Evidence for clock genes circadian rhythms in human full-term placenta

Area of Science:

• Reproductive biology
• Chronobiology
• Genetics

Background:

• Biological rhythms are regulated by endogenous clocks, with the suprachiasmatic nucleus (SCN) acting as the master clock in mammals.
• Peripheral oscillators in various tissues synchronize with the master clock, influencing functions like endocrine and reproductive processes.
• The existence and function of an endogenous clock within the human placenta remain largely unexplored, with no prior studies on full-term placentas.

Purpose of the Study:

• To investigate the presence and characteristics of an endogenous biological clock in the full-term human placenta.
• To analyze the expression patterns of key circadian clock genes within placental tissue.

Main Methods:

• Quantitative PCR (qPCR) was employed to measure the mRNA expression levels of four core circadian clock genes: Clock, Bmal1, Per2, and Cry1.
• Gene expression was assessed at six time points throughout a 24-hour cycle (00:00, 04:00, 08:00, 12:00, 16:00, and 20:00).
• Fourier series analysis was utilized to determine the presence of circadian rhythms in gene expression data.

Main Results:

• All four studied clock genes (Clock, Bmal1, Per2, Cry1) were found to be expressed in the full-term human placenta.
• Fourier analysis revealed that the expression of Clock and Bmal1 genes exhibited a significant circadian rhythm.
• The expression of Per2 and Cry1 did not show a statistically significant circadian pattern under the study conditions.

Conclusions:

• The human placenta possesses a peripheral oscillator, indicating the presence of an endogenous biological clock.
• Circadian regulation, specifically involving Clock and Bmal1, appears to be a feature of human placental tissue.
• Further research is warranted to fully elucidate the role and mechanisms of this placental clock in pregnancy and fetal development.