hFIX production in culture by muscle cells carrying pdLMe4βAhIXm1 and LIXSN. (A) Transient expression of hFIX by muscle cells transfected with pdLMe4βAhIXm1 (▪), LIXSN (•), and pSV2Neo (○). Medium was collected every 24 hours for ELISA and replaced with fresh medium. Arrow indicates the differentiation initiation time point. Vertical bars are standard deviations of triplicated assays. (B) Stable expression of hFIX. (▪) indicates pdLMe4βAhIXm1; (•), LIXSN. Results shown are averages of three independent experiments with standard deviations shown in vertical bars. Signals in ELISA from cells transduced with BAG were subtracted as background from the results. The others are the same as described for transient assay (A).