164. Evidence of senescence in post-mature and pathological human placentas; a possible contributing factor in pre-eclampsia?

Abstract

Introduction Cell senescence, which can be activated by oxidative stress and DNA damage, has also been implicated in cell fusion. Placental oxidative stress is a key intermediary event in the pathophysiology of pre-eclampsia. Objectives/hypothesis The aim was to examine senescence markers in normal placentas across gestation, and in pathological and post-mature pregnancies. Inducers of oxidative stress were used to mimic senescence changes in term explants. Methods Placental samples were collected with ethical approval. First and second trimester samples were from surgical terminations; term and pre-term controls, and early-onset pre-eclampsia (PE + IUGR) placentas were from caesarean deliveries. Paraffin and EM blocks of post-mature placentas (7–21 d post-term) were from an archival collection. Oxidative stress was induced by subjecting term explants to cyclical hypoxia-reoxygenation (HR) or H2O2 (0–1 M) for 24–48 h. Results p21 was increased significantly in term homogenates compared to first and second trimester samples, and was significantly higher in both preterm controls and PE + IUGR compared to term controls. Immunostaining revealed nuclear localisation of p21 and phosphorylated histone, γH2AX, in the syncytiotrophoblast, with abundant foci in pathological and post-mature placentas. Abnormal nuclear appearances were observed in post-mature placentas. Sudan-Black-B staining demonstrated abundant expression of lipofuscin, an aggregate of oxidised proteins, lipids and metals, in post-mature and pathological placentas. In addition, an increased percentage of nuclei were positive for 8-hydroxy-2’-deoxy-guanosine, a marker of oxidised DNA, in pathological placentas compared to age-matched controls. These changes could be mimicked in vitro by challenge with HR or H2O2. Conclusions Evidence of senescence markers increases with gestational age in normal placentas, and is exaggerated in post-mature and pathological placentas. Oxidative stress triggers these changes in placental explants, and may be the precipitating insult in vivo. The consequent pro-inflammatory senescence-associated secretory phenotype may contribute to the pathophysiology of early-onset pre-eclampsia. Supported by the Centre for Trophoblast Research.