Impact of reducing lipid content during in vitro embryo production: A systematic review and meta-analysis

There is still no consensus regarding the role of lipid modulators during in vitro embryo production. Thus, we investigated how lipid reducers during the in vitro maturation of oocytes (IVM) or in vitro culture (IVC) of embryos impact their cryotolerance. A literature search was performed using three databases, recovering 43 articles for the systematic review, comprising 75 experiments (13 performed in IVM, 62 in IVC) and testing 13 substances. In 39 % of the experiments, an increase in oocyte and/or embryo survival after cryopreservation was reported, in contrast to 48 % exhibiting no effect, 5 % causing negative effects, and 8 % influencing in a dose-dependent manner. Of the 75 experiments extracted during IVM and IVC, 41 quantified the lipid content. Of those that reduced lipid content (n = 26), 50 % increased cryotolerance, 34 % had no effect, 8 % harmed oocyte/embryo survival, and 8 % had different results depending on the concentration used. Moreover, 28 out of the 43 studies were analyzed under a meta-analytical approach at the IVC stage in cattle. There was an improvement in the cryotolerance of bovine embryos when the lipid content was reduced. Forskolin, l-carnitine, and phenazine ethosulfate positively affected cryotolerance, while conjugated linoleic acid had no effect and impaired embryonic development. Moreover, fetal bovine serum has a positive impact on cryotolerance. SOF and CR1aa IVC media improved cryotolerance, while mSOF showed no effect. In conclusion, lipid modulators did not unanimously improve cryotolerance, especially when used in IVM, but presented positive effects on cryotolerance during IVC when reaching lipid reduction.

Adding L-carnitine to antagonist ovarian stimulation doesn't improve the outcomes of IVF/ ICSI cycle in patients with polycystic ovarian syndrome: a double-blind randomized clinical trial

OBJECTIVE

To investigate the effect of L-carnitine supplementation during the controlled ovarian stimulation (COS) cycle with antagonist protocol in patients with polycystic ovary syndrome (PCOS) diagnosis undergoing IVF/ICSI treatment.

METHODS AND MATERIALS

This was a double-blind clinical trial study including 110 patients with PCOS attended to Royan Institute between March 2020 and February 2023. At the beginning of the COS cycle, the eligible patients were allocated into two groups randomly according to the coding list of the drugs prepared by the statistical consultant. In the experimental group, patients received 3 tablets daily (L-carnitine 1000 mg) from the second day of menstruation of the previous cycle until the puncture day in the cases of freeze-all embryos (6 weeks) or until the day of the pregnancy test (8 weeks) in fresh embryo transfer cycle. In the control group, patients received 3 placebo tablets for the same period of time. Weight assessment and fasting blood sugar and insulin tests, as well as serum lipid profile were also measured at the baseline and ovum pick-up day. The results of the COS cycle as well as the implantation and pregnancy rates were compared between groups.

RESULTS

Finally, 45 cases in L-carnitine group versus 47 cases in the placebo group were completed study per protocol. Data analysis showed that the two groups were homogeneous in terms of demographic characteristics and baseline laboratory tests and severity of PCOS. There is no statistically significant difference in terms of the oocyte recovery ratio and oocyte maturity rate, and the number and quality of embryos, as well as the rates of the fertilization, chemical and clinical pregnancy between groups. However, the means of weight (P < 0.001) and serum levels of fasting blood sugar (P = 0.021), fasting insulin (P = 0.004), triglyceride (P < 0.001) and cholesterol (P < 0.001), LDL (P < 0.001) have significantly decreased in women after consuming L-carnitine supplementation.

CONCLUSION

The oral intake of L-carnitine during COS in PCOS women for 6 weeks had no effect on COS and pregnancy outcomes. However, taking this supplement for 6 weeks has been associated with weight loss and improved lipid profile and serum glucose.

TRIAL REGISTRATION

The study was registered in the Clinicaltrials.gov site on December 17, 2020 (NCT04672720).

The effect of adding L-Carnitine to the GnRH-antagonist protocol on assisted reproductive technology outcome in women with polycystic ovarian syndrome: a randomized clinical trial

OBJECTIVE

This study aimed to investigate the effect of adding L-Carnitine to the gonadotropins on ART outcome in frozen-thawed embryo transfer cycles among PCOS women.

METHODS

In this randomized clinical trial, 83 patients with PCOS were randomized to either L-Carnitine supplemented (n = 42) or control (n = 41) groups. The L-Carnitine group was given 3000 mg of oral L-Carnitine daily until the final day of ovulation. The numbers of metaphase II (MII) oocytes, 2-pronuclears (2PNs), oocyte maturity rate, fertilization rate, fertilization proportion as well as implantation, chemical and clinical pregnancy rates were compared between the two groups.

RESULTS

Even though the duration of stimulation and endometrial thickness were comparable between groups (p > .05), serum estradiol level on the day of oocyte triggering, was significantly higher in the L-Carnitine group compared to the control group (p < .05). In contrast, the number of retrieved and MII oocytes as well as the number of 2PNs and obtained embryos were similar between groups (p > .05). Moreover, oocyte maturity rate (0.85 ± 0.38 vs. 1.02 ± 0.90), fertilization proportion (0.62 ± 0.44 vs. 0.80 ± 0.86), fertilization rate (0.70 ± 0.22 vs. 0.76 ± 0.19) along with implantation rate (18.1 vs. 13.7%), chemical (26.8 vs. 30.7%) and clinical (24.3 vs. 25.6%) pregnancy rates, were all comparable between L-Carnitine and control groups respectively (p > .05).

CONCLUSIONS

Our result showed that oral L-Carnitine administration during induction of ovulation among PCOS women could not improve laboratory and pregnancy outcome.

L-Carnitine improves follicular survival and function in ovarian grafts in the mouse

CONTEXT

Ovarian tissue transplantation is performed to preserve fertility in patients undergoing chemotherapy and radiotherapy. However, the ischemia-reperfusion injury which occurs after the ovarian tissue transplantation causes follicular depletion and apoptosis. l -Carnitine has antioxidant and anti-inflammation properties.

AIMS

Therefore, we aimed to investigate the beneficial effect of l -carnitine on mouse ovaries following heterotopic autotransplantation.

