish-grey concretions. Total length of UC resulted significantly shorter in ICSI group (49 ± 9 cm; p < 0.03) compared to AI (60 ± 17 cm) and ET (59 ± 15 cm). However, there were no differences in the incidence of foals' diseases at birth and in foals' survival among groups (p > 0.05). The results demonstrate that transfer of in vivo or in vitro produced embryos may lead to alterations of placental development, as observed in other species, without being associated with a higher incidence of neonatal morbidity and mortality. Further studies about trophoblast development, FM histological evaluation, and placental gene expression should be carried out to clarify the mechanisms underlying the placental alterations.

Cloning horses by somatic cell nuclear transfer: Effects of oocyte source on development to foaling

The cloning of horses is a commercial reality, yet the availability of oocytes for cloned embryo production remains a major limitation. Immature oocytes collected from abattoir-sourced ovaries or from live mares by ovum pick-up (OPU) have both been used to generate cloned foals. However, the reported cloning efficiencies are difficult to compare due to the different somatic cell nuclear transfer (SCNT) techniques and conditions used. The objective of this retrospective study was to compare the in vitro and in vivo development of equine SCNT embryos produced using oocytes recovered from abattoir-sourced ovaries and from live mares by OPU. A total of 1,128 oocytes were obtained, of which 668 were abattoir-derived and 460 were OPU-derived. The methods used for in vitro maturation and SCNT were identical for both oocyte groups, and the embryos were cultured in Dulbecco's Modified Eagle's Medium/Nutrient Mixture F-12 Ham medium supplemented with 10% fetal calf serum. Embryo development in vitro was assessed, and Day 7 blastocysts were transferred to recipient mares. The embryos were transferred fresh when possible, and a cohort of vitrified-thawed OPU-derived blastocysts was also transferred. Pregnancy outcomes were recorded at Days 14, 42 and 90 of gestation and at foaling. The rates of cleavage (68.7 ± 3.9% vs 62.4 ± 4.7%) and development to the blastocyst stage (34.6 ± 3.3% vs 25.6 ± 2.0%) were superior for OPU-derived embryos compared with abattoir-derived embryos (P < 0.05). Following transfer of Day 7 blastocysts to a total of 77 recipient mares, the pregnancy rates at Days 14 and 42 of gestation were 37.7% and 27.3%, respectively. Beyond Day 42, the percentages of recipient mares that still had a viable conceptus at Day 90 (84.6% vs 37.5%) and gave birth to a healthy foal (61.5% vs 12.5%) were greater for the OPU group compared with the abattoir group (P < 0.05). Surprisingly, more favourable pregnancy outcomes were achieved when blastocysts were vitrified for later transfer, probably because the uterine receptivity of the recipient mares was more ideal. A total of 12 cloned foals were born, 9 of which were viable. Given the differences observed between the two oocyte groups, the use of OPU-harvested oocytes for generating cloned foals is clearly advantageous. Continued research is essential to better understand the oocyte deficiencies and increase the efficiency of equine cloning.

Genetic Manipulation of the Equine Oocyte and Embryo

As standard in vitro fertilization is not a viable technique in horses yet, many different techniques have been used to create equine embryos for research purposes. One such method is parthenogenesis in which an oocyte is induced to mature into an embryo-like state without the introduction of a spermatozoon, and thus they are not considered true embryos. Another method is somatic cell nuclear transfer (SCNT), in which a somatic cell nucleus from an extant horse is inserted into an enucleated oocyte, creating a genetic clone of the donor horse. Due to limited availability of equine oocytes in the United States, researchers have investigated the potential for combining equine somatic cell nuclei with oocytes from other species to make embryos for research purposes, which has not been successful to date. There has also been a rising interest in producing transgenic animals using sperm exposed to exogenous DNA. The successful creation of transgenic equine blastocysts shows the promise of sperm mediated gene transfer (SMGT), but this method is not ideal for other applications, like gene therapy, because it cannot be used to induce targeted mutations. That is why technologies like CRISPR/Cas9 are vital. In this review, we argue that parthenogenesis, SCNT, and interspecies SCNT can be considered genetic manipulation strategies as they create embryos that are genetically identical to their parent cell. Here, we describe how these methods are performed and their applications and we also describe the few methods that have been used to directly modify equine embryos: SMGT and CRISPR/Cas9.

