Publication Date:
2007-11-16
Description:
Ectopic delivery of coagulation factor VIII (FVIII) to megakaryocytes (Mk) represents a viable approach for localized tenase generation by effectively concentrating the FVIIIa/FIXa enzyme-cofactor complex onto the negatively-charged phospholipid surface of activated platelets. While phenotypic correction has been demonstrated using hemophilia A (FVIII−/−) murine models in vivo, the activation state of platelet FVIII (pFVIII), optimal promoter choice, and phenotypic correction in the setting of a thrombocytotic stimulus remain unestablished. Preliminary microarray experiments using human platelets (N=5) demonstrated that the Mk-specific platelet factor 4 (PF4) transcripts were among the most abundant, prompting use of the 1.1 Kb PF4 promoter for Mk/platelet-restricted expression of human B-domain-deleted (hBDD) FVIII within the background of an exon 17-deleted mouse model of hemophilia A (PF4/hBDD/FVIII−/−). A chromogenic tenase assay using gel-filtered platelets from PF4/hBDD/FVIII−/− mice confirmed the presence of functional FVIII equivalent to 73 mU·1x109 platelets·mL−1 (N = 10 mice). In contrast, FVIII was not detectable in PF4/hBDD/FVIII−/− plasma (assay sensitivity
Print ISSN:
0006-4971
Electronic ISSN:
1528-0020
Topics:
Biology
,
Medicine
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