METHODS

Mice were randomly divided into three groups (six mice per group): control, autografted and autografted+l -carnitine (200mg/kg daily intraperitoneal injections). Seven days after ovary autografting, the serum levels of malondialdehyde (MDA), total antioxidant capacity, tumor necrosis factor alpha (TNF-α), interleukin (IL)-6 and IL-10 were measured. Ovary histology, serum concentrations of progesterone and estradiol were also measured 28days after autotransplantation. Data were analysed using one-way analysis of variance (ANOVA) and Tukey test, and the means were considered significantly different at P Key results: In the autografted+l -carnitine group, the total volume of the ovary, the volume of the cortex, the number of follicles, the serum concentrations of IL-10, estradiol and progesterone significantly increased compared to the autografted group. In the autografted+l -carnitine group, serum concentrations of IL-6, TNF-α and MDA were significantly decreased compared to the autografted group.

CONCLUSIONS

Our results indicated that l -carnitine can ameliorate the consequences of ischemia-reperfusion on the mice ovarian tissue following autotransplantation.

IMPLICATIONS

l -carnitine improves the structure and function of transplanted ovaries.

In vitro maturation medium supplementation: utilization of repaglinide, L-carnitine, and mesenchymal stem cell-conditioned medium to improve developmental competence of oocytes derived from endometriosis mouse models

Endometriosis (EMS) is one of the most prevalent causes for female infertility. Herein, we investigated the effect of the repaglinide (RG), L-carnitine (LC), and bone marrow mesenchymal stem cell-conditioned medium (BMSC-CM) supplementation during in vitro maturation (IVM) on the quality, maturation, and fertilization rates, as well as embryonic quality and development of oocytes derived from normal and EMS mouse model. Immature oocytes were collected from two groups of normal and EMS-induced female NMRI mice at 6-8 weeks of age. Oocytes were cultured in IVM medium unsupplemented (control group), or supplemented with 1 M RG, 0.3 and 0.6 mg/mL LC, and 25 and 50% BMSC-CM. After 24 h of oocyte incubation, IVM rate and antioxidant status were assessed. Subsequently, the rates of fertilization, cleavage, blastulation, and embryonic development were assessed. Our results demonstrated that supplementation of IVM medium with LC and BMSC-CM, especially 50% BMSC-CM, significantly enhanced IVM and fertilization rates, and markedly improved blastocyst development and total blastocyst cell numbers in EMS-induced mice compared to the control group (53.28±0.24 vs 18.09±0.10%). Additionally, LC and BMSC-CM were able to significantly modulate EMS-induced nitro-oxidative stress by boosting total antioxidant capacity (TAC) and mitigating nitric oxide (NO) levels. Collectively, LC and BMSC-CM supplementation improved oocyte quality and IVM rates, pre-implantation developmental competence of oocytes after in vitro fertilization, and enhanced total blastocyst cell numbers probably by attenuating nitro-oxidative stress and accelerating nuclear maturation of oocytes. These outcomes may provide novel approaches to refining the IVM conditions that can advance the efficiency of assisted reproductive technologies in infertile couples.

Impact of L-carnitine supplementation on the in vitro developmental competence and cryotolerance of buffalo embryos

Background and Aim: Despite many trials, buffalo embryos have poor cryosurvivability because of their high lipid content. L-carnitine was found to be a lipid-reducing agent when added to oocyte and embryo culture media. The study aimed to determine the most effective concentration of L-carnitine to improve the oocyte developmental competence and cryotolerance of buffalo embryos. Materials and Methods: In vitro maturation and embryo culture media were supplemented with four concentrations of L-carnitine: 0 (control), 0.25, 0.5, and 1 mM. Good-quality embryos on 7 days were vitrified using mixtures of dimethyl sulfoxide and ethylene glycol at two concentrations (3.5 and 7 M). Results: The result showed that the cleavage and morula rates were significantly (p<0.05) higher in the 0.5 mM group. Blastocyst rates were significantly (p<0.05) higher at both 0.5 and 1 mM. The rates of viable embryos directly after thawing were significantly (p<0.05) increased in the 0.5 mM group. No significant difference was found in embryos cultured for 24 h after warming among all the groups. Conclusion: The addition of L-carnitine at a concentration of 0.5 mM to the culture media improves the oocyte developmental competence and cryotolerance of buffalo embryos directly after warming but not after 24 h of culture. Nevertheless, further studies must identify how L-carnitine exerts its beneficial micromechanisms.

Treatment of mouse cumulus-oocyte complexes with L-carnitine during vitrification and in vitro maturation affects maturation and embryonic developmental rate after parthenogenetic activation

The technique of oocyte vitrification remains a challenge in most animal species. The present study aimed to evaluate the effects of cumulus cell presence and L-carnitine (LC) treatment during vitrification of selected immature oocytes by brilliant cresyl blue (BCB) staining on maturation and embryonic developmental rate after parthenogenetic activation. Immature oocytes were obtained from C57BL/6 female mice ovaries and stained with BCB. The BCB⁺ cumulus-oocyte complexes (COCs) were then selected and random parts of COCs were denuded from cumulus cells (denuded oocytes: DOs). COCs and DOs were treated with/out LC (0.6 mg/ml) during vitrification and in vitro maturation (IVM) procedures. A number of non-vitrified COCs were also treated with LC during the IVM process (fresh group). Maturation rate, intracellular glutathione (GSH) contents, and developmental competence of oocytes were also examined. The GSH levels in vitrified DOs+LC and vitrified COCs+LC groups were significantly higher (p < 0.01) than untreated vitrified-warmed COCs and DOs. Maturation rate and blastocyst developmental rate were reduced after the vitrification-warming procedure compared with the fresh group. The vitrified COCs+LC group showed a higher percentage of mature oocytes and the ability to develop to blastocyst stage than the vitrified-warmed DOs group (p < 0.01). These data indicated that the presence of cumulus cells around the competent oocyte and LC treatment during vitrification and IVM procedure could improve parthenogenetic developmental competence of vitrified-warmed oocytes by increasing GSH levels and accelerating oocyte maturation.

