Follicular fluid exosomes regulate OVGP1 secretion in yak oviduct epithelial cells via autophagy in vitro.

After mammalian ovulation, oocytes enter the oviduct, causing oocyte and oviduct changes. Some studies have shown that follicular fluid exosomes (FEVs) play an important role in this regulatory process, but the specific mechanism is remains unclear. Here, we investigate the effect of FEVs on autophagy and on the synthesis and secretion of oviductal glycoprotein 1 (OVGP1) in yak oviduct epithelial cells (OECs). We added FEVs to yak OECs and collected samples at intervals. The effect of autophagy on OVGP1 synthesis and secretion was detected by manipulating the level of autophagy in OECs. The results showed that autophagy gradually increased as early as 6 h after exosome intake level increased, and the increase was most obvious 24 h after. At that time, the synthesis and secretion of OVGP1 also reached its highest levels. When the autophagy level of OECs is changed through the PI3K/AKT/mTOR pathway, OVGP1 synthesis and secretion levels also change, along with the OVGP1 levels in oviduct exosomes also change. More importantly, the addition of FEVs treatment while using 3-MA to inhibit the autophagy level in yak OECs did not change the synthesis and secretion level of OVGP1. Our results indicate that FEVs can affect the synthesis and secretion of OVGP1 by regulating the level of autophagy in OECs, and that the completion of this process may depend on the PI3K/AKT/mTOR pathway, indicating that exosomes and autophagy play important roles in the reproductive physiology of yak OECs. Our results provide new ideas in to characterizing the role of exosomes in yak reproduction.

Leukemia inhibitory factor enhances the development and subsequent blastocysts quality of yak oocytes in vitro.

Leukemia inhibitory factor (LIF) is a multipotent cytokine of the IL-6 family which plays a critical role in the maturation and development of oocytes. This study evaluated the influence of LIF on the maturation and development ability of yak oocytes, and the quality of subsequent blastocysts under in vitro culture settings. Different concentrations of LIF (0, 25, 50, and 100 ng/mL) were added during the in vitro culture of oocytes to detect the maturation rate of oocytes, levels of mitochondria, reactive oxygen species (ROS), actin, and apoptosis in oocytes, mRNA transcription levels of apoptosis and antioxidant-related genes in oocytes, and total cell number and apoptosis levels in subsequent blastocysts. The findings revealed that 50 ng/mL LIF could significantly increase the maturation rate (p < 0.01), levels of mitochondria (p < 0.01) and actin (p < 0.01), and mRNA transcription levels of anti-apoptotic and antioxidant-related genes in yak oocytes. Also, 50 ng/mL LIF could significantly lower the generation of ROS (p < 0.01) and apoptosis levels of oocytes (p < 0.01). In addition, blastocysts formed from 50 ng/mL LIF-treated oocytes showed significantly larger total cell numbers (p < 0.01) and lower apoptosis rates (p < 0.01) than the control group. In conclusion, the addition of LIF during the in vitro maturation of yak oocytes improved the quality and the competence of maturation and development in oocytes, as well as the quality of subsequent blastocysts. The result of this study provided some insights into the role and function of LIF in vitro yak oocytes maturation, as well as provided fundamental knowledge for assisted reproductive technologies in the yak.

Determination of annual reproductive cycle in male sterlet, Acipenser ruthenus using histology and ultrasound imaging.

The aim of this study was to evaluate seasonal testicular development in the cultured sterlet, Acipenser ruthenus. During annual sexual cycle of male sterlet, stages of gonad maturity were examined using histology and ultrasonography approaches. The histology identified males at different stages of maturity among fish sampled monthly. According to the seasonal changes in the testes, reproductive cycle was divided into four stages including resting, pre-spawning, spawning, and post-spawning. The histology examination revealed considerable variation in testicular developmental stages. These changes were identified based on persistent spermatogenesis and asynchronous gonad development in testes, showing that regulation of annual gonadal cycle is influenced by season. Also, the results obtained using ultrasound suggested that reproductive stages can be identified based on morphology and tissue echogenicity. At each phase of testicular development, gonadosomatic index (GSI) and number of spermatogenic cysts were variable. The present study focused on determination of annual reproductive development in cultured male sterlet which clearly identifies reproductive stage in each season as valuable guide for future researches on reproductive biology of sterlet. This study presents basic knowledge about reproductive biology in sterlet contributing to optimal broodstocks management that allows comparison of reproductive development among sturgeon species.

