Golgi apparatus and endoplasmic reticulum dynamic during meiotic development in canine oocytes

Astaxanthin protects oocyte maturation against cypermethrin-induced defects in pigs

Cypermethrin (CYP), a pyrethroid insecticide, exerts the detrimental effect on the reproductive system, while astaxanthin (AST), a xanthophyll carotenoid, possesses the powerful antioxidant property and can protect oocyte maturation. However, the toxicity of CYP and the protective role of AST against CYP during oocyte maturation remain unclear. Here, porcine oocytes were applied to investigate the potential effects and underlying mechanisms of CYP and AST during oocyte maturation. This work demonstrated that CYP significantly decreased oocyte maturation rate and subsequent embryo development in a dose-dependent manner (P < 0.05). And, CYP obviously induced the overproduction of reactive oxygen species and the reduction of glutathione content by downregulating the expression of redox genes in oocytes (P < 0.05). Moreover, CYP significantly caused oocyte DNA damage and disturbed the function of endoplasmic reticulum by altering the transcription of DNA damage repair and endoplasmic reticulum stress related genes (P < 0.05). Whereas CYP-exposed oocytes were treated with AST, these defects caused by CYP were significantly ameliorated (P < 0.05). In conclusion, this study demonstrated that CYP exerted the toxic effect on porcine oocytes, while AST effectively alleviated CYP-induced defects. This work provides a potential strategy to prevent pesticide toxicity and protect oocyte maturation in mammalian reproduction.

Human globozoospermia-related genes and their role in acrosome biogenesis

The mammalian acrosome is a secretory vesicle attached to the sperm nucleus whose fusion with the overlying plasma membrane is required to achieve fertilization. Acrosome biogenesis starts during meiosis, but it lasts through the entire process of haploid cell differentiation (spermiogenesis). Acrosome biogenesis is a stepwise process that involves membrane traffic from the Golgi apparatus, but it also seems that the lysosome/endosome system participates in this process. Defective sperm head morphology is accompanied by defective acrosome shape and function, and patients with these characteristics are infertile or subfertile. The most extreme case of acrosome biogenesis failure is globozoospermia syndrome, which is primarily characterized by the presence of round-headed spermatozoa without acrosomes with cytoskeleton defects around the nucleus and infertility. Several genes participating in acrosome biogenesis have been uncovered using genetic deletions in mice, but only a few of them have been found to be deleted or modified in patients with globozoospermia. Understanding acrosome biogenesis is crucial to uncovering the molecular basis of male infertility and developing new diagnostic tools and assisted reproductive technologies that may help infertile patients through more effective treatment techniques. This article is categorized under: Reproductive System Diseases > Environmental Factors Infectious Diseases > Stem Cells and Development Reproductive System Diseases > Molecular and Cellular Physiology.

Tannin Reduces the Incidence of Polyspermic Penetration in Porcine Oocytes

Tannin (TA) improves porcine oocyte cytoplasmic maturation and subsequent embryonic development after in vitro fertilization (IVF). However, the mechanism through which TA blocks polyspermy after IVF remains unclear. Hence, the biological function of organelles (cortical granule [CG], Golgi apparatus, endoplasmic reticulum [ER], and mitochondria) and the incidence of polyspermic penetration were examined. We found no significant difference in oocyte nuclear maturation among the 1 µg/mL, 10 µg/mL TA, and control groups. Moreover, 100 μg/mL TA significantly reduced 1st polar body formation rate compared to the other groups. Additionally, 1 and 10 μg/mL TA significantly increased the protein levels of GDF9, BMP15, and CDK1 compared to the control and 100 μg/mL TA groups. Interestingly, 1 and 10 μg/mL TA improved the normal distribution of CGs, Golgi, ER, and mitochondria by upregulating organelle-related gene expression and downregulating ER stress (CHOP) gene expression. Simultaneously, 1 and 10 μg/mL TA significantly increased the proportion of normal fertilized oocytes (2 pronuclei; 2 PN) and blastocyst formation rate compared to the control, as well as that of 100 μg/mL TA after IVF by upregulating polyspermy-related genes. In conclusion, TA during IVM enhances 2PN and blastocyst formation rates by regulating organelles’ functions and activities.

