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

Abstract

Biological rhythms are driven by endogenous biological clocks; in mammals, the master clock is located in the suprachiasmatic nucleus (SCN) of the hypothalamus. This master pacemaker can synchronize other peripheral oscillators in several tissues such as some involved in endocrine or reproductive functions. The presence of an endogenous placental clock has received little attention. In fact, there are no studies in human full-term placentas. To test the existence of an endogenous pacemaker in this tissue we have studied the expression of circadian locomoter output cycles kaput (Clock), brain and muscle arnt-like (Bmal)1, period (Per)2, and cryptochrome (Cry)1 mRNAs at 00, 04, 08, 12, 16, and 20 hours by qPCR. The four clock genes studied are expressed in full-term human placenta. The results obtained allow us to suggest that a peripheral oscillator exists in human placenta. Data were analyzed using Fourier series where only the Clock and Bmal1 expression shows a circadian rhythm.

• Circadian rhythm
• clock genes
• full-term human placenta
• qPCR

Declaration of interest

The authors report no declarations of interest.

Author contributions

Conceived and designed the experiments: ED, CG. Performed the experiments: SP, LM, CFP. Analyzed the data: ID, LM. Contributed reagents, materials, analysis tools: JO, SP, CFP, CG, ID. Wrote the manuscript: ED, ID, SP. All authors approved revisions and the final paper.