Inhibition of bovine sperm-oocyte fusion by the p-aminophenyl derivative of D-mannose

Single-Cell RNA-Seq Revealed the Gene Expression Pattern during the In Vitro Maturation of Donkey Oocytes

Donkeys are an important domesticated animal, providing labor, meat, milk, and medicinal materials for humans. However, the donkey population is continuously declining and even at risk of extinction. The application of modern animal production technology, such as oocyte in vitro maturation, is a promising method to improve the donkey population. In this study, we explore the gene expression patterns of donkey germinal vesicle (GV) and in vitro matured metaphase II (MII) oocytes using single cell RNA-seq of the candidate genes along with the regulatory mechanisms that affect donkey oocyte maturation. We identified a total of 24,164 oocyte genes of which 9073 were significant differentially expressed in the GV and MII oocytes. Further Gene Ontology (GO) and Kyoto Encyclopedia of Genes and Genomes (KEGG) analysis indicated that these genes were associated with the meiotic cell cycle, mitochondrion activity, and N-glycan biosynthesis, which might be the key genes and regulatory mechanisms affecting the maturation of donkey oocytes. Our study provides considerable understanding regarding the maturation of donkey oocytes and serves as a theoretical basis for improving the development of donkey oocytes, which could ultimately benefit the expansion of the donkey population and conservation of biodiversity and genetic resources.

The activity of three glycosidases (β-Ν-acetyloglucosaminidase, α-mannosidase, and β-galactosidase) in the follicular fluid and in the maturation medium affects bovine oocyte maturation

We studied the role of follicular fluid's (FF) glycosidase (α-mannosidase [α-ΜΑΝ], β-Ν-acetyloglucosaminidase [NAGASE], β-galactosidase [β-GAL]) activity during IVM of bovine oocytes. Oocytes were allocated into two groups according to the follicular size (small follicle [SF]: 2-5 mm, large follicle [LF]: >5-8 mm). In experiment 1, cumulus-oocyte complexes (COCs) quality was evaluated according to morphologic criteria (grades A, B-C, D); oocyte (n = 801) nuclear maturation was assessed after 24 hours of incubation. Bovine embryos were produced in vitro in groups (experiment 2, n = 1503 oocytes) or individually (experiment 3, n = 50 oocytes). More grade-A and -BC COCs were collected from SF and LF groups, respectively (P < 0.05). Maturation rate (experiment 1) and cleavage rate (experiments 2 and 3) were similar in SF and LF groups. Activity of all glycosidases in FF was higher (P < 0.05) in SF group than in LF group, whereas in maturation medium of SF group it was, overall, significantly lower than in that of LF (experiments 2 and 3). In FF of SF group, NAGASE positively associated with grade-A oocytes and negatively with BC oocytes; increased β-GAL was associated with degenerated oocytes. Cleavage rate in LF group, related negatively to NAGASE and positively to α-MAN in maturation medium. These results indicate that during maturation, COCs release NAGASE and consume β-GAL, but differences probably exist between individual and group maturation.

Cumulus cell gene expression associated with pre-ovulatory acquisition of developmental competence in bovine oocytes

The final days before ovulation impact significantly on follicular function and oocyte quality. This study investigated the cumulus cell (CC) transcriptomic changes during the oocyte developmental competence acquisition period. Six dairy cows were used for 24 oocyte collections and received FSH twice daily over 3 days, followed by FSH withdrawal for 20, 44, 68 and 92 h in four different oestrous cycles for each of the six cows. Half of the cumulus-oocyte complexes were subjected to in vitro maturation, fertilisation and culture to assess blastocyst rate. The other half of the CC underwent microarray analysis (n=3 cows, 12 oocyte collections) and qRT-PCR (n=3 other cows, 12 oocyte collections). According to blastocyst rates, 20 h of FSH withdrawal led to under-differentiated follicles (49%), 44 and 68 h to the most competent follicles (71% and 61%) and 92 h to over-differentiated ones (51%). Ten genes, from the gene lists corresponding to the three different follicular states, were subjected to qRT-PCR. Interestingly, CYP11A1 and NSDHL gene expression profiles reflected the blastocyst rate. However most genes were associated with the over-differentiated status: GATM, MAN1A1, VNN1 and NRP1. The early period of FSH withdrawal has a minimal effect on cumulus gene expression, whereas the longest period has a very significant one and indicates the beginning of the atresia process.

