Lab Creates Human Blood Cells

For the first time, researchers have used embryonic stem cells to produce human blood cells, a step that could lead to a new source of cells for transfusion and other therapies.

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.

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 that could be used to treat diabetes, heart disease or other disorders.

Although development of these cells holds promise, Kaufman stressed that it will take years before they can be used in people. “I don’t want to raise any false hope,” he said.

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 set last month by President Bush. Kaufman said this particular work was done without 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.

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. Scientists studying these early human blood cells have had to rely on such sources as bone marrow and umbilical cord blood.

Although 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.

“The possibilities of using such a system for [bone marrow] transplantation are somewhat greater,” he added, “but it is not at all clear that such cells would not be rejected by the immune system. 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.”