Utero-tubal embryo transfer and vasectomy in the mouse model

Suitability of a universal electroporation device for genome editing and production of transgenic rats

Mammalian genome editing has utilized expensive and highly specialized electroporator devices. The "Gene Pulser XCell," a modular electroporation system for transfecting all cell types, has not been used extensively in mammalian embryo genome editing. The present experiment was undertaken to determine the usefulness of the Gene Pulser XCell for inserting the CRISPR/Cas9 system into intact zygotes in order to obtain the enhanced green fluorescent protein reporter rats (eGFP-R). An electroporation pulse response test using mCherry mRNA was performed to optimize the settings of the electroporator. Forty-five combinations of five pulse voltages (15, 25, 30, 35 and 40 V), three pulse durations (5, 10 and 25 ms), and three pulse frequencies (2, 5 and 6 pulses) applied at a constant 100-ms pulse interval and temperature of 37.5 °C were evaluated. The test revealed that the 35 V was the only voltage suitable for insertion of mCherry mRNA into intact rat zygotes and the only one that resulted in the production of embryos attaining the blastocyst stage. The incorporation of mCherry mRNA increased but the survival of the electroporated embryos declined with an increment in the number of pulses. Subsequent transfer of 1112 surviving Sprague Dawley rat embryos (after 8 h of incubating 1800 zygotes electroporated with the CRISPR/Cas9) resulted in the production of 287 offspring (25.8%). Ensuing PCR and phenotypic evaluation confirmed that twenty animals (6.96%) expressed eGFP in all body organs/tissues except for blood and blood vessels. The mortality of males and females before the attainment of puberty was 2 and 3 pups, respectively, and the final number/ratio of male to female of offspring was 9:11. All the surviving rats mated naturally and successfully transmitted the GFP transgene to their progeny. The Gene Pulser XCell total system with the settings predetermined in the present experiment can effectively be used to produce transgenic rats through the CRISPR/Cas9-mediated genome editing of zygotes.

Maternal Ezh1/2 deficiency in oocyte delays H3K27me2/3 restoration and impairs epiblast development responsible for embryonic sub-lethality in mouse

How maternal Ezh1 and Ezh2 function in H3K27 methylation in vivo in pre-implantation embryos and during embryonic development is not clear. Here, we have deleted Ezh1 and Ezh2 alone or simultaneously from mouse oocytes. H3K27me3 was absent in oocytes without Ezh2 alone, while both H3K27me2 and H3K27me3 were absent in Ezh1/Ezh2 (Ezh1/2) double knockout (KO) oocytes. The effects of Ezh1/2 maternal KO were inherited in zygotes and early embryos, in which restoration of H3K27me3 and H3K27me2 was delayed by the loss of Ezh2 alone or of both Ezh1 and Ezh2. However, the ablation of both Ezh1 and Ezh2, but not Ezh1 or Ezh2 alone, led to significantly decreased litter size due to growth retardation post-implantation. Maternal Ezh1/2 deficiency caused compromised H3K27me3 and pluripotent epiblast cells in late blastocysts, followed by defective embryonic development. By using RNA-seq, we examined crucial developmental genes in maternal Ezh1/2 KO embryos and identified 80 putatively imprinted genes. Maternal Ezh1/2-H3K27 methylation is inherited in offspring embryos and has a critical effect on fetal and placental development. Thus, this work sheds light on maternal epigenetic modifications during embryonic development.

