Extracellular vesicles from human saliva promote hemostasis by delivering coagulant tissue factor to activated platelets.

Essentials Human salivary extracellular vesicles (EVs) expose coagulant tissue factor (TF). Salivary EVs expose CD24, a ligand of P-selectin. CD24 and coagulant TF co-localize on salivary EVs. TF+ /CD24+ salivary EVs bind to activated platelets and trigger coagulation. SUMMARY: Background Extracellular vesicles (EVs) from human saliva expose coagulant tissue factor (TF). Whether such TF-exposing EVs contribute to hemostasis, however, is unknown. Recently, in a mice model, tumor cell-derived EVs were shown to deliver coagulant TF to activated platelets at a site of vascular injury via interaction between P-selectin glycoprotein ligand-1 (PSGL-1) and P-selectin. Objectives We hypothesized that salivary EVs may deliver coagulant TF to activated platelets via interaction with P-selectin. Methods We investigated the presence of two ligands of P-selectin on salivary EVs, PSGL-1 and CD24. Results Salivary EVs expose CD24 but PSGL-1 was not detected. Immune depletion of CD24-exposing EVs completely abolished the TF-dependent coagulant activity of cell-free saliva, showing that coagulant TF and CD24 co-localize on salivary EVs. In a whole blood perfusion model, salivary EVs accumulated at the surface of activated platelets and promoted fibrin generation, which was abolished by an inhibitory antibody against human CD24. Conclusions A subset of EVs in human saliva expose coagulant TF and CD24, a ligand of P-selectin, suggesting that such EVs may facilitate hemostasis at a site of skin injury where the wound is licked in a reflex action.

Recent developments in the nomenclature, presence, isolation, detection and clinical impact of extracellular vesicles.

The research field of extracellular vesicles (EVs), such as microparticles and exosomes, is growing exponentially. The goal of this review is to provide an overview of recent developments relevant to the readers of the Journal of Thrombosis and Haemostasis. We will discuss nomenclature, the presence of EVs in fluids, methods of isolation and detection, and emerging clinical implications. Although research on EVs has been performed within the ISTH for over a decade, most of the recent research on EVs has been brought together by the International Society on Extracellular Vesicles (ISEV). To achieve an overview of recent developments, the information provided in this review comes not only from publications, but also from latest meetings of the ISEV (April 2015, Washington, DC, USA), the International Society on Advancement of Cytometry (June 2015, Glasgow, UK), and the ISTH (June 2015, Toronto, Canada).

Light-induced migration behaviour of Daphnia modified by food and predator kairomones.

Lake-dwelling waterfleas, Daphnia, often face a dilemma. Food availability is highest, near the water surface, but predation by visually hunting predators is also most severe. Swimming downward at dawn reduces predation risk, but food availability and temperature also decrease with depth. We tested whether Daphnia process information derived from food and predator presence to estimate the costs and benefits of migration, and to determine when it pays to swim down. We studied downward swimming of D. galeataxhyalina in response to stepwise accelerations of relative increases in the intensity of light at several food and fish kairomone concentrations. Both had a modifying, additive, although independent effect. We studied in six clones the clonal differences of this environmentally induced plasticity of photobehaviour. These clones were caught at two depths at noon during a period of vertical migration in Lake Maarsseveen (the Netherlands), and so presumably differed in vertical migration behaviour. Two clones, one from the epilimnion and one from the hypolimnion, showed a particularly significant difference in migration behaviour. Copyright 1998 The Association for the Study of Animal Behaviour.