One of these scientists, Elmer Price, an associate professor of biomedical sciences at MU's Dalton Cardiovascular Research Center, has recently brought life scientists closer to just such an understanding. Earlier this year, Price, working with samples of blood drawn from swine, isolated a line of adult stem cells -- defined as cells from mature mammals that share some of the same changeable qualities as the embryonic variety -- that he then directed to form the biological precursors to bone, blood vessel and nerve cells.

"Embryonic stem cells are able to give rise to the remarkable diversity of cell types that constitute a whole organism such as a human," Price reports. "However, this pluripotency can also be a curse, because ES cells can be misled by biochemical signals when they are transplanted into an adult during cell-transplantation experiments. This often leads to the generation of unwanted cell types and, on occasion, to tumor formation. Because of this, ES cell transplantation can raise serious safety issues. In this study, we developed adult stem cells from the blood of a mature animal that we were able to direct into specific cell types, such as neurons and blood vessel cells, but they were not as pluripotent as ES cells. We have not observed any evidence of tumor formation."

Price and other researchers have long known that adult stem cells play an important role in the body's ability to repair tissue damaged by disease or injury, and that they thus have great potential for patient care. But developing useful therapies has lagged, chiefly due to a host of unanswered questions related to the hows and whys of differentiation, the process by which stem cells eventually come to form the specialized cells that serve as the basis of the body's complex physical structures.

Adult stem cells are found in a variety of human organs and tissues, where they reside in what biologists refer to as a quiescent, or non-dividing state until ordered into action by the body. But they are notoriously tough to identify. One reason is that in any given organ or tissue sample there are precious few stem cells, perhaps as few as one in 100,000 cells. Another is that those that are present are virtually indistinguishable from other cells.

Scientists have overcome identification difficulties by ingeniously employing what they call "surface cell markers," chemical formulations containing molecules that adhere, or bind, to the "receptor" proteins found on the surface of every cell in the body. Because each cell type has its own combination of receptors, researchers have been able to develop a variety of these molecular markers to distinguish adult stem cells from their more numerous brethren.

For his current study, published in the August edition of the journal Stem Cells and Development, Price took the process a step further, identifying stem cells from special swine developed by his colleague and co-author Randy Prather, distinguished professor of reproductive biotechnology in MU's animal sciences department. Prather's genetically modified pigs are unique in that they have been engineered to contain a fluorescent gene that glows brightly when stem cells are exposed to a black light -- a circumstance that allows scientists to track the stem cells as they begin to form the precursors of tissues and organs.

Published by the Office of Research.

©2006 Curators of the University of Missouri. Click here to contact the editor.