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Developmental Biology - Pregnancy
How Mother & Fetal Cells Communicate
Scientists find a way to monitor the crosstalk between mother and fetal cells during pregnancy...
University of Texas Medical Branch (UTMB) at Galveston has teamed with colleagues in South Korea to develop a non-invasive method for monitoring fetal health through exosomes. Their findings are now available in the American Journal of Obstetrics and Gynecology.
"In pregnancy, there is constant communication between maternal and fetal cells using sacs — exosomes — filled with molecules. Our prior studies showed that fetal exosomes signal the mother when fetal organs are fully mature, triggering labor and delivery! We want to learn more about this system and develop new ways to monitor/support a fetus throughout pregnancy."
Ramkumar Menon PhD, Associate Professor, Obstetrics and Gynecology UTMB, and senior author.
To distinguish between fetal and maternal exosomes, researchers genetically engineered mice to make specific exosome proteins glow either florescent red or florescen green under a microscope. In this way they tracked movement of exosomes between mice mothers and fetal pups to develop useful indicators of pup development and health. Measuring exosome flow was minimally invasive as only maternal blood samples are needed.
"We will [now] test the usefulness of drugs enclosed in exosomes that can potentially cross the placenta barrier, reach the fetus and prevent fetal inflammation, a major cause of preterm birth for which there is currently no drug treatment. Fetal inflammatory response is primarily responsible for preterm delivery, which impacts 15 million pregnancies yearly and is responsible for 1 million neonatal deaths."
Ramkumar Menon PhD.
Abstract
Background
During pregnancy, feto-maternal communication can be mediated through extracellular vesicles, specifically exosomes, 30- to 150-nm particles released from each cell. Exosomes carry cellular signals, and traffic between fetal and maternal tissues to produce functional changes in recipient cells. Exosomes may function as a biomarker indicative of the physiologic status of their tissue of origin. These properties of exosomes during pregnancy are not well studied.
Objective
To test exosome trafficking and function, we used a transgenic mouse model containing membrane-targeted, red fluorescent protein tdTomato and enhanced green fluorescent protein cyclic recombinase-reporter construct expressed only in fetal tissues. This model allows fetal tissues and their exosomes to express red fluorescent protein tdTomato under normal conditions or green fluorescent protein if fetal tissues are exposed to cyclic recombinase that will excise red fluorescent protein tdTomato. As maternal tissue remains negative for this construct, red fluorescent protein tdTomato/green fluorescent protein expression and their switching can be used to determine fetal-specific cell and exosome trafficking.
Materials and Methods
Red fluorescent protein tdTomato/green fluorescent protein-homozygous male mice were mated with wild-type females to have all fetal tissues express the red fluorescent protein tdTomato/green fluorescent protein allele. Red fluorescence due to red fluorescent protein tdTomato expression of the red fluorescent protein tdTomato/green fluorescent protein allele in fetal tissues (placenta, fetal membranes) was confirmed by confocal microscopy on embryonic day 16. Localization of fetal exosomes in maternal uterine tissues were performed by immunostaining for exosome marker CD81 and red fluorescent protein tdTomato expression followed by confocal microscopy. Fetal exosomes (red fluorescent protein tdTomato-positive) in maternal plasma were immunoprecipitated using anti-red fluorescent protein tdTomato, followed by confirmation with flow cytometry. To further illustrate the fidelity of fetal exosomes in maternal samples, exosomes bioengineered to contain cyclic recombinase (1.0 × 1010 exosomes) were injected intraperitoneally on embryonic day 13. On embryonic day 16, fetal (placenta and fetal membranes) tissues were imaged to show red fluorescent protein tdTomato-to-green fluorescent protein transition. The green fluorescent protein-expressing exomes were localized in maternal tissues (confocal microscopy) and plasma (flow cytometry).
Results
Mating between male with the red fluorescent protein tdTomato/green fluorescent protein construct and null female resulted in fetal tissues and their exosomes expressing red fluorescent protein tdTomato positivity. Total fetal exosomes in maternal plasma was about 35%. Red fluorescent protein tdTomato-positive exosomes were isolated from maternal plasma and immunostaining localized red fluorescent protein tdTomato-positive exosomes in maternal uterine tissues. Maternal intraperitoneal injection of cyclic recombinase-enriched exosomes crossed placenta, excised red fluorescent protein tdTomato from the red fluorescent protein tdTomato/green fluorescent protein construct in the fetal tissues, and caused green fluorescent protein expression in fetal cells. Furthermore, green fluorescent protein-positive exosomes released from fetal cells were isolated from maternal blood.
Conclusion
In this pilot study, we report feto-maternal and maternal-fetal trafficking of exosomes indicative of paracrine signaling during pregnancy. Exosomes from the maternal side can produce functional changes in fetal tissues. Trafficking of exosomes suggests their potential role in pregnancy as biomarkers of fetal functions and usefulness as a carrier of drugs and other cargo to the fetal side during pregnancy. Isolation and characterization of fetal exosomes can advance fetal research without performing invasive procedures.
Authors
Samantha Sheller-Miller, Kyungsun Choi, Chulhee Choi and Ramkumar Menon MS PhD.
Acknowledgements
The authors report no conflict of interest.
This study was supported by grant funds from AMAG Pharmaceuticals (to R.M.).
Cite this article as: Sheller-Miller S, Choi K, Choi C, et al. Cre-reporter mouse model to determine exosome communication and function during pregnancy. Am J Obstet Gynecol 2019;XX:x.ex-x.ex.
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Aug 29 2019 Fetal Timeline Maternal Timeline News
 Exosomes from the mother carry molecules that can produce changes in fetal tissues. They may have a potential role as (1) biomarkers of fetal function and (2) as a delivery system for drugs. CREDIT abcam.com
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Commons License.