P–208 Oleic acid rescues altered autophagy induced by palmitic acid during mouse preimplantation development

Study question

The aim of the study is to identify the autophagic profile and the effects of fatty acid treatments on autophagic activity in preimplantation mouse embryos.

Summary answer

Autophagic activity varies significantly in early stages of mouse preimplantation development; exposure to fatty acids alters the embryonic autophagy profile.

What is known already

Obesity is one of the top comorbidities for infertility, and obese individuals have elevated fatty acid levels. In serum, palmitic acid (PA) and oleic acid (OA) are the most abundant saturated and unsaturated fatty acids, respectively. We recently reported that PA impairs blastocyst development, affects mitochondrial reactive oxygen species, triacylglycerol levels, and endoplasmic reticulum stress pathways during mouse preimplantation development. Interestingly, the addition of OA counteracts those effects. Autophagy plays an essential role in embryo development, as knock-out of a key autophagy protein is embryonic lethal. Little is known about the autophagic profile in fatty acid treated mouse preimplantation embryos.

Study design, size, duration

Pools of 20 – 25 mouse embryos were collected from gonadotrophin super-ovulated and mated CD1 female mice. Two-cell stage embryos were treated with 100 µM PA and 250 µM OA, alone and in combination, and 1.5% bovine serum albumin media (control) within KSOMaa media for 18, 24, and 48 hours in vitro. The detection of various autophagic markers were evaluated by immunofluorescence microscopy and RT-qPCR.

Participants/materials, setting, methods

mRNA levels of autophagic markers were measured using RT-qPCR with the Taqman primers and Universal PCR Mix. Immunofluorescence staining of LC3 puncta (marker for autophagosome formation) was performed using LC3A/B polyclonal antibody (Invitrogen PA1–16931) and DAPI (4′,6-Diamidino–2-phenylindole dihydrochloride) was used to stain for cell nuclei. Analysis of LC3 puncta was performed using ImageJ software. Images were acquired using an LSM 800 laser scanning confocal microscope. Data analysis was completed by GraphPad Prism software.

Main results and the role of chance

Mouse preimplantation embryos showed no change in mRNA levels of autophagic markers (Bcln1, ATG3, ATG5, and LC3) relative to the control group after 48-hours exposure of 100 µM PA and 250 µM OA treatments, alone and in combination.

The number of LC3 puncta was measured and analyzed as a reflection of autophagic activity in mouse preimplantation embryos. Under the fatty acid-free condition, the average number of LC3 puncta per blastomere was significantly decreased after 18 hours of development (p < 0.005). However, the average number of LC3 puncta per blastomere at 18, 24, and 48 hours were not significantly different from each other (p = 0.2724).

Following 100 µM PA and 250 µM OA treatments, alone and in combination, autophagic activity was impacted by the presence of fatty acids. Mouse preimplantation embryos exposed to control and fatty acid treatment groups demonstrated no significant differences in LC3 puncta per blastomere at 18- and 24-hours treatment time (p = 0.5381; p = 0.7829). However, embryos exposed to 48 hours of PA treatment had a significantly greater number of LC3 puncta per blastomere than embryos exposed to 48 hours of OA and PA and OA combination treatments (p < 0.05).

Limitations, reasons for caution

Although LC3 puncta count (autophagosome formation) is impacted by fatty acid treatment, autophagic flux must be measured to fully investigate autophagic activity during mouse preimplantation development. These processes need to be measured in human embryos cultured in vitro.

Wider implications of the findings: Profiling autophagic activity in fatty acid treated mouse preimplantation embryos would guide future investigations on pharmacological modulation of autophagy as a therapeutic intervention for developmentally delayed embryos. With the information gained, we aim to develop strategies to assist overweight and obese patients with their fertility needs.

Trial registration number

Not applicable

P–227 Fatty acid regulation of Nrf2/Keap1 pathway during mouse preimplantation embryo development

Study question

Our objective is determining whether supplementing embryo culture media with palmitic acid and/or oleic acid impacts Nrf2/Keap1 antioxidant response pathways during preimplantation mouse embryo development.

Summary answer

Supplementation of embryo culture media with palmitic acid increases cellular Nrf2 levels per embryo after 48-hour culture, while oleic acid reverses this effect.

What is known already

Obese women experience higher incidence of infertility than women with healthy BMIs. The obese reproductive tract environment supporting preimplantation embryo development is likely to include enhanced free fatty acid (FFA) levels and increased accumulation of reactive oxygen species. Exposure to palmitic acid (PA) in vitro significantly impairs mouse embryo development while increasing ER stress mRNAs. Oleic acid (OA) reverses these effects. To further define effects of FFA exposure, we are characterizing the influence of FFAs on the Nrf2–Keap1 pathway and its downstream antioxidant defense systems. We hypothesize that PA treatment induces Nrf2-Keap1 activity, while OA treatment alleviates pathway activity.

