Abstract
Small extracellular vesicles (EVs) are among the most frequently investigated EVs and play major roles in intercellular communication by delivering various cargo molecules to target cells. They could potentially represent an alternative delivery strategy to treat ocular toxoplasmosis, a parasitosis affecting the retinal pigment epithelium (RPE). To date, the uptake of human small EVs by RPE cells has never been reported. In this study, we report on the intracellular uptake of fluorescently labelled human urine and fibroblast-derived small EVs by human RPE cells. In summary, both dye-labelled urinary small EVs and small EVs obtained from fibroblasts stably expressing membrane-bound green fluorescent protein were successfully internalized by RPE cells as revealed by immunohistochemistry. In recipient ARPE19 cells, BODIPY-labelled small EVs were found in close vicinity to the parasite Toxoplasma gondii. Additionally, an ultrastructural method was enabled to distinguish between labelled exogenous and endogenous small EVs within target cells.
Highlights
Ocular toxoplasmosis (OT) is the most frequent cause of retinochoroiditis worldwide, and it can lead to partial or complete loss of vision
Urinary small extracellular vesicles (EVs) were isolated from human morning urine using an ultrafiltration (UF) method consisting of a combination of low-speed centrifugation, filtration, and concentration
Transmission electron microscopy (TEM) corroborated the spherical cup shape, double membranes, and size range consistent with membrane-bound vesicles, which were identified as small EVs based on size (Figure 1A)
Summary
Ocular toxoplasmosis (OT) is the most frequent cause of retinochoroiditis worldwide, and it can lead to partial or complete loss of vision. Parasites are able to persist within host cells and repeated infections may occur, making treatment difficult. Novel approaches such as the use of nanomedicine to deliver antiparasitic drugs might pave the way to a new anti-parasitic therapy [1]. Liposomes, solid lipid nanoparticles, and polymer nanoparticles are under investigation as potential vehicles for antiparasitic drug delivery. The first results are encouraging, and they have prompted us to investigate small extracellular vesicles (EVs) as yet another previously neglected drug delivery taxi. The use of small EVs aims at improving absorption and targeting and at reducing systemic drug concentrations by means of a drug carrier that is safe, inexpensive and reliable
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