Chaperonin 10 in the rat oocytes and early embryos: its expression and activity for early pregnancy factor

Heat Shock-Binding Protein 21 Regulates the Innate Immune Response to Viral Infection

The innate immune system is the first-line host defense against microbial pathogen invasion. The physiological functions of molecular chaperones, involving cell differentiation, migration, proliferation and inflammation, have been intensively studied.

Completion of Meiosis I of preovulatory oocytes and facilitation of preimplantation embryo development by glial cell line-derived neurotrophic factor

Optimal maturation of oocytes and successful development of preimplantation embryos is essential for reproduction. We performed DNA microarray analyses of ovarian transcripts and identified glial cell line-derived neurotrophic factor (GDNF) secreted by cumulus, granulosa, and theca cells as an ovarian factor stimulated by the preovulatory LH/hCG surge. Treatment of cumulus-oocyte complexes with GDNF enhanced first polar body extrusion with increase in cyclin B1 synthesis and the GDNF actions are likely mediated by its receptor GDNF family receptor-alpha1 (GFRA1) and a co-receptor ret proto-oncogene (Ret), both expressed in oocytes. However, treatment with GDNF did not affect germinal vesicle breakdown and cytoplasmic maturation of oocytes. During the preimplantation stages, GDNF was expressed in pregnant oviducts and uteri, whereas GFRA1 and Ret were expressed in embryos throughout early development with an increase after the early blastocyst stage. In blastocysts, both GDNF and GFRA1 were exclusively localized in trophectoderm cells, whereas Ret was detected in both cell lineages. Treatment with GDNF promoted the development of two-cell-stage embryos into blastocysts showing increased cell proliferation and decreased apoptosis mainly in trophectoderm cells. Our findings suggest potential paracrine roles of GDNF in the promotion of completion of meiosis I and the development of early embryos.

Early pregnancy factor in marsupials

Maternal recognition of pregnancy in marsupials occurs in more subtle ways than it does in eutherians. For instance, unlike in eutherians, the plasma progesterone profiles of pregnant and non-pregnant animals are similar during the luteal phase. It is typically during the brief luteal phase that both gestation and parturition occur in marsupials. Yet histological and physiological changes have been documented between gravid and non-gravid uteri in certain monovular marsupials and between pregnant and non-pregnant animals in polyovular marsupials. Early pregnancy factor (EPF), a 10.8-kDa serum protein known to be homologous to chaperonin 10, is associated with maternal immunosuppression, embryonic development and pregnancy in eutherian mammals. It has been reported in two Australian marsupials: the dasyurid Sminthopsis macroura and the phalangerid Trichosurus vulpecula. This paper documents its occurrence in the New World didelphid Monodelphis domestica. EPF is detectable by rosette inhibition assay in the peripheral circulation of pregnant but not of non-pregnant or pseudopregnant animals. Our work focuses on the embryo–maternal signalling role of EPF during pregnancy. Because progesterone-driven changes are similar in pregnant and non-pregnant marsupials, these animals are an excellent laboratory model in which to investigate the role of EPF in orchestrating the physiological changes necessary to sustain pregnancy.

Partial Purification of Mare Early Pregnancy Factor

PROBLEM

Early pregnancy factor (EPF) is an immunosuppressive protein detected in the serum in early pregnancy. We have already reported the development of the rosette inhibition test for mare EPF and have detected EPF in thoroughbreds and ponies. Here, we attempted to purify equine EPF from pregnant mare serum.

METHODS OF STUDY

Mare EPF was purified by ultrafiltration and ion-exchange chromatography. Purified EPF was analyzed by sodium dodecyl sulfate-polyacrylamide gel electrophoresis (SDS-PAGE), immunoblotting and a neutralization test. EPF activity was estimated as the rosette inhibition titer (RIT) by the rosette inhibition test.

RESULTS

Purified EPF bound to carboxymethyl (CM) sepharose and did not adsorb to diethylaminoethyl (DEAE) sepharose. SDS-PAGE revealed that in the final purified fraction there were many proteins. In the immunoblotting analysis, a protein band of 25.8 kDa was detected as the pregnancy-specific band. Further, antibody gained from the 20 to 30 kDa protein band of the final purified fraction neutralized the RIT activity of pregnant mare serum.

