Platelet-derived extracellular vesicles expressing phosphatidyl serine associate with benign and malignant neoplasia and regional metastasis in dogs: a study of 113 dogs

Objective: To examine the concentration of platelet-derived extracellular vesicles (PEVs) and procoagulant PEVs in a population of dogs with different types of neoplasia and varying stages of disease. Methods: In this observational cross-sectional study, platelets and PEVs were obtained from dogs with neoplasia. Platelet-derived extracellular vesicle concentrations and expression of phosphatidyl serine (PS) as a marker of procoagulant potential were analyzed by use of flow cytometry. Results: Samples were obtained from 113 dogs with benign (n = 33) or malignant (80) neoplasia as well as from 15 healthy dogs. The overall PEV concentration did not differ between the groups. The concentration of PS-positive (PS+) PEVs was significantly higher for both benign (median, 4.4 X 103 PEVs/µL; IQR, 2.9 to 7.0) and malignant neoplasia (median, 4.4 X 103 PEVs/µL; IQR, 2.8 to 6.8) compared to the group of healthy dogs (2.1 X 103 PEVs/µL; IQR, 1.4 to 4.6). This was especially the case for dogs with regional metastatic disease, which, on average, had a 5 X 103 PEVs/μL higher PS+ PEV concentration compared to other groups (95% CI, 0.6 X 103 to 8.6 X 103 PEVs). The platelet expression of PS did not differ between the groups. Conclusions: Dogs with neoplasia had higher concentrations of PS+ PEVs than healthy dogs but not higher overall PEV concentrations. Clinical Relevance: The findings in this study could indicate that the concentration of PS+ PEVs plays a role in both benign and malignant neoplasia, and their relationship with regional metastatic disease needs further evaluation.