Variability in in vitro fertilization outcomes of prepubertal goat oocytes explained by basic semen analyses

Effects of Nobiletin supplementation on the freezing diluent on porcine sperm cryo-survival and subsequent in vitro embryo development

Nobiletin (NOB) is a bioflavonoid compound isolated from citrus fruit peels. The present study aimed to elucidate whether NOB facilitates the porcine sperm cryosurvival and embryo development after in vitro fertilization (IVF). To this end, spermatozoa were diluted and cryopreserved in a freezing extender supplemented with 0 (control), 50, 100, 150, and 200 μM Nobiletin. The kinematic patterns of frozen-thawed (FT) sperm were assessed after 30 and 90 min incubation using a Sperm Class Analyzer (SCA). Viability, acrosome integrity, and mitochondrial membrane potential (MMP) were measured by fluorescence microscopy 30 min after thawing using SYBR-14/PI, PSA/FITC, and R123/PI, respectively. Lipid peroxidation was determined using MDA assay after incubation for 90 min. The addition of 100 μM and 150 μM NOB to the extender significantly improved sperm progressive motility, and acrosome integrity compared to the control group (P < 0.05). The proportion of viable spermatozoa was significantly higher in the 150 μM NOB group. MDA levels were less in 50 μM and 150 μM NOB treated groups compared to the control. In addition, IVF with FT sperm was used to assess the embryo developmental competence. Treatment with 150 μM NOB before cryopreservation increased the cleavage and blastocyst formation rates compared to the control group. Furthermore, the relative expression of POU5F1 and AMPK, genes related to pluripotency and cell differentiation were significantly upregulated in embryos resulting from NOB-treated sperm compared to the control group. These results suggest that Nobiletin is a functionally novel phytochemical to mitigate oxidative stress during the freezing-thawing of porcine spermatozoa as reflected by improved FT sperm quality and IVF outcome.

Dimethylformamide Preserves the Integrity of Cryopreserved Goat Semen in a Soybean Lecithin-Based Extender

This study investigated the cryoprotectant effects of dimethylformamide (DMF), ethylene glycol (EG), and dimethyl sulfoxide (DMSO) as substitutes for glycerol (GLY) in a soybean lecithin (SL)-based extender in the cryopreservation of buck sperm. In this study, the semen of three Saanen bucks was individually extended in SL supplemented with 5% GLY (control), DMF, EG, or DMSO. After this, the extended semen was cryopreserved and two straws from each group were thawed (37°C for 30 seconds), pooled, and analyzed for sperm motion parameters, plasma membrane integrity (PMI), acrosomal integrity (ACI), and high mitochondrial membrane potential (HMMP). Samples were analyzed after 15 minutes (T0) and after 2 hours of incubation at 37°C (T2). The results revealed higher values of motility (total and progressive) and sperm motion parameters for DMF than the other cryoprotectants (p < 0.0001). PMI and HMMP did not differ (p > 0.05) between GLY and DMF, but ACI was higher (p < 0.01) for DMF compared with GLY. Based on these results, DMF and GLY samples were used in heterologous in vitro fertilization assays by using bovine oocytes (n = 337) obtained from a slaughterhouse. No differences (p > 0.05) were observed between GLY and DMF for unfertilized (GLY: 38.8%; DMF: 25.33%), pronucleus (GLY: 25.68%; DMF: 27.92%), and cleavage rates (GLY: 35.52%; DMF: 46.75%). Based on these results, it is concluded that DMF preserves sperm motion characteristics and ACI better than GLY, EG, and DMSO, and it is the penetrating cryoprotectant of choice for the cryopreservation of buck sperm in SL extender.

Sperm traits on in vitro production (IVP) of bovine embryos: Too much of anything is good for nothing

Sperm samples used on fertilization strongly influence the in vitro production (IVP) rates. However, sperm traits behind this effect are not stated consistently until now. This study aimed to evaluate the isolated and combined effect of some sperm traits (MB: total motility before Percoll^® gradient, MA: total motility after Percoll^® gradient, AI: acrosome integrity, MI: membrane integrity, MP: mitochondrial membrane potential, and CR: chromatin resistance) on IVP rates. This is the first study focusing on the isolated effect of distinct traits. For this purpose, the experiment was divided in three steps. In first step, to study behavior of traits sperm samples (n = 63 batches) were analyzed and ranked based on each trait. In second step, samples ranked were selected from target ranks regions and allocated in groups of four to five batches, creating Higher and Lower groups, according to two different approaches. One aimed to form groups that differed to all sperm traits simultaneously (effect of combined traits). The other aimed to form groups that differed only to a single sperm trait while no differences were observed for the remaining traits (effect of each isolated trait). In third step, for each group successfully formed in step 2, sperm samples were individually and prospectively used for IVP. Cleavage, embryo development and blastocyst rates were recorded and compared between Higher and Lower of respective trait groups. Surprisingly, evaluation of isolated effects revealed that lower levels of MB, AI and MP resulted in higher embryo development and blastocyst rates (p<0.05), which was not observed on cleavage rate. We conclude that sperm traits strongly influence embryo development after in vitro fertilization (IVF), affecting the zygote competence to achieve blastocyst stage. Individually, levels of MB, AI or MP could be some of the key traits that may define IVP efficiency on current systems of embryo production.