Yasuhisa Munakata

Effects of reaggregated granulosa cells and oocytes derived from early antral follicles on the properties of oocytes grown in vitro.

In this study, we examined the effects of reconstructed oocyte–granulosa cell complexes (OGCs) on the development of porcine oocytes derived from early antral follicles (EAFs; 0.5–0.7 mm in diameter). When denuded oocytes were cocultured with granulosa cells derived from other EAFs, the oocytes and granulosa cells aggregated to form OGCs after 2 days of culture. After 14 days of culture, we compared cell number, oocyte diameter, and oocyte chromatin configuration in unmanipulated (natural) OGCs, reconstructed OGCs, and OGCs collected from antral follicles (AFs, 3.0–6.0 mm in diameter). The diameters of oocytes from reconstructed OGCs grown in vitro were not different from those of oocytes from natural OGCs, although they were significantly smaller than those of oocytes from antral follicle (AF) OGCs. Oocyte chromatin configuration did not differ among the 3 OGC groups, but the oocyte nuclear maturation rate was lower in the reconstructed OGCs and higher in the AF OGCs. However, when the in vitro culture period for the reconstructed OGCs was extended by 2 days, the nuclear maturation rate of oocytes from reconstructed OGCs was similar to that of oocytes from natural OGCs. In addition, blastocysts were successfully obtained from oocytes from reconstructed OGCs. In conclusion, we established an innovative culture method that allows oocytes and granulosa cells from EAFs to reaggregate as reconstructed OGCs, which yield oocytes with the ability to develop to the blastocyst stage.

Gene expression patterns in granulosa cells and oocytes at various stages of follicle development as well as in in vitro grown oocyte-and-granulosa cell complexes

Follicle development is accompanied by proliferation of granulosa cells and increasing oocyte size. To obtain high-quality oocytes in vitro, it is important to understand the processes that occur in oocytes and granulosa cells during follicle development and the differences between in vivo and in vitro follicle development. In the present study, oocytes and granulosa cells were collected from early antral follicles (EAFs, 0.5–0.7 mm in diameter), small antral follicles (SAFs, 1–3 mm in diameter), large antral follicles (LAFs, 3–7 mm in diameter), and in vitro grown oocyte-and-granulosa cell complexes (OGCs), which were cultured for 14 days after collection from EAFs. Gene expression was analyzed comprehensively using the next-generation sequencing technology. We found top upstream regulators during the in vivo follicle development and compared them with those in in vitro developed OGCs. The comparison revealed that HIF1 is among the top regulators during both in vivo and in vitro development of OGCs. In addition, we found that HIF1-mediated upregulation of glycolysis in granulosa cells is important for the growth of OGCs, but the cellular metabolism differs between in vitro and in vivo grown OGCs. Furthermore, on the basis of comparison of upstream regulators between in vivo and in vitro development of OGCs, we believe that low expression levels of FLT1 (VEGFA receptor), SPP1, and PCSK6 can be considered causal factors of the suboptimal development under in vitro culture conditions.

Low oxygen level increases proliferation and metabolic changes in bovine granulosa cells

The present study addresses molecular backgrounds underlying low oxygen induced metabolic changes and 1.2-fold change in bovine granulosa cell (GCs) proliferation. RNA-seq revealed that low oxygen (5%) upregulated genes associated with HIF-1 and glycolysis and downregulated genes associated with mitochondrial respiration than that in high oxygen level (21%). Low oxygen level induced high glycolytic activity and low mitochondrial function and biogenesis. Low oxygen level enhanced GC proliferation with high expression levels of HIF-1, VEGF, AKT, mTOR, and S6RP, whereas addition of anti-VEGF antibody decreased cellular proliferation with low phosphorylated AKT and mTOR expression levels. Low oxygen level reduced SIRT1, whereas activation of SIRT1 by resveratrol increased mitochondrial replication and decreased cellular proliferation with reduction of phosphorylated mTOR. These results suggest that low oxygen level stimulates the HIF1-VEGF-AKT-mTOR pathway and up-regulates glycolysis, which contributes to GC proliferation, and downregulation of SIRT1 contributes to hypoxia-associated reduction of mitochondria and cellular proliferation.

Promotion of glucose utilization by insulin enhances granulosa cell proliferation and developmental competence of porcine oocyte grown in vitro.

In vitro culture of the oocyte granulosa cell complexes (OGCs) from early antral follicles (EAFs) shows granulosa cell (GC) proliferation, but to a lesser extent than that observed in vivo during follicle development. As the number of GCs closely relates to energy sufficiency of the oocytes, enhancement of GC proliferation influences oocyte development. GC proliferation depends on glycolysis and insulin-mediated AKT/mTOR signaling pathway; therefore, addition of culture medium containing insulin and glucose may potentially promote GC proliferation and hence improve oocyte development. In the present study, we assessed the effect of exogenous insulin and glucose concentration on GC proliferation and oocyte energy status as well as developmental abilities of porcine oocytes grown in vitro. In the presence of 5.5 mM of glucose (Low), a comparison of 10 versus 20 μg/ml insulin showed that high insulin enhanced GC proliferation but exhausted glucose from the medium, which resulted in low energy status including lipid and adenosine triphosphate of the oocyte. Whereas, in the presence of 20 μg/ml insulin, medium with 11 mM glucose (High) enhanced GC proliferation and oocyte energy status as well as developmental ability up to the blastocyst stage. Considering that there was no difference in OGCs development observed with medium (10 μg/ml insulin) containing 5.5 versus 11 mM glucose, we concluded that the combination of high insulin and glucose enhanced GC proliferation and energy status of oocytes as well as the developmental ability of the oocytes grown in vitro.

