In vivo Analyse der zellulären und molekularen Mechanismen der arteriellen und venösen Thrombose in der Maus

In vivo analysis of the cellular and molecular mechanisms in
arterial and venous thrombosis in a mouse model The detailed
molecular and cellular mechanisms that lead to arterial and venous
thrombosis and trigger heart attack and stroke, as well as
pulmonary emboli in the case of venous thrombosis, are not yet
fully understood. Therefore in the present study, arterial as well
as venous thrombi were created in a mouse model in order to analyse
the cellular and molecular processes that contribute to arterial
and venous thrombosis in vivo. Two thrombosis mouse models (one
arterial and one venous) were established. In contrast to existing
models, these models include the diverse formation of arterial
(endothelial damage) and venous thrombi (stasis with intact
endothelium). In addition to histological and electron microscopic
analyses intravital microscopy was performed in order to analyse
the cellular and molecular phenomena in venous and arterial
thrombosis. Wild type animals (C57BL/6J) were compared to
genetically modified animals in order to determine the impact of
platelets, leukocytes, fibrin and microparticles in both forms of
thrombosis. Mice with defective platelet adhesion/aggregation
(glycoprotein [GP]IIb-/-) as well as defective leukocyte adhesion
(P-Selectin-/-) were used. In addition to investigate the role of
the coagulation cascade protein “tissue factor” (TF), the primary
initiator of the coagulation cascade, we took advantage of “TF”
deficient mice (Low TF, HCV 100). By means of these newly
established models, we showed that in arterial thrombosis platelets
adhere rapidly, whereas few leukocytes are recruited into the
thrombus. In contrast leukocyte adhesion is the prominent initial
phenomena in venous thrombosis. The loss of platelet P-Selectin in
arterial thrombosis reduced the stability of the thrombus, but had
no effect on platelet adhesion and aggregation per se. In contrast
the loss of GPIIb led to a complete lack of platelet adhesion and
aggregation in arterial thrombosis. In venous thrombosis,
P-Selectin-/- mice showed a massive reduction in leukocyte
accumulation. The reduced leukocyte adhesion was accompanied by a
reduction of the thrombus size 48 hours after stasis. However
platelets also appear to contribute to venous thrombosis. While,
initially very few platelets adhered to the endothelial cell layer,
the loss of GPIIb did reduce thrombus size. Besides cellular
mechanisms, the expression of “TF” is essential for venous
thrombosis. Accordingly, low TF mice showed a dramatically reduced
thrombus size, whereas neither platelet adhesion nor leukocyte
adhesion initially is affected by the “TF” defect. Altogether,
platelets appear to be the major trigger of arterial thrombosis,
whereas venous thrombosis strictly requires the contribution of
leukocytes. Together the present study for the first time
strikingly points out the diverse cellular and molecular mechanisms
that contribute to arterial and venous thrombosis in vivo.
Consequently distinct new future strategies for prevention and
therapy of both arterial and venous thrombosis are suggested.