Vitrification-induced activation of lysosomal cathepsin B perturbs spindle assembly checkpoint function in mouse oocytes

As the age of child-bearing increases and correlates with infertility, cryopreservation of female gametes is becoming common-place in ART. However, the developmental competence of vitrified oocytes has remained low. The underlying mechanisms responsible for reduced oocyte quality post-vitrification are largely unknown. Mouse cumulus-oocyte complexes were vitrified using a cryoloop technique and a mixture of dimethylsulphoxide, ethylene glycol and trehalose as cryoprotectants. Fresh and vitrified/thawed oocytes were compared for chromosome alignment, spindle morphology, kinetochore-microtubule attachments, spindle assembly checkpoint (SAC) and aneuploidy. Although the majority of vitrified oocytes extruded the first polar body (PB), they had a significant increase of chromosome misalignment, abnormal spindle formation and aneuploidy at metaphase II. In contrast to controls, vitrified oocytes extruded the first PB in the presence of nocodazole and etoposide, which should induce metaphase I arrest in a SAC-dependent manner. The fluorescence intensity of mitotic arrest deficient 2 (MAD2), an essential SAC protein, at kinetochores was reduced in vitrified oocytes, indicating that the SAC is weakened after vitrification/thawing. Furthermore, we found that vitrification-associated stress disrupted lysosomal function and stimulated cathepsin B activity, with a subsequent activation of caspase 3. MAD2 localization and SAC function in vitrified oocytes were restored upon treatment with a cathepsin B or a caspase 3 inhibitor. This study was conducted using mouse oocytes, therefore confirming these results in human oocytes is a prerequisite before applying these findings in IVF clinics. Here, we uncovered underlying molecular pathways that contribute to an understanding of how vitrification compromises oocyte quality. Regulating these pathways will be a step toward improving oocyte quality post vitrification and potentially increasing the efficiency of the vitrification program.

Melatonin promotes in vitro maturation of vitrified-warmed mouse GV oocytes potentially by modulating MAD2 protein expression of SAC component through MTRs

Previous studies have shown that melatonin (MT) can ameliorate vitrification-inflicted damage in mouse germinal vesicle (GV) oocytes, however, the key mechanistic basis of this improvement still remains poorly understood. This study was conducted to investigate whether MT can improve in vitro developmental potential of vitrified-warmed GV oocytes through its receptors. The fresh oocytes were randomly divided into four groups: untreated (control group, F), vitrified by open-pulled straw method (vitrification group, V), vitrification group with 100 nmol/L MT supplementation (vitrification + MT group, VM), and with 100 nmol/L MT plus 100 nmol/L luzindole administration (vitrification + MT + luzindole group, VML) or with 50 nmol/L ramelteon addition (vitrification + ramelteon group; VR). After warming, oocytes were cultured in vitro, and MT receptors (MTRs), MAD2 (mitotic arrest deficient 2), Securin and CyclinB1 protein levels and spindle morphology were evaluated. The ratio of oocytes developed to the metaphase I (MI) and metaphase II (MII) stages was also assessed. The results showed that after vitrification-warming, the in vitro maturation rate of GV oocytes was significantly lower compared to the control (F) group. Vitrification also significantly impaired the spindle morphology, decreased the protein level of MTRs and Securin, and decreased MAD2 levels in MI oocytes. However, when MT or ramelteon (MTRs agonist) were added (group wise) to warming and maturation media, the maturation rate of GV oocytes was significantly increased, the normal proportion of the spindle morphology increased, and the expression level of MAD2 increased in their resulting MI oocytes compared to the vitrification group. However, following addition of both MT and ramelteon, the maturation rate of GV oocyte showed no significant difference between VML and vitrification groups. The spindle morphology and MAD2 levels in MI oocytes were comparable to the vitrification group but differed significantly from the VM group. Taken together, finding of the present study shows that MT (100 nmol/L) can ameliorate the in vitro maturation of vitrified-warmed mouse GV oocytes, potentially by improving the spindle morphology, modulating MAD2 protein level and promoting the development of MI stage oocytes through MTRs.

Antioxidants increase blastocyst cryosurvival and viability post-vitrification

STUDY QUESTION

What is the effect of antioxidants acetyl-L-carnitine, N-acetyl-L-cysteine and α-lipoic acid (A3) in vitrification and warming solutions on mouse blastocyst development and viability?

SUMMARY ANSWER

The combination of three antioxidants in vitrification solutions resulted in mouse blastocysts with higher developmental potential in vitro and increased viability as assessed by both an outgrowth model in vitro and fetal development following uterine transfer.

WHAT IS KNOWN ALREADY

The antioxidant combination of acetyl-L-carnitine, N-acetyl-L-cysteine and α-lipoic acid present in IVF handling and embryo culture media has significant beneficial effects on mouse embryo and fetal development, especially under oxidative stress.

STUDY DESIGN, SIZE, DURATION

The study was a laboratory-based analysis of an animal model. Rapid cooling through vitrification was conducted on F1 mouse blastocysts, with antioxidants (A3) supplemented in vitrification and/or warming solutions, followed by culture and embryo transfer.

PARTICIPANTS/MATERIALS, SETTINGS, METHODS

Pronucleate oocytes were collected and cultured in groups to Day 4 blastocysts. Expanded blastocysts were vitrified and warmed in solutions with and without the A3 antioxidants and cultured for a further 24 h. Blastocyst cell number and allocation, apoptosis and histone acetylation levels were all quantified, and viability through outgrowths and transfers assessed.

MAIN RESULTS AND THE ROLE OF CHANCE

Mouse blastocysts vitrified with no antioxidants had significantly lower cell numbers (P  < 0.001) and higher apoptotic cells (P  < 0.05) compared to non-vitrified embryos. Addition of combined A3 antioxidants to the vitrification and warming solutions resulted in a significant increase in inner cell mass cell (ICM) number (P  < 0.001) and total cell number (P  < 0.01), and an increase in outgrowth area (P < 0.05), which correlated with the increased fetal weight (P < 0.05), crown rump length (P < 0.05) and limb development (P < 0.05) determined following transfer compared to embryos with no antioxidants. Furthermore, while blastocyst vitrification significantly reduced acetylation levels (P < 0.05) compared to non-vitrified embryos, the inclusion of A3 antioxidants helped to ameliorate this.

