Blood stem cells make mouse bone marrow, brain cells

WASHINGTON, Jan 16 (Reuters) Stem cells taken from bone marrow replenished the radiation-ravaged immune systems and bone marrow of mice and can also make brain and liver cells, scientists reported.

These so-called adult stem cells can grow almost indefinitely in the lab and have many of the other valued properties of more controversial embryonic stem cells, Dr Catherine Verfaillie of the University of Minnesota and colleagues reported yesterday.

''The cells not only survived when transplanted but they completely repopulated the blood system of the mice,'' Verfaillie said.

Writing in the Journal of Experimental Medicine, the researchers said the findings suggest adult stem cells can be manipulated to regenerate a range of cells and tissues.

The cells are called multipotent adult progenitor cells or MAPCs and their discovery in 2001 provoked a furor among opponents of human embryonic stem cell research, who said the findings proved scientists do not need to experiment on human embryos in order to regenerate tissue and organs and produce tailored medicine.

Most stem cell experts, including Verfaillie, repudiate this argument.

''My research has been misused the whole time. There is a huge reason why we have to continue studying embryonic stem cells,'' Verfaillie said in a telephone interview.

READY TO VETO Last week, the U.S. House of Representatives voted to expand federal funding of human embryonic stem cell research and the Senate is expected to also pass the bill. But President George W Bush, who opposes the work, has promised to veto it again, as he did last July.

The White House issued a report saying work such as Verfaillie's make embryonic stem cell research unnecessary.

Verfaillie and other experts whose work is cited in the report say experiments are needed on all kinds of stem cells to truly understand them, and US federal funding and oversight is the best way to move the promising field forward.

Stem cells are the body's master cells, and depending on how developed they are, they can give rise to all the cells and tissues in an organism, or to a family of cell types.

For instance, neural stem cells can be directed to form various types of nerve cells, while hematopoietic stem cells form blood, immune system and bone marrow cells.

Verfaillie's multipotent adult progenitor cells or MAPCs are more powerful than hematopoietic stem cells.

''Scientists must now understand that mouse MAPCs can make normal blood, and we need to explore how they do it,'' said Stanford University's Dr Irving Weissman, who has been skeptical of Verfaillie's work but who collaborated with her on this study, published in the Journal of Experimental Medicine.

These cells might help rebuild damaged immune systems, treat blood cancers and might help transplant patients by ''tricking'' their immune systems.

And there is evidence the cells might be used to build entire new arteries, the researchers said.

''We could come up with a way of making arteries in a dish with a single cell population,'' Verfaillie said.

Verfaillie does not yet understand how the cells are reprogrammed. ''We don't know,'' she said. One reason scientists want to study all types of stem cells, including those taken from human embryos, is to unerstand the reprogramming process.

REUTERS BDP BD0937