Fragments of cells in the blood known as plateletswhich form blood clots and assist in wound healinghave internal clocks that act like ticking time bombs, predetermining their death from the moment they are born, according to a new study in the March 23 issue of the journal Cell, published by Cell Press.

The researchers said that the findings could have profound implications for the diagnosis and treatment of platelet disorders. Perhaps even more importantly, they said the discovery suggests that chemical treatments that effectively set those clocks back might increase the shelf life of donated blood platelets, which expire after just five days under the storage conditions now required.

The researchers discovered that platelets characteristically short life span, which for humans is 10 days, is set by the amount of a prosurvival protein they contain. As that protein dwindles, its cellular nemesis takes over, causing the specialized clotting cells to commit a programmed form of suicide called apoptosis.

We found that platelets undergo really classical apoptosis, said David Huang of The Walter and Eliza Hall Institute of Medical Research in Australia. Its surprising in many ways because platelets are an unusual cell type that lacks a nucleus. We didnt know what was controlling their life span. Cell nuclei contain the genetic instructions that ultimately direct the activities of other kinds of cells.

The finding has a whole list of potential implications, added study collaborator Benjamin Kile, also of The Walter and Eliza Hall Institute of Medical Research. For us, probably the most important is the possibility for extending platelet life span in blood banks. Such an extension might be achieved by increasing levels of the prosurvival protein, called Bcl-xL, or by blocking its rival death protein, Bak.

If the platelet storage time could be extended from five to eight or 10 days, it would make a lot of difference for
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Contact: Erin Doonan
edoonan@cell.com
617-397-2802
Cell Press
22-Mar-2007