Optimising the isolation of placental-derived extracellular vesicles from maternal plasma

Background: Extracellular vesicles (EVs) are nanoparticles released by the majority of organs hypothesised to be involved with cell to cell communication. The concentration of EVs in maternal plasma increase over the course of pregnancy, with a 30 fold increase seen by the end of the third trimester. With the majority of these EVs hypothesised to be of placental origin, it is important to develop a method of isolating placental derived EVs from maternal plasma.

Method: Pre-delivery maternal plasma samples were col-lected from 18 pregnancies diagnosed with early-onset FGR (estimated fetal weight <3rd centile at 20+0–26+6 weeks). EVs were isolated using IZON size-exclusion columns. Once concentrated, they were bound to immunomagnetic beads conjugated with placental alkaline phosphatase antibody (PLAP) to seperate those of placental origin from EVs from other maternal organs. The PLAP bound EVs were then lysed, and their cargo analysed using qPCR for mRNA and m i c r oR NA's.

Results: Whilst it was not possible to analyse the mRNA pro-file of these EVs, it was found that microRNAs which have been identified to be produced by the placenta were found in the placental EVs, but not in the maternal EVs.

Conclusions: Whilst this is preliminary findings, it is believed that this method is successful at isolating placental EVs from a pool of total EVs in maternal plasma. Since it is known that the mRNA and microRNA profile of placental tissue changes in pregnancy complications such as FGR, the translation of this method calls further research into whether these changes are also reflected in the cargo of placental derived EVs. This would aid the development of a non-invasive placental biopsy