Estrogen improves the development of yak (Bos grunniens) oocytes by targeting cumulus expansion and levels of oocyte-secreted factors during in vitro maturation.

The estrogen-signalling pathway is critical for normal follicular development; however, little is known about its importance during in vitro maturation (IVM) in large animals, particularly yaks (Bos grunniens). Through the present study, we aimed to determine the mechanisms underlying estrogen involvement in cumulus expansion and the subsequent development of cumulus-oocyte complexes (COCs). COCs were cultured in the maturation medium supplemented with different concentrations (10-6-10-3 mM) of 17ß-estradiol (E2) or its receptor antagonist, fulvestrant, and quantitative reverse-transcription polymerase chain reaction (qRT-PCR) and western blot were performed to determine the expression of cumulus-expansion related factors and oocyte-secreted factors (OSFs). The cumulus expansion of COCs was observed using an inverted microscope, and COCs developmental ability were judged by the evaluation of cleavage and blastulation rates per inseminated oocytes by IVF, and the number of cells in the blastocyst. Cumulus expansion increased with 10-6-10-3 mM E2, but decreased with fulvestrant. HAS2, PTGS2, PTX3 and OSFs expression increased in the 10-6-10-3 mM E2 groups. Significantly higher cleavage and blastocyst rates were observed in the 10-4 mM E2 group than in the fulvestrant and 0 mM E2 groups. Moreover, in the 10-4 mM group, blastocysts at 7 days had higher cell counts than the other groups. In conclusion, the increase in cumulus expansion and subsequent oocyte development after the addition of E2 to IVM medium may have resulted from increased cumulus-expansion-related factor expression and OSF levels.

Delivery of Iron Oxide Nanoparticles into Primordial Germ Cells in Sturgeon.

Nanoparticles are finding increasing applications in diagnostics, imaging and therapeutics in medicine. Iron oxide nanoparticles (IONs) have received significant interest of scientific community due to their distinctive properties. For the first time, we have delivered IONs into germ cells in any species. Our results showed that sturgeon primordial germ cells (PGCs) delivered with IONs could be detected until seven days post fertilization (dpf) under fluorescent microscope and at 22 dpf by micro-CT. Delivery of IONs into cells could be helpful for studying germ cell biology and the improvement of germ cell-based bio-technologies as isolation of PGCs using magnetic activated cell sorting or application of hyperthermia for a host sterilization purpose. Intriguingly, in our study, we did not find any toxic effects of IONs on the survival and hatching rates of sturgeon embryos when compared with embryos injected with FITC-dextran only.

FGF10 enhances yak oocyte fertilization competence and subsequent blastocyst quality and regulates the levels of CD9, CD81, DNMT1, and DNMT3B.

The fusion of sperm and oocytes determines the fertilization competence and subsequent development of embryos, which, in turn, can be affected by various proteins and DNA methylation. However, several factors in this whole regulation process remain unknown, especially in yaks. Here, we report that fibroblast growth factor 10 (FGF10) is an important growth factor that can enhance the maturation rate of yak oocytes and the motility of frozen spermatozoa. Subsequent blastocyst quality was also improved by increasing the total cell number and level of pregnancy-associated protein in blastocysts. These effects were significantly high in the group that received the 5 ng/ml FGF10 treatment, during both in vitro maturation (IVM) and capacitation. Our data show that the effects of FGF10 were dose-dependent at vital steps of embryogenesis in vitro. Furthermore, quantitative polymerase chain reaction, western blot analysis, and immunofluorescence demonstrated that the levels of CD9, CD81, DNMT1, and DNMT3B in both mature cumulus-oocyte complexes and capacitated sperms were regulated by FGF10, which was also highly expressed in the group treated with 5 ng/ml FGF10 during both IVM and capacitation. From our present study, we concluded that FGF10 promotes yak oocyte fertilization competence and subsequent blastocyst quality, and could also regulate CD9, CD81, DNMT1, and DNMT3B to optimize sperm-oocyte interactions and DNA methylation during fertilization.

