Embryo aggregation does not improve the development of interspecies somatic cell nuclear transfer embryos in the horse

Different Methods for Seminal Plasma Removal and Sperm Selection on the Quality and Fertility of Collared Peccary Sperm

Methods for seminal plasma (SP) removal and the selection of collared peccary sperm for fertilization were compared. The experiments evaluated the following: the (I) impact of centrifugation for SP removal before swim-up for sperm selection and (II) a comparison of different Percoll^® gradient densities (PG 45-90% and PG 35-70%). Non-selected sperm served as the control. Sperm quality was assessed based on motility patterns, morphology, membrane functional integrity, viability, reactive oxygen species (ROS), glutathione (GSH), and DNA integrity. Subsequently, the most successful group in the previous experiment and washing by centrifugation (WC) were compared for motility patterns and fertilization using pig oocytes. Swim-up decreased motility and enhanced ROS compared to the control. Centrifugation before swim-up harmed integrity and viability compared to the control. PG 45-90% (96.8 vs. 69.7 vs. 40.7 µm/s) allowed for a better velocity average pathway (VAP), a better velocity straight line, and better linearity (LIN) than those of the control and PG 35-70% (88.4 vs. 56.0 vs. 27.3 µm/s). Thus, PG 45-90% was used for fertilization. PG 45-90% obtained a higher VAP, a higher amplitude of the lateral head, straightness, and higher LIN than those of the control and WC. Cleavage (25.2-26.3%) and morula (8.1-10.5%) rates did not differ between the groups. Therefore, PG 45-90% and WC were efficient in isolating collared peccary sperm capable of fertilizing pig oocytes.

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.

Embryo aggregation allows the production of kodkod (Leopardus guigna) blastocysts after interspecific SCNT

The kodkod (Leopardus guigna) is a small felid endemic of Chile and is considered a vulnerable species. Domestic cat oocytes have been successfully used as recipient cytoplast to reprogram somatic cells from different felids by interspecific somatic cell nuclear transfer (iSCNT). The developmental competence of felid embryos generated by iSCNT can be improved by the aggregation method using a zona-free culture system. The objective of this research was to evaluate the developmental competence of kodkod embryos generated by iSCNT using domestic cat oocytes and the aggregation method. For this purpose, five experimental group were done: (1) cat embryos generated by IVF, (2) cat embryos generated by SCNT (Ca1x), (3) aggregated cat embryos generated by SCNT (Ca2x), (4) kodkod embryos generated by iSCNT (K1x) and (5) aggregated kodkod embryos generated by iSCNT (K2x). Cleavage, morulae and blastocyst rates were estimated. The blastocyst diameter was evaluated. The gene expression level of pluripotency (OCT4, SOX2 and NANOG) and differentiation markers (CDX2 and GATA6) was analyzed in blastocysts. Morulae rate was higher in the IVF group and when cloned embryos were cultured in aggregates (IVF: 68.2%, Ca2x: 58.0% and K2x: 62.4%) compared to individually cultured kodkod embryos (K1x: 37.0%) (P < 0.05). Embryo aggregation increased blastocysts formation in the Ca2x group (30.9%) to a similar rate compared to the IVF group (44.5%) (P > 0.05). No blastocysts were generated in the K1x group, whereas blastocysts formation was obtained in K2x group (5.9%). The diameter of blastocysts from the K2x group (172.8 μm) was significantly lower than blastocysts from the Ca2x group (P < 0.05). The relative expression of OCT4 was lower in blastocysts from Ca1x than in blastocysts from IVF (P < 0.05). Furthermore, CDX2 expression was lower in blastocysts from Ca2x than in blastocysts from Ca1x and IVF groups (P < 0.05). In kodkod embryos, only one blastocyst from the K2x group expressed OCT4. No expression of SOX2, NANOG, CDX2 and GATA6 was detected in kodkod blastocysts. In conclusion, after iSCNT, domestic cat oocytes support the development of kodkod embryos until the morula stage. The aggregation method increases the morulae rate of kodkod cloned embryos and allows blastocysts formation. However, kodkod blastocysts have a poor morphological quality and a lacking expression of pluripotency and differentiation markers, probably caused by an incomplete nuclear reprogramming.

Horse ooplasm supports in vitro preimplantation development of zebra ICSI and SCNT embryos without compromising YAP1 and SOX2 expression pattern

Several equids have gone extinct and many extant equids are currently considered vulnerable to critically endangered. This work aimed to evaluate whether domestic horse oocytes support preimplantation development of zebra embryos obtained by intracytoplasmic sperm injection (ICSI, zebroid) and cloning, and to study the Hippo signaling pathway during the lineage specification of trophectoderm cells and inner cell mass cells. We first showed that zebra and horse sperm cells induce porcine oocyte activation and recruit maternal SMARCA4 during pronuclear formation. SMARCA4 recruitment showed to be independent of the genetic background of the injected sperm. No differences were found in blastocyst rate of ICSI hybrid (zebra spermatozoon into horse egg) embryos relative to the homospecific horse control group. Interestingly, zebra cloned blastocyst rate was significantly higher at day 8. Moreover, most ICSI and cloned horse and zebra blastocysts showed a similar expression pattern of SOX2 and nuclear YAP1 with the majority of the nuclei positive for YAP1, and most SOX2+ nuclei negative for YAP1. Here we demonstrated that horse oocytes support zebra preimplantation development of both, ICSI and cloned embryos, without compromising development to blastocyst, blastocyst cell number neither the expression of SOX2 and YAP1. Our results support the use of domestic horse oocytes as a model to study in vitro zebra embryos on behalf of preservation of valuable genetic.