CONCLUSIONS

Mare EPF was detected in the final purified fraction and had a molecular weight of 25.8 kDa. EPF in the mare is similar to that obtained from the serum of pregnant cows.

The role of leptin during the development of mouse preimplantation embryos

Leptin is known to regulate diverse reproductive functions, and recent studies have implicated involvement of leptin in the early mouse embryo development. The aim of the present study was to investigate the expression of leptin and its functional receptor (OB-Rb) in mouse oocyte and preimplantation embryo, and to examine whether leptin influenced the early embryo development. Leptin mRNA was detected in blastocyst and hatched blastocyst, and OB-Rb mRNA was detected in oocytes, 1-cell, 2-cell, morula, blastocyst and hatched blastocyst. As for the origin of leptin, leptin mRNA was identified in both the oviduct and uterus of the pregnant mouse. Furthermore, in the pregnant mouse, the levels of leptin in uterine fluid were higher than those in the non-pregnant mouse. Supplementation of culture medium with leptin promotes the development of preimplantation embryos from 2-cell stage to the blastocysts, fully expanded blastocysts and hatched blastocysts. Leptin significantly increased the total cell number of blastocysts, and the effect was preferentially observed in the trophectoderm. These findings raise the possibility that leptin regulates the development of mouse preimplantation embryo through a paracrine pathway.

Expression of LDL receptor and uptake of LDL in mouse preimplantation embryos

OBJECTIVES

The aim of this study is to address the role of low-density lipoprotein (LDL) on mouse preimplantation embryos.

METHODS

The temporal expression of low-density lipoprotein receptor (LDLR) and side-chain cleavage cytochrome P450 (P450scc) mRNAs in mouse oocytes and preimplantation embryos up to the hatched blastocyst stage were analyzed by RT-PCR and nested PCR techniques. Simultaneously, the expression of LDLR in the protein level was analyzed by fluorescent immunohistochemistory at oocyte, 4-cell embryo and blastocyst. Uptake of LDL was analyzed using the LDL labeled with the fluorescent probe DiO.

RESULTS

LDLR mRNA was detected at oocyte, 8-cell, morula, blastocyst and hatched blastocyst stages. P450scc mRNA was detected at oocyte, 1-cell, 2-cell, 4-cell, blastocyst and hatched blastocyst stages. LDLR protein was detected in blastocyst. P450scc protein was detected in oocyte, 4-cell, and blastocyst. LDL-DiO was taken into embryo at blastocyst stage and this uptake was competitively suppressed by excess unlabeled LDL.

CONCLUSIONS

It is suggested from the present study that LDLR may play an essential role in uptake of exogenous LDL into blastocyst stage and cholesterol derived from LDL may be the source of steroid hormone synthesis.

Leptin promotes the development of mouse preimplantation embryos in vitro

Leptin acts as a modulator of diverse reproductive functions, and recent studies have implicated involvement of leptin in the early embryo development in mammal. The aim of this study was to investigate the expression of leptin and its receptor (OB-R) in mouse oocyte and preimplantation embryo, and to examine whether leptin influenced the early embryo development. Leptin mRNA was detected in blastocyst and hatched blastocyst, and two splice variants of OB-R (OB-Ra and OB-Rb) mRNAs were detected in oocytes, 1-cell, 2-cell, morula, blastocyst, and hatched blastocyst. As for the origin of leptin, both leptin mRNA and protein were identified in the oviduct epithelium and endometrium of pregnant mouse. In the pregnant mouse, the levels of leptin in uterine fluid were higher than those in nonpregnant mouse. Addition of leptin to embryo culture media promotes the development from 2-cell stage embryos to the blastocysts, fully expanded blastocysts and hatched blastocysts. This effect was neutralized by an antibody against the extracellular domain of OB-R. Leptin significantly increased the total cell number of blastocysts, and the effect was preferentially observed in the trophectoderm. These findings raise the possibility of a paracrine/autocrine leptin signaling system regulating the development of mouse preimplantation embryo.