Pitfalls in assessment of progesterone production by granulosa cells cultured in contact with silicone rubber or paraffin oil

Evaluation of a small volume oil-free in vitro production system for bovine embryos

Background:

Embryos are usually produced in culture systems with an oil overlay, which conveys protection against the evaporation of water and microbial contamination. The oil can also release toxic substances and absorb essential components, such as hormones, which adversely affect the quality of the oocytes and the development of embryos in vitro.

Objective:

The aim of this study was to validate an oil‐free bovine in vitro production (IVP) system.

Method:

Cumulus–oocyte complexes collected from abattoir‐derived ovaries were matured, fertilized and cultured employing a standard system. The quantity of medium in both groups (with and without an oil overlay) and throughout all stages of IVP was maintained at a volume of 100 μl. The oil group was covered with paraffin oil. The maturation stage of oocytes was assessed using fluorescence staining after 24 hr and developmental stages of embryos were evaluated on day 8. The expanded day 8 blastocysts were assessed by live–dead staining.

Results:

Oocytes matured in the absence of an oil overlay had significantly higher maturation rates when compared against matured oocytes in medium with an oil overlay. Steroid concentration is higher in medium after maturation without oil cover. The developmental rate was significantly higher after culture without oil overlay. The total cell number and the live–dead ratio was not significantly different. The osmolality did not differ between both groups during maturation and slightly decreased during culture without oil.

Conclusion:

Based on the current study, bovine oil‐free IVP systems can be suggested as an alternative to oil‐covered medium.

Rapid and Effective Isolation of Dissolved Organic Matter Using Solid-Phase Extraction Cartridges Packed with Amberlite XAD 8/4 Resins

Using the conventional XAD 8/4 method with general columns to isolate dissolved organic matter (DOM) is extremely time-consuming and labor-intensive. This study presents a rapid and effective method using solid-phase extraction (SPE) cartridges packed with XAD 8/4 resins for isolating various DOMs. The relative fraction (percentage hydrophobic, transphilic, and hydrophilic) of the various DOMs processed by both methods showed similar values. Moreover, changes in the molecular weight distribution of effluent from XAD 8/4 resins processed by both methods showed the same ultraviolet (UV) and fluorescence absorbance pattern s. The biopolymer compositions of eluates from XAD 8/4 resins also showed no significant difference between the two methods. However, higher carbon recovery of the isolation method using SPE cartridges was found (with columns: 88.9%; with SPE: 95.9%). In addition, the proposed method using SPE cartridges packed with XAD 8/4 resins is much faster than that using general columns (with columns: 1468 min; with SPE: 485 min). The proposed isolation method is highly efficient and accurate; it is an excellent candidate method for isolating various DOMs.

A novel technique for in vitro maturation of sheep oocytes in a liquid marble microbioreactor

PURPOSE

The aim of this work was to develop a microbioreactor using liquid marble (LM) as a novel system for oocyte in vitro maturation (IVM) in small volumes.

METHODS

Cumulus-oocyte complexes (COCs) obtained from slaughterhouse sheep ovaries were in vitro matured in a LM system prepared by placing a drop (30 μl containing 10 COCs) suspended in TCM 199 supplemented with 10 % (v/v) oestrus sheep serum (OSS) and 0.1 IU FSH and LH onto a polytetrafluoroethylene (PTFE) particle bed (LM group). As a control group (CTRL group), COCs were in vitro matured in standard volume and conditions (600 μl of IVM medium in a four-well dish). After 24-h culture at 38.5 °C in 5 % CO2 in air, COCs were released from LM and the following parameters were evaluated: (a) percentage of MII oocytes, (b) oocyte developmental competence following in vitro fertilization (IVF) or parthenogenetic activation (PA) and embryo culture for 8 days in synthetic oviductal fluid (SOF) medium at 38.5 °C in 5 % O2, 5 % CO2, and 90 % N2.

RESULTS

The results indicated similar percentage of MII oocytes in LM and CTRL groups (88.0 vs. 92.0 %). No differences were observed in blastocyst rate after IVF (LM 47.5 % vs. CTRL 50.2 %, P=0.637) or PA (LM 44.4 % vs. CTRL 48.3 %, P=0.426).

