| Stem Cells |
Certainly some plant cells, like the totipotent meristems, are more versatile than animal cells. Recent discoveries, however, show that the difference in the retention of competence between animals and plant cells is not as great as once thought. During the late 1990s scientists found that adult humans have a reservoir of cells that retain some ability to become other cell types.
Cells derived from fetal tissue have been used to generate so-called embryonic stem cells. In addition to the ethical dilemmas raised by the source of embryonic stem cells, there are practical limitations to the use of these cells for treating and curing diseases and regenerating tissues. Because the donors of these cells are immunologically different from the recipient, immunosuppression would have to be used as in an organ transplantation. Because adult stem cells can be derived from the individual patient, concerns about compatibility of the cells would be obviated.
But do adult stem cells have the same ability to differentiate as embryonic stem cells? Recent studies suggest that adult stem cells may be more versatile than had been previously thought. Catherine Verfaillie and her colleagues at the University Stem Cell Institute derived what they call Multipotent Adult Progenitor Cells (MAPC) from the bone marrow of adult mice. These cells appear to be able to differentiate into virtually all cell types of mouse when injected into mouse blastocysts. These MAPCs have also been injected into living adult mice and have differentiated into liver, lung, and intestine tissue.