Engrafted mice demonstrated a phenotypic cure of SCD.

Peripheral blood smear from representative untreated (A) and engrafted (B) animals, prepared under ambient air. Arrows point to representative irreversibly sickled cells in the untreated blood. Engrafted animals have a normal peripheral smear. Original magnification, × 250. (C) Hematologic parameters are normalized in engrafted mice. Normalization of hematologic parameters was present within 1 month after transplantation and was stable for the entire experimental period (> 150 days). Shown are the mean ± SEM for C57BL/6 controls (n = 6, ░), nonengrafted mice (n = 4, ▪), and engrafted mice (n = 7, ■) in a representative experiment performed 3 months after transplantation. Hb indicates hemoglobin; Hct, hematocrit; Retic, thiazole⁺ reticulocyte percent; WBC, white blood cell count. (D) Engrafted mice have a normal RBC half-life. Peripheral blood was biotinylated at time 0, and the decay of biotinylation in RBCs (identified as Ter-119⁺, CD45⁻, biotinylated cells) was monitored by flow cytometry. Untreated sickle animals (▪) had an exceedingly short RBC half-life, while engrafted animals (■) had an RBC half-life that was indistinguishable from normal C57BL/6 controls (▴). These data represent the average of 2 animals that were biotinylated 3 months after transplantation. (E) The engrafted RBC population is healthy as determined by normalization of the percentage of transferrin⁺ stress reticulocytes, PS exposure as measured by annexin V binding, and scramblase activity as measured by NBD-PC internalization. C57BL/6 control (░, n = 6), nonengrafted (▪, n = 4), and engrafted (■, n = 7) animals were analyzed. Shown are the mean ± SEM of animals analyzed 3 months after transplantation. Normalization of RBC parameters in engrafted animals occurred within 1 month after transplantation and was stable for the entire observation period (> 150 days).