Autogenous transfer of intracytoplasmic sperm injection-produced equine embryos into the uterus of the oocyte donor during the same oestrous cycle

The clinical use of intracytoplasmic sperm injection (ICSI) in horses usually involves the transfer of embryos into recipient mares, resulting in substantial cost increases. This is essential when subfertile mares are oocyte donors; but some donors are fertile, with ICSI compensating for limited or poor-quality spermatozoa. Fertile oocyte donors could carry pregnancies, eliminating the need for a recipient. We assessed the potential of using oocyte donors as recipients for their own ICSI-produced embryos during the same cycle. Donors in oestrus and with large dominant follicles were administered ovulation-inducing compounds to cause follicle and oocyte maturation. Maturing oocytes were collected, cultured and fertilised using ICSI. At 6 or 7 days after ICSI, developing blastocysts were transferred into respective donors' uteri, and pregnancy rates were determined. Twenty follicles were aspirated from nine mares and 12 oocytes were collected. After ICSI, 10 of the 12 oocytes (83%) cleaved, and eight (67% of injected oocytes) developed into blastocysts for transfer. Five pregnancies resulted from the eight transferred embryos (pregnancy rate 62% per embryo and 42% per sperm-injected oocyte). Following this synchronisation regime, ICSI-produced embryos can be transferred into oocyte donors' uteri during the same cycle, allowing donors to carry pregnancies after assisted fertilisation.

Transcriptome-wide analysis of the SCNT bovine abnormal placenta during mid- to late gestation

The dysfunction of placenta is common in somatic cell nuclear transfer (SCNT) cloned cattle and would cause aberrant fetal development and even abortion, which occurred with highest rate at the mid- to late gestation. However, the mechanism of abnormal placentas was unclear. To analyze the transcriptome-wide characteristics of abnormal placentas in SCNT cloned cattle, the mRNA, lncRNA and miRNA of placental cotyledon tissue at day 180 after gestation were sequenced. A total of 19,055 mRNAs, 30,141 lncRNAs and 684 miRNAs were identified. Compared with control group, 362 mRNAs, 1,272 lncRNAs and nine miRNAs (six known and three novel miRNAs) were differentially expressed (fold change ≥ 2 and P-value < 0.05). The differentially expressed genes were functionally enriched in urea and ions transmembrane transport, which indicated that the maternal-fetal interactions were disturbed in impaired placentas. Furthermore, the competing endogenous RNAs (ceRNAs) networks were identified to illustrate their roles in abnormal placental morphology. The present research would be helpful to discover the mechanism of late gestational abnormality of SCNT cattle by provides important genomic information and insights.

Comparative analysis of bovine maternal corpus luteum microRNAs with aberrant and normal developed cloned fetus at late gestation

BACKGROUND

The development efficiency of cloned cattle is extremely low (< 5%), most of them were aborted at late gestation. Based on our previous studies, some recipient cows with a cloned fetus would present as engorged uterine vessels and enlarged umbilical vessels randomly. Abortion involves both maternal and fetal factors.

OBJECTIVE

Our aim was to explore this phenomenon by microRNAs expression profile analysis of maternal corpus luteum (CL), which was related to pregnancy maintenance.

METHODS

The present study provided the comparison of maternal CL miRNAs expression of abnormally and normally developed cloned bovine fetus at late gestation (~ 210 days) using RNA-Seq technology.

RESULTS

We selected two abnormally pregnant cows (abnormal group, AG) and three normally pregnant cows (normal group, NG) and acquired valid reads of 9317,261-12,327,185 (~ 84.53-91.28%) from five libraries. In total, we identified 981 conserved miRNAs and 223 novel miRNAs. 1052 miRNAs were co-expressed, 124 miRNAs were uniquely expressed in AG, and 93 miRNAs were uniquely expressed in the NG. Compared with NG, 11 were significantly overexpressed, and 22 were downregulated (p < 0.05) at AG among 1052 co-expressed miRNAs. The differentially expressed miRNAs-targeted genes were further analyzed by Gene Ontology and KEGG pathway analysis. Notably, the steroid biosynthesis pathway was a significantly enriched term (p < 0.01), which may affect the secretion of progesterone.

CONCLUSION

Our research suggested that abnormal miRNAs expression of bovine maternal CL may affect the pregnant status at late gestation.

CircRNA expression profile of bovine placentas in late gestation with aberrant SCNT fetus

BACKGROUNDS

One of the limitations of somatic cell nuclear transfer (SCNT) strategy to generate genetically modified offspring is the low birth rate. Placental dysfunction is one of the causes of abortion. Circular RNA (circRNA) is noncoding RNA which functions as microRNA (miRNA) sponges in biological processes.

