Transcriptomic Analysis of CBD-Exposed Rat Placentae Reveals Down-Regulated Angiogenic Pathways and Up-Regulated Metabolic Processes

Abstract

Following nicotine, cannabis is the most used drug during pregnancy. In utero cannabis exposure is linked to adverse outcomes, including fetal growth restriction. Cannabidiol (CBD), the non-hallucinogenic constituent of cannabis, is perceived as safe for use during pregnancy by ~25% of women. While studies assessing the effects of Δ-9-THC, the other principal cannabinoid in cannabis, have been initiated, research examining the impact of CBD on pregnancy is scarce. The placenta facilitates the exchange of gas, nutrients and waste between the fetus and mother. Our group has recently identified altered placental morphology and reduced fetal growth after in utero CBD exposure in rats. However, the influence of CBD on genes, transcription factors and biological processes in the placenta has not been assessed. This study aimed to identify biological pathways in the placenta that were significantly altered by CBD-exposure and correlate the findings with previously performed histological analysis. Pregnant rats were administered a daily dose of 3 mg/kg CBD or a vehicle control from embryonic day (E) 6.5-18.5. On E19.5, placentae were harvested for transcriptomic analysis. RNA extraction, library construction and bulk RNA sequencing was performed by Genome Quebec. The top differentially expressed genes were analysed using Metascape software, revealing the most up- and down-regulated Gene Ontology (GO) biological process pathways. Down-regulated GO biological processes included tube morphogenesis, angiogenesis, and blood vessel morphogenesis, which supported the angiogenic complications identified by histology. Further, the most significantly up-regulated GO biological processes were metabolic, including peptide, glycoprotein, glycosaminoglycan, and tetrahydrofolate. This is significant, as the histological analysis identified elevated Glut3 expression in the placentae from CBD-exposed pregnancies. Elevated Glut3 in fetal growth restriction is associated with changes to metabolic pathways. Consequently, additional studies will include analysis of CBD-exposed rat trophoblast cells to establish whether metabolic changes may underlie the altered morphology identified in CBD-exposed placentae.