Retroviral vector-modified bone marrow stromal cells secrete biologically active factor IX in vitro and transiently deliver therapeutic levels of human factor IX to the plasma of dogs after reinfusion.

ABSTRACT Canine bone marrow stromal cells (BMSCs), transduced ex vivo with retroviral vectors, expressed and secreted biologically active human and canine coagulation factor IX (hFIX and cFIX) in vitro, and on autologous reinfusion expressed hFIX into the circulation of normal (nonhemophiliac) dogs. Human FIX, when expressed in vitro by BMSCs of two dogs at 1.22 and 1.39 μg/106 cells/24 hr in medium supplemented with vitamin K, respectively, exhibited 28.1 and 27.3% normal biological activity as determined on the basis of a one-stage clotting assay. BMSCs of two additional dogs expressed 1.54 and 4.81 μg of cFIX/106 cells/24 hr in vitamin K-supplemented medium and the expressed cFIX possessed 58.4 and 32.9% normal activity, respectively. Between 2.33 and 3.35 × 108 transduced BMSCs, expressing 1.22 and 2.61 μg of hFIX/106 cells/24 hr or 3.24 and 7.82 μg of cFIX/106 cells/24 hr were reintroduced into the four donor dogs by intravenous infusion. Human FIX was detected in plasma for 7 or 12 days after BMSC r...