Effect of different surgical methods in the mouse embryo transfer: Electrosurgery versus cold surgical technique effects on repeated use of surrogate mothers, pregnancy rate and post-surgical behavior

Using the cold surgical technique (CST) is the most common practice to accomplish embryo transfer (ET). However, it can lead to uncontrolled bleeding and mortality in laboratory animals. Electrosurgery technique (EST) has provided the opportunity to prevent such complications. This study was aimed to evaluate CST versus EST in terms of repeated use of surrogate mothers, litter size, implantation rate and post-surgical behavior. Virgin female NMRI mice were allocated into two different surgical groups (n = 40): 1) CST-ET (control) and 2) EST-ET. Results showed that the first ET in EST-ET and CST-ET groups did not affect litter size, pregnancy rate and survival of surrogate mothers. Following the second and the third ETs, litter size was significantly affected through CST compared to EST, pregnancy rate and survival of surrogate mothers. Litter size, pregnancy rate and surrogate mothers survival rate did not show any significant reduction following the first and the second ETs in EST group. On the other hand, the third ET showed dramatic reduction for all aforementioned parameters regardless of the chosen surgical method for ET. Mice in EST-ET group did not show any significant change in their behavior indicating reduced well-being during the first 24 hr following the first, the second and the third ETs compared to CST-ET group. In conclusion, using EST for ET in mouse made it feasible to reuse surrogate mothers with minimum animal mortality; this could be pivotal with regard to reproductive and animal welfare aspects and research costs. Also, the results indicated that bleeding has severe diverse effects on ET efficiency.

Assisted Hatching Treatment of Piezo-Mediated Small Hole on Zona Pellucida in Morula Stage Embryos Improves Embryo Implantation and Litter Size in Mice

For in vitro produced embryos generated from in vitro fertilization (IVF) or intracytoplasmic sperm injection (ICSI) procedure, the intra- and extra-environmental factors during in vitro culture have significant impact on latter embryo development and fetus growth. Assisted hatching (AH), an effective approach to facilitate hatchability for in vitro generated embryos, is an essential step for successful embryo implantation in the uterus. However, regarding the different AH methods reported in clinical practice, it is still unknown whether zona pellucida (ZP) broken is based on AH applied in diverse stages of embryos affect implantation and fetal development. Here, piezo-mediated AH treatments were classified into four categories: (1) drilling one small hole (SH) with a diameter of 10 μm on ZP (SH); (2) drilling one large hole (LH) with a diameter of 40 μm on ZP (LH); (3) made a small area with diameter of 40-μm thinner on ZP [small area thinner (ST)]; (4) made a large area with a diameter of 80-μm thinner [large area thinner (LT)]. These four AH treatments were applied in different stage embryos including two-cell, four-cell, and morula. The most efficient AH approach was chosen according to the final hatch rate at 120 h after fertilization. We found that the approach of SH applied in morula-stage embryos obtained the highest hatch rate. To further investigate if this treatment has any side effect on later development after embryo transfer, we evaluated embryo implantation, gestational period, litter size, and growth. Our results showed that SH applied in morula-stage embryos could facilitate the implantation process and increase litter size. Meanwhile, this approach had no side effect on birth weight, growth, or gender ratio in the offspring. We conclude that drilling a SH on ZP in morula-stage embryos is an effective and reliable AH approach for in vitro cultured embryos in rodent. And this approach is worth further investigating in human-assisted reproductive technology.

Seminal Plasma and Seminal Plasma Exosomes of Aged Male Mice Affect Early Embryo Implantation via Immunomodulation

Seminal plasma (SP), particularly SP exosomes (sExos), alters with age and can affect female mouse uterine immune microenvironment. However, the relationship between fertility decline in reproductively older males, and SP and sExos age-related changes, which may compromise the uterine immune microenvironment, remains unclear. The present study demonstrated that the implantation rate of female mice treated with SP from reproductively older male mice (aged-SP group) was lower than that of those treated with SP from younger male mice (young-SP group). RNA-sequencing analysis revealed altered levels of dendritic cell (DC)-related cytokines and chemokines in the uteri of the former group compared with those of the latter group. In vivo and in vitro experiments demonstrated a weaker inhibitory effect of aged SP on DC maturation than of young SP upon stimulation. After isolating and characterizing sExos from young and advanced-age male mice, we discovered that insemination of a subset of the aged-SP group with sExos from young male mice partially recovered the implantation rate decline. Additional in vivo and in vitro experiments revealed that sExos extracted from age male mice exerted a similar effect on DC maturation as SP of aged mice, indicating an age-related sExos inhibitory effect. In conclusion, our study demonstrated that age-related alterations of sExos may be partially responsible for lower implantation rates in the aged-SP group compared with those in the young-SP group, which were mediated by uterine immunomodulation. These findings provide new insights for clinical seminal adjuvant therapy.

