Protein Profile Changes in Circulating Placental Extracellular Vesicles in Term and Preterm Births: A Longitudinal Study

Abstract

Spontaneous preterm birth (PTB) is a major obstetrical problem around the globe and the mechanisms leading to PTB are unclear. Recently, changes in the circulating levels of placental extracellular vesicles (EVs) during pregnancy have been associated with various pregnancy complications. However, progress in the field is hindered by the inability to isolate placental EVs from the maternal circulation. A longitudinal study design was used to determine the protein cargo present in circulating placental EVs in maternal plasma of term and PTB across gestation (ie, first, second, and third trimester). Placental-derived EVs were enriched from the total EV population based on their expression of membrane-bound placental alkaline phosphatase (PLAP). A quantitative, information-independent acquisition (sequential windowed acquisition of all theoretical mass spectra [SWATH]) approach identified and quantified the placental EV protein contents. PLAP+ EVs did not change in characteristics (size, shape, and markers) but did differ in numbers across gestation with low levels in PTB. A comparison analysis between the PLAP+ EV proteome from term and PTB revealed 96 proteins differing significantly (P < 0.05, false discovery rate 1%) across gestation. Bioinformatics analysis of differentially expressed proteins revealed consistent upregulation of inflammatory pathways in both upregulation of epithelial mesenchymal transition pathways at term and downregulation of coagulation/complement activation in preterm. Characterization of the proteomic profile in PLAP+ EVs across gestation demonstrates dramatic changes, which might be used to understand the biological process associated with early parturition and develop biomarkers for predicting high-risk status for PTB.

Exosomes as Messengers between Mother and Fetus in Pregnancy

“…Identification of miRNAs transported by EVs also revealed potential biomarkers for the prediction of pre-term birth [98]. Changes of the protein composition of circulating placental EVs could also be used for the identification of a high-risk status for pre-term birth across gestation [99]. Ninety-six proteins were expressed at significantly different levels, and a bioinformatics analysis revealed their connection to inflammatory pathways, epithelial mesenchymal transition, and coagulation/complement activation.…”

Pregnancy-Related Extracellular Vesicles Revisited

“…In this regard, Menon and colleagues have analyzed placental EVs during pregnancy and at delivery, and found that samples at term associated a group of upregulated genes known to be regulators of epithelial mesenchymal transition (EMT). They hypothesized that, when approaching term, fetal components of the placenta undergo EMT, which leads to an increase in mesenchymal cells susceptible to oxidative stress followed by subsequent inflammation that precipitates delivery [ 112 , 113 ]. Moreover, as a response to increased oxidative stress, it has been demonstrated that phosphorylation of p38 mitogen-activated protein kinase (MAPK), an indicator of term parturition, takes place in amniotic epithelial cell (AEC)-derived exosomes [ 114 ].…”

Syncytiotrophoblast extracellular microvesicles in preeclampsia

“…Therefore, profiling their quantitative and intraexosomal cargoes may reflect conditional stress imposed on the placenta, and possibly on the fetus. In this context, several placental specific proteins have been studied, especially placental alkaline phosphatase (PLAP), syncytin-1, and syncytin-2 [1,[41][42][43][44][45][46][47]. These STEVs are released directly into the maternal circulation, where they may influence the surrounding tissue or may have systemic effects.…”