Dynamic analysis of Ca²+ level during bovine oocytes maturation and early embryonic development

Glycine Ameliorates Endoplasmic Reticulum Stress Induced by Thapsigargin in Porcine Oocytes

The endoplasmic reticulum (ER) is a multifunctional organelle in the cytoplasm that plays important roles in female mammalian reproduction. The endoplasmic reticulum and mitochondria interact to maintain the normal function of cells by maintaining intracellular calcium homeostasis. As proven by previous research, glycine (Gly) can regulate the intracellular free calcium concentration ([Ca²⁺]_i) and enhance mitochondrial function to improve oocyte maturation in vitro. The effect of Gly on ER function during oocyte in vitro maturation (IVM) is not clear. In this study, we induced an ER stress model with thapsigargin (TG) to explore whether Gly can reverse the ER stress induced by TG treatment and whether it is associated with calcium regulation. The results showed that the addition of Gly could improve the decrease in the average cumulus diameter, the first polar body excretion rate caused by TG-induced ER stress, the cleavage rate and the blastocyst rate. Gly supplementation could reduce the ER stress induced by TG by significantly improving the ER levels and significantly downregulating the expression of genes related to ER stress (Xbp1, ATF4, and ATF6). Moreover, Gly also significantly alleviated the increase in reactive oxygen species (ROS) levels and the decrease in mitochondrial membrane potential (ΔΨ m) to improve mitochondrial function in porcine oocytes exposed to TG. Furthermore, Gly reduced the [Ca²⁺]_i and mitochondrial Ca²⁺ ([Ca²⁺]_m) levels and restored the ER Ca²⁺ ([Ca²⁺]_ER) levels in TG-exposed porcine oocytes. Moreover, we found that the increase in [Ca²⁺]_i may be caused by changes in the distribution and expression of inositol 1,4,5-triphosphate receptor (IP₃R1) and voltage-dependent anion channel 1 (VDAC1), while Gly can restore the distribution and expression of IP₃R1 and VDAC1 to normal levels. Apoptosis-related indexes (Caspase 3 activity and Annexin-V) and gene expression Bax, Cyto C, and Caspase 3) were significantly increased in the TG group, but they could be restored by adding Gly. Our results suggest that Gly can ameliorate ER stress and apoptosis in TG-exposed porcine oocytes and can further enhance the developmental potential of porcine oocytes in vitro.

Effect of perfluorodecanoic acid on pig oocyte viability, intracellular calcium levels and gap junction intercellular communication during oocyte maturation in vitro

Perfluorodecanoic acid (PFDA) is a synthetic perfluorinated compound, which has been reported to exert adverse effects on somatic cells. However, its effects on germ cells have not been studied to date. The aim of the present study was to analyze the effects of PFDA on the viability, intracellular calcium levels and gap junction intercellular communication (GJIC) during porcine oocyte maturation in vitro. PFDA negatively impacted oocyte viability (medium lethal concentration, LC₅₀ = 7.8 μM) and maturation (medium inhibition of maturation, IM₅₀ = 3.8 μM). Oocytes exposed to 3.8 μM PFDA showed higher levels of intracellular calcium relative to control oocytes. In addition, GJIC among the cumulus cells and the oocyte was disrupted. The effects of PFDA on oocyte calcium homeostasis and intercellular communication seem to be responsible for the inhibition of oocyte maturation and oocyte death. In addition, since the deleterious effects of PFDA on oocyte viability, maturation and GJIC are significantly stronger than the previously reported effects of another widely used perfluorinated compound (Perfluorooctane sulfonate) in the same model, the use of PFDA in consumer products is questioned.

Calcium ion regulation by BAPTA-AM and ruthenium red improved the fertilisation capacity and developmental ability of vitrified bovine oocytes

Vitrification reduces the fertilisation capacity and developmental ability of mammalian oocytes; this effect is closely associated with an abnormal increase of cytoplasmic free calcium ions ([Ca²⁺]i). However, little information about the mechanism by which vitrification increases [Ca²⁺]i levels or a procedure to regulate [Ca²⁺]i levels in these oocytes is available. Vitrified bovine oocytes were used to analyse the effect of vitrification on [Ca²⁺]i, endoplasmic reticulum Ca²⁺ (ER Ca²⁺), and mitochondrial Ca²⁺ (mCa²⁺) levels. Our results showed that vitrification, especially with dimethyl sulfoxide (DMSO), can induce ER Ca²⁺ release into the cytoplasm, consequently increasing the [Ca²⁺]i and mCa²⁺ levels. Supplementing the cells with 10 μM 1,2-bis (o-aminophenoxy)ethane-N,N,N′,N′-tetraacetic acid (BAPTA-AM or BAPTA) significantly decreased the [Ca²⁺]i level and maintained the normal distribution of cortical granules in the vitrified bovine oocytes, increasing their fertilisation ability and cleavage rate after in vitro fertilisation (IVF). Treating vitrified bovine oocytes with 1 μM ruthenium red (RR) significantly inhibited the Ca²⁺ flux from the cytoplasm into mitochondria; maintained normal mCa²⁺ levels, mitochondrial membrane potential, and ATP content; and inhibited apoptosis. Treating vitrified oocytes with a combination of BAPTA and RR significantly improved embryo development and quality after IVF.

