Membrane lipid changes in mouse blastocysts induced by ovarian stimulation, IVF and oocyte vitrification.

RESEARCH QUESTION: Is the membrane lipid profile of mice blastocysts affected by ovarian stimulation, IVF and oocyte vitrification? Could supplementation of vitrification media with L-carnitine and fatty acids prevent membrane phospholipid changes in blastocysts from vitrified oocytes? DESIGN: Experimental study comparing the lipid profile of murine blastocysts produced from natural mating, superovulated cycles or after IVF submitted or not to vitrification. For in-vitro experiments, 562 oocytes from superovulated females were randomly divided into four groups: fresh oocytes fertilized in vitro and vitrified groups: Irvine Scientific (IRV); Tvitri-4 (T4) or T4 supplemented with L-carnitine and fatty acids (T4-LC/FA). Fresh or vitrified-warmed oocytes were inseminated and cultured for 96 h or 120 h. The lipid profile of nine of the best quality blastocysts from each experimental group was assessed by multiple reaction monitoring profiling method. Significantly different lipids or transitions between groups were found using univariate statistics (P < 0.05; fold change = 1.5) and multivariate statistical methods. RESULTS: A total of 125 lipids in blastocysts were profiled. Statistical analysis revealed several classes of phospholipids affected in the blastocysts by ovarian stimulation, IVF, oocyte vitrification, or all. L-carnitine and fatty acid supplements prevented, to a certain extent, changes in phospholipid and sphingolipid contents in the blastocysts. CONCLUSION: Ovarian stimulation alone, or in association with IVF, promoted changes in phospholipid profile and abundance of blastocysts. A short exposure time to the lipid-based solutions during oocyte vitrification was sufficient to induce changes in the lipid profile that were sustained until the blastocyst stage.

Equilibration solution composition and extended exposure to equilibration phase affect embryo development and lipid profile of mouse oocytes.

RESEARCH QUESTION: Can exposure time to equilibration solutions during oocyte vitrification affect the lipid profile of oocytes and embryonic development? Could vitrification media supplemented with oleic, linoleic acids and L-carnitine effectively minimize damage induced by vitrification on embryo development and oocyte membrane lipid profile? DESIGN: Experimental study including 936 oocytes from C57BL/6J mice, randomly divided into fresh IVF (control) and equilibration solution groups. Oocytes were exposed to equilibration solution from Irvine Scientific, Tvitri-4 or Tvitri-4 supplemented with L-carnitine and fatty acids for 7 or 10 min, vitrified-warmed, and submitted to IVF. The lipid profile of oocytes immediately after equilibration solution exposure was also asessed using the same equilibration times and solution compositions. RESULTS: Longer equilibration time resulted in lower oocyte survival and blastocyst rates, and reduced relative abundance of structural lipids, i.e. phosphatidylcholines and sphingomyelins, varying according to equilibration solution composition. It also induced membrane disruptions resembling bubbles in the oocyte surface predominantly in equilibration solution from Irvine Scientific, rarely in Tvitri-4 and absent in Tvitri-4 supplemented with L-carnitine and fatty acids. To reveal the metabolic pathways associated with the equilibration phase of vitrification, lipid pathway analysis was conducted; both P-values and pathway impact values showed that the linoleic acid metabolism (P = 0.00223; impact =1) and alpha-Linolenic acid metabolism (P = 0.00084; impact = 0.33) were the most pathway perturbed, followed by glycerophospholipid metabolism (P = 0.0167; impact = 0.25) CONCLUSION: A longer equilibration phase pre-vitrification can influence embryo development and induce changes in oocyte lipid composition related to membrane integrity. The results suggest internalization of oleic and linoleic acids added to equilibration solution by the oocyte, which, to some extent, contributed to membrane phospholipids preservation, regardless of the equilibration times assessed.

Impact of superovulation and in vitro fertilization on LINE-1 copy number and telomere length in C57BL/6 J mice blastocysts.

OBJECTIVE: Millions of babies have been conceived by IVF, yet debate about its safety to offspring continues. We hypothesized that superovulation and in vitro fertilization (IVF) promote genomic changes, including altered telomere length (TL) and activation of the retrotransposon LINE-1 (L1), and tested this hypothesis in a mouse model. MATERIAL AND METHODS: Experimental study analyzing TL and L1 copy number in C57BL/6 J mouse blastocysts in vivo produced from natural mating cycles (N), in vivo produced following superovulation (S), or in vitro produced following superovulation (IVF). We also examined the effects of prolonged culture on TL and L1 copy number in the IVF group comparing blastocysts cultured 96 h versus blastocysts cultured 120 h. TL and L1 copy number were measured by Real Time PCR. RESULTS: TL in S (n = 77; Mean: 1.50 ± 1.15; p = 0.0007) and IVF (n = 82; Mean: 1.72 ± 1.44; p < 0.0001) exceeded that in N (n = 16; Mean: 0.61 ± 0.27). TL of blastocysts cultured 120 h (n = 15, Mean: 2.14 ± 1.05) was significantly longer than that of embryos cultured for 96 h (n = 67, Mean: 1.63 ± 1.50; p = 0.0414). L1 copy number of blastocysts cultured for 120 h (n = 15, Mean: 1.71 ± 1.49) exceeded that of embryos cultured for 96 h (n = 67, Mean: 0.95 ± 1.03; p = 0.0162). CONCLUSIONS: Intriguingly ovarian stimulation, alone or followed by IVF, produced embryos with significantly longer telomeres compared to in vivo, natural cycle-produced embryos. The significance of this enriched telomere endowment for the health and longevity of offspring born from IVF merit future studies.

