Researchers find way to grow thriving stem cells outside the body

An extra hormone can help elusive blood stem cells multiply and thrive outside the body, offering cancer patients and others a ready supply of the life-giving cells, scientists said Tuesday.

Doctors have long been trying to find a way to grow large numbers of the cells, which give rise to red blood cells and the white blood cells of the immune system and are used to replace bone marrow after intense chemotherapy or radiotherapy.

The cells are very difficult to find and filter out of the blood and usually die after about a month in a laboratory dish.

Writing in the Proceedings of the National Academy of Sciences, scientists at the University of Washington in Seattle and the Veterans Affairs Puget Sound Health Care System they said they had transplanted their 4-month-old cells into mice whose bone marrow was destroyed by radiation, and saved the lives of the mice.

One of the secrets was thrombopoietin, a hormone the team tested to try to encourage the growth of platelet cells involved in blood clotting.

A company based in Ann Arbor, Mich., Aastrom Biosciences Inc. has patented a system for growing and multiplying such stem cells.

Dr. Patrick Stiff of Loyola University Medical Center in west suburban Maywood is principal investigator in an ongoing study of the Aastrom system's effectiveness in growing stem cells from umbilical cord blood for use in adults.

Although the process has shown encouraging results, saving four of eleven patients in the final stages of leukemia, some experts say the difficulty of detecting blood stem cells in humans makes it impossible to know whether the technique actually improves patients' conditions by expanding the number of stem cells.

Tribune staff writer Jeremy Manier contributed to this report.