Effects of sperm insemination on the final meiotic maturation of mouse oocytes arrested at metaphase I after in vitro maturation

Objective

The aims of this study were to investigate whether fertilization could induce the resumption of meiosis in mouse oocytes arrested at metaphase I (MI) after in vitro maturation (IVM), and to investigate the effect of Ca²⁺ chelator treatment at the time of fertilization on the transition from MI to metaphase II (MII).

Methods

MII-stage and arrested MI-stage mouse oocytes after IVM were fertilized, and then embryonic development was monitored. Blastocysts from each group were transferred into 2.5 days post-coitum pseudo-pregnant ICR mice. MI oocytes after IVM were treated with a Ca²⁺ chelator to investigate the effect of Ca²⁺ oscillations on their maturation.

Results

As insemination time increased, the number of oocytes in the MI group that reached the MII stage also increased. The blastocyst rates and total cell numbers in the MII group were significantly higher than in the MI group. No pregnancy occurred in the MI group, but 10 pregnancies were achieved (10 of 12) in the MII group. The proportion of MI oocytes that matured to MII oocytes after fertilization was significantly higher in the non-treated group than in the Ca²⁺ chelator-treated group.

Conclusion

The findings that a higher proportion of MI-arrested oocytes progressed to MII after fertilization and that the MI-to-MII transition was blocked by Ca²⁺ chelator treatments before fertilization indicate that the maturation of MI oocytes to MII oocytes is associated with intracellular Ca²⁺ oscillations driven by fertilization.

Vitamin D Receptor TaqI Gene Variant in Exon 9 and Polycystic Ovary Syndrome Risk

BACKGROUND

Polycystic ovary syndrome (PCOS) is known as a metabolic disorder. The results of recent studies implied that vitamin D receptor (VDR) genetic variants may impact PCOS and insulin resistance in women with PCOS. The aim of the present study was to determine the VDR TaqI gene variant in exon 9 (T/C) (rs731236) in normal controls and patients with PCOS for the first time in Iranian Azeri women.

MATERIALS AND METHODS

In this case control study between April 2011 and June 2012, a total of 76 women aged 18-40 years (38 patients with PCOS and 38 healthy women as normal controls) participated. Genotypes of VDR TaqI in exon 9 (T/C) (rs731236) were determined using the PCR-RFLP method.

RESULTS

The frequencies of VDR TaqI T anc C alleles were 0.605 and 0.395 in cases and 0.697 and 0.303 in controls. Also, the genotypic frequencies of VDR TaqI were 16) (42.11), 14(36.84), and 8(21.05) in cases, and 17(44.74), 19(50), and 2(5.26) in controls for TT, TC and CC genotypes respectively. There was no difference in genotype and allele frequencies between PCOS and controls (p value>0.05) with the exception of the CC genotype (p value=0.04).

CONCLUSION

This report, a first of its own kind in Iranian Azeri patients, suggests that the CC genotype of VDR TaqI in exon 9 (rs731236) is associated with PCOS.

Lack of Association of Vitamin D Receptor FokI (rs10735810) (C/T) and BsmI (rs1544410) (A/G) Genetic Variations with Polycystic Ovary Syndrome Risk: a Case-control Study from Iranian Azeri Turkish Women

INTRODUCTION

In this study we evaluate the involvement of Vitamin D Receptor (VDR) FokI (rs10735810) Exon 2 (C/T) and BsmI (rs1544410) Intron 8 (A/G) gene variations in genetic susceptibility to polycystic ovary syndrome (PCOS) in Iranian Azeri Turkish women.

MATERIALS AND METHODS

The RFLP-PCR method was performed on peripheral blood lymphocyte for a total of 46 females with PCOS and 46 controls.

OUTCOMES

VDR FokI (rs10735810) CC,CT,TT,C and T genotypic/allelic frequencies were 22(47.83), 20(43.48), 4(8.696), 64(69.57) and 28(30.43) in cases and 29(63.04), 15(32.61), 2(4.348), 73(79.35) and 19(20.65) in controls, respectively. The frequencies of VDR FokI C and T alleles were 0.7 and 0.3 in cases, and 0.79 and 0.21 in controls, respectively. VDR BsmI (rs1544410) Intron 8 (A/G) AA,AG,GG,A and G genotypic/allelic frequencies were 15(32.6), 27(58.7), 4(8.7), 57(62), and 35(38) in cases and 20(43.5), 24(52.2), 2(4.35), 64(69.6), and 28(30.4) in controls, respectively. The frequencies of VDR BsmI (rs1544410) Intron 8 A and G alleles were 0.7 and 0.3 in cases, and 0.62 and 0.38 in controls, respectively. Statistical analysis showed that the differences in genotypic/allelic frequencies between the cases and controls were not statistically significant regarding of VDR FokI(rs10735810) Exon 2 (C/T) and VDR BsmI (rs1544410) Intron 8 (A>G) (p >0.05).

CONCLUSIONS

It can be concluded that FokI (rs10735810) Exon 2 (C/T) and VDR BsmI (rs1544410) Intron 8 (A>G) were not associated with PCOS susceptibility in studied group. Present investigation is the first study in its own kind in Iranian Azeri Turkish women.