How Uterine Fluid Informs The Fetus

Uterine fluid, which contains molecules that can reprogram a developing embryo, could one day be used as a biomarker of fetal health.

AsianScientist (July 4, 2017) – Once assumed to be little more than a simple pH buffer, uterine fluid is now thought to play an important role in preparing fetuses for life outside the womb. These findings have been published in Trends in Molecular Medicine.

A developing fetus bathes in a mixture of cellular secretions and proteins unique to its mother’s uterus. Before fertilization, the pH of uterine fluid creates a conducive environment for sperm migration. Thereafter, its volume supports the embryo as it implants onto the wall of the uterus.

Studies in livestock, rodents, and humans have shown that information from a mother’s environment (e.g., food availability, stress, and pollutant exposure) can leave epigenetic tags on the DNA of her fetus, potentially influencing the progression and long-term health of the developing embryo.

Scientists have hypothesized that blood flow via the placenta might constitute one way the body communicates the mother’s condition to the fetus. However, there is evidence that the fetus reacts to changes such as those stemming from the mother’s diet, long before the establishment of the placenta.

“This suggests the involvement of uterine fluid as the communication medium to transfer information between the maternal environment and the floating embryo,” said senior author Dr. Duan En-Kui, a reproductive biologist at the Institute of Zoology, Chinese Academy of Sciences. “The preimplantation period is a critical time for programming offspring health, and thus, expecting mothers should keep a good diet and good mood, and stay away from harmful chemicals during this critical window.”

While there is much to be learned about how mother-fetus communication takes place, the theory is that information in extracellular vesicles (molecular packages that move from cell to cell) within uterine fluid and tissue deliver cargo such as microRNAs and amino acids to the fetus. These molecules may be tagging fetal cell DNA in ways that alter gene expression, and thus, they ‘program’ how the embryo and placenta develop.

Consequently, researchers are interested in learning which specific maternal environmental exposures and behaviors could change the composition of molecules transported via the uterine fluid to the fetus.

For example, mouse studies have shown that a low-protein maternal diet can reduce the level of certain amino acids in uterine fluid and affect gene expression of nutrition- and transport-related genes. While these changes might prevent malnutrition in the developing embryo, once grown, the mouse offspring are more predisposed to heart disease when compared to animals on a regular diet.

Dr. Wang Hongmei, co-senior author of the paper, speculates that uterine fluid could someday be used to analyze or even manipulate what signals are being received by a fetus.

“For now, uterine fluid collection is not a standard biomarker, yet many studies have revealed its potential role for non-invasive analysis, and we also see great potential in it,” she said. “One, it can be screened by using ultrasound recording coupled with computational or biomechanical analysis; and two, uterine fluid can also be collected during an endometrial examination.”

The article can be found at: Zhang et al. (2017) Uterine Fluid in Pregnancy: A Biological and Clinical Outlook.


Source: Chinese Academy of Sciences; Photo: Shutterstock.
Disclaimer: This article does not necessarily reflect the views of AsianScientist or its staff.

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