Assessment of platelet function in horses: ultrastructure, flow cytometry, and perfusion techniques.

This study explores the functionality and activation of platelets in horses using ultrastructural examination, flow cytometry, and perfusion techniques. The research mainly aims at understanding horse blood clotting mechanisms via these methods.

Ultrastructural Examination

• Through this technique, it was observed that under both resting and activated conditions, equine platelets lack a properly formed open canalicular system, which is the communication system within the platelet that plays a role in coagulation and combatting disease invasion.
• It was found that the release of granule contents, which are charged with promoting coagulation and inflammation, in horses occurs through the fusing of adjacent granule membranes, which end up connecting to the external membranes. This is different from the open canalicular system in humans.

Flow cytometry

• The use of flow cytometry led to the discovery of changes in the binding of antibodies to major platelet glycoproteins (GPIIb-IIIa, GPIV, and GPIb) and activation dependent antigens (like P-selectin and the lysosomal integral membrane protein, LIMP).
• Notably, there was a twofold increase in the binding of GPIIb-IIIa and GPIV antibodies post-activation while the binding of antibodies against P-selectin and LIMP moderately increased.
• Annexin V, an indicator of platelet activation response, also increased moderately after activation.

Perfusion Techniques

• Perfusion experiments helped to evaluate the platelet function in response to injury, particularly how they interact with damaged subendothelium (the thin layer of cells lining the interior of blood vessels) in horses.
• It was observed that horse platelets react more strongly to subendothelium, as compared to human platelets, thus suggesting higher efficiency.
• However, when blood was treated with a low molecular weight heparin (a type of anticoagulant), a serious decrease in platelet interaction was noted.

Conclusions

• Despite some differences between human and equine platelet function, the study concluded that techniques used to assess human platelet function could potentially be valid for evaluating equine platelets too.
• These findings contribute to the body of knowledge about horse platelet functioning and might have implications for better understanding and treating conditions related to blood clotting and coagulation in horses.