WASHINGTON — Researchers for the first time have produced human blood cells from embryonic stem cells.
Primitive human blood cells, known as hematopoietic precursor cells, were produced from human embryonic stem cells by researchers at the University of Wisconsin, led by James A. Thomson.
Similar work has been done in mice, but this is the first time human blood cells have been developed from embryonic stem cells, said Dan S. Kaufman, one of the authors of the study appearing in Tuesday's issue of Proceedings of the National Academy of Sciences.
Development of these cells holds promise, but Kaufman stressed that it will take years before they can be developed to the point of use in people. "I don't want to raise any false hope," he said.
Embryonic stem cells are the basic building blocks for the 260 or so cell types in the body. During development, stem cells transform into heart, muscle, brain, skin or other tissue.
Researchers hope that by guiding this transformation in the laboratory, they can coax stem cells to make new cells for transfusion and other therapies.
Embryonic stem cells have become the focus of debate because they are derived from blastocysts, one of the earliest stages of human embryos before they become implanted. Opponents of the research argue that it destroys a human life.
President Bush has ordered that federal funds be made available only for research on cell lines that were in existence on Aug. 9, restricting the establishment of new lines.
Thomson is a pioneer in the development of embryonic stem cells and his university holds five cell lines that are available for research under federal rules. Kaufman said this particular work was not done using federal funds.
Thomson's team grew the embryonic stem cells in a culture containing mouse tissue that encouraged development of blood cells, a procedure used in attempting to develop stem cells in specific ways.
The result, they report, was cell colonies that "appear identical to those produced from human bone marrow cells." Bone marrow produces blood cells.
The development of these early blood cells is important because stem cells have the ability to continue reproducing themselves. Scientists studying these early human blood cells have had to rely on such sources as bone marrow and umbilical cord blood.
While more work is needed to develop highly purified populations of the cells, the team said the finding "could lead to a novel source of cells for transfusion and transplantation therapies."
Dr. Ernest Beutler, chairman of the Department of Molecular and Experimental Medicine at The Scripps Research Institute, cautioned that the cost of producing cells this way may make it impractical for transfusions.
"With respect to using such a system for the production of red cells or white cells for transfusion, the cost of producing such cells would be absolutely prohibitive," Beutler said.
"The possibilities of using such a system for (bone marrow) transplantation are somewhat greater, but it is not at all clear that such cells would not be rejected by the immune system," he said. "In short, these are high quality basic studies, but much remains to be done before it would be at all clear that embryonic stem cell-derived hematopoietic cells could play any practical role in the treatment of disease."
On the Net: Proceedings of the National Academy of Sciences: www.pnas.org