Polyacrylamide gel as a culture substrate improves in vitro oocyte growth from porcine early antral follicles

A major difference between in vivo and in vitro follicle culture is the stiffness of the substrate in which the follicles grow. In this study, we examined the effect of polyacrylamide gel (PAG), as a culture substrate, on the development of porcine oocytes derived from early antral follicles. Oocyte‐granulosa cell complexes (OGCs) were collected from the early antral follicles of gilts, and incubated individually for 14 days in a 96‐well culture plate without or with PAG. We then evaluated the number of granulosa cells present in OGCs as well as the abundance of ATP, lipid, and acetylated lysine in oocytes. OGCs cultured on PAG showed significantly greater antrum formation and granulosa cell proliferation than controls cultured on standard plastic. Oocytes grown on PAG also possessed significantly larger diameter, ATP and lipid content, and lysine acetylation, as well as competence to develop to the blastocyst stage. Transcriptome analysis of the granulosa cells revealed that genes involved in follicular development and mechanosensing are up‐regulated under PAG culturing conditions. Thus, in vitro culturing OGCs on PAG profoundly induced granulosa cell proliferation, resulting in improved developmental competence of the oocytes. Mol. Reprod. Dev. 84: 44–54, 2017.

Mitochondrial dysfunction in cumulus-oocyte complexes increases cell-free mitochondrial DNA

This study examined the concentration of cell-free mitochondrial DNA (cf-mtDNA) in porcine follicular fluid (FF) and explored whether the cfDNA level in the culture medium could reflect mitochondrial dysfunction in cumulus cell-oocyte complexes (COCs). cfDNA concentration was higher in the fluid of small-sized follicles, compared to that in larger follicles. The length of cfDNA ranged from short (152 bp) to long (1,914 bp) mtDNA in FF, detected by polymerase chain reaction (PCR). cfDNA concentration in FF significantly correlated with the mtDNA copy number in FF but not with the number of one-copy gene (nuclear DNA) in FF. When the COCs were treated with the mitochondrial uncoupler, namely carbonyl cyanide m-chlorophenyl hydrazone (CCCP), for 2 h and incubated for 42 h, subsequent real-time PCR detected significantly higher amount of cf-mtDNA, compared to nuclear cfDNA, in the spent culture medium. The mtDNA number and viability of cumulus cells and oocytes remained unchanged. When the oocytes were denuded from the cumulus cells following CCCP treatment, PCR detected very low levels of cfDNA in the spent culture medium of the denuded oocytes. In contrast, CCCP treatment of granulosa cells significantly increased the amount of cf-mtDNA in the spent culture medium, without any effect on other markers, including survival rate, apoptosis of cumulus cells, and lactate dehydrogenase levels. Thus, cf-mtDNA was present in FF in a wide range of length, and mitochondrial dysfunction in COCs increased the active secretion of cf-mtDNA in the cultural milieu.

The effect of high glucose concentration on the quality of oocytes derived from different growth stages of follicles

Abstract This study examined the effect of hyperglycemic culture conditions on the development of oocytes derived from early antral follicles (EAFs). Oocyte—granulosa cell complexes (OGCs) derived from EAFs were cultured for 12 days in medium containing 5.56 mM or 11 mM glucose, and the rate of antrum formation and glucose consumption by the OGCs, and the characteristics of the oocytes grown in vitro were studied. The results were compared with those obtained from in vivo grown oocytes derived from antral follicles (AFs; 3–5 mm in diameter). In addition, the effect of a high glucose concentration in the maturation medium on the quality of oocytes derived from AFs was examined. The high glucose condition increased the glucose consumption of the OGCs but did not affect antrum formation, oocyte diameter, chromatin configuration, levels of histone 4 K12 acetylation, nuclear maturation, and the developmental ability of oocytes grown in vitro. In contrast, high glucose-maturation medium increased the amount of reactive oxygen species and adversely affected the developmental ability of the oocytes. In conclusion, the results of this study suggest that culture under hyperglycemic conditions is detrimental to oocyte maturation but not for oocyte growth from the EAF stage to the AF stage.

Addition of granulosa cells collected from differential follicle stages supports development of oocytes derived from porcine early antral follicles

Improvement of in vitro oocyte growth by addition of granulosa cells derived from differential developmental stages of follicles.

Aggregation of Human Trophoblast Cells into Three-Dimensional Culture System Enhances Anti-Inflammatory Characteristics through Cytoskeleton Regulation

Background: Three-dimensional (3D) culture changes cell characteristics and function, suggesting that 3D culture provides a more physiologically relevant environment for cells compared with 2D culture. We investigated the differences in cell functions depending on the culture model in human trophoblast cells (Sw.71). Methods: Sw.71 cells were incubated in 2D monolayers or simple 3D spheroids. After incubation, cells were corrected to assess RNA-seq transcriptome or protein expression, and culture medium were corrected to detect cytokines. To clarify the role of actin cytoskeleton, spheroid Sw.71 cells were treated mycalolide B (inhibitor of actin polymerization) in a 3D culture. Results: RNA-seq transcriptome analysis, results revealed that 3D-cultured cells had a different transcriptional profile compared with 2D-cultured cells, especially regarding inflammation-related molecules. Although interleukin-6 (IL-6) mRNA level was higher in 3D-culured cells, its secretion levels were higher in 2D-cultured cells. In addition, the levels of mRNA and protein expression of regnase-1, regulatory RNase of inflammatory cytokine, significantly increased in 3D culture, suggesting post-translational modification of IL-6 mRNA via regnase-1. Treatment with mycalolide B reduced cell-to-cell contact to build 3D formation and increased expression of actin cytoskeleton, resulting in increased IL-6 secretin. Conclusion: Cell dimensionality plays an essential role in governing the spatiotemporal cellular outcomes, including inflammatory cytokine production and its negative regulation associated with regnase-1.