Wolbachia Promotes an Anti-Angiogenic Response Using an In Vitro Model of Vascular Endothelial Cells in Relation to Heartworm Disease.

Heartworm disease caused by Dirofilaria immitis is a vector-borne zoonotic disease responsible for the infection of mainly domestic dogs and cats, or these are those for which the most data are known. Humans are an accidental host where a benign, asymptomatic pulmonary nodule may originate. Dirofilaria immitis also harbours the endosymbiont bacteria of the genus Wolbachia, which play a role in moulting, embryogenesis, inflammatory pathology, and immune response. When Wolbachia sp. is released into the bloodstream, endothelial and pulmonary damage is exacerbated, further encouraging thrombus formation and pulmonary hypertension, facilitating congestive heart failure and death of the animal. Previous studies have shown that parasite excretory/secretory products are able to activate the pro-angiogenic pathway (formation of new vessels) to facilitate parasite survival. The aim of this study was to analyse the role of Wolbachia sp. and its relationship with the cellular processes and the angiogenic pathway in a model of human endothelial cells in vitro. The use of recombinant Wolbachia Surface Protein (rWSP) showed that its stimulation exerted an anti-angiogenic effect by detecting an increase in the production of VEGFR-1/sFlt1 and sEndoglin and did not affect the production of VEGFR-2 and mEndoglin (pro-angiogenic molecules). Furthermore, it did not stimulate cell proliferation or migration, although it did negatively stimulate the formation of pseudocapillaries, slowing down this process. These cellular processes are directly related to the angiogenic pathway so, with these results, we can conclude that Wolbachia sp. is related to the stimulation of the anti-angiogenic pathway, not facilitating the survival of D. immitis in vascular endothelium.