The Role of Placental Maternal Vascular Underperfusion in Neonatal Pulmonary Hypertension

Pulmonary hypertension (PH), characterized by increased pulmonary arterial blood pressures and right ventricular hypertrophy, is a serious condition affecting 10% of all neonates with respiratory failure. In premature infants, PH complicates up to one third of cases of neonatal chronic lung disease, also known as bronchopulmonary dysplasia (BPD). This entity, known as BPD-associated PH (BPD-PH), is established at 1-3 months of age and incurs a four-fold increased risk of death. Survivors of BPD-PH have prolonged and recurrent hospitalizations, and are at risk for chronic cardiopulmonary and metabolic problems. Therefore, early therapeutic strategies to prevent the development of BPD-PH in premature infants are critically needed. A promising therapeutic target is the intermediate monocytes (iMNC) derived from cord blood and plays a proangiogenic and regenerative role in many diseases. Our central hypothesis is that cord blood-derived iMNCS are adversely programmed by chronic fetal hypoxia of placental maternal vascular underperfusion (MVU), and contribute to early delayed lung angiogenesis leading to BPD-PH. In Aim #1, we will elucidate the mechanism by which MVU leads to delayed cord blood angiogenesis. Using fetal growth restriction (FGR, birth weight <5th percentile) as the proxy for chronic fetal hypoxia, we will use flow cytometric analysis to compare frequency of 3 MNC subsets from cord blood of infants with the following profiles: 1) preterm MVU with FGR; 2) preterm MVU without FGR; 3) preterm no MVU with FGR; 4) preterm no MVU no FGR (preterm control); 5) term no MVU no FGR (term control). In iMNCs isolated by fluorescence activated cell sorting (FACS) we will compare gene expression profiles using a custom PCR array of angiogenic genes. In Aim #2 we will identify perinatal mechanisms by which MVU-exposed fetal iMNCs contribute to delayed neonatal lung angiogenesis. In cultured iMNCs, we will use qRT-PCR coupled with EIA to compare VEGFA, VEGFR1 gene and protein expression among the 5 groups in Aim 1, exposed to hypoxia followed by hyperoxia. We will use chemotaxis assays to compare iMNC migration in response to exogenous PIGF and GCSF. We will measure iMNC expression of VEGFA in bronchoalveolar lavage from intubated preterm infants. Lastly, in Aim #3, we will use a human GM-CSF knock-in (humanized) mouse model, coupled with a hypoxia-induced lung injury model (85% oxygen x 14 days) to test the hypothesis that transplantation of cord blood-derived intermediate MNC from non-MVU, non-FGR infants (controls) will aid in the prevention of BPD-PH.