Marijuana is the most commonly used illicit drug in pregnancy, it has been associated with stillbirth, abnormal placental hemodynamics, and fetal neurodevelopmental consequences. However, the literature in humans is limited and conflicting; most studies are observational or retrospective and are heavily confounded by polysubstance abuse and self-reporting bias. Animal models, however, can allow for experimental standardization, minimization of confounders, and subject variability. Previous rodent and rabbit studies performed in the 1960-1980s have provided some information on the absorption, distribution, placental transfer, metabolism and excretion of lower historical doses of the active ingredient of marijuana (delta-9- tetrahydrocannabinol, THC). Given prenatal marijuana use is becoming more commonplace and the significant increase in potency, understanding the longitudinal effect of prenatal marijuana use on placental and fetal pharmacokinetics and outcomes in-vivo is vital to establish evidence-driven recommendations on the safety of use during pregnancy. Our group has extensive experience establishing non-human primate (NHP) pregnancy models of maternal adverse behavior and have the infrastructure and expertise to establish a NHP model of standardized prenatal marijuana exposure. As NHPs have a gestational term, marijuana plasma disposition, and developmental ontogeny similar to humans, including their placental structure and timing of fetal development, the NHP is a suitable translational model of human conditions. We propose to study the effects of chronic moderate versus heavy maternal marijuana exposure in pregnancy using a relevant and contemporary NHP model. This proposed NHP model will permit longitudinal sampling of maternal, fetal and placental tissue in-utero, not feasible or ethical in humans especially early in pregnancy, to directly measure levels of THC and its primary metabolites throughout gestation. Tissue concentrations will be correlated with known quantities and timing of maternal THC exposure to determine bioavailability and metabolism by trimester, since maternal, fetal and placental physiology changes throughout pregnancy. Additionally, we will use advanced, non-invasive, in-vivo imaging modalities, a combination of ultrasound and MRI techniques, for functional assessment of the direct effects of marijuana on placental perfusion and oxygen availability. In-vivo MR imaging will be correlated with in-vitro studies to link the degree of adverse placental perfusion and oxygenation with the extent of placental tissue damage. Antenatal longitudinal sampling would permit correlation of tissue drug concentrations with detected altered placental function on in-vivo imaging and post- natal pathology at matched gestational time points. Ultimately, we anticipate that this work will generate high- quality maternal-placental-fetal pharmacokinetic data, not achievable in humans, that is essential for obstetricians to facilitate appropriate counseling of women regarding marijuana use in pregnancy and facilitate the design for future larger prenatal marijuana studies to research the effects on early childhood development.
The main objective of this proposal is to determine the maternal, fetal and placental pharmacokinetics and impairments of chronic moderate vs. heavy marijuana prenatal exposure in a relevant and contemporary non- human primate model. Longitudinal maternal, fetal and placental sampling will be performed in-utero to directly measure levels of delta-9-tetrahydrocannabinol (THC) and its main metabolites, not feasible or ethical in humans, to obtain pharmacokinetic information throughout gestation. We also propose to utilize advanced non-invasive imaging techniques to characterize the effect of marijuana exposure in pregnancy on placental function and oxygenation in-vivo; in-vivo findings would be correlated with in-vitro studies of THC pharmacokinetics to link structure and function.