LIMITATIONS, REASONS FOR CAUTION

Embryo development was only examined in the mouse.

WIDER IMPLICATIONS OF THE FINDINGS

Results in this study demonstrate that vitrification and warming of blastocysts have significant detrimental effects on embryo histone acetylation and subsequent viability. The presence of antioxidants in the vitrification solutions helps to alleviate the negative effects of cryopreservation. Our data indicate that antioxidants need to be present in the medium at the time of exposure to increased oxidative stress associated with vitrification and that prior exposure (i.e. during culture or IVF alone) is insufficient to protect cells against cryo-induced injury. Hence, A3 antioxidants may assist in maintaining the viability of vitrified human embryos in ART through the reduction of oxidative stress.

STUDY FUNDING/COMPETING INTEREST(S)

This work was funded by a research grant from Vitrolife AB (Sweden). The authors have no conflict of interest to declare.

Mitochondrial Dysfunction and Oxidative Stress Caused by Cryopreservation in Reproductive Cells

Mitochondria, fundamental organelles in cell metabolism, and ATP synthesis are responsible for generating reactive oxygen species (ROS), calcium homeostasis, and cell death. Mitochondria produce most ROS, and when levels exceed the antioxidant defenses, oxidative stress (OS) is generated. These changes may eventually impair the electron transport chain, resulting in decreased ATP synthesis, increased ROS production, altered mitochondrial membrane permeability, and disruption of calcium homeostasis. Mitochondria play a key role in the gamete competence to facilitate normal embryo development. However, iatrogenic factors in assisted reproductive technologies (ART) may affect their functional competence, leading to an abnormal reproductive outcome. Cryopreservation, a fundamental technology in ART, may compromise mitochondrial function leading to elevated intracellular OS that decreases sperm and oocytes' competence and the dynamics of fertilization and embryo development. This article aims to review the role played by mitochondria and ROS in sperm and oocyte function and the close, biunivocal relationships between mitochondrial damage and ROS generation during cryopreservation of gametes and gonadal tissues in different species. Based on current literature, we propose tentative hypothesis of mechanisms involved in cryopreservation-associated mitochondrial dysfunction in gametes, and discuss the role played by antioxidants and other agents to retain the competence of cryopreserved reproductive cells and tissues.

Beneficial Effects of L-Carnitine Supplementation during IVM of Canine Oocytes on Their Nuclear Maturation and Development In Vitro

Simple Summary

In vitro production of canine embryos is a technique that can be used as a model to conserve endangered species and to establish efficient breeding systems for domestic dogs. However, compared with other species, the success rates of in vitro embryo production (IVEP) in dogs are low. L-Carnitine (LC) is a small water-soluble molecule; it plays an essential role in fatty acid metabolism and acts as a potent antioxidant. Various studies have reported the beneficial impacts of LC on IVEP in many mammalian species other than dogs. Therefore, these experiments investigated the effects of LC supplementation during in vitro maturation (IVM) on canine oocytes maturation, fertilization, and development in vitro. We show that the supplementation of IVM media with LC has positive impacts on oocyte maturation, fertilization, and preimplantation embryo development rates. We also demonstrate that 0.6 mg/mL LC is the most beneficial concentration to be used. It resulted in significantly higher maturation, fertilization, and embryo developmental rates than the control and other LC concentrations. These outcomes are essential for refining the IVM conditions that can advance the efficiency of assisted reproductive technologies (ARTs) in dogs.

Abstract

This study aimed to investigate the effect of L-Carnitine (LC) supplementation during in vitro maturation (IVM) of canine oocytes on nuclear maturation, fertilization status, and preimplantation development. Cumulus–oocyte complexes (COCs) collected from the ovaries of ovariohysterectomized female dogs were matured in vitro for 72 h in a TCM-199 medium supplemented with (0.1, 0.3, 0.6, 1.0, or 2.0 mg/mL) or without (0.0 mg/mL) LC. Matured oocytes were fertilized in vitro with frozen–thawed spermatozoa, and zygotes were cultured in a SOF medium for 7 days. IVM rates were higher (p ≤ 0.05) in 0.3 and 0.6 mg/mL LC supplemented groups than in the control (0.0 mg/mL LC) and other LC groups. Fertilization (18 h postinsemination (pi)) and cleavage (2–16-cell stage at day 3 pi) rates were higher (p ≤ 0.05) in the 0.6 mg/mL LC group than in the control and 0.1, 1.0, and 2 mg/mL LC supplemented groups. Interestingly, 4.5% of fertilized oocytes developed to morula (day 5 pi) in the 0.6 mg/mL LC group, which was higher (p ≤ 0.05) than those developed in the 0.3 mg/mL group (1.0%). No cleaved embryos developed to morula in other groups. In conclusion, LC supplementation at 0.6 mg/mL during IVM of canine oocytes improved their maturation, fertilization, and preimplantation embryo development rates following IVF and in vitro culture (IVC).

Mass Spectrometric Analysis of L-carnitine and its Esters: Potential Biomarkers of Disturbances in Carnitine Homeostasis

PURPOSE

After a golden age of classic carnitine research three decades ago, the spread of mass spectrometry opened new perspectives and a much better understanding of the carnitine system is available nowadays. In the classic period, several human and animal studies were focused on various distinct physiological functions of this molecule and these revealed different aspects of carnitine homeostasis in normal and pathological conditions. Initially, the laboratory analyses were based on the classic or radioenzymatic assays, enabling only the determination of free and total carnitine levels and calculation of total carnitine esters' amount without any information on the composition of the acyl groups. The introduction of mass spectrometry allowed the measurement of free carnitine along with the specific and sensitive determination of different carnitine esters. Beyond basic research, mass spectrometry study of carnitine esters was introduced into the newborn screening program because of being capable to detect more than 30 metabolic disorders simultaneously. Furthermore, mass spectrometry measurements were performed to investigate different disease states affecting carnitine homeostasis, such as diabetes, chronic renal failure, celiac disease, cardiovascular diseases, autism spectrum disorder or inflammatory bowel diseases.

RESULTS

This article will review the recent advances in the field of carnitine research with respect to mass spectrometric analyses of acyl-carnitines in normal and various pathological states.

