Individuals with beta-thalassemia develop progressive systemic iron overload, resulting in high morbidity and mortality. These complications are caused by labile plasma iron, which is taken up by parenchymal cells in a dysregulated manner; in contrast, erythropoiesis depends on transferrin-bound iron uptake via the transferrin receptor. We hypothesized that the ineffective erythropoiesis and anemia observed in beta-thalassemia might be ameliorated by increasing the amount of circulating transferrin. We tested the ability of transferrin injections to modulate iron metabolism and erythropoiesis in Hbb(th1/th1) mice, an experimental model of beta-thalassemia. Injected transferrin reversed or markedly improved the thalassemia phenotype in these mice. Specifically, transferrin injections normalized labile plasma iron concentrations, increased hepcidin expression, normalized red blood cell survival and increased hemoglobin production; this treatment concomitantly decreased reticulocytosis, erythropoietin abundance and splenomegaly. These results indicate that transferrin is a limiting factor contributing to anemia in these mice and suggest that transferrin therapy might be beneficial in human beta-thalassemia.

We report here production and characterization of transgenic mice carrying human LCR-f3s and human LCR-a2 constructs cointegrated in the genome. The original transgenic mice were bred to mice with deletions of mouse pmajor or a genes to increase expression of human globins and reduce mouse globins. These mice were either homozygous for f8major deletion (/3MDD; MD, mouse deletion) or also heterozygous for an a-globin deletion (a MD) and had a normal mean corpuscular Hb (MCH), no anemia, reticulocytosis, a small number of ISCs, and an increased mean corpuscular Hb concentration (MCHC).In ref. 5, we report observations on organ damage under ambient conditions and the induction of hematological and renal abnormalities by hypoxia. A preliminary report of this work has appeared (6).

A line of transgenic mice with two cointegrated transgenes, the human 1s-and a2-globin genes, linked to the 13-globin locus control region was produced and bred with mice carrying a deletion of the mouse p1iW°r-globin gene.In transgenic mice homozygous for the pOdoEr deletion (aHI3S [PMDD]; where aH is human a-globin and MD is mouse deletion), 72.5 ± 2.4% (mean ± SD) of the 1-chains are .3s and the ratio of aH_ to 1s-globin was 0.73. Introduction of a heterozygous mouse a-globin deletion into mice homozygous for the Poor deletion (aHjis[aMDI3MDDJ) resulted in 65.1 ± 8.5% %.s and a human er/P ratio of 0.89 ± 0.2. Sickling occurs in 95% of erythrocytes from aHplS [PMDD] mice after slow deoxygenation. Transmission electron microscopy revealed polymer fiber formation but not fascicles of fiber. Increased organ weight was noted in lung, spleen, and kidney of transgenic mice vs. controls that may be due to hypertrophy or increased blood volume in the lungs and/or increased tissue water content. The hemoglobin content of lung, spleen, and kidney was also elevated in transgenic animals due to trapped hemoglobin and/or increased blood volume. When transgenic and control mice were examined by magnetic resonance imaging at 9.4 tesla, some transgenic animals had enlarged kidneys with prolonged relaxation time, consistent with increased organ weight and water content. The glomerular filtration rate was elevated in transgenic animals, which is characteristic of young sickle cell patients. Furthermore, exposure to hypoxia resulted in signifcantly decreased hematocrit, increased erythrocyte density, and induced a urineconcentrating defect. We conclude that the transgenic mouse line reported here has chronic organ damage and further hematological and organ dysfunction can be induced by hypoxia.The development of several different transgenic mouse models for sickle cell disease (1-7) has the potential ofelucidating the mechanism of vasoocclusion in sickle cell anemia. Sickle cell vasoocclusion is a multifactorial event that involves obstruction of the microcirculation by irreversibly sickled cells (8), nondeformable polymer-filled deoxygenated cells, and adhesion by deformable discocytes capable of contributing to the initiation or aggravation of vasoocclusion (9-11). The time interval or delay time between deoxygenation and the onset ofpolymer formation may play a role in determining both the frequency and severity of vasoocclusion (12).Several organs are particularly susceptible to obstruction and ensuing damage in sickle cell disease. In this paper we will focus on the spleen, the kidneys, and the lungs. In the mouse, the spleen is both the site of erythrocyte (RBC) production and destruction. In sickle cell patients, the spleen is the site of infarction (13), potential sequestration (14), and autospenectomy in the second decade of life. The detailed pathophysiology of vasoocclusion need not be the same in each organ. For example, in some organs, such as the lung and kidney, the response to hypoxia is vasoconstriction...