Pharmacokinetic studies in WT and Hbb^th3/+ mouse models. Wild type (WT) and β-thalassemic (Hbb^th3/+) animals were implanted with murine primary dermal fibroblasts (Fib) overexpressing Epo. Three groups were generated for each genotype (1 × 10⁵, 5 × 10⁵, and 1 × 10⁶ transduced cells). Increased expression of Epo leads to significant increased Hb levels in both WT (A) and Hbb^th3/+ (B) mice. As expected, enhanced erythropoiesis was also associated with splenomegaly in WT (C) and worsening of it in β-thalassemic animals (D). Dotted red line indicates mean values for untreated WT mice. Dashed black lines indicates mean values for untreated Hbb^th3/+ mice. Bars represent SD. Asterisks refer to statistically significant differences (****P ≤ .001; ***P ≤ .005; **P ≤ .01; *P ≤ .05).