CONCLUSION

The growing number of publications using mass spectrometry as a tool to investigate normal physiological conditions or reveal potential biomarkers of primary and secondary carnitine deficiencies shows that this tool brought a new perspective to carnitine research.

Transcriptome analysis of porcine immature oocytes and surrounding cumulus cells after vitrification and in vitro maturation

Cryopreservation impairs oocyte quality, which may be associated with abnormal gene expression. Currently, alteration of mRNA levels in vitrified porcine oocytes has not been well characterized. The aim of this study was to analyze transcriptome profiles with RNA sequencing (RNA-seq) in porcine immature oocytes and their surrounding cumulus cells (CCs) after vitrification and in vitro maturation (IVM). There were 19 upregulated and 18 downregulated genes differentially expressed in vitrified oocytes, with no significant GO enrichment or KEGG pathway identified for these genes. In addition, CCs derived from vitrified oocytes had 40 significantly upregulated and 100 significantly downregulated genes. In total, 7 GO terms were significantly enriched in molecular function and biological process, and only MAPK signaling pathway reached significant enrichment based on KEGG analysis. Moreover, selected differentially expressed genes had similar expression patterns through comparison between results from qRT-PCR and RNA-Seq. In conclusion, our data provided detailed information on mRNA transcriptomes in porcine immature oocytes and CCs after vitrification and IVM, which offered now insights regarding reduced developmental potential of the vitrified oocytes.

Caffeine and oocyte vitrification: Sheep as an animal model

Oocyte cryopreservation is valuable way of preserving the female germ line. Vitrification of immature ovine oocytes decreased the levels of both maturation promoting factor (MPF) and mitogen-activated protein kinase (MAPK) in metaphase II (MII) oocytes after IVM. Our aims were 1) to evaluate the effects of vitrification of ovine GV-oocytes on spindle assembly, MPF/MAP kinases activities, and preimplantation development following IVM and IVF, 2) to elucidate the impact of caffeine supplementation during IVM on the quality and development of vitrified/warmed ovine GV-oocytes. Cumulus-oocyte complexes (COCs) from mature ewes were divided into vitrified, toxicity and control groups. Oocytes from each group were matured in vitro for 18 h in caffeine free IVM medium and denuded oocytes were incubated in maturation medium supplemented with 10 mM (+) or without (−) caffeine for another 6 h. At 24 h.p.m., oocytes were evaluated for spindle configuration, MPF/MAP kinases activities or fertilized and cultured in vitro for 7 days. Caffeine supplementation did not significantly affect the percentages of oocytes with normal spindle assembly in all the groups. Caffeine supplementation during IVM did not increase the activities of both kinases in vitrified groups. Cleavage and blastocyst development were significantly lower in vitrified groups than in control. Caffeine supplementation during the last 6 h of IVM did not significantly improve the cleavage and blastocyst rates in vitrified group. In conclusion, caffeine treatment during in vitro maturation has no positive impact on the quality and development of vitrified/warmed ovine GV-oocytes after IVM/IVF and embryo culture.

Oral administration of l-carnitine improves the clinical outcome of fertility in patients with IVF treatment

Age-dependent decline of mitochondrial function has been proposed to be a main cause of decline of embryo quality. Then, l-carnitine plays important roles in reducing the membranous toxicity of free-fatty acids by forming acyl-carnitine and promoting β-oxidation, preventing cell damage. Recent research revealed that l-carnitine played important roles in vitro in oocyte growth, oocyte maturation and embryo development. However, such beneficial effects of l-carnitine in vivo have yet to be verified. The effect of oral l-carnitine supplementation on embryo quality and implantation potential was examined. A total of 214 patients were included in this study. They all previously received in vitro fertilization-embryo transfer (IVF-ET) and failed to conceive. Then they were administered l-carnitine for 82 days on average and underwent IVF-ET again. There were no significant differences in the total number of retrieved oocytes, and their maturation and fertilization rates between before and after l-carnitine administration. The quality of embryos on Days 3 and 5 after insemination was improved following l-carnitine administration (p < .05) in cycles after l-carnitine administration compared with previous cycles. Healthy neonates were born after IVF-ET following l-carnitine administration. Our data suggested that oral administration of l-carnitine to fertility patients improved the developmental competence of their oocytes after insemination.

Mitochondrial regulation of [Ca2+]i oscillations during cell cycle resumption of the second meiosis of oocyte

Oocyte is arrested at metaphase of the second meiosis until fertilization switching on [Ca²⁺]i oscillations. Oocyte activation inefficiency is the most challenging problem for failed fertilization and embryonic development. Mitochondrial function and intracellular [Ca²⁺]i oscillations are two critical factors for the oocyte's developmental potential. We aimed to understand the possible correlation between mitochondrial function and [Ca²⁺]i oscillations in oocytes. To this end, mitochondrial uncoupler CCCP which damages mitochondrial function and two small molecule mitochondrial agonists, L-carnitine (LC) and BGP-15, were used to examine the regulation of [Ca²⁺]i by mitochondrial functions. With increasing CCCP concentrations, [Ca²⁺]i oscillations were gradually diminished and high concentrations of CCCP led to oocyte death. LC enhanced mitochondrial membrane potential and [Ca²⁺]i oscillations and even improved the damage induced by CCCP, however, BGP-15 had no beneficial effect on oocyte activation. We have found that mitochondrial function plays a vital role in the generation of [Ca²⁺]i oscillations in oocytes, and thus mitochondria may interact with the ER to generate [Ca²⁺]i oscillations during oocyte activation. Improvement of mitochondrial functions with small molecules can be expected to improve oocyte activation and embryonic development in infertile patients without invasive micromanipulation.

