Lipidomics of fetal membranes in labour and the initiation of parturition by fetal lung maturation markers

Abstract

Abstract Introduction: The timing of human labour is key to pregnancy success. Although the stages of parturition are well defined, its initiation and point of origin remain elusive. Fetal membranes are tissues that encapsulate the fetus and amniotic fluid in the intrauterine cavity, and are considered a site for conveying maturation signals from the fetus to the maternal uterus. Reports point strongly to lipid mediators in instigating parturition; supported by the clinical use of Arachidonic Acid (AA)-derived prostanoids; prostaglandin E2 (PGE2) and F2α (PGF2α), to induce labour onset. In pregnancy, both sides of the fetal membrane (amnion and choriodecidua) show upregulation of cyclooxygenase-2 (COX-2), a rate-limiting enzyme in prostanoid synthesis, as labour begins. Endocannabinoids and ceramides are additional bioactive lipid mediators altered in maternal blood and/or intrauterine tissues at this time. Near to term, fetal lung maturation is achieved by the synthesis of lung surfactants, with the main components being amniotic fluid DPPC (Dipalmitoylphosphatidylcholine) and LPC (lyso-form lysophosphatidylcholine), both palmitic acid (PA)-enriched compounds. This study explores lipidomes within the amnion and choriodecidua of the fetal membranes in various types of labour; term and preterm, compared to women at term whose labour is yet to begin. The influence of DPPC/LPC on fetal membrane lipid changes, prostanoid production and pro-inflammatory cytokine liberation are also considered; to pinpoint (for the first time) the epicentre for induction of normal human parturition, and the role of fetal lung surfactant in instigating/propagating this physiological chain-reaction. Method: Amnion and choriodecidua were collected post-delivery from (i) term non-labouring women (TNL), (ii) those in spontaneous term human labour (STL), (iii) those with drug-induced term labour (ITL), and (iv) those in spontaneous preterm labour (PTL) without identified infection. Eicosanoids and related mediators, endocannabinoids, ceramides and structural lipids, were profiled using state-of-art mass spectrometry lipidomics, and relative abundances of fatty acids determined with gas chromatography. For in vitro experiments with DPPC and LPC, primary amnion and decidual mesenchymal cells were isolated and propagated from human fetal membranes. Resultant lipidomes were observed and matched to secreted pro-inflammatory cytokines by multiplex immunoassays. Result: The choriodecidua actively produced contractile prostanoids in all labouring women, compared to those with no overt signs of labour at term. The amnion likewise produced labour associated prostanoids, but only in term labouring conditions (TNL) and more noticeably following induction (ITL). Physiological (i.e. non-induced) spontaneous labour enhanced LOX- and CYP450-derived lipid mediators, but this was more apparent in the choriodecidua than amnion. For classical endocannabinoids, the amnion and choriodecidua both expressed 2-arachidonoylglycerol (2-AG), whilst N-arachidonoylethanolamine (AEA) was only detected in the choriodecidua. In both tissues, AEA was upregulated in spontaneous term and preterm labour, with a further increase in 2-AG with labour induction. N-acylethanolamine (NEA) profiles varied under different labour conditions, but linoleoyl-ethanolamide was consistently increased in spontaneous term and preterm parturition. Total ceramide (CER) content was also elevated in amnion and choriodecidua under both term labouring scenarios. The CER classes showed variability across study groups, but generally the amnion was most active following induction, and choriodecidua in spontaneous term labour. Notably, CER(NS) and CER(ADS) were the only classes enhanced during preterm labour. For glycerophospholipids, phosphatidylcholine (PC) and phosphatidylethanolamine (PE) were elevated within the choriodecidua under spontaneous term labour. In addition, AA-containing species were exaggerated wit

Date of Award	1 Aug 2021
Original language	English
Awarding Institution	The University of Manchester
Supervisor	Ian Crocker (Supervisor), Melissa Whitworth (Supervisor) & Anna Nicolaou (Supervisor)