Poster Presentation First Malaria World Congress 2018

The role of extracellular vesicles in the modulation of endothelial junctions in an in vitro model of cerebral malaria (#378)

Benjamin C Sealy 1 , Iris Cheng 1 , Valery Combes 1
  1. University of Technology, Sydney, Ultimo, NSW, Australia

Aims & Methods: Extracellular Vesicles (EVs) are functional sub-cellular fragments capable of transferring surface markers, proteins, mRNAs and miRNAs to cells that internalise them. Recent studies by our group and others have suggested that EVs participate to the development of the vascular lesion during Cerebral Malaria (CM). Using an in vitro Blood-Brain barrier (BBB) model, we aim to investigate the affects EVs have on the modulation of endothelial integrity by measuring the expression of junctional protein, VE-cadherin and the activation status of the endothelial monolayer. EVs released by both normal and Plasmodium falciparum-parasitised red blood cells (NRBCs and PRBCs) after 48h culture were purified from the supernatant by sequential centrifugation.

Primary human brain endothelial cells (HBECs) were incubated with NRBCs, PRBCs, nRBC- and PRBCs-EVs (nEVs, pEVs), or a combination of them. Modulation in VE-cadherin expression both local and in relation to the presence of PRBCs and/or EVs was assessed by a combination of high-content, high-resolution and OMX super-resolution microscopy. Expression of cell adhesion molecules (CAMs) was measured by flow cytometry.

Results: Quantitative image analysis showed that nRBC, and both nEVs and pEVs triggered up-regulation of VE-cadherin expression, whereas PRBC and PRBC-Mix conditions resulted in a significant down-regulation. We also observed that p-EVs were taken up by HBEC at twice the rate of n-EVs and resulted in an inverse correlation between p-EV internalisation and VE-cadherin expression. Expression of CAMs was increased in the presence of PRBCs and further increased with PRBC-Mix.

Conclusion: These results suggest that interactions between EVs and their cells of origin do not always trigger the same cellular response in their target cell. Therefore, the combined presence of both EVs and cells may either potentiate or compensate each other effects. Further studies are needed to determine which molecular pathways are involved in the changes observed.