Transplanting hepatocytes was ineffective, but liver endothelial cells were effective.In the blood, it mainly circulates in a stable 
noncovalent complex with von Willebrand factor. Upon activation by thrombin (factor IIa), it dissociates from the complex to interact with factor IXa in the coagulation cascade. It is a cofactor to factor IXa in the activation of factor X, which, in turn, with its cofactor factor Va, activates more thrombin. Thrombin cleaves fibrinogen into fibrin which polymerizes and crosslinks (using factor XIII) into a blood clot. The factor VIII protein has a half-life of 12 hours in the blood stream when stabilized by the von Willebrand factor. No longer protected by vWF, activated FVIII is proteolytically inactivated in the process (most prominently by activated protein C and factor IXa) and quickly cleared from the blood stream. Factor VIII is not affected by liver disease. In fact, levels usually are elevated in such instances. Medical use
FVIII concentrated from donated blood plasma, or alternatively recombinant FVIIa can be given to hemophiliacs to restore hemostasis. Antibody formation to factor VIII can also be a major concern for patients receiving therapy against bleeding; the incidence of these inhibitors is dependent of various factors, including the factor VIII product itself. Immunostain target
Factor VIII related antigen is used as a target for immunohistochemistry, where endothelial cells, megakaryocytes, platelets and mast cells normally stain positive. Contamination scandal
In the 1980s, some pharmaceutical companies such as Baxter International and Bayer sparked controversy by continuing to sell contaminated factor VIII after new heat-treated versions were available.
Under FDA pressure, unheated product was pulled from US markets, but was sold to Asian, Latin American, and some European countries. The product was tainted with HIV, a concern that had been discussed by Bayer and the U.S. Food and Drug Administration (FDA).In the early 1990s, pharmaceutical companies began to produce recombinant synthesized factor products, which now prevent nearly all forms of disease transmission during replacement therapy. History
Factor VIII  was first discovered in 1937, but it was not until 1979 that its purification by Edward Tuddenham, Frances Rotblat and coworkers led to the molecular identification of the protein. See also
Ralph Kekwick
Frances Rotblat
Edward Shanbrom
Edward Tuddenham
Ryan White

References
Further reading
External links
GeneReviews/NCBI/NIH/UW entry on Hemophilia A
The Coagulation Factor VIII Protein
Factor+VIII at the US National Library of Medicine Medical Subject Headings (MeSH)
Overview of all the structural information available in the PDB for UniProt: P00451 (Human Factor VIII) at the PDBe-KB.