Expression of Recombinant Coagulation Factor IX in Human Amniotic Membrane-derived Mesenchymal Stem Cells: A New Strategy to Gene Therapy of Hemophilia B

Background: Hemophilia B is an X-linked hereditary disorder of blood coagulation system which is caused by factor IX (FIX) deficiency. Factor IX is a plasma glycoprotein that participates in the coagulation process leading to the generation of fibrin. Replacement of factor IX with plasma-derived or recombinant factor IX is the conventional treatment for hemophilia B to raise the factor IX level to therapeutic range. Recently, gene therapy has been regarded as a promising approach to treat hemophilia B. This study was aimed to express the factor IX in human amniotic membrane-derived mesenchymal stem cells (hAM-MSCs). Materials and Methods: Human amniotic membrane-derived mesenchymal stem cells were isolated and characterized from amnion membrane. Factor IX from commercially available plasmid was sub-cloned into pcDNA3.1 vector. Recombinant pcDNA3.1-FIX construct was confirmed by PCR, enzymatic digestion and DNA sequencing. Mesenchymal stem cells were transfected with the recombinant vector. Expression of factor IX was determined by RT-PCR, ELISA and its biological activity assay was performed using aPTT. Results: Isolated hAM-MSCs expressed specific mesenchymal stem cells markers and were able to differentiate to osteocytes and adipocytes lineages. hAM-MSCs expressed hrFIX at mRNA and protein level. The maximum amount of hrFIX was 120 ng/ml at 72 hrs after hAM-MSCs transfection. This hrFIX was biologically active (11% activity), formed fibrin clot in aPTT test and caused more than two fold decrease in clotting time. Conclusion: The hAM-MSCs expressing factor IX would be useful for gene therapy of hemophilia B. However further studies are required to prove these finding. Key words: Hemophilia B, amnion membrane, mesenchymal stem cell, factor IX, gene therapy.