Delta 9-Tetrahydrocannabinol Signaling Through Cannabinoid Receptor 1 Alters Trophoblast Differentiation

Area of Science:

• Reproductive biology
• Developmental toxicology
• Pharmacology

Background:

• Cannabis use in pregnancy is rising, raising concerns about fetal exposure to delta-9 tetrahydrocannabinol (Δ9-THC).
• Rodent studies link prenatal Δ9-THC exposure to placental pathology, particularly compromised labyrinth development.
• Cannabinoid receptor 1 (CB1) mediates Δ9-THC effects, but its precise expression in the placenta is debated.

Purpose of the Study:

• To map the spatiotemporal expression of CB1/Cnr1 in the rodent placenta.
• To determine if CB1 mediates Δ9-THC-induced changes in trophoblast differentiation.
• To investigate the mechanism of Δ9-THC's impact on placental growth.

Main Methods:

• Immunohistochemistry to detect CB1 expression in placental tissues.
• In vitro studies using mouse trophoblast stem (mTS) cells, including CB1 knockout (mTS^Cnr1KO) models.
• Analysis of trophoblast differentiation markers (proliferating, differentiating, and specialized cell types) following Δ9-THC exposure.

Main Results:

• CB1 is expressed in all maternal blood-facing trophoblast cells, contrary to previous reports.
• Δ9-THC exposure significantly altered markers of differentiating trophoblast cells more than proliferating cells.
• Δ9-THC impaired syncytiotrophoblast (SynT) marker expression in a CB1-dependent manner, promoting junctional zone/trophoblast giant cell differentiation.

Conclusions:

• CB1/Cnr1 expression is more widespread in the placenta than previously thought.
• Δ9-THC disrupts trophoblast differentiation pathways crucial for placental development.
• This study reveals a potential mechanism by which prenatal cannabis exposure may adversely affect placental growth and fetal development.