Blastocyst hatching site is regularly distributed and does not influence foetal development in mice

Hatching out from the zona pellucida (ZP) is a crucial step for blastocyst implantation and development. However, it is still unknown whether the location of the hatching site relative to the inner cell mass (ICM) affects embryo implantation and foetal development. Here, we classified hatching blastocysts into three categories, 0° ≤ θ ≤ 30°, 30° < θ ≤ 60°, and 60° < θ ≤ 90°, in which θ is determined based on the relative position of the hatching site to the arc midpoint of the ICM. Non-surgical embryo transfer (NSET) devices were employed to evaluate blastocyst implantation and embryo development. Of 1,827 hatching blastocysts, 43.84%, 30.60%, and 21.67% were categorized as 30° < θ ≤ 60°, 0° ≤ θ ≤ 30°, and 60° < θ ≤ 90°, respectively. Embryos with different hatching sites showed no distinct differences in blastocyst implantation; surrogate female pregnancy; embryo development to term; litter size, or offspring survival, gender, or body weight. Our results indicate that mouse blastocyst hatching site is not randomly distributed. Embryo implantation and development are not correlated with the blastocyst hatching site in mice. Thus, assessment of the blastocyst hatching site should not be recommended to evaluate mouse blastocyst implantation and developmental potential.

Female Urine-induced Ultrasonic Vocalizations in Male C57BL/6J Mice as a Proxy Indicator for Postoperative Pain

Objectively recognizing postoperative pain in mice is challenging, making it difficult to determine an appropriate postoperative analgesic regimen. Adult male mice produce ultrasonic vocalizations after exposure to adult female urine (FiUSV). To determine if FiUSV can be used as a indicator of postoperative pain, FiUSV produced by male C57BL/6J mice were assessed for 5 d before and after vasectomy or sham surgery with or without sustained-release buprenorphine. Postoperative pain was assessed by monitoring vocalization using an ultrasonic microphone and by evaluating orbital tightness, posture, and piloerection at postoperative time points. Before vasectomy or sham surgery, 25 of 38 male mice produced FiUSV on 4 of 5 d (143 ± 93 FiUSV). Vasectomized mice without postoperative analgesia produced significantly fewer FiUSV (59 ± 26 FiUSV) compared with baseline (212 ± 102 FiUSV) at 4 h postoperatively, but returned to baseline by 28 h. Vasectomized mice treated with buprenorphine and sham-surgery mice had no change in FiUSV from baseline at any time point after surgery. Activity was decreased compared with baseline in vasectomized mice, regardless of receiving postoperative analgesia or not, but only at the 4-h time point. There were no differences in behavior scores between vasectomized mice and sham-surgery mice at any time point. These results show that FiUSV can be used to detect postoperative pain in male C57BL/6J mice after vasectomy.

Effect of Predator Stress on the Reproductive Performance of Female Mice After Nonsurgical Embryo Transfer