Binding of Sperm to the Zona Pellucida Mediated by Sperm Carbohydrate-Binding Proteins is not Species-Specific in Vitro between Pigs and Cattle

Carbohydrates are candidates for the basis of species-selective interaction of gametes during mammalian fertilization. In this study, we sought to clarify the roles of sugar residues in the species-selective, sperm-oocyte interaction in pigs and cattle. Acrosome-intact porcine and bovine sperm exhibited their strongest binding affinities for β-Gal and α-Man residues, respectively. Porcine-sperm specificity changed from β-Gal to α-Man after the acrosome reaction, while bovine-sperm specificity did not. Binding of acrosome-intact and acrosome-reacted sperm decreased after trypsinization, indicating that the carbohydrate-binding components are proteins. While immature oocytes bound homologous sperm preferentially to heterologous sperm, oocytes matured in vitro bound similar numbers of homologous and heterologous sperm. Lectin staining revealed the aggregation of α-Man residues on the outer surface of the porcine zona during maturation. In both species, zona-free, mature oocytes bound homologous sperm preferentially to heterologous sperm. The lectin-staining patterns of the zona pellucida and zona-free oocytes coincided with the carbohydrate-binding specificities of acrosome-intact and acrosome-reacted sperm, respectively, supporting the involvement of carbohydrates in gamete recognition in pigs and cattle. These results also indicate that sperm-zona pellucida and sperm-oolemma bindings are not strictly species-specific in pigs and cattle, and further suggest that sperm penetration into the zona and/or fusion with oolemma may be species-specific between pigs and cattle.

Equivalency of buffalo (Bubalus bubalis) embryonic stem cells derived from fertilized, parthenogenetic, and hand-made cloned embryos

This study was aimed at establishing buffalo embryonic stem cells (ESCs) from in vitro fertilized (IVF), parthenogenetic, and hand-made cloned (HMC) embryos and to check their equivalency in terms of stem cell marker expression, longevity, proliferation, and differentiation pattern. ESCs derived from all three sources were found by immunofluorescence to express the pluripotency markers SSEA-4, TRA-1-60, TRA-1-81, OCT4, and SOX2 and were able to form embryoid bodies containing cells expressing genes specific to endoderm (AFP, HNF4, and GATA4), mesoderm (MSX1, BMP4, and ASA), and ectoderm (cytokeratin 8 and NF68). Reverse transcriptase PCR (RT-PCR) showed cells from all sources to be positive for pluripotency markers OCT4, SOX2, NANOG, STAT3, REX1, FOXD3, NUCLEOSTEMIN, and TELOMERASE. Pluripotency markers OCT4, SOX2, NANOG, and c-MYC were also analyzed by real-time PCR. No significant differences were observed among ESCs from all three sources for all these genes except NANOG, whose expression was higher (p<0.05) in HMC-derived ESCs (6.897±2.3) compared to that in parthenogenesis- and IVF-derived cells (1.603±0.315 and 1±0, respectively). Pluripotent, stable buffalo ESC lines derived from IVF, parthenogenesis, and HMC embryos may be genetically manipulated to provide a powerful tool for studies involving embryonic development, genomic imprinting, gene targeting, cloning, chimera formation, and transgenic animal production.

Expression and putative function of fibronectin and its receptor (integrin alpha(5)beta(1)) in male and female gametes during bovine fertilization in vitro

Fibronectin (Fn) is a 440 kDa glycoprotein assumed to participate in sperm-egg interaction in human. Recently, it has been demonstrated that Fn--when present during bovine IVF--strongly inhibits sperm penetration. The present study was conducted firstly to evaluate the expression of Fn and its integrin receptor (alpha(5)beta(1)) on male and female bovine gametes using indirect immunofluorescence and secondly, to determine the function of Fn during bovine IVF. Endogenous Fn was detected underneath the zona pellucida (ZP) and integrin alpha(5) on the oolemma of cumulus-denuded oocytes. Bovine spermatozoa displayed integrin alpha(5) at their equatorial segment after acrosome reaction. We established that the main inhibitory effect of exogenously supplemented Fn was located at the sperm-oolemma binding, with a (concurrent) effect on fusion, and this can probably be attributed to the binding of Fn to spermatozoa at the equatorial segment, as shown by means of Alexa Fluor 488-conjugated Fn. Combining these results, the inhibitory effect of exogenously supplemented Fn seemed to be exerted on the male gamete by binding to the exposed integrin alpha(5)beta(1) receptor after acrosome reaction. The presence of endogenous Fn underneath the ZP together with integrin alpha(5) expression on oolemma and acrosome-reacted (AR) sperm cell surface suggests a 'velcro' interaction between the endogenous Fn ligand and corresponding receptors on both (AR) sperm cell and oolemma, initiating sperm-egg binding.

