Abstract
Platelets are small anucleate blood cells involved in haemostasis. Platelet activation, caused by agonists such as thrombin or by contact with the extracellular matrix, leads to platelet adhesion, aggregation, and coagulation. Activated platelets undergo shape changes, adhere, and spread at the site of injury to form a blood clot. We investigated the morphology and morphological dynamics of human platelets after complete spreading using fast scanning ion conductance microscopy (SICM). In contrast to unstimulated platelets, thrombin-stimulated platelets showed increased morphological activity after spreading and exhibited dynamic morphological changes in the form of wave-like movements of the lamellipodium and dynamic protrusions on the platelet body. The increase in morphological activity was dependent on thrombin concentration. No increase in activity was observed following exposure to other activation agonists or during contact-induced activation. Inhibition of actin polymerization and inhibition of dynein significantly decreased the activity of thrombin-stimulated platelets. Our data suggest that these morphological dynamics after spreading are thrombin-specific and might play a role in coagulation and blood clot formation.
Highlights
Platelets are small cell fragments circulating down the vascular branch[1]
In this study we investigated the influence of different activation agonists on the morphology of spread human platelets
We visualized and quantified morphological dynamics of spread platelets with high spatial and temporal resolution using scanning ion conductance microscopy (SICM)[22], a non-contact scanning probe microscopy technique excellently suited for imaging the topography of living cells[23,24,25]
Summary
Upon endothelial injury of the blood vessel wall, they become exposed to the subendothelial extracellular matrix, which leads to platelet activation and adhesion[2,3,4,5]. SICM has been used for imaging living platelets[28, 29], for investigating the shape[30] and the spreading process[31] of platelets, and for measuring their mechanical properties during activation[32]. We found that thrombin-stimulated platelets exhibit highly dynamic changes in their morphology after completing the spreading process. These dynamics were dependent on thrombin concentration and did not occur in platelets stimulated with other agonists or in platelets activated by contact with various substrates. Our data suggest that these dynamics in spread platelets are thrombin-specific and might affect coagulation when high thrombin concentrations occur during blood clot formation
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