Transgenic Human α-Hemoglobin Stabilizing Protein Could Partially Relieve βIVS-2-654-Thalassemia Syndrome in Model Mice

Abstract

Beta-thalassemia is an anemia caused by a relative excess of alpha-hemoglobin (alphaHb) due to absent or reduced beta-hemoglobin (betaHb) synthesis. In this study, we explore whether the introduction of alpha-hemoglobin stabilizing protein (AHSP), a chaperone protein for proper folding and stabilization of free alphaHb in red blood cells, thus aiding hemoglobin A (HbA) assembly, could relieve the pathogenic state of red blood cells in beta-thalassemia. For that, a human ahsp vector was constructed to generate transgenic human ahsp mice in a model of beta(IVS-2-654)-thalassemia by microinjecting the vector into fertilized eggs, resulting in the production of double heterozygous mice (h-ahsp(+)/beta(IVS-2-654+)). Real-time quantitative RT-PCR and Western blot analysis confirmed AHSP expression in three h-ahsp(+)/beta(IVS-2-654+) mice. Hematologic determination showed an improvement in the red blood cell indices of these h-ahsp(+)/beta(IVS-2-654+) mice. The red blood cell count and hemoglobin level were elevated to various extents as compared with their diseased siblings. A dramatic reduction in anisocytosis in the peripheral blood of h-ahsp(+)/beta(IVS-2-654+) mice was observed (16.2 +/- 4.6 vs. 30.0 +/- 5.2%). Few erythroid precursors appeared in the liver sinusoids of h-ahsp(+)/beta(IVS-2-654+) mice. Splenomegaly with extramedullary hematopoiesis was also ameliorated. Significantly, serum iron concentration was remarkably reduced as compared with that of h-ahsp(-)/beta(IVS-2-654+) mice (43.2 +/- 14.9 vs. 82.4 +/- 12.9 microM), and iron deposition in the liver was decreased in h-ahsp(+)/beta(IVS-2-654+) mice. All these results suggested amelioration of the anemia phenotype in h-ahsp(+)/beta(IVS-2-654+) mice after introduction of the ahsp gene. We therefore propose that an ahsp transgene could provide an adjuvant method for gene therapy of beta-thalassemia.