High Temperature Disrupts Organelle Distribution and Functions Affecting Meiotic Maturation in Porcine Oocytes

Heat stress (HS) has been known to cause reproductive failure in animals, especially in summer. HS severely affects the developmental potential of oocytes and leads to low fertility rates. Previous studies have reported that HS compromises embryo development in bovine oocytes, and reduces ovarian development in mice, thereby impairing reproductive function in animals. However, the effect of high temperature (HT) on the organelles of porcine oocytes is unknown. In this study, we reported that exposure to HT for 24 h (41°C) significantly decreased meiotic maturation in porcine oocytes (p < 0.05). Further experiments on organelles found that HT induced mitochondrial dysfunction, increased abnormal mitochondrial distribution, and decreased mitochondrial membrane potential (MMP). We also found that HT induced abnormal endoplasmic reticulum (ER) distribution and higher expression of glucose regulatory protein 78 (GRP78), suggesting that HT exposure induces ER stress. Our results also indicated that exposure to HT induced abnormal distribution and dysfunction of the Golgi apparatus, which resulted from a decrease in the expression of the vesicle transporter, Ras-related protein Rab-11A (RAB11A). In addition, we found that HT exposure led to lysosomal damage by increasing the expression of lysosome-associated membrane protein 2 (LAMP2) and microtubule-associated protein 1A/1B-light chain 3 (LC3). In summary, our study revealed that HT exposure disrupts organelle dynamics, which further leads to the failure of meiotic maturation in porcine oocytes.

Luteolin Orchestrates Porcine Oocyte Meiotic Progression by Maintaining Organelle Dynamics Under Oxidative Stress

Increasing evidence has demonstrated that oxidative stress impairs oocyte maturation, but the underlying mechanisms remain largely unknown. Here, for the first time, we examined the antioxidant role of luteolin in meiotic progression and the underlying mechanisms. Supplementation of 5 μM luteolin increased the rates of first polar body extrusion and blastocyst formation after parthenogenetic activation, and the expression levels of oocyte competence (BMP15 and GDF9)-, mitogen-activated protein kinase (MOS)-, and maturation promoting factor (CDK1 and Cyclin B)-related genes were also improved. Luteolin supplementation decreased intracellular reactive oxygen species levels and increased the expression levels of oxidative stress-related genes (SOD1, SOD2, and CAT). Interestingly, luteolin alleviated defects in cell organelles, including actin filaments, the spindle, mitochondria, the endoplasmic reticulum, and cortical granules, caused by H₂O₂ exposure. Moreover, luteolin significantly improved the developmental competence of in vitro-fertilized embryos in terms of the cleavage rate, blastocyst formation rate, cell number, cellular survival rate, and gene expression and markedly restored the competencies decreased by H₂O₂ treatment. These findings revealed that luteolin supplementation during in vitro maturation improves porcine meiotic progression and subsequent embryonic development by protecting various organelle dynamics against oxidative stress, potentially increasing our understanding of the underlying mechanisms governing the relationship between oxidative stress and the meiotic events required for successful oocyte maturation.

Influence of growth differentiation factor 9 and bone morphogenetic protein 15 on in vitro maturation of canine oocytes