Impact of l-carnitine on lipid content and post thaw survivability of buffalo embryos produced in vitro

The aim of the present study was to see the impact of L-Carnitine (LC) on lipid biosynthesis and metabolism of buffalo embryos, and post thaw blastocyst survivability. In vitro fertilized (IVF) embryos were derived from slaughterhouse derived COCs and cultured in different doses of LC i.e. 0, 1 mM, 1.5 mM, 2 mM starting at 48 h post IVF. Blastocyst rate was significantly (p < 0.05) higher in 1.5 mM group than control and 1.0 mM group. Lipid content was measured indirectly by fluorescent intensity of lipid droplets after Nile red staining, and it was lower (p < 0.05) in treated than control groups. CPT1B, DGAT2 and DGAT1 mRNA expression was up regulated (p < 0.05) while AMPKg1 expression was down regulated in 1.5 mM and 2 mM groups compared to other groups (p < 0.05). mRNA expression of GLUT1, OCT4 and IFN-tau was higher (P < 0.05) in 1.5 mM group than the control group. Expression of BAX was down regulated at 1.5 mM LC. Blastocyts were vitrified by a modified OPS method and post thaw survivability of blastocysts was higher (P < 0.05) in 1.5 mM LC than other groups. In post thaw blastocysts, mRNA expression of GLUT1, OCT4 and IFN-tau was higher (P < 0.05) in 1.5 mM than other groups. Thus, it can be concluded that supplementation of l-carnitine (1.5 mM) in embryo culture media improved the quality of buffalo embryo production and post thaw blastocysts survivability by reducing fatty acid synthesis, enhancing fatty acid metabolism, and reducing lipid droplet formation.

Production of blastocysts following in vitro maturation and fertilization of dromedary camel oocytes vitrified at the germinal vesicle stage

Cryopreservation of oocytes would serve as an alternative to overcome the limited availability of dromedary camel oocytes and facilitate improvements in IVP techniques in this species. Our goal was to develop a protocol for the vitrification of camel oocytes at the germinal vesicle (GV) stage using different cryoprotectant combinations: 20% EG and 20% DMSO (VS1), 25% EG plus 25% DMSO (VS2) or 25% EG and 25% glycerol (VS3) and various cryo-carriers; straws or open pulled-straw (OPS) or solid surface vitrification (SSV); and Cryotop. Viable oocytes were cultured in vitro for 30 h. Matured oocytes were fertilized with epididymal spermatozoa and then cultured in vitro in modified KSOMaa medium for 7 days. Survival and nuclear maturation rates were significantly lower (P ≤ 0.05) in oocytes exposed to VS3 (44.8% and 34.0%, respectively) than those exposed to VS1 (68.2% and 48.0%, respectively) and VS2 (79.3% and 56.9%, respectively). Although recovery rates were significantly lower (P ≤ 0.05) in SSV and Cryotop vitrified oocytes (66.9% to 71.1%) than those vitrified by straws with VS1 or VS2 solutions (86.3% to 91.0%), survival rates were higher in the SSV and Cryotop groups (90.7% to 94.8%) than in the straw and OPS groups (68.2% to 86.5%). Among vitrified groups, maturation and fertilization rates were the highest in the Cryotop-VS2 group (51.8% and 39.2%, respectively). These values were comparable to those seen in the controls (59.2% and 44.6%, respectively). Cleavage (22.5% to 27.9%), morula (13.2% to 14.5%), and blastocyst (6.4% to 8.5%) rates were significantly higher (P ≤ 0.05) in SSV and Cryotop groups than in straws. No significant differences were observed in these parameters between the Cryotop and control groups. We report for the first time that dromedary oocytes vitrified at the GV-stage have the ability to be matured, fertilized and subsequently develop in vitro to produce blastocysts at frequencies comparable to those obtained using fresh oocytes.

Deficiency of peroxiredoxin 6 or inhibition of its phospholipase A2 activity impair the in vitro sperm fertilizing competence in mice

Prdx6 -/- male mice are subfertile, and the deficiency or inactivation of Peroxiredoxins (PRDXs) is associated with human male infertility. We elucidate the impact of the lack of PRDX6 or inhibition of its calcium-independent phospholipase A2 (Ca2+-iPLA2) activity by MJ33 on fertilization competence of mouse spermatozoa. Sperm motility, viability, fertilization and blastocyst rates were lower in Prdx6 -/- spermatozoa than in C57BL/6J wild-type (WT) controls (p ≤ 0.05). MJ33 inhibited the PRDX6 Ca2+-iPLA2 activity and reduced these parameters in WT spermatozoa compared with controls (p ≤ 0.05). Levels of lipid peroxidation and of superoxide anion (O2•─) were higher in Prdx6 -/- than in WT spermatozoa (p ≤ 0.05). MJ33 increased the levels of lipid peroxidation and mitochondrial O2•─ production in treated versus non-treated WT spermatozoa. Acrosome reaction, binding to zona pellucida and fusion with the oolemma were lower in Prdx6 -/- capacitated spermatozoa than WT capacitated controls and lower in WT spermatozoa treated with the PRDX6 inhibitor. In conclusion, the inhibition of the PRDX6 Ca2+-iPLA2 activity promotes an oxidative stress affecting viability, motility, and the ability of mouse spermatozoa to fertilize oocytes. Thus, PRDX6 has a critical role in the protection of the mouse spermatozoon against oxidative stress to assure fertilizing competence.

L-carnitine enhances oocyte maturation and improves in vitro development of embryos in dromedary camels (Camelus dromedaries)

The aim of the present study was to investigate the effect of L-carnitine (LC) addition during either IVM or IVC on the developmental potential of camel oocytes. In Experiment 1; camel oocytes were matured in the absence (control) or presence of different concentrations of LC (0.25 mg, 0.5 mg, 0.75 mg and 1 mg/ml) for 30 h followed by in vitro fertilization and culture up to blastocyst stage. Our results demonstrated that oocytes treated with 0.5 mg/ml LC showed higher (P < 0.05) rates of maturation (74.7%) and fertilization (62.2%) compared with control group, 0.25 and 1 mg/ml of LC (60.2, 63.9, 59.7; 46.2, 48.7, 47.6%, respectively). Addition of 0.5 mg/ml of LC to IVM medium improved the rates of cleavage and embryo development (morula and blastocyst) than those obtained in the control group, 0.25 and 1 mg/ml of LC. No significant differences were noticed between 0.5 and 0.75 mg/ml of LC supplemented groups in term of maturation, fertilization and culture. In Experiment 2; zygotes resulting from in vitro matured (without LC) and fertilized were cultured in embryo culture medium supplemented with different concentrations of LC (0.25 mg, 0.5 mg, 0.75 mg and 1 mg/ml) or without LC (control). Also, the results showed a higher developmental rates to morula and blastocyst stages while adding L-carnitine at a level of 0.5 or 0.75 mg/ml concentration in the culture medium during IVC when compared with other groups. In conclusion, the results demonstrated the usefulness of L-carnitine supplementation at the level of 0.5 mg/ml during IVM or IVC after on the developmental potential of camel oocytes.