METHODS

Two aberrant pregnant placenta (aberrant group, AG) and three normal pregnant placenta (normal group, NG) during late gestation (180-210 days) with bovine SCNT fetus were collected for high-throughput sequencing and analyzed. The host genes of differentially expressed (DE) circRNAs were predicted. And the microRNAs (miRNAs) which could interact with DE circRNAs were analyzed. Then, the expressional level of partial DE circRNAs and corresponding host genes was verified through qRT-PCR. At last, the function of host genes was analyzed through Gene Ontology (GO) and Kyoto Encyclopedia of Genes and Genomes (KEGG).

RESULTS

Altogether 123 differentially expressed circRNAs between two groups were identified, which were found related to 60 host genes and 32 miRNAs. The top 10 upregulated circRNAs were bta_circ_0012985, bta_circ_0013071, bta_circ_0013074, bta_circ_0016024, bta_circ_0013068, bta_circ_0008816, bta_circ_0012982, bta_circ_0013072, bta_circ_0019285, and bta_circ_0013067. The top 10 downregulated circRNAs were bta_circ_0024234, bta_circ_0017528, bta_circ_0008077, bta_circ_0003222, bta_circ_0007500, bta_circ_0020328, bta_circ_0011001, bta_circ_0016364, bta_circ_0008839, and bta_circ_0016049. The qRT-PCR results showed consistent trend with sequencing analysis result, while host genes had no statistic difference. The GO and KEGG analyses of the host genes suggested that abnormal circRNA expression may play multiple roles in placental structure and dysfunction.

CONCLUSION

The abnormal circRNA expression may be one of reasons of placental dysfunction, leads to abortion of bovine SCNT fetus.

Epigenetic Alteration of Donor Cells with Histone Deacetylase Inhibitor m-Carboxycinnamic Acid Bishydroxymide Improves the In Vitro Developmental Competence of Buffalo (Bubalus bubalis) Cloned Embryos

Epigenetic reprogramming is an indispensable process during the course of mammalian development, but aberrant in cloned embryos. The aim of this study was to examine the effect of donor cell treatment with histone deacetylase (HDAC) inhibitor m-carboxycinnamic acid bishydroxymide (CBHA) on cloned embryo development and establish its optimal concentration. Different concentrations of CBHA (2.5, 5.0, 10.0, and 20.0 μM) were used to treat buffalo adult fibroblast cells for 24 hours and effect on cell proliferation, gene expression, and histone modifications was analyzed. Based on these experiments, the best concentration was chosen to determine the effect of enhanced gene activation mark on developmental rates. Among the different concentrations, CBHA at higher concentration (20 μM) shows the sign of apoptosis and stress as indicated by proliferation rate and gene expression data. CBHA treatment significantly decreased the activity of HDACs and increased the level of gene activation mark H3K9ac and H3K4me3, but could not alter the level of H3K27ac. Based on these experiments, 5 μM CBHA was chosen for treatment of donor cells used for the production of cloned embryos. There was no significant difference in cleavage rate between the control and CBHA treatment group (98.5% ± 1.5% vs. 99.0% ± 1.0%), whereas, blastocyst rate markedly improved (46.65% ± 1.94% vs. 57.18% ± 2.68%). The level of H3K9ac and H3K27me3 did not differ significantly in cloned blastocyst produced from either control or CBHA-treated cells. Altogether, these results suggested that donor cell treatment with CBHA supports the reprogramming process and improves the cloned preimplantation development.

Characterization of the cervical mucus plug in mares

The cervical mucus plug (CMP) is believed to play an integral role in the maintenance of pregnancy in the mare, primarily by inhibiting microbial entry. Unfortunately, very little is known about its composition or origin. To determine the proteomic composition of the CMP, we collected CMPs from mares (n = 4) at 9 months of gestation, and proteins were subsequently analyzed by nano-LC–MS/MS. Results were searched against EquCab2.0, and proteomic pathways were predicted by Ingenuity Pathway Analysis. Histologic sections of the CMP were stained with H&E and PAS. To identify the origin of highly abundant proteins in the CMP, we performed qPCR on endometrial and cervical mucosal mRNA from mares in estrus, diestrus as well as mares at 4 and 10 m gestation on transcripts for lactotransferrin, uterine serpin 14, uteroglobin, uteroferrin, deleted in malignant brain tumors 1 and mucins 4, 5b and 6. Overall, we demonstrated that the CMP is composed of a complex milieu of proteins during late gestation, many of which play an important role in immune function. Proteins traditionally considered to be endometrial proteins were found to be produced by the cervical mucosa suggesting that the primary source of the CMP is the cervical mucosa itself. In summary, composition of the equine CMP is specifically regulated not only during pregnancy but also throughout the estrous cycle. The structural and compositional changes serve to provide both a structural barrier as well as a physiological barrier during pregnancy to prevent infection of the fetus and fetal membranes.