Multivalent mannose-displaying nanoparticles constructed from poly{styrene-co-[(maleic anhydride)-alt-styrene]}

Micellar mannose nanoparticles were constructed from poly{styrene-co-[(maleic anhydride)-alt-styrene]} with fluorophores or quenchers doped into the hydrophobic inner cores, allowing the direct monitoring of multivalent lectin-glycan interactions. The mannose-displaying nanoparticles bind Con A and sperm surface lectins with high affinity, suggesting their broad utility for modulating protein-carbohydrate interaction mediated cell surface biology.

Poly(styrene-alt-maleic anhydride) derivatives as potent anti-HIV microbicide candidates

Topical microbicides offer women the opportunity to protect themselves from sexual HIV transmission under their own control. A series of poly[styrene-alt-(maleic anhydride)] derivatives were prepared by amidation or hydrolysis of the anhydride moiety. The derivatives were shown to be of low cell toxicity and effectively inhibited HIV-1 infections in an in vitro cellular model. Poly[styrene-alt-(maleic acid, sodium salt)] was the most potent inhibitor, being 100-fold more potent than dextran sulfate suggesting its potential application as a new class of polyanionic microbicides.

Glycosidase determination in bovine oviducal fluid at the follicular and luteal phases of the oestrous cycle

Gamete recognition and binding of spermatozoa to the oviduct are carbohydrate-mediated processes in which several glycosidases are thought to have a role, although this has not been demonstrated unequivocally. Oviducal fluid is the biological milieu in which fertilisation and early embryo development take place, but the enzyme composition of oviducal fluid is largely unknown. The aim of the present study was to determine glycosidase activity and protein content in bovine oviducal fluid (bOF) and the volume of fluid collected per oviduct. Oviducts obtained from a slaughterhouse were classified as either in the follicular or luteal phase on the basis of ovarian luteal morphology. Oviducal fluid was aspirated, centrifuged and the volume determined. Samples were then frozen until assay. Substrates conjugated to 4-methylumbelliferyl were used to screen for the activity of seven glycosidases at pH 7.2. The results indicate that bOF has alpha-l-fucosidase, beta-N-acetyl-glucosaminidase, beta-d-galactosidase, alpha-D-mannosidase and beta-N-acetyl-galactosaminidase activity during both phases of the cycle, with the specific activity of the latter two enzymes being higher during the follicular phase. There was no N-acetyl-neuraminidase or alpha-d-galactosidase activity detected in bOF at either phase of the oestrous cycle at pH 7.2, but activity for both glycosidases was detected at pH 4.4. There were no differences in protein concentration or the volume of bOF collected between the two phases of the cycle. These findings indicate that oviducal fluid exhibits glycosidase activity, with specific variations throughout the oestrous cycle, suggesting that these enzymes play a role in carbohydrate-mediated events.

Effects of modification of in vitro fertilization techniques on the sex ratio of the resultant bovine embryos

The duration of sperm-oocyte co-incubation has been observed to affect the sex ratio of in vitro produced bovine embryos. The purpose of this study was to investigate some factors that may be responsible for the skewed sex ratio. The factors studied were selected combinations of the duration of co-incubation, the presence or absence of cumulus cells, and the level of hyaluronic acid (HA) in the culture medium. Experiment 1 examined the effect of selected combinations of different factors during the fertilization phase of in vitro oocyte culture. The factors were the nature of the sperm or its treatment, the duration of the sperm-oocyte co-incubation, and the level of hyaluronic acid in the culture medium. In experiment 2, the capacitation of frozen-thawed-Percoll-washed sperm (control), pre-incubated, and non-binding sperm was evaluated by the zona pellucida (ZP) binding assay and the hypo-osmotic swelling test (HOST). The purpose of experiment 3 was to determine the oocyte cleavage rate and sex ratio of the embryos (>5 cells) produced as a consequence of the 10 treatments used in experiment 1. In treatments 1-3 (experiments 1 and 3) COC were co-cultured with sperm for 1, 5 or 18 h. Polyspermic fertilization rose as the co-incubation period increased (1 h 6.5%, 5 h 15.9%, 18 h 41.8%; P<0.05), and the highest rate of normal fertilization was observed for 5h culture (73.4%; P<0.05). The sex ratio was significantly (P<0.05) skewed from the expected 50:50 towards males following 1 h (64.4%) and 5 h (67.3%) co-incubation, but was not affected by 18 h incubation (52.3%). In treatment 4, sperm was pre-incubated for 1h and cultured with COC for 5 h. Relative to control sperm, pre-incubation of sperm increased ZP binding (116 versus 180 per ZP; P<0.05) and decreased the proportion of HOST positive sperm (65.8-48.6%; P<0.05; experiment 2). Pre-incubation did not affect the rates of polyspermy, normal fertilization or the sex ratio of the embryos (experiments 1 and 3). The oocytes used in treatments 5-10 of experiments 1 and 3 were denuded prior to fertilization. Co-incubation of denuded oocytes for 1h (treatment 5) or 5h (treatment 6) resulted in levels of polyspermic fertilization similar to that for treatment 2 with significantly lower levels of normal fertilization (41.7% and 52.6%, respectively; P<0.05), and the 1h co-incubation significantly skewed (P<0.05) the proportion of male embryos to 70.0%. Denuded oocytes were fertilized for 5h with sperm unable to bind to cumulus cells (NB sperm) in treatment 7 or those that bound to cumulus cells (B) in treatment 8. These two treatments had similar rates of polyspermic, normal and non-fertilization. However, the B sperm caused the sex ratio of the embryos to be significantly skewed to males (63.9%; P<0.05). Fertilization of denuded oocytes in medium containing hyaluronic acid (0.1 mg/ml, treatment 9; 1.0 mg/ml treatment 10) significantly (P<0.05) reduced the incidence of polyspermic fertilization relative to treatments 2 and 6, and normal fertilization relative to treatment 2, but did not affect the sex ratio of the embryos. It was concluded that exposure of sperm to cumulus cells, either before fertilization of denuded oocytes or during the process of fertilization of complete COC, increased the proportion of male embryos produced by in vitro culture. It was hypothesized that this may be due to the capacitation state of the sperm, the cumulus-sperm interaction, and/or the ability of the sperm to bind to cumulus cells or oocytes.

