Factors affecting transgene expression in rHIV-pWPT-EF1-a-GFP-W vector modified MSCs. (A) Significant dose response (*p < 0.05 vs. MOI0) with increasing MOI (1-100) following rHIV-pWPT-EF1-a-GFP-W transduction of rMSC. (B) Effect of rMSC passage number on lentiviral vector transduction efficiency (*p < 0.05 vs. P1 cells). (C) Comparison of lentiviral vector transduction of human and rat MSCs. (D) Effect of cryopreservation on GFP transgene expression levels. Data are shown as mean ±SD (n = 3) of three independent experiments.