Cellular aspects of corpus luteum function in the primate

Area of Science:

• Reproductive biology
• Endocrinology
• Cell biology

Background:

• The primate corpus luteum produces progesterone for 14-16 days before regression in non-fertile cycles.
• Luteinizing hormone (LH) is essential for maintaining steroidogenesis but not the direct cause of luteolysis.
• Previous studies suggest LH secretion changes do not initiate luteal regression.

Purpose of the Study:

• To investigate the regulation of luteal steroidogenesis and luteolysis in primates.
• To determine the role of messenger ribonucleic acid (mRNA) levels of steroidogenic enzymes in luteal function.
• To identify potential non-steroidal factors involved in corpus luteum angiogenesis.

Main Methods:

• Measurement of steady-state mRNA levels for steroidogenic enzymes in luteal cells.
• Assessment of progesterone and LH secretion patterns.
• Detection of mRNA encoding vascular endothelial growth factor (VEGF) in the corpus luteum.

Main Results:

• Luteal cell synthetic capacity, indicated by mRNA levels, peaks post-ovulation and declines independently of progesterone and LH.
• Loss of mRNA expression for steroidogenic enzymes after LH withdrawal lags behind progesterone decline by 24 hours.
• Vascular endothelial growth factor (VEGF) mRNA is detected throughout the luteal phase in subhuman primates.

Conclusions:

• Luteal cell steroidogenic capacity declines intrinsically, not solely driven by LH or progesterone withdrawal.
• The timing of mRNA decline suggests a downstream effect of LH withdrawal on steroidogenic enzyme expression.
• VEGF may be a key non-steroidal factor mediating angiogenesis within the primate corpus luteum.