Fetal growth restriction (FGR) is one of the leading causes of stillbirth and neonatal mortality. The majority of these cases are due to placental dysfunction and treatment options for FGR in utero are limited. We aimed to determine the suitability of a polymer-based, biodegradable nanoparticle in delivering DNA to human syncytiotrophoblasts using an ex vivo perfusion model and an in vitro culture model.
Nanoparticles (NP) were created by complexing Texas-Red fluorophore labelled polymer with plasmid (human Insulin-like Growth Factor 1 (hIGF1) under the placenta specific promotor PLAC1). Term, human placenta cotyledons (n=6) were perfused for 3.5 hrs including approximately 1 hr with nanoparticle. Fluorescence (625 nm) was quantified in maternal and fetal perfusate using a fluorescent microplate-reader. For in vitro transgene expression, term, human cytotrophoblasts were isolated from placenta tissue (n=4) and allowed to spontaneously syncytialise into syncytiotrophoblasts. Syncytiotrophoblasts were treated with nanoparticle for 48 hr and harvested to isolate RNA.
Fluorescence of the maternal perfusate significantly increased on addition of nanoparticle and declined by the conclusion of the experiment (mean minimum relative fluorescence units (RFU): baseline: -1.2±1.3 vs. NP addition: 322.4±62.1 vs. conclusion: 74.9±7.2; P<0.001, ANOVA). In contrast, negligible levels of Texas-Red were detected in the fetal perfusate (mean minimum RFU: baseline -0.7±0.6 vs. NP addition 1.5±1.5 vs. conclusion 3.7±2.0; NS). Histological analysis of placenta following perfusion showed Texas-Red localisation within the syncytiotrophoblasts of the placental villi. In vitro, treatment with NP significantly increased hIGF1 expression after 48 hr compared to untreated and treatment with plasmid only (mean normalised gene expression: untreated 1.03±0.12 vs. plasmid-only 4.97±2.83 vs. NP 362.12±196.13; P<0.001, ANOVA).
We demonstrate successful NP-mediated delivery of nucleic acids to multiple models of human syncytiotrophoblast and increased expression of the transgene under a specific promoter representing a crucial advance in the development of treatment for placental dysfunction.