Blood outgrowth endothelial cells as a vehicle for transgene expression of hepatocyte-secreted proteins via sleeping beauty

The therapeutic use of autologous cells with the capacity for extensive in vitro expansion and manipulation prior to host administration has been an area of significant investigation over the last decade. Blood outgrowth endothelial cells (BOECs) are derived from the circulation and exhibit proliferative growth, in vivo engraftment, and survival characteristics for long-term expression of endogenously secreted proteins, such as factor VIII (FVIII). The authors describe a modified method for the isolation, culture, and expansion of these cells that is readily accomplished using standard laboratory methods. Using a commercially available transfection reagent, ∼30% of these primary cells can be routinely transfected with the nonviral Sleeping Beauty transposon for long-term, stable transgene expression. Moreover, the results indicate that these cells have the ability to secrete functionally active proteins that are synthesized endogenously by hepatocytes and require post-translational modification including α1-antitrypsin and clotting factors VII and IX. This, coupled with their notably long half-life of years, suggests that these cells may provide an appropriate vehicle for secretion of a variety of proteins produced by different cell types in vivo. Thus, BOECs have the potential to provide clinically relevant secreted proteins for diseases other than those of endothelial origin.