Nanoparticle-mediated transgene expression of insulin-like growth factor 1 in the growth restricted guinea pig placenta increases placenta nutrient transporter expression and fetal glucose concentrations

Abstract

Fetal growth restriction (FGR) occurs in up to 10% of pregnancies and is a leading cause of infant morbidity and mortality. Additionally, FGR has been implicated in contributing to the development of long-term health outcomes including increasing the risk for future cardiovascular and endocrine diseases. Currently, there is limited preventative strategies and no effective treatment options for FGR. To address this need, we are developing a therapeutic targeting the placenta to increase expression of human insulin-like growth factor 1 (hIGF-1) and enhance placental development and function, with the goal of correcting fetal growth trajectories.MethodsInitially, an ultrasound-guided, transcutaneous, intra-placental injection of a non-viral, Texas-red conjugated polymer-based nanoparticle containing a plasmid with the green fluorescent protein (GFP) gene under the control of the placenta-specific promotors Plac1 or Cyp19a1 was performed to determine nanoparticle uptake and transgene expression in the guinea pig placenta. Subsequently, using the established maternal nutrient restriction (MNR) guinea pig model of FGR, placentas were treated with an unconjugated nanoparticle containing a plasmid with the hIGF-1 gene under the Cyp19a1 promotor at mid-pregnancy (gestational day (GD) 30-33). Five days after treatment placentas and fetal liver tissue was collected, weighed, and fixed for histology or snap-frozen for qPCR analysis of mRNA expression.ResultsHistological analysis of Texas-red and GFP fluorescence in placenta and fetal liver tissue confirmed nanoparticle uptake and transgene expression and that nanoparticle was unable to cross the placenta to fetal circulation. In situ hybridization for plasmid-specific mRNA confirmed sustained hIGF-1 expression five days after treatment. MNR resulted in 20-25% decreased fetal weight at mid-pregnancy (P<0.001) that was not changed with nanoparticle treatment (P>0.05). There was no effect of nanoparticle treatment on the volume densities of trophoblasts or fetal capillaries in the placenta (P>0.05 for both). However, treatment did reduce the interhaemal distance between the maternal blood space and fetal circulation in the MNR placentas compared to sham treated MNR placentas (P<0.001). In the fetuses, placental nanoparticle treatment increased circulating glucose by 38-50% (P<0.001) and was associated with differential changes to fetal liver mRNA expression of genes associated with gluconeogenesis. Gene expression changes were dependent on if the fetus was growth restricted or not; nanoparticle treatment: down-regulated gluconeogenesis gene expression in the normal growing fetuses but increased expression in the FGR fetuses.ConclusionsThe current study shows that treatment of the guinea pig placenta with a polymer-based nanoparticle causes expression of hIGF-1 and ultimately increases fetal glucose concentrations within five days of treatment. Furthermore, the data shows that the placenta and fetal liver respond differently to nanoparticle treatment depending on fetal growth conditions.Graphical Abstract