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Editorials
mentation relates to platelet clearance, or what percentage of activated platelets undergo fragmentation in vivo. It is widely accepted that activated platelets are quickly cleared from the body, but the actual molecular mechanism has been elusive. Recent work on platelet clearance has focused on investigating how platelets expose a ‘clear-me’ signal, perhaps through desialylation of platelet surface proteins.11 The occurrence of platelet fragmentation following activa- tion has raised the possibility that in some cases the reduc- tion in platelet counts, which has been uniformly used as the indicator of platelet clearance, may be attributed to some extent to platelet fragmentation. It remains to be seen whether certain receptors responsible for platelet clearance can also recognize and clear platelet fragments.
If this fragmentation can be observed and tracked in vivo, perhaps the question of where fragmented platelets go after activation can be answered. A recent publication by Tomaiuolo et al.12 included high resolution images of hemo- static plugs in response to a puncture in the jugular vein. What can be gleaned from these images is the notable pres- ence of small platelet fragments in both the intravascular and extravascular boundaries of the injury site. Determining the roles that these fragments play in hemo- static plug formation and/or thrombus formation would be crucial to a complete understanding of in vivo platelet plug formation. Potentially, this mechanism could also be a phar- macological target to reduce thrombus formation or aid in thrombolysis in pathological conditions. This exciting find- ing may point to a novel mechanism of platelet behavior and has major implications for thrombus dissolution and platelet clearance in general.
Acknowledgments
This work was supported in part by National Institutes of Health grant HL082808.
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