Development of a bovine luteal cell in vitro culture system suitable for co-culture with early embryos

Coculture with porcine luteal cells during in vitro porcine oocyte maturation affects lipid content, cortical reaction and zona pellucida ultrastructure

CONTEXT

In pigs, in vitro fertilisation (IVF) is associated with high polyspermy rates, and for this reason, in vitro embryo production (IVP) is still an inefficient biotechnology. Coculture with somatic cells is an alternative to improve suboptimal in vitro maturation (IVM) conditions.

AIM

This study was conducted to test a coculture system of porcine luteal cells (PLC) and cumulus-oocyte complexes (COC) to improve oocyte metabolism.

METHODS

COC were matured in vitro with PLC. Oocyte lipid content, mitochondrial activity, zona pellucida (ZP) digestibility and pore size, cortical reaction and in vitro embryo development were assessed.

KEY RESULTS

Coculture reduced cytoplasmic lipid content in the oocyte cytoplasm without increasing mitochondrial activity. Although ZP digestibility and ZP pore number were not different between culture systems, ZP pores were smaller in the coculture. Coculture impacted the distribution of cortical granules as they were found immediately under the oolemma, and more of them had released their content in the ZP. Coculture with porcine luteal cells during IVM increased monospermic penetration and embryo development after IVF.

CONCLUSIONS

The coculture of COC with PLC affects the metabolism of the oocyte and benefits monospermic penetration and embryo development.

IMPLICATIONS

The coculture system with PLC could be an alternative for the conventional maturation medium in pigs.

Coculture of porcine luteal cells during in vitro porcine oocyte maturation affects blastocyst gene expression and developmental potential

Oocyte maturation in culture is still the weakest part of in vitro fertilization (IVF) and coculture with somatic cells may be an alternative to improve suboptimal culture conditions, especially in the pig in which maturation takes more than 44 h. In the present study, we investigated the effect of a coculture system of porcine luteal cells (PLC) during in vitro maturation (IVM) on embryo development and gene expression. Cumulus-oocyte complexes were matured in vitro in TCM-199 with human menopausal gonadotrophin (control) and in coculture with PLC. IVF was performed with frozen-thawed boar semen in Tris-buffered medium. Presumptive zygotes were cultured in PZM for 7 days. The coculture with PLC significantly increased blastocysts rates. Gene expression changes were measured with a porcine embryo-specific microarray and confirmed by RT-qPCR. The global transcription pattern of embryos developing after PLC coculture exhibited overall downregulation of gene expression. Following global gene expression pattern analysis, genes associated with lipid metabolism, mitochondrial function, endoplasmic reticulum stress, and apoptosis were found downregulated, and genes associated with cell cycle and proliferation were found upregulated in the PLC coculture. Canonical pathway analysis by Ingenuity Pathway revealed that differential expression transcripts were associated with the sirtuin signaling pathway, oxidative phosphorylation pathway, cytokines and ephrin receptor signaling. To conclude, the coculture system of PLC during IVM has a lasting effect on the embryo until the blastocyst stage, modifying gene expression, with a positive effect on embryo development. Our model could be an alternative to replace the conventional maturation medium with gonadotrophins with higher rates of embryo development, a key issue in porcine in vitro embryo production.

Coculture of porcine cumulus–oocyte complexes with porcine luteal cells during IVM: effect on oocyte maturation and embryo development

Coculture with somatic cells is an alternative to improve suboptimal invitro culture conditions. In pigs, IVF is related to poor male pronuclear formation and high rates of polyspermy. The aim of this study was to assess the effect of a coculture system with porcine luteal cells (PLCs) on the IVM of porcine cumulus–oocyte complexes (COCs). Abattoir-derived ovaries were used to obtain PLCs and COCs. COCs were matured invitro in TCM-199 with or without the addition of human menopausal gonadotrophin (hMG; C+hMG and C-hMG respectively), in coculture with PLCs from passage 1 (PLC-1) and in PLC-1 conditioned medium (CM). In the coculture system, nuclear maturation rates were significantly higher than in the C-hMG and CM groups, but similar to rates in the C+hMG group. In cumulus cells, PLC-1 coculture decreased viability, early apoptosis and necrosis, and increased late apoptosis compared with C+hMG. PLC-1 coculture also decreased reactive oxygen species levels in cumulus cells. After IVF, monospermic penetration and IVF efficiency increased in the PLC-1 group compared with the C+hMG group. After invitro culture, higher blastocysts rates were observed in the PLC-1 group. This is the first report of a coculture system of COCs with PLCs. Our model could be an alternative for the conventional maturation medium plus gonadotrophins because of its lower rates of polyspermic penetration and higher blastocysts rates, key issues in porcine invitro embryo production.

