Correction of Preeclampsia by Intraplacental Gene Transfer of IGF-1 in the BPH/5 Mouse via NF-KB Mediated Induction of Angiogenic Gene Expression

Introduction. Preeclampsia causes severe complications for the mother, fetus, and newborn, yet the underlying mechanisms remain poorly understood. The BPH/5 mouse is the only spontaneous mouse model that recapitulates key features of human preeclampsia. Although impaired angiogenesis and endothelial dysfunction are hallmarks of this disease, the molecular pathways capable of restoring placental vascular integrity remain undefined. Existing animal models of preeclampsia have not directly targeted the placenta. We hypothesized that hIGF-1 rescues placental endothelial function by driving angiogenic gene expression through the IKK-β/NF-κB signaling axis, thereby correcting the maternal pathophysiologic features of preeclampsia. Methods. Placental morphometric analysis for CD31 immunostaining was performed on human placental samples from early onset preeclampsia (EOPE), gestational age-matched preterm premature rupture of membranes (PPROM), and term healthy controls. Next, primary human placental microvascular endothelial cells were cultured to evaluate IGF-1–mediated responses using in vitro angiogenesis assays under normoxic and hypoxic conditions, in the presence or absence of established NF-κB inhibitors. Cell proliferation was assessed using Ki-67 immunostaining and flow cytometry, and PCR-chromatin immunoprecipitation was used to quantify NF-κB binding to promoter regions of angiogenic genes in human placenta vascular endothelial cells as well as BeWo cells. In parallel, BPH/5 and C57BL/6 mice were time-mated and habituated to blood pressure cuff monitoring. Intraplacental gene delivery of 1x10 ⁸ PFU of Ad-hIGF-1 (referred to as Ad-IGF-1) or Ad-LacZ was performed on embryonic day 16 with cerclage, followed by harvest on e21. Maternal endpoints of blood pressure and proteinuria were assessed at non-pregnant, first-trimester, pre-injection, and post-injection time points. Kidney histology, sFlt-1 levels, and placental endothelial microvascular density assessment were evaluated. Fetal endpoints included litter outcomes. Results. Morphometric placental analysis of EOPE vs. term healthy and PPROM controls showed that microvascular density is markedly reduced while villous architecture remains preserved. BPH/5 placentas similarly exhibit reduced microvascular density in comparison to C57BL/6 placentas. Restoration of microvasculature was appreciated after IGF-1 gene transfer. Angiogenesis and proliferation assays in HPVECs demonstrated that IGF-1 robustly enhances both angiogenic activity and cell proliferation under normoxic and hypoxic conditions, primarily through IKKβ/NF-κB–dependent transcriptional activation of key angiogenic genes. Interestingly, IGF-1 was found to enhance NF-κB signal transduction of angiogenic gene promoters in BeWo cells, but not HPVECs. In the BPH/5 mouse, intraplacental gene transfer of IGF-1 reduced the post-injection systolic, diastolic, and mean arterial pressures comparable to C57BL/6 controls, with the SBP consistently reduced at all delta comparisons across timepoints. Urinary protein levels in BPH/5 were also comparable to controls after gene transfer with Ad-IGF-1. Litter size, demise rate, reabsorptions, and pup weight were unaffected by Ad-IGF-1 gene transfer. Ad-IGF-1 treatment reduced glomerulosclerosis (47.2% vs. surgical sham; 58% vs. Ad-LacZ controls) while liver histology and s-Flt-1 were unchanged. Conclusion. IGF-1 gene transfer reverses the preeclampsia-like phenotype in BPH/5 mice by restoring placental microvascular density without affecting fetal outcomes in the first animal model of preeclampsia treatment that directly targets the placenta. Furthermore, IGF-1’s pro-angiogenic effects are suggested to occur via IKKβ/NF-κB–dependent activation.