Oocyte recovery after overnight ovary transport provides an alternative source of cumulus oocyte complexes that are competent to produce live piglets

COVID-19 impacted abattoirs worldwide. The processing lines became a hotspot for the spread of COVID-19 resulting in plant restructuring and ultimately a critical loss of pig material for research. Commercial sources of pig oocytes are available but are costly and companies were already operating at a maximum capacity for supplying the oocyte needs around the United States. Here, we provide an alternative source of oocytes that are competent to produce live, healthy piglets.

Evaluation of luteinizing hormone regulation of maturation and apoptosis, expression of LHR and FSHR in cumulus-oocyte complexes in Lanzhou fat-tailed sheep

The present study aimed to assess LH effects on in vitro maturation (IVM) and apoptosis and also to explore the gene expressions of LHR and FSHR in cumulus-oocyte complexes (COCs) of the sheep. COCs were in vitro matured 24h in the IVM medium supplemented with varying concentrations of LH (0, 5, 10, 20 and 30 μg/mL). They were allocated into LH-1 (control group), LH-2, LH-3, LH-4 and LH-5 groups, respectively. FSH (10 IU/mL) addition was as a positive control (FSH group). COCs apoptosis was assessed by TUNEL. The qPCR and Western blotting were utilized to detect mRNA and protein expressions of FSHR and LHR, respectively. The results showed maturation rates of oocytes improved as LH concentration increased from 0 to 10 μg/mL (IU/mL), reaching a peak value of 44.3% in the LH-3 group. Maturation rate of LH-5 group was lower than that of LH-3 and FSH-treated groups. The lowest apoptosis rate was found in LH-3 group. The germinal vesicle break down (GVBD) rates of LH-2, LH-3 and LH-4 groups were also increased in comparison with that found in LH-1 group (control group). GVBD rate of LH-5 was lower than that in LH-3 group. The germinal vesicle (GV) rates in LH-3 and LH-4 groups were lower than those in LH-1 and LH-5 groups (p<0.05, or p<0.01). The lowest GV rate was found in LH-3 group. GV rates in LH-2, LH-4 and LH-5 groups were higher than that in FSH group (p<0.05). At hours 20, 22 and 24 after oocytes IVM, caspase-3 concentrations in four LH-treated groups were decreased in comparison with that in LH-1 group. At 24h, caspase-3 concentrations of LH-2 and LH-3 groups were lower than that in LH-1 group (p<0.05). Expression levels of FSHR and LHR mRNAs rose when LH concentrations in IVM medium increased. The greatest expressions of FSHR and LHR mRNAs were found in LH-5 and LH-3 groups (p<0.01) in comparison with those in the control group (LH-1). Meanwhile, FSHR mRNA expressions in LH-2, LH-3 and LH-4 groups were lower than that in FSH group (p<0.01 or p<0.05). Expression levels of FSHR proteins revealed no significant differences among all groups. Expression levels in LHR proteins were increased. LHR protein level in LH-2 group was higher than that in LH-1 group. In conclusion, LH treatment could promote the maturation rate and GVBD rate. LH reduced apoptosis rate, GV rate of sheep oocytes, and caspase-3 concentrations in IVM medium fluids and additionally enhanced expressions of FSHR and LHR mRNAs of sheep COCs.

Moderate increase of reactive oxygen species triggers meiotic resumption in rat follicular oocytes

AIM

The mammalian ovary generates reactive oxygen species (ROS) on an extraordinary scale; however, the role of ROS during meiotic cell cycle progression in follicular oocytes remains poorly understood. The present study was aimed to determine whether a moderate increase of ROS level in the ovary is beneficial for meiotic resumption from diplotene arrest in follicular oocytes.

METHODS

Cumulus oocyte complexes were collected from the ovaries of female rats that had been treated with either: (i) pregnant mare's serum gonadotrophin; or (ii) pregnant mare's serum gonadotrophin + human chorionic gonadotrophin. We analyzed morphological changes, ROS and hydrogen peroxide levels, catalase activity, 3',5'-cyclic adenosine monophosphate and 3',5'-cyclic guanosine monophosphate levels, Thr14/Tyr15, Th-161, total cyclin-dependent kinase 1 (Cdk1) and cyclin B1 levels.

RESULTS

Human chorionic gonadotrophin treatment induced meiotic resumption from diplotene arrest and extrusion of first polar body in cumulus oocyte complexes collected from ovaries and cultured for 3 h in vitro. Meiotic resumption from diplotene arrest was associated with increased ROS and hydrogen peroxide levels but decreased 3',5'-cyclic adenosine monophosphate as well as 3',5'-cyclic guanosine monophosphate levels. The reduced cyclic nucleotide levels were associated with decreased Thr161 phosphorylated Cdk1 and cyclin B1 level but increased Thr14/Tyr15 phosphorylated Cdk1 level leading to maturation promoting factor destabilization. Destabilized maturation-promoting factor triggered meiotic resumption from diplotene arrest and progression to metaphase-I as well as metaphase-II stage in follicular oocytes.

CONCLUSION

Our findings suggest that a moderate increase of ROS in the ovary is beneficial for meiotic resumption from diplotene arrest and extrusion of first polar body in follicular oocytes.

Knockdown of TrkA in cumulus oocyte complexes (COCs) inhibits EGF-induced cumulus expansion by down-regulation of IL-6

Tyrosine kinase receptor A (TrkA), the high-affinity receptor of nerve growth factor (NGF), is known to play key roles in ovarian follicular development, such as assembly of early follicles and follicular ovulation. However, little is known about the roles of TrkA in cumulus oocyte complex (COC) expansion. In this study, we found that TrkA was abundant in large antral follicles and knockdown of TrkA in COCs attenuated epidermal growth factor (EGF)-induced COC expansion and further decreased the ovulation rate. The effect of TrkA on COC expansion was not mediated through downstream EGF effectors, phosphorylation of extracellular regulated protein kinases 1/2 (ERK1/2) or drosophila mothers against decapentaplegic protein (SMAD), or through up-regulation of COC expansion-related transcripts such as prostaglandin-endoperoxide synthase 2 (Ptgs2), hyaluronan synthase 2 (Has2), TNF-induced protein 6 (Tnfaip6) or pentraxin 3 (Ptx3). However, pharmacological blockade of TrkA transducing activity (K252α) in COCs decreased the mRNA expression and protein secretion of interleukin-6 (IL-6), identified from mRNA microarray of K252α-treated COCs. Meanwhile, knockdown of IL-6 attenuated EGF-induced COC expansion. In addition, IL-6 rescued the inhibitory effect of K252α on EGF-induced cumulus expansion. Therefore, IL-6 may act as a new potential cumulus expansion-related transcript, which may be involved in the integration of TrkA and EGF signaling in affecting COC expansion. Here, we provide mechanistic insights into the roles of TrkA in EGF-induced cumulus expansion. Understanding potential cross-points between TrkA and EGF affecting cumulus expansion will help in the discovery of new therapeutic targets in ovulation-related diseases.