| Stem cells are the group of cells owning the self-renewal ability and multiple directional differentiation potential. Stem cells can sustain their population by cell division without injuring their characteristics. Meanwhile, they can differentiate into various types of cells of tissues and organs under specific microenvironment. Embryonic stem cells (ESCs) are derived from the inner cell mass (ICM) of the blastocysts. Embryonic stem cells have the potential to self-renew and give rise to any of the hundreds of cell types in the body, raising exciting new prospects for biomedical research and for regenerative medicine. Many of the diseases that place the greatest burden on whole society are, at their root, the diseases of cellular deficiency. Heart failure, diabetes, hematological disorders, neurodegenerative disorders, and kidney failure all result from the absence of one or more critical populations of cells that the body is unable to replace. However, the extreme shortage of embryonic stem cells sources and the immunological rejection caused by individual specificity after transplantation greatly limit the application of embryonic stem cells in tissue substitute and organ transplantation. To overcome such obstacles, people are trying to induce differentiated somatic cells back to the pluripotency state by reprogramming. So far, three ways of reprogramming are mostly adopted:nuclear transfer, cell fusion and defined factors induced reprogramming.Defined factor induced reprogramming is to reprogram somatic cells to the pluripotent state by over-expression of specific key transcriptional factors, such as OCT4, SOX2, and KLF4 ect. The pluripotent cells produced by this technology are named induced pluripotent stem cells (iPSCs). The generation of iPS cells is not only helpful in reprogramming mechanism research, but also of great medical interests. Additionally, the derivation of patient-specific iPS cells provides stable sources for the treatment of genetic and degenerative diseases. Moreover, combined with classic gene-targeting technique, iPS technology provides new ways for such diseases treatments.β-thalassemia is a kind of hemolytic genetic disease caused by disequilibrium betweenα-chain and non-α-chain due to the reduction or shortage ofβ-globin synthesis. In clinical,β-thalassemia can be divided into four types, that is major, minor, middletype, and HPFH.β-thalassemia major, also called Cooley's anemia, is caused by either a point mutation or the deletion of several nucleotides in theβ-globin gene, and threatens the lives of millions of people in China. In this study, we tried to build a genetic disease treatment model based on stem cell and reprogramming techniques. Usingβ-thalassemia as the disease model, we derived patient-specific iPS cells from aβ-41/42 homologues adult patient through defined factors induced reprogramming, and characterized the pluripotency property of the cells. Moreover, we corrected the mutation of p-globin in these patient-specific iPS cells by homologous recombination. Finally, we performed hematopoietic differentation on the patient-specific iPS cells and gene-corrected iPS cells both in vitro and in vivo. Although the in vitro differentiation results showed no evident differences between the two types of iPS cells, in vivo transplantation results distinct phenotypes. In SCID mice transplanted with hematopoietic progenitors derived from gene-corrected iPS cells, both levels of hemoglobin and red blood cells in peripheral blood recovered up to the normal levels rapidly after irradiation. Moreover, human β-globins could be detected two months after transplantation. However, opposite results were observed in the SCID mice transplanted with hematopoietic progenitors derived from patient-specific iPS cells. In summary, Our study provides strong evidence that iPSCs generated from a patient with a genetic disease can be corrected by homologous recombination and that the corrected iPSCs have potential clinical uses.
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