CONCLUSIONS

The results indicate that LM microbioreactor is a viable technique that provides a suitable microenvironment to induce oocyte in vitro maturation.

Unravelling the needs of singly in vitro-produced bovine embryos: from cumulus cell co-culture to semi-defined, oil-free culture conditions

Producing bovine in vitro embryos individually is a challenge as it generally leads to impaired embryo development. Earlier research optimised a single embryo in vitro production (IVP) protocol using serum, cumulus cells and oil during culture. As some of these factors are undesirable in certain circumstances, the present study investigated their necessity and possible interactions, and defined their role during single-embryo culture. Although the cumulus cell monolayer produced progesterone, it appeared not to be a key factor in supporting single-embryo development. Because in vitro culture in large medium volumes was shown to impair single-embryo development, two new oil-free culture protocols were tested. Using a 30-µL droplet of medium in 96-well plates with a small surface area resulted in comparable blastocyst rates to those obtained under oil. When serum was used, co-culture with cumulus cells seems necessary, leading to consistently high blastocyst rates. Finally, a serum-free, oil-free culture system using insulin, transferrin, selenium and BSA resulted in embryos with similar total cell numbers and apoptotic cell ratios, but blastocyst rates did not equal those obtained with serum and co-culture. This research additionally stresses the fact that specific interaction mechanisms between somatic cells and a developing in vitro embryo are far from unravelled.

The effect of glucocorticoids on ERK-1/2 phosphorylation during maturation of lamb oocytes and their subsequent fertilization and cleavage ability in vitro

High levels of glucocorticoids may alter reproduction, but little is known about their direct actions on oocyte maturation, fertilization and subsequent development. Earlier work suggested negative effects of cortisol or dexamethasone on oocyte maturation but differences were noted between animal models. Both glucocorticoids reduce the p34(cdc2)-cyclin B1 complex but it is unknown if other signaling pathways important for meiosis progression are affected. In this study, using sheep oocytes as a model system, we assessed in vitro the effects of increasing concentration of glucocorticoids (0-250 microM) on oocyte maturation and underlying changes in the MAP kinase pathway, and the ability of oocytes to undergo fertilization and embryo development. Cortisol decreased oocyte maturation but only at the highest concentration, whereas dexamethasone had no effect. Fertilization and cleavage were not affected. On the other hand, both cortisol and dexamethasone inhibited ERK-1/2 activation in a concentration-dependent manner. It thus seems that oocytes can overcome deleterious effects of glucocorticoids during maturation despite the decrease in ERK-1/2 activity, but repercussions in vivo should be further explored.

The effect of glucocorticoids on mouse oocyte in vitro maturation and subsequent fertilization and embryo development

Increased glucocorticoid levels, due to medical therapy or stress-related, may affect reproduction via the hypothalamus-pituitary-axis or directly at the oocyte level. We examined the effects of natural (corticosterone) or synthetic (dexamethasone) glucocorticoids on mouse oocyte maturation and underlying changes in extracellular signal-regulated kinase (ERK) phosphorylation patterns. Fertilization and progression up to the blastocyst stage were also evaluated. Oocytes were exposed to corticosterone or dexamethasone (0, 0.25, 2.5, 25 or 250microM) for 17h during in vitro maturation. After maturation, ERK-1/2 activation in oocytes was assessed by SDS-PAGE and immunoblotting, and fertilization and developmental capacity were examined in vitro. Corticosterone exposure during oocyte maturation significantly decreased progression to metaphase II, fertilization and embryo development at the highest concentration. Corticosterone caused a concentration-dependent inhibition of ERK-1/2 activation, with the highest concentration resulting in considerable inhibition of oocyte ERK-1/2 phosphorylation and no blastocyst development. In contrast, dexamethasone had no effect on maturation, fertilization and cleavage, and no effect was seen on ERK-1/2 phosphorylation. Based on these in vitro findings, high glucocorticoid levels may have consequences for subsequent development, although a short exposure to physiologic or stress-related glucocorticoid levels may not represent a hazard to meiosis progression of the oocyte.