Inhibition of bovine sperm–zona binding by bovine herpesvirus-1

The purpose of the present study was to identify a potential interference of bovine herpesvirus-1 (BoHV-1) with sperm–oocyte interactions during bovinein vitrofertilization. An inhibition of almost 70% of sperm–zona binding was observed when bovine cumulus-denuded oocytes were inseminated in the presence of 10750% tissue culture infective dose/ml BoHV-1. The inhibitory effect of BoHV-1 on sperm–zona binding was mediated by an interaction of the virus with spermatozoa, but not with oocytes. Treatment of spermatozoa with BoHV-1, however, did not affect sperm motility and acrosomal status. Antiserum against BoHV-1 prevented the virus-induced inhibition of sperm–zona binding, indicating that BoHV-1 itself affects the fertilization process. In order to investigate which BoHV-1 glycoprotein(s) are responsible for the virus–sperm interaction, BoHV-1 was treated with monoclonal antibodies against the viral glycoproteins gB, gC, gD and gH prior to insemination. Anti-gC completely prevented the inhibitory effect of BoHV-1 on sperm–zona binding, while anti-gD caused a reduction of this inhibition. Further evidence for the involvement of gC and gD in the virus–sperm interaction was provided by the fact that purified gC and gD decreased sperm–zona binding in a dose-dependent way with gC being more effective than gD. These results indicated that BoHV-1 inhibits bovine sperm–zona binding by interacting with spermatozoa. The binding of BoHV-1 to a spermatozoon is mediated by the viral glycoproteins gC and gD, and therefore seems to be comparable with the mechanisms of BoHV-1 attachment to its natural host cell.

Carbohydrates and glycoproteins involved in bovine fertilization in vitro

In the present study, efforts were made towards identifying carbohydrates and glycoproteins involved in bovine in vitro fertilization (IVF). In vitro matured cumulus-oocyte complexes (COCs) were inseminated in the presence of a variety of carbohydrates and glycoproteins to determine which glycoconjugates act as competitive inhibitors of oocyte penetration. Among the carbohydrates and glycoproteins tested, D-mannose, fucoidan, dextran sulfate, and fibronectin were the most potent inhibitors of oocyte penetration (90% or more inhibition), while L-fucose and vitronectin inhibited the penetration rate to a lesser extent (around 50% inhibition). Other carbohydrates caused less than 40% inhibition (i.e., D-galactose, N-acetyl-D-galactosamine, D-fucose, and sialic acid) or were not effective as inhibitors of oocyte penetration (i.e., mannan, N-acetyl-D-glucosamine, dextran, and heparan sulfate). Heparin was the only carbohydrate that significantly increased the penetration rate. To exclude a possible toxic effect on spermatozoa, sperm motility was evaluated over time by means of computer-assisted sperm analysis in the presence of carbohydrates and/or glycoproteins that inhibited the penetration rate with 40% or more. L-fucose, dextran sulfate, and vitronectin did not significantly influence total and progressive sperm motility, whereas D-mannose, fucoidan, and fibronectin caused a significant, but slight reduction in both motility parameters. These results are indicative for the involvement of D-mannose, L-fucose, fucoidan, dextran sulfate, fibronectin, and vitronectin in bovine IVF.