Associate Professor University of Pennsylvania, United States
Introduction:: Pre-eclampsia is a placental insufficiency disorder that develops in 3–8% of all pregnancies and is a leading cause of maternal and fetal mortality. Frequently associated with fetal growth restriction (FGR), pre-eclampsia is thought to develop due to dysregulation in placental development whereby maternal blood pressure rises to compensate for constricted placental blood vessels in order to supply sufficient nutrients and oxygen to the fetus. While preterm delivery is the only curative treatment option for pre-eclampsia, the clinical standard of treatment focuses on the use of small molecule drugs to manage blood pressure and prevent seizures. However, these treatment options address the associated symptoms of the condition rather than the underlying placental pathology. Previous work by our lab has reported the design of an ionizable lipid nanoparticle (LNP) platform for mRNA delivery to the placenta through a standard in vitro screening approach to identify a lead candidate for mRNA delivery from a small library of LNPs. This current work utilizes an in vivo, high-throughput screening approach with a large library of novel LNP formulations to identify a placenta-tropic LNP formulation (ptLNP) that mediates an order of magnitude higher mRNA delivery to the placenta than industry standard ionizable lipids. This ptLNP was then used in a mouse model of pre-eclampsia during pregnancy to deliver vascular endothelial growth factor (VEGF) mRNA, rescuing maternal blood pressure and fetal weight compared to untreated controls (Fig. 1a).
Materials and Methods:: A library of 98 LNPs with novel ionizable lipid materials and varied excipient compositions was formulated with barcoded DNA (b-DNA) via pipette mixing. The 98 LNP formulations were pooled and administered to non-pregnant and pregnant mice; 6 h following administration organs were collected, processed, and samples were prepared for next generation sequencing (NGS). Demultiplexing and subsequent data analysis identified lead LNP formulations for extrahepatic delivery to the placenta. Counter screening was performed to validate the efficacy of lead placenta-tropic ptLNP for luciferase mRNA delivery to the placenta in pregnant mice. Finally, VEGF mRNA ptLNP was evaluated in a lipopolysaccharide (LPS)-induced pregnancy model of severe, early onset pre-eclampsia. Maternal weight and blood pressure were recorded daily throughout gestation while fetal and placental weight, placental vasculature, and immune response were evaluated at the study endpoint before parturition.
Results, Conclusions, and Discussions:: High-throughput in vivo DNA barcoding was used to assess the biodistribution of a 98 LNP library in non-pregnant and pregnant mice. Many of our LNP formulations with novel ionizable lipid materials enabled extrahepatic LNP delivery compared to industry standard formulations containing the C12-200 or DLin-MC3-DMA ionizable lipids. One lead placenta-tropic particle identified from high-throughput screening — ptLNP — was formulated encapsulating luciferase mRNA to assess functional protein expression in vivo. Consistent with the results from the high-throughput screen, ptLNP mediated potent luciferase expression to the placentas of pregnant mice, significantly more than liver-tropic C12-200 and DLin-MC3-DMA LNPs (Fig. 1b). ptLNP was then formulated with vascular endothelial growth factor (VEGF) mRNA for an LPS-induced model of pre-eclampsia during pregnancy. Following LNP administration on gestational day E12, maternal blood pressure was significantly lower than the untreated pre-eclamptic mice through the end of gestation (Fig. 1c). Finally, at the model endpoint, fetal weight was significantly higher for the VEGF mRNA ptLNP treatment group compared to the untreated pre-eclamptic mice (Fig. 1d). These results demonstrate the potential of placenta-tropic VEGF mRNA LNPs to treat pre-eclampsia during pregnancy. Future work will focus on using this ptLNP platform to encapsulate other therapeutic nucleic acid cargoes for treating a broad range of placental insufficiency disorders during pregnancy.
