Expression of factor VIII by murine liver sinusoidal endothelial cells.

Factor VIII (fVIII) is the procoagulant plasma glycoprotein that is missing or decreased in hemophilia A. The cellular origin of fVIII synthesis is controversial. Liver transplantation cures hemophilia A, demonstrating that the liver is a major site of fVIII synthesis. We detected fVIII mRNA in purified populations of murine liver sinusoidal endothelial cells (LSECs) and hepatocytes, but not Kupffer cells. LSECs and hepatocytes contained comparable numbers of fVIII mRNA (40 and 70 transcripts per cell, respectively) by quantitative competitive reverse transcriptase-polymerase chain reaction analysis. There was not detectable mRNA for factor IX, a hepatocyte marker, in the LSEC preparation, nor was there detectable mRNA for von Willebrand factor, an endothelial cell marker, in the hepatocyte preparation. This excludes the possibility that detectable fVIII mRNA is due to cross-contamination in the hepatocyte or LSEC preparations. Primary cultures of LSECs were established in which fVIII mRNA levels were indistinguishable from purified LSECs. LSECs secreted active fVIII into the culture medium. This finding represents the first demonstration of homologous expression of fVIII mRNA and protein in cell culture and should facilitate studies of fVIII gene regulation. Additionally, LSECs potentially are targets for a fVIII transgene during gene therapy of hemophilia A.