March 21, 2002
by Leon Henderson, M.D.
Bennett Weintraub, Ph.D.
One of the most interesting scientific debates of recent years concerns whether or not adult stem cells have the potential to "differentiate" into any cell type. Blood stem cells can become all types of white and red blood cells, but can they also become liver cells or neurons? Can stem cells isolated from the brain become blood cells? While many scientists were skeptical, several landmark papers have demonstrated the ability of adult stem cells to differentiate into many disparate cell types. These papers suggest that adult stem cells are not committed to certain fates, but can in fact become almost any type of cell in the body. If true, these results show that the potential of adult stem cells for therapeutic purposes is greater than expected, and that adult stem cells may suffice for many applications that previously were thought to require embryonic stem cells.
The debate is not yet resolved, as evidenced by two papers that will be published this week in the journal Nature. Both papers question recent results, offering an alternate explanation. The two papers, one from a British group and the second from researchers in Florida, suggest that adult stem cells are not able to develop into any cell type by themselves, but in fact acquire new properties by fusing with a differentiated cell. For example, a neural stem cell can fuse with a differentiated blood cell to create a cell with the properties of a blood stem cell.
Cell fusions are routinely induced in the laboratory, but are more rare in nature. The studies suggest that stem cells have a particular propensity towards fusing with other cells, and begin to describe the factors that promote such fusion.
Although some people have suggested that the new work demonstrates the limited potential of adult stem cells, we feel that in fact the studies will accelerate the development of stem cell therapeutics. In order to use adult stem cells to treat diseases like Parkinson disease, diabetes, and spinal cord injury, we must understand the behavior of these cells and how to manipulate them. Cell fusion may in fact be a new way to manipulate adult stem cells. By understanding this process, we are one step closer to using adult stem cells in the clinic.
Several small biotech companies are developing adult stem cell technologies. Stem Cells, Inc. (NASDAQ: STEM) is focusing on neural stem cells. Incara (NASDAQ: INCR) develops liver stem cells. Aastrom (NASDAQ: ASTM) and Nexell (NASDAQ: NEXL) are making reagents and incubators that can be used to grow and manipulate stem cells.
The long awaited pivotal Vanlev (omapatrilat) trial results were disappointing.
Bristol Myers Squibb's (NYSE: BMY) novel drug for the treatment of hypertension
(high blood pressure) failed to improve upon the treatment effect of enalapril
(Merck's Vasotec). Enalapril is one of the widely used classes of anti-hypertensive
drugs known as ACE inhibitors and Vanlev is a novel, developmental vasopeptidase
inhibitor. These data do not support FDA approval for Vanlev.
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