Molecular epidemiology and characterization of bovine leukemia virus in domestic yaks (Bos grunniens) on the Qinghai-Tibet Plateau, China.

Bovine leukemia virus (BLV) is a member of the genus Deltaretrovirus of the family Retroviridae and cause a chronic lymphosarcoma, which is extensive in cattle. In yaks (Bos grunniens), the distribution, strains and genetic characteristics of BLV have rarely been studied. The aim of our study was to investigate BLV infections in domestic yaks and determine the genetic variability of BLV circulating in a region of the Qinghai Tibet Plateau, China. Blood samples were collected from 798 yaks, which were from different farms from Gansu, Qinghai and Sichuan provinces surrounding the Qinghai-Tibet Plateau. Nested PCR targeting BLV long terminal repeats was used to detect the BLV provirus. The highest prevalence of BLV infection was in Gansu province, where it was 18.93% (39/206) in white yaks from Tianzhu City and 19.14% (31/162) in black yaks from Gannan City. In Qinghai and Sichuan provinces, the prevalence of BLV in black yaks was 14.83% (35/236) and 14.94% (29/194), respectively. The prevalence of BLV was not significantly different in yaks up to one year old than in older animals. Phylogenetic analysis was performed using 16 different env-gp51 (497-bp) gene sequences from the three provinces and 71 known BLV strains, which revealed that in both Gansu and Qinghai provinces, genotypes 6 and 10 of the BLV strains were at high levels, whereas only genotype 10 was prevalent in Sichuan Province. Phylogenetic analysis and sequence comparisons revealed 95.7-99.8% sequence identity among the full-length env genes of 16 strains, nearly full-length genome sequences of six BLV strains, and those of the known genotypes 6 and 10 of BLV. This study provides comprehensive information is regarding the widespread infection of domestic yaks with BLV on the Qinghai-Tibet Plateau of China, and shows that at least two BLV genotypes (genotypes 6 and 10) are circulating in this population.

Insulinlike growth factor I improves yak (Bos grunniens) spermatozoa motility and the oocyte cleavage rate by modulating the expression of Bax and Bcl-2.

The aim of our present study was to examine the effects of insulinlike growth factor 1 (IGF-1) on yak sperm motility during in vitro capacitation and the relationship between the effects of IGF-1 on yak sperm motility and apoptosis was evaluated. Frozen-thawed yak spermatozoa were incubated at 38 °C for 1 hour in Tyrode's bicarbonate-buffered medium for sperm culture (Sp-TALP) with different concentrations (0, 50, 100, and 200 ng/mL) of IGF-1. In every treatment, the sperm motility was measured by a computer-assisted sperm analyzer system. The fertilizing ability of spermatozoa was evaluated on the basis of oocyte cleavage rate after insemination. The expression of Bax and Bcl-2 was examined by real-time polymerase chain reaction and Western blot for the messenger RNA and protein levels. It is interesting to note that IGF-1 improved yak spermatozoa motility and the cleavage rate of oocytes; these improvements were highest in the 100 ng/mL IGF-1 group, followed by the 200 ng/mL and 50 ng/mL groups, with the lowest improvements in motility and cleavage rates in groups without IGF-1. The expression level of Bax was downregulated by IGF-1, whereas Bcl-2 was upregulated. Both messenger RNA and Bax proteins were lowest in groups with 100 ng/mL IGF-1, where the Bcl-2 was the highest. Bax expression in the groups with IGF-1 was lower than that in the group without IGF-1, and Bcl-2 expression was higher in groups with IGF-1 than that in the group without IGF-1. In conclusion, this research reports that improvements in yak spermatozoa motility and the oocyte cleavage rate after the addition of IGF-I may be a result of the reduction of spermatozoa apoptosis rates by modulating the expression of Bax and Bcl-2.