New studies at the Boston Children’s Hospital, the Hebrew University of Jerusalem, and European centres may have found genetic and epigenetic differences between induced pluripotent stem cells and embryonic stem cells, researchers have announced. Stem cells are a type of basic cell capable of transforming into one of the many