In vivo imaging of the buccal mucosa shows loss of the endothelial glycocalyx and perivascular hemorrhages in pediatric Plasmodium falciparum malaria

Severe malaria is mostly caused by Plasmodium falciparum resulting in considerable, systemic inflammation and pronounced endothelial activation. The endothelium forms an interface between blood and tissue and vasculopathy has previously been linked with malaria severity. We studied to what extent the endothelial glycocalyx that normally maintains endothelial function is involved in falciparum malaria pathogenesis by using incident dark field imaging in the buccal mucosa. This enabled calculation of the perfused boundary region, which indicates to what extent erythrocytes can permeate into the endothelial glycocalyx. The perfused boundary region was significantly increased in severe malaria patients and mirrored by an increase of soluble glycocalyx components in plasma. This is suggestive of a substantial endothelial glycocalyx loss. Patients with severe malaria had significantly higher plasma levels of sulfated glycosaminoglycans than patients with uncomplicated malaria, whereas other measured glycocalyx markers were raised to comparable extent in both groups. In severe malaria, plasma levels of the glycosaminoglycan hyaluronic acid were positively correlated with perfused boundary region in the buccal cavity. Plasma hyaluronic acid and heparan sulfate were particularly high in severe malaria patients with low Blantyre Coma Score suggesting involvement in its pathogenesis. In vivo imaging also detected perivascular hemorrhages and sequestering late-stage parasites. In line with this, plasma angiopoietin-1 was decreased while angiopoietin-2 was increased suggesting vascular instability. Density of hemorrhages correlated negatively with plasma levels of angiopoietin-1. Our findings indicate that, similar to experimental malaria, loss of endothelial glycocalyx is associated with vascular dysfunction in human malaria and related to severity.