A prospective randomized study to compare four different mineral oils used to culture human embryos in IVF/ICSI treatments

OBJECTIVE(S)

We aimed to evaluate and compare the embryo quality at early cleavage stages using different oils overlaying media to culture human embryos during IVF/ICSI treatments.

STUDY DESIGN

A total of 500 IVF/ICSI treatments from 500 women were analyzed in a prospective randomized study. Oocytes/embryos were treated into microdroplets of appropriate media overlaid with (i) Mineral Oil (CryoBioSystem, L'Aigle, France) (group 1, n=129), (ii) Liquid Paraffin (Medicult, Lyon, France) (group 2, n=126), (iii) Nidoil (Nidacon International, Guthenburg, Sweden) (group 3, n=126) and (iv) Ovoil (Vitrolife, Kungsbacka, Sweden) (group 4, n=119). Comparisons between groups were done using two by two post hoc tests, with 5% significance. The primary endpoint was the embryo quality, defined as good or top quality when embryos were with (i) less than 20% of fragmentation and (ii) 3-5/4 cells at day 2 or 6-10/8 cells at day 3, respectively.

RESULTS

At day 2, the embryo quality was similar in all groups. However, the mean number of top quality embryos at day 3 was statistically higher into the group 4 (1.4+/-1.8) compared to the group 1 (0.9+/-1.0; p=0.03) and 2 (0.8+/-1.3; p=0.05). Furthermore, a significant increase of the mean number of good quality embryos was observed at day 3 into the group 4 (2.6+/-2.6) compared to the group 1 (1.6+/-1.6; p=0.02).

CONCLUSION(S)

The embryo quality could be modified according to commercial oils used to overlay culture media.

Studies of the role of steroid hormone in the regulation of oocyte maturation in cattle

BACKGROUND

The objective of this study was to investigate whether the steroid hormone(s) secreted from cumulus-oocyte complexes (COCs) is a prerequisite for bovine oocyte maturation and cumulus expansion using aminoglutethimide (AGT), a P450 cholesterol side-chain cleavage inhibitor.

METHODS

In experiment 1, COCs were cultured in maturation medium with various concentrations of AGT for 22 h to determine the effective concentration of AGT to inhibit steroid hormone secretion, meiotic maturation and cumulus expansion. In experiment 2, COCs were cultured in conditioned medium (CM) and TCM-199 medium with or without 10 mM AGT to check whether steroid hormones secreted from COCs were responsible for oocyte maturation and cumulus expansion. Experiments 3 and 4 were carried out to determine whether exogenous progesterone or estradiol-17beta was able to overcome the inhibitory effects of AGT on oocytes maturation and cumulus expansion. COCs cultured in 10 mM AGT-containing medium supplemented with various concentrations of progesterone or estradiol-17beta for 22 h were examined for oocyte maturation and cumulus expansion.

RESULTS

Experiment 1 showed that a concentration of 10 mM AGT in medium was sufficient to block steroid hormone secretion, oocyte maturation and cumulus expansion, and that these inhibitory effects were fully reversible. In experiment 2, the addition of 10 mM AGT to CM did not significantly prevent oocyte maturation and cumulus expansion, implying that CM contains the steroid hormone(s) secreted from COCs, which are closely associated with oocyte maturation and cumulus expansion. The results in experiments 3 and 4 demonstrated that the addition of any concentration of progesterone or estradiol-17beta in the medium did not reduce the inhibitory effects of AGT on oocyte maturation and cumulus expansion.

CONCLUSION

Our results indicate that bovine oocytes surrounded by cumulus cells are prevented from maturation and cumulus expansion through the inhibition of steroid secretion due to AGT, and that these inhibitory effects of AGT on oocyte maturation and cumulus expansions can not be overcome by the addition of either progesterone or estradiol-17beta in the medium. These observations suggest that some steroid hormone(s) other than P4 and E2 secreted from bovine COCs is essential for their meiotic maturation and cumulus expansion.