Predator Stress Can Exert Detrimental Effects on Female Mammals, Leading to Disrupted Reproduction. Although Many Studies Have Addressed the Effects of Predator Stress on Reproductive Output in Rodents, Few Studies Have Focused on the Effect of Visual or Auditory Stress on Pregnant Females. in This Study, We Investigated the Possible Effect of Predator Stress, Either Visual Only or Combined Visual and Auditory (visual+auditory), on the Reproductive Performance of Female Mice After Nonsurgical Embryo Transfer. Reproductive Performance Was Assessed As Pregnancy Rate, Implantation Rate, Gestation Length, Live Pup Rate, and Neonatal Birth Weight. Moreover, Serum Cortisol and Progesterone Levels in Dams Were Measured by Using Electrochemiluminescence Immunoassay. Exposure to Predator (cat) Stress Did Not Lead to a Significant Change in Pregnancy Rates in the Tested Mice. However, the Stressed Mice Showed Significantly Decreased Implantation Rates Compared with the Control Group. Similarly, the Live Pup Rate and Neonatal Birth Weight Were Significantly Lower in the Group Exposed to Preda- Tor Stress Than in the Control Group. Furthermore, Mice Exposed to Visual+auditory Stress Showed a Significant Reduction in Gestation Length Compared with the Control Mice. Our Data Showed That Predator Visual+auditory Stress As Combined Stimuli Significantly Increased Serum Cortisol Level. in Contrast, Progesterone Levels Did Not Significantly Vary Among the Experimental Groups. Taken Together, Our Findings Imply That Predator Stress Adversely Affects the Reproductive Efficiency of Pregnant Mice By Decreasing the Implantation Rate, Live Birth Rate, and Neonatal Birth Weight and by Prolonging Gestation Length.

A Simple and Fast Method for Derivation of blastocyst-like cell aggregates (BLCAs) from Murine Embryonic Stem Cells

The study of blastocyst differentiation from stem cells is still at its stage of infancy. In this study, a simple and efficient method was developed to derive blastocyst-like cell aggregates (BLCAs) from murine embryonic stem cells (mESCs). This was achieved by culturing the mESCs in non-adherent dishes.0020BLCAs (13±2 per million mESCs) were obtained in only 5 days and they were found to express the protein and gene markers of trophoblasts. Furthermore, the BLCAs showed the normal trophoblasts' capability of penetrating the uterine wall after being transferred into pseudo-pregnant mice, indicating the trophoblast-like functionality of the derived BLCAs. Collectively, we successfully developed a simple and fast 3D suspension culture approach to differentiate mESCs into BLCAs, which may provide important clues into the development of early embryos and stem cells. This may also offer a simple and efficient approach to isolate trophoblast cells for studying the native microenvironment of pluripotent stem cells without the need to sacrifice animals.

Uterine Expression of NDRG4 Is Induced by Estrogen and Up-Regulated during Embryo Implantation Process in Mice

Embryo implantation is an essential step for the establishment of pregnancy and dynamically regulated by estrogen and progesterone. NDRG4 (N-myc down-regulated gene 4) is a tumor suppressor that participates in cell survival, tumor invasion and angiogenesis. The objective of this study was to preliminarily explore the role of NDRG4 in embryo implantation. By immunohistochemistry (IHC) and quantitive RT-PCR (qRT-PCR), we found that uterine expression of NDRG4 was increased along with puberal development, and its expression in adult females reached the peak at the estrus stage during the estrus cycle. Furthermore, uterine NDRG4 expression was significantly induced by the treatment of estradiol (E₂) both in pre-puberty females and ovariectomized adult females. Uterine expression pattern of NDRG4 during the peri-implantation period in mice was determined by IHC, qRT-PCR and Western blot. It was observed that NDRG4 expression was up-regulated during the implantation process, and its expression level at the implantation sites was significantly higher than that at the inter-implantation sites. Meanwhile, an increased expression in NDRG4 was associated with artificial decidualization as well as the activation of delayed implantation. By qRT-PCR and Western blot, we found that the in vitro decidualization of endometrial stromal cells (ESCs) was accompanied by up-regulation of NDRG4 expression, whereas knockdown of its expression in these cells by siRNA inhibited the decidualization process. In addition, Western blot analysis showed that NDRG4 protein expression was decreased in human villus tissues of recurrent miscarriage (RM) patients compared to normal pregnant women. Collectively, these data suggested that uterine NDRG4 expression could be induced by estrogen, and NDRG4 might play an important role during early pregnancy.