PB0790 - Procoagulant platelets and thrombus architecture in mouse tail vein bleeding model

Background: Platelets during activation can be divided into two different subpopulations - procoagulant and proaggregate. Physiological role of procoagulant platelets and their real impact to thrombus growth is not clear yet.

Aims: To study in vivo localization of procoagulant platelets in the thrombus structure.

Methods: Mouse venous tail bleeding model (air condition) has been used to form thrombus. After the bleeding had stopped, the tail tip with the formed thrombi was prepared for ultrastructural and morphological study by transmission electron microscopy or fluorescence microscopy.

Results: Photographs of thrombi were obtained in longitudinal and transverse sections to the orientation of the tail.
Procoagulant platelets in electron microscopy were defined as pale balloon-like cells in thrombus mass (according to platelet subpopulation morphology of single activated platelets in suspension). Procoagulant platelets were localized in two areas: next to the junction of thrombus with collagen and on the periphery of the platelet thrombi, predominantly at the side of the fibrin/erythrocyte clot.
The architecture of the thrombus formed by vein cut has a vaulted structure as had been described previously for venous puncture damage by Rhee et.al.
Special platelet-fibrin layer was observed, which is the boundary of structured blood clots.

Conclusion(s): 1) procoagulant platelets had two various specific localizations: next to the collagen, and outer surface of thrombus.
2) there is the same vaulted thrombus structure for vessel’s cut as for venous puncture.
3) special platelet-fibrin layer tightens the thrombus.
This work was supported by the Russian Science Foundation grant 23-75-10120.