The Angiotensin II type 1 receptor mediates the effects of low oxygen on early placental angiogenesis

• Published in: Placenta (Eastbourne) 2019-01, Vol.75, p.54-61
• Main Authors: Delforce, Sarah J., Lumbers, Eugenie R., Morosin, Saije K., Wang, Yu, Pringle, Kirsty G.
• Format: Article
• Language: English
• Subjects: Angiotensin II; Angiotensin II - metabolism; Cell Line; Female; Human Umbilical Vein Endothelial Cells; Humans; Hypoxia - metabolism; Losartan; Neovascularization, Physiologic; Oxygen; Placenta - physiology; Placental development; Pregnancy; Receptor, Angiotensin, Type 1 - metabolism; Renin-angiotensin system; Signal Transduction
• ISSN: 0143-4004; 1532-3102
• DOI: 10.1016/j.placenta.2018.12.001

Placental development occurs in a low oxygen environment, which stimulates angiogenesis by upregulating vascular endothelial growth factor A (VEGFA), plasminogen activator inhibitor-1 (SERPINE1) and the angiopoietin-2/-1 ratio (ANGPT2/1). At this time, Angiotensin II type 1 receptor (AT1R) is highly expressed. We postulated that the early gestation placental oxygen milieu, by stimulating the angiotensin (Ang) II/AT1R pathway, increases expression of proliferative/angiogenic factors. HTR-8/SVneo cells were cultured in 1%, 5% or 20% O2 with the AT1R antagonist (losartan) for 48 h. mRNA and protein levels of angiogenic factors were determined by qPCR and ELISA. Angiogenesis and cell viability were assessed by HUVEC tube formation and resazurin assay. Culture in low oxygen (1%) increased angiogenic VEGFA, SERPINE1 and placental growth factor (PGF) mRNA and VEGFA and SERPINE1 protein levels, and reduced anti-angiogenic ANGPT1, endoglin (ENG) and soluble fms-like tyrosine kinase-e15a (sFlt-e15a) mRNA (all P = 0.0001). At 1% oxygen, losartan significantly reduced intracellular VEGFA and SERPINE1 levels and secreted VEGF levels (P = 0.008, 0.0001 and 0.0001). HUVEC tube formation was increased in cells grown in HTR-8/SVneo conditioned medium from 1 to 5% cultures (all P = 0.0001). HUVECs cultured in medium from losartan treated HTR-8/SVneo cells had a reduced number of meshes, branching points and total branching length (P = 0.004, 0.003 and 0.0002). At 1% oxygen, losartan partially inhibited the oxygen-induced increase in cell viability (P = 0.0001). Thus, AT1R blockade antagonised the low oxygen induced increase in pro-angiogenic factor expression and cell viability. Our findings highlight a role for an oxygen-sensitive Ang II/AT1R pathway during placentation. •The human placenta develops in a low oxygen environment.•Culture in 1% O2 increases the proliferative/angiogenic placental RAS pathway.•Culture in 1% O2 culture increases proliferative/angiogenic factors in trophoblasts.•These effects were more modest after culture in 5% O2.•The O2-sensitive Ang II/AT1R pathway promotes placental angiogenesis/proliferation.