Erythropoietin gene transfer by mCD105-LV. (A) Immunodeficient NOD/SCID mice (N = 5) or (B) immunocompetent C57Bl/6 mice (N = 3) were injected once intravenously with 3 × 10⁶ transducing units mCD105-LV^Epo (solid symbols) or medium (open symbols, dotted lines) on day 0. Two days before tail-vein injection, blood samples were taken and hematological baseline levels were determined. Erythropoietin levels in blood (left panel) as well as hematocrit values (right panel) were determined regularly at the indicated time points. **P < .01; ***P < .001; ****P < .0001, as determined by unpaired 2-sided t tests.