Putrescine supplementation during in vitro maturation of aged mouse oocytes improves the quality of blastocysts

Mouse ovaries exhibit a peri-ovulatory rise of ornithine decarboxylase and its product putrescine concurrent with oocyte maturation. Older mice exhibit a deficiency of both the enzyme and putrescine. Peri-ovulatory putrescine supplementation in drinking water increases ovarian putrescine levels, reduces embryo resorption and increases live pups in older mice. However, it is unknown if putrescine acts in the ovaries to improve oocyte maturation. This study examined the impact of putrescine supplementation during oocyte in vitro maturation (IVM) on the developmental potential of aged oocytes. Cumulus–oocyte complexes from 9–12-month-old C57BL/6 mice were subjected to IVM with or without 0.5 mM putrescine, followed by in vitro fertilisation and culture to the blastocyst stage. Putrescine supplementation during IVM did not influence the proportion of oocyte maturation, fertilisation or blastocyst formation, but significantly increased blastocyst cell numbers (44.5 ± 1.9, compared with 36.5 ± 1.9 for control; P = 0.003). The putrescine group also had a significantly higher proportion of blastocysts with top-grade morphology (42.9%, compared with 26.1% for control; P = 0.041) and a greater proportion with octamer-binding transcription factor 4 (OCT4)-positive inner cell mass (38.3%, compared with 19.8% for control; P = 0.005). Therefore, putrescine supplementation during IVM improves egg quality of aged mice, providing proof of principle for possible application in human IVM procedures for older infertile women.

Glycine increases preimplantation development of mouse oocytes following vitrification at the germinal vesicle stage

Ice-free cryopreservation, referred to as vitrification, is receiving increased attention in the human and animal assisted reproduction. However, it introduces the detrimental osmotic stress by adding and removing high contents of cryoprotectants. In this study, we evaluated the effects of normalizing cell volume regulation by adding glycine, an organic osmolyte, during vitrification of mouse germinal vesicle stage oocyte and/or subsequent maturation on its development. The data showed that glycine supplementation in either vitrification/thawing or maturation medium significantly improved the cytoplasmic maturation of MII oocytes manifested by spindle assembly, chromosomal alignment, mitochondrial distribution, euploidy rate, and blastocyst development following fertilization in vitro, compared to the control without glycine treatment. Furthermore, glycine addition during both vitrification/thawing and maturation further enhanced the oocyte quality demonstrated by various markers, including ATP contents and embryo development. Lastly, the effect of anti-apoptosis was also observed when glycine was added during vitrification. Our result suggests that reducing osmotic stress induced by vitrification could improve the development of vitrified mouse oocyte.

Intrafollicular transfer of fresh and vitrified immature bovine oocytes

Embryo production by intrafollicular oocyte transfer (IFOT) represents an alternative for production of a large number of embryos without requiring any hormones and only basic laboratory handling. We aimed to (1) evaluate the efficiency of IFOT using immature oocytes (IFIOT) and (2) compare embryo development after IFIOT using fresh or vitrified immature oocytes. First, six IFIOTs were performed using immature oocytes obtained by ovum pickup. After insemination and uterine flush for embryo recovery, 21.3% of total transferred structures were recovered excluding the recipient's own oocyte or embryo, and of those, 26% (5.5% of transferred cumulus-oocyte complexes [COCs]) were morula or blastocyst. In the second study, we compared fresh and vitrified-warmed immature COCs. Four groups were used: (1) fresh immature COCs (Fresh-Vitro); (2) vitrified immature COCs (Vit-Vitro), with both groups 1 and 2 being matured, fertilized, and cultured in vitro; (3) fresh immature COCs submitted to IFIOT (Fresh-IFIOT); and (4) vitrified immature COCs submitted to IFIOT (Vit-IFIOT). Cumulus-oocyte complexes (n = 25) from Fresh-IFIOT or Vit-IFIOT groups were injected into dominant follicles (>10 mm) of synchronized heifers. After excluding one structure or blastocyst, the recovery rates per transferred oocyte were higher (P < 0.05) for Fresh-IFIOT (47.6%) than for Vit-IFIOT (12.0%). Blastocyst yield per initial oocyte was higher (P < 0.05) for Fresh-Vitro (42.1%) than for Fresh-IFIOT (12.9%). Vit-Vitro presented higher (P < 0.05) embryo development (6.3%), compared to Vit-IFIOT, which did not result in any extra embryo. Although IFOT did not improve developmental competence of vitrified oocytes, we achieved viable blastocysts and pregnancies produced after IFIOT of fresh bovine immature oocytes. Further work on this technique is warranted as an option both for research studies and for clinical bovine embryo production in the absence of laboratory facilities for IVF.

Effects of Different Maturation Systems on Bovine Oocyte Quality, Plasma Membrane Phospholipid Composition and Resistance to Vitrification and Warming