Study design, size, duration

Female CD–1 mice (4–6 weeks) were super-ovulated via intraperitoneal injections of PMSG, followed 48 hours later by hCG. Female mice were mated with male CD–1 mice (6–8 months) overnight. Females were euthanized using CO2 and two-cell embryos were collected by flushing oviducts. Two-cell embryos were placed into KSOMaa-based treatment groups: 1) BSA (control); 2) 100µM PA; 3) 100µM OA; 4) 100µM PA+OA, and cultured for 48 hours (37 °C; 5% O2, 5% CO2, 90% N2).

Participants/materials, setting, methods

After 48-hour embryo culture, developmental stages of all mouse embryos were recorded. Immunofluorescence analysis of Nrf2 and Keap1 localization was performed for embryo treatments (BSA, 100µM PA, 100µM OA & 100µM PA+OA) using rabbit polyclonal anti-Nrf2 antibody, with Rhodamine-Phalloidin and DAPI staining. Embryos were imaged using confocal microscopy and Nrf2-positive cells were counted using ImageJ. Nrf2 and Keap1 mRNA abundances were assessed after culture in each treatment condition using RT-qPCR and the delta-delta Ct method.

Main results and the role of chance

Inclusion of 100µM PA in embryo culture significantly decreased blastocyst development frequency from 70.06±16.38% in the BSA (control) group to 11.61±8.19% in the PA-treated group (p < 0.0001). Embryo culture with 100µM OA and 100µM PA+OA co-treatment did not significantly impair blastocyst development (OA: 61.59±8.07%, p = 0.4053; PA+OA: 63.53±7.63%, p = 0.6204).

Embryo culture with PA treatment significantly increased the mean percentage of Nrf2-positive cells to 56.83±30.49% compared with 21.22±15.63% in the control group (p < 0.0001). Conversely, 100µM OA and 100µM PA+OA treatments did not significantly affect Nrf2-positive cell frequencies compared with the control group (OA: 33.28±21.83%, p = 0.1825; PA+OA: 34.84±12.66%, p = 0.0691). Immunofluorescence results show that treating embryos with 100µM PA for 48 hours results in increased levels of cellular Nrf2, while combining 100µM PA with 100µM OA reversed these effects.

Preliminary qPCR analysis showed no significant differences in Nrf2 or Keap1 relative transcript abundance between any embryo treatment groups. Nrf2 and Keap1 mRNA levels were both higher after embryo culture with 100µM OA than all other culture groups (p = 0.6268; p = 0.3201). Notably, Keap1 relative transcript levels dropped to undetectable levels after culture with 100µM PA, which suggests an increase in Nrf2 activation.Limitations, reasons for caution: While immunofluorescence localization of Nrf2/Keap1 provides insight into how the proteins behave during preimplantation embryo development, confocal images cannot determine protein-protein interactions or activity levels. Similarly, transcript information from RT-qPCR analysis only provides information about Nrf2 and Keap1 at the transcript level. Nrf2 activity will be assessed via downstream targets.

Wider implications of the findings: The Nrf2–Keap1 pathway coordinates numerous cellular defence mechanisms, and is implicated in various diseases, including cancer. Establishing an impact of free fatty acid exposure on Nrf2–Keap1 during preimplantation embryo development will provide valuable information regarding the effects of maternal obesity on outcomes for embryos produced from these patients.

Trial registration number

Not applicable

P–553 Women with molar pregnancies have a genetic susceptibility to aneuploid miscarriages

Study question

What causes non-molar miscarriages in women with one hydatidiform mole (HM)?

Summary answer

We found a higher rate of aneuploidies in the non-molar miscarriages of women with HM than in those from women with sporadic or recurrent miscarriages.

What is known already

Women with hydatidiform moles have higher rates of miscarriages and women with recurrent miscarriages have higher rates of moles than women from the general population.

Study design, size, duration

We retrieved archived formalin-fixed paraffin embedded tissues from non-molar miscarriages of patients with one HM and analyzed them for the presence of aneuploidies using single nucleotide polymorphism (SNP)-microarray. We next determined the meiotic origin of the aneuploidies by genotyping the aneuploid non-molar miscarriages along with the parental genomes using microsatellite markers.

Participants/materials, setting, methods

All participants and some of their partners provided written consent to participate in our study, agreed to a blood draw for genotyping analysis, and agreed for us to retrieve their molar and non-molar tissues from various histopathology laboratories for research purposes.

Main results and the role of chance

We demonstrate for the first time that patients with an HM and miscarriages are at higher risk for aneuploid miscarriages [83.3%, 95% confidence interval (CI): 0.653–0.944] than women with sporadic (51.5%, 95% CI: 50.3–52.7%, p value = 0.0003828) or recurrent miscarriages (43.8%, 95% CI: 40.7–47.0%, p value = 0.00002). Genotyping the aneuploid miscarriages and the parental genomes demonstrated that most of the aneuploidies originated from errors in maternal meiosis I or II.

Limitations, reasons for caution

We were able to retrieve only 30 non-molar miscarriages from women with one HM for analysis. Expanding such analysis to a larger and independent cohort of miscarriages from such patients will be important to validate our observations.

Wider implications of the findings: Our data suggest common genetic female germline defects predisposing to HM and aneuploid non-molar miscarriages in some patients.

Trial registration number

Not applicable