The Impact of Oocyte Vitrification on Offspring: a Systematic Review.

Oocyte vitrification is a widespread and well-established assisted reproduction technique that has enabled some patient groups to obtain clinical results equivalent to those using fresh oocytes. However, as the number of babies born from vitrified oocytes has increased, so has the discussion regarding the method's safety for the offspring. Cryogenic oocyte damage caused by chemical, mechanical, and thermal stress has raised concern. In this systematic review, we asked the question of whether oocyte vitrification impacts offspring health. From 2007 to 2021, 13 studies were included in the analysis. All studies were observational and presented neonatal outcomes. A total of 4,159 babies were analyzed. Data from these studies were used to assess the following outcomes: multiple pregnancies, cesarean section, gestational age at delivery, the number of live births, birth weight, Apgar scores, congenital anomalies, and baby health. The most extended follow-ups evaluated children until 1, 2, and 6 years of age. According to the evidence appraised in this systematic review, vitrification seems to be a safe method for oocyte cryopreservation and child health, at least in the short term. Nevertheless, there is an urgent need for additional long-term data results from big databases and also for randomized controlled trials to improve the levels of evidence.

Altered transcriptome in cumulus cells of infertile women with advanced endometriosis with and without endometrioma.

RESEARCH QUESTION: Is the transcriptome of cumulus cells of infertile women with advanced endometriosis (EIII/IV), with and without endometrioma, altered? DESIGN: In this prospective case-control study, next-generation RNA sequencing was used to compare the transcript profile of cumulus cells among infertile patients undergoing ovarian stimulation for intracytoplasmic sperm injection with EIII/IV, with (n = 9) and without endometrioma (n = 9), and controls (n = 9). An in-silico enrichment analysis was conducted to establish the possibly altered pathways in cumulus cells of patients with endometriosis. RESULTS: Most of the differentially expressed genes (DEG) were found when cumulus cells from women with EIII/IV with endometrioma were compared with controls (DEG, n = 461). In women with EIII/IV without endometrioma, only 66 DEG were verified compared with controls. The enrichment analysis showed that some DEG in cumulus cells of endometriosis are involved in important pathways for the oocyte competence acquisition, such as oxidative phosphorylation, metabolism, mitochondrial function, acetylation and steroid biosynthesis. No DEG were found when cumulus cells from women with EIII/IV with and without endometrioma were compared. CONCLUSION: RNA sequencing results suggest that cumulus cells of infertile women with EIII/IV have an altered transcriptome, regardless of endometrioma. The present findings offer a better understanding of the genes and molecular mechanisms that may be involved in endometriosis-related infertility, mostly in the oocyte competence acquisition process.

PTGS2 down-regulation in cumulus cells of infertile women with endometriosis.

A deleterious effect of endometriosis on oocyte quality has been proposed. Evidence suggests that cumulus cells could be used as indirect biomarkers of oocyte quality. The PTGS2 gene, which encodes cyclooxygenase 2 (COX-2), is deregulated in endometriotic lesions and plays a crucial role in the acquisition of oocyte competence. To date, research evaluating PTGS2 expression in cumulus cells of infertile patients with endometriosis has not been conducted. The aim this study was to compare the expression levels of PTGS2 in cumulus cells of infertile women, with and without endometriosis, undergoing ovarian stimulation for intracytoplasmic sperm injection (ICSI). Therefore, a case-control study compared PTGS2 gene expression in the cumulus cells of 38 infertile patients with endometriosis and 40 without, using real-time polymerase chain reaction. For the first time, decreased expression of PTGS2 was found in cumulus cells of infertile women with endometriosis compared with controls (7.2 ± 10.5 versus 12.4 ± 15.7), which might be related to reduced levels of COX-2 in the cumulus cells of women with the disease. Consequently, we hypothesize that lower transcript levels of PTGS2 in cumulus cells may be involved in the impairment of oocyte quality, suggesting a possible mechanism involved in disease-related infertility.