Reproduction Abstracts

Introduction: The corpus luteum (CL) is a temporal endocrine organ secreting large amount of progesterone essential for the establishment and maintenance of pregnancy. The CL undergoes luteolysis in a non-fertile cycle, while the CL is rescued from luteolysis by human chorionic gonadotrophin (hCG) secreted from the conceptus during pregnancy. We recently revealed that a β-galactoside-binding lectin, galectin-1, plays important roles in the regulation of luteal rescue in the human CL. To explore the function and the ligand glycoconjugates for galectin-1, we examined the effect of i) lactose, which is a competing saccharide for the binding of galectins to glycoconjugates and ii) hCG without N-glycans, on the hCG-mediated gene expression in cultured human luteinized granulosa cells (LGCs).

Materials and methods: LGCs were isolated from the follicular fluids obtained from the patients undergoing IVF treatment with informed consent. Cultured LGCs were treated by i) 100 ng/ml hCG with or without 30 mM lactose and ii) 100 ng/ml hCG pre-treated with PNGase F to remove N-glycans. LGCs were collected 24 h after the treatments and changes in the gene expression were analyzed by quantitative PCR.

Results and discussion: Both treatments diminished hCG-induced cAMP/PKA-mediated steroidogenic acute regulatory protein and prostaglandin (PG) E synthase expression, while enhancing the expression of PI3 kinase-mediated AKR1C1 and AKR1C2 which are involved in progesterone degradation and the conversion from luteotrophic PGE to luteolytic PGF. These results suggest that an interaction between galectin-1 to glycoconjugates on luteal cells or hCG is required for luteotrophic function of hCG through the cAMP/PKA pathway.