Functional and Morphological Characterization of Small and Large Steroidogenic Luteal Cells From Domestic Cats Before and During Culture

The current study aimed to isolate, culture and characterize small (SLC) and large (LLC) steroidogenic cells from the corpora lutea (CL) of non-pregnant domestic cats. Isolation of feline SLC was based on an enzymatic digestion of luteal tissue, whereas LLC were obtained by mechanical disruption of CL. To assess function of both cell types, progesterone secretion and mRNA expression of selected genes involved in steroid and prostaglandin synthesis were measured, as well as relative transcript abundance of hormone receptors and anti-oxidative enzymes, before and during culture. The cells were cultured for 3 or 5 days without gonadotropins. Isolated feline SLC and LLC had different sizes (12 ± 3 μm vs. 34 ± 5 μm, respectively), morphologies (amount of lipid droplets) and behaved differently in culture. SLC attached and proliferated or spread quickly, but lost their steroidogenic function during culture (significant decrease in progesterone secretion and expression of steroidogenic genes). The expression of receptors for gonadotropins and prolactin also decreased. Prostaglandin synthase (PTGS2) decreased steadily over time, whereas mRNA expression of PGE2 synthase (PGES) increased. The gene expression of anti-oxidative enzyme glutathione peroxidase 4 (GPX4), also increased during culture, but not of superoxide dismutase 1 (SOD1). In comparison to SLC, LLC did not attach to culture plates, secreted more progesterone per inoculated cells and maintained steroidogenic function during culture. Expression of prostaglandin synthases (PTGS2 and PGES) was almost non-detectable. The gene expression of hormone receptors for prostaglandin F2 alpha (PTGFR), gonadotropins (LHCHR and FSHR), and prolactin (PRLR), as well as of anti-oxidative enzymes (GPX4, SOD1), increased over time. To conclude, we successfully isolated and cultured different types of feline steroidogenic luteal cells and comprehensively characterized both isolated cell types. This knowledge can be used to better understand the CL lifecycle in felines more broadly, and the established cell cultures will provide a foundation for future studies on luteolytic and luteotrophic factors in the domestic cat, and for comparison with other feline species, particularly lynx.

Development of In Vitro Embryo Production System Using Collagen Matrix Gel Attached with Vascular Endothelial Growth Factor Derived from Interleukin-1 Beta-Treated Porcine Endometrial Tissue

The aim of this study was to establish an embryo culture system using collagen gel attached with vascular endothelial growth factor (VEGF) derived from interleukin-1 beta (IL-1β)-treated endometrial tissues from pigs. Endometria were separated from the porcine uterus at the follicular phase of the estrous cycle and were cultured with IL-1β. The collagen gels coincubated with IL-1β-treated endometria (C, without endometrial tissue; CE, with endometrial tissue; and CEI, IL-1β-treated endometrial tissue) were used for embryo culture. We found that, compared with the comparable figures in the control group, prostaglandin synthase-2 (PTGS-2) mRNA was increased in IL-1β-treated endometrial tissue (p < 0.05). The VEGF protein was not observed in collagen gel coincubated without endometrial tissue (C); however, it was detected in collagen gels coincubated with endometrial tissue (CE and CEI). The embryo cleavage rates and blastocyst formation did not differ among the treatment groups. The proportion of blastocysts did not differ among the groups. However, the number of blastocyst cells was significantly (p < 0.05) higher in the CEI group than in the other groups. These results clarify the effects of the intrauterine environment on preimplantation embryos and may be useful in research on the effects of extracellular matrix- and cytokine-treated endometrial tissue on embryo development.