Two failed attempts to transplant adult stem cells into the hearts of laboratory mice are casting doubt on the value and safety of clinical trials testing a similar approach to repair the hearts of humans.
In two separate papers released Sunday in the online version of the journal Nature, researchers at Stanford University and another team of scientists from Indiana University and the University of Washington describe how efforts to use adult stem cells from a mouse to regenerate heart muscle in other mice simply did not work.
The setback raises questions about similar experiments among human subjects in Brazil, Germany, Britain and China.
The Bush administration has sharply restricted federal funding for research on human embryonic stem cells, which are derived from living human embryos only a few days old. Opponents of such research contend that the necessary destruction of these embryos destroys a human being. They favor using adult stem cells, such as those found in bone marrow. These stem cells can differentiate into blood cells and can make other human organs and tissues.
The failed mice experiments employed these adult bone marrow cells, attempting to replicate earlier studies that seemed to show they could be coaxed into making new heart muscle if injected into the site of damaged tissue from a heart attack.
Stanford researchers led by Dr. Robert C. Robbins transplanted bone marrow stem cells containing a firefly gene that causes them to glow faintly, but the cells blinked out within 30 days in mice whose heart tissue was damaged by a lab-induced heart attack. The second study, led by Indiana biologist Loren John Field, also transplanted bone marrow stem cells that failed to create new muscle in damaged mouse hearts.
Researchers are not sure why earlier experiments appeared to show the transplantation of bone marrow stem cells worked. They said it may be because the initial studies employed a less precise method of identifying genes from transplanted cell lineage, picking up from host cells false signals of a successful transplant.