Growth differentiation factor 9 (GDF-9) and bone morphogenetic protein 15 (BMP-15) have pivotal roles in oocyte development in many species, therefore the aim was to investigate these factors during in vitro maturation (IVM) of canine oocytes. Canine cumulus oocytes complexes (COCs) were cultured in six groups for 72 hr in a supplemented TCM199-Hepes medium as (a) Control group; (b) GDF-9 antibody (Ab); (c) BMP-15 Ab; (d) recombinant human (rh) GDF-9; (e) rh BMP-15 or (f) rh BMP-15 and GDF-9. Data were evaluated by ANOVA. The Abs against GDF-9 or BMP-15 had a negative impact on meiotic development. Higher (p < 0.05) number of oocytes was arrested at GVBD stage when they were incubated with either GDF-9 Ab (64.4 ± 2.1%) or BMP-15 Ab (67.2%± 4.9%) in comparison to those in control group (32.4 ± 7.8%). In contrast, more (p < 0.05) oocytes in control group reached MI (37.4 ± 1.3%) and MII stages (10.2 ± 2.1%) comparing to those groups with GDF-9 Ab (23.1 ± 4.7% MI; 0.0% MII) or BMP-15 Ab (16.4 ± 2.4%MI; 5.9% ± 2.1 MII). Higher rates (p < 0.05) of oocytes in control group stayed still arrested at GV (19.9 ± 8.6%) in comparison to those cultured with either rhGDF-9 (3.7 ± 0.4%) or rhBMP-15 (10.9 ± 0.7%). However, there were no differences in MII rates between oocytes cultured with GDF-9 (14.7 ± 3.1) and BMP-15 (7.8 ± 2.5) separately. But, more oocytes (p < 0.05) reached the MII stage (20.5 ± 3.8%) compared to those exposed to each protein separately and to the control group. These results suggest that these proteins likely contribute to the meiotic development in dogs.

Differential gene-expression profiles from canine cumulus cells of ovulated versus in vitro-matured oocytes

We compared the nuclear maturation status and gene-expression profiles of canine cumulus cells (CCs) derived from cumulus-oocyte complexes (COCs) that were spontaneously ovulated versus those that were matured in vitro. Cumulus-oocyte complexes were retrieved from uteri by surgical flushing (after spontaneous ovulation) or by ovariectomy follicle aspiration and in vitro maturation. The objective of Experiment 1 was to investigate the nuclear maturation status of in vivo- versus in vitro-matured oocytes. The objective of Experiment 2 was to compare gene-expression profiles of CCs derived from in vivo- versus in vitro-matured COCs. Genes analysed are related to cell maturation, development and apoptosis, including GDF9, MAPK1, PTX3, CX43, Bcl2 and BAX; mRNA expression for all of these genes, except for GDF9, differed (P<0.05) between in vivo- and in vitro-matured CCs. In conclusion, we found that gene-expression profiles are related to the quality of CCs and therefore posit that monitoring gene expression could be a useful strategy to guide attempts to improve in vitro culture systems.

Temporal expression of GDF-9 and BMP-15 mRNAs in canine ovarian follicles

This study aimed to investigate the expression profiles of growth differentiation factor 9 (GDF-9) and bone morphogenetic protein 15 (BMP-15) mRNA in canine oocytes and follicular cells throughout development at the different phases of the estrus cycle. Ovarian structures (follicles and CL) and plasma progesterone concentration were used to confirm the physiological status of each donor. Denuded oocytes and their follicular cells were recovered from follicles (n = 675) distributed into 4 types (preantral, small antral ∼0.2-0.39 mm, medium antral ∼0.4-5.9 mm, and large antral ∼6-8 mm). Total RNA was extracted and reverse transcribed, and the levels of expression for these 2 genes were determined using a quantitative real-time polymerase chain reaction technique; the data were evaluated by ANOVA. Relative expressions levels of GDF-9 and BMP-15 transcripts were detected in the oocyte and follicular cells in all follicular stages evaluated, showing differential changes (P < 0.05) during development over the estrus cycle. The expression patterns of both transcripts were highly correlated between follicles cells and oocytes (r > 0.8; P < 0.05 for GDF-9 and BMP-15), although GDF-9 was expressed at higher levels (P < 0.05) in the oocyte compared with the follicle cells. All cell types showed more GDF-9 mRNA abundance at early developing stages, mainly in the anestrus phase, and declining levels in the later stages (P < 0.05), whereas BMP-15 mRNA levels increased (P < 0.05) in follicular cells and oocytes from the preantral to the later stages, and remained constant during the final preovulatory stage. In conclusion, these two genes were detected in follicular cells and oocytes and were differentially expressed during the follicular development across the estrus cycle.