In vitro characterization of genetically modified MSCs. SDS-PAGE analysis of MSC-derived (lanes 1-2) and BHK-M–derived (lanes 3-4) BDD porcine fVIII. Samples in lanes 2 and 4 were pretreated with thrombin to demonstrate proteolytic activation. Single chain (SC), heavy chain (HC), light chain (LC), and A3-C1-C2, A1, and A2 polypeptides are labeled. Proteins were visualized by silver stain. The positions of the molecular weight (MW) standards (in kDa) are shown to the right of the gel image.