Stanching the Flow

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Science  25 Feb 2005:
Vol. 307, Issue 5713, pp. 1171
DOI: 10.1126/science.307.5713.1171b

Hemophilia B is an X-linked genetic disorder caused by decreased levels of factor IX, which functions as part of the blood-clotting cascade. Deficiencies in blood clotting result in uncontrolled bleeding in response to even the slightest trauma. Another problem is bleeding into joints, where subsequent inflammation contributes to deterioration of the joint. Injecting factor IX serves as treatment to stop bleeding, and restoring a fraction of the normal amount can make a difference; however, factor IX does not survive for long in the bloodstream.

Fair et al. have shown in mice how embryonic stem cells can be used as a therapy for factor IX deficiency, an approach that would avoid the need for repeated injections and could supply a steady stream of factor IX. In these experiments, the mice carried a mutation in their factor IX gene, and the embryonic stem cells were derived from mice with a normal factor IX gene. In vitro culture conditions were defined to direct the embryonic stem cells to differentiate into cells with features of endodermal precursors. These putative endodermal precursors were then injected into the livers of factor IX-deficient mice. Mice treated in this way showed factor IX expression and improved long-term survival. Engraftment of the differentiated embryonic stem cells did not require injury or hepatectomy. The results provide a promising step toward a cell-based therapy for factor IX deficiency. — PJH

Proc. Natl. Acad. Sci. U.S.A. 102, 2958 (2005).

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