The objective of this study was to evaluate the effects of different maturation systems on oocyte resistance after vitrification and on the phospholipid profile of the oocyte plasma membrane (PM). Four different maturation systems were tested: 1) in vitro maturation using immature oocytes aspirated from slaughterhouse ovaries (CONT; n = 136); 2) in vitro maturation using immature oocytes obtained by ovum pick-up (OPU) from unstimulated heifers (IMA; n = 433); 3) in vitro maturation using immature oocytes obtained by OPU from stimulated heifers (FSH; n = 444); and 4) in vivo maturation using oocytes obtained from heifers stimulated 24 hours prior by an injection of GnRH (MII; n = 658). A sample of matured oocytes from each fresh group was analyzed by matrix associated laser desorption-ionization (MALDI-TOF) to determine their PM composition. Then, half of the matured oocytes from each group were vitrified/warmed (CONT VIT, IMA VIT, FSH VIT and MII VIT), while the other half were used as fresh controls. Afterwards, the eight groups underwent IVF and IVC, and blastocyst development was assessed at D2, D7 and D8. A chi-square test was used to compare embryo development between the groups. Corresponding phospholipid ion intensity was expressed in arbitrary units, and following principal components analyses (PCA) the data were distributed on a 3D graph. Oocytes obtained from superstimulated animals showed a greater rate of developmental (P<0.05) at D7 (MII = 62.4±17.5% and FSH = 58.8±16.1%) compared to those obtained from unstimulated animals (CONT = 37.9±8.5% and IMA = 50.6±14.4%). However, the maturation system did not affect the resistance of oocytes to vitrification because the blastocyst rate at D7 was similar (P>0.05) for all groups (CONT VIT = 2.8±3.5%, IMA VIT = 2.9±4.0%, FSH VIT = 4.3±7.2% and MII VIT = 3.6±7.2%). MALDI-TOF revealed that oocytes from all maturation groups had similar phospholipid contents, except for 760.6 ([PC (34:1) + H]+), which was more highly expressed in MII compared to FSH (P<0.05). The results suggest that although maturation systems improve embryonic development, they do not change the PM composition nor the resistance of bovine oocytes to vitrification.

l-carnitine supplementation during vitrification of mouse germinal vesicle stage-oocytes and their subsequent in vitro maturation improves meiotic spindle configuration and mitochondrial distribution in metaphase II oocytes

STUDY QUESTION

How does l-carnitine (LC) supplementation during vitrification and in vitro maturation (IVM) of germinal vesicle stage (GV)-oocytes improve the developmental competence of the resultant metaphase II (MII) oocytes?

SUMMARY ANSWER

LC supplementation during both vitrification of GV-oocytes and their subsequent IVM improved nuclear maturation as well as meiotic spindle assembly and mitochondrial distribution in MII oocytes.

WHAT IS KNOWN ALREADY

Vitrification of GV-oocytes results in a lower success rate of blastocyst development compared with non-vitrified oocytes. LC supplementation during both vitrification and IVM of mouse GV-oocytes significantly improves embryonic development after IVF.

STUDY DESIGN, SIZE, DURATION

GV-oocytes were collected from (B6.DBA)F1 and B6 mouse strains and subjected to vitrification and warming with or without 3.72 mM LC supplementation. After IVM with or without LC supplementation, the rate of nuclear maturation and the quality of MII oocytes were evaluated. At least 20 oocytes/group were examined, and each experiment was repeated at least three times. All experiments were conducted during 2013-2014.

PARTICIPANTS/MATERIALS, SETTING, METHODS

Extrusion of the first polar body in IVM oocytes was observed as an indication of nuclear maturation. Spindle assembly and chromosomal alignment were examined by immunostaining of α-tubulin and nuclear staining with 4,6-diamidino-2-phenylindole (DAPI). Mitochondrial distribution and oxidative activity were measured by staining with Mitotracker Green Fluorescence Mitochondria (Mitotracker Green FM) and chloromethyltetramethylrosamine (Mitotracker Orange CMTMRos), respectively. ATP levels were determined by using the Bioluminescent Somatic Cell Assay Kit.

MAIN RESULTS AND THE ROLE OF CHANCE

LC supplementation during both vitrification and IVM of GV-oocytes significantly increased the proportions of oocytes with normal MII spindles to the levels comparable with those of non-vitrified oocytes in both mouse strains. While vitrification of GV-oocytes lowered the proportions of MII oocytes with peripherally concentrated mitochondrial distribution compared with non-vitrified oocytes, LC supplementation significantly increased the proportion of such oocytes in the (B6.DBA)F1 strain. LC supplementation decreased the proportion of oocytes with mitochondrial aggregates in both vitrified and non-vitrified oocytes in the B6 strain. The oxidative activity of mitochondria was mildly decreased by vitrification and drastically increased by LC supplementation irrespective of vitrification in both mouse strains. No change was found in ATP levels irrespective of vitrification or LC supplementation. Results were considered to be statistically significant at P < 0.05 by either χ(2)- or t-test.

LIMITATIONS, REASONS FOR CAUTION

It remains to be tested whether beneficial effect of LC supplementation during vitrification and IVM of GV-oocytes leads to fetal development and birth of healthy offspring after embryo transfer to surrogate females.

WIDER IMPLICATIONS OF THE FINDINGS

This protocol has the potential to improve the quality of vitrified human oocytes and embryos during assisted reproduction treatment.

STUDY FUNDING/COMPETING INTEREST

Partially supported by the Natural Sciences and Engineering Research Council of Canada (NSERC) Discovery Grant and Mitacs Elevate Postdoctoral Fellowship, Canada.

Acylcarnitine esters profiling of serum and follicular fluid in patients undergoing in vitro fertilization

BACKGROUND

L-carnitine-mediated beta-oxidation of fatty acids has a well established role in energy supply of oocytes and embryos. Disturbed carnitine metabolism may impair the reproductive potential in IVF and can serve as a biomarker of pregnancy outcome.

METHODS

Our study was performed between March 24, 2011 and May 9, 2011. We performed 44 unselected IVF cycles, (aged 23-40 years (mean: 32.3+/-5.1 years) and had BMI of 17.3-34.7 (mean: 23.80+/-4.9). Samples were also obtained from 18 healthy women of similar age admitted for minor elective surgery to serve as control for plasma carnitine profile. Serum and follicular fluid (FF) free carnitine (FC) and 20 major acylcarnitines (ACs) were measured by ESI/MS/MS method.

RESULTS

Serum FC and AC levels in IVF patients were comparable to those in healthy control women. In FF FC and short-chain AC concentrations were similar to those in maternal serum, however, the levels of medium-chain, and long-chain AC esters were markedly reduced (p<0.05). The serum to FF ratio of individual carnitine compounds increased progressively with increasing carbon chain length of AC esters (p<0.05). There was a marked reduction in total carnitine, FC and AC levels of serum and FF in patients with oocyte number of >9 and/or with embryo number of >6 as compared to the respective values of <9 and/or <6 (p<0.05).

CONCLUSIONS

In IVF patients with better reproductive potential the carnitine/AC pathway appears to be upregulated that may result in excess carintine consumption and relative depletion of carnitine pool. Consequently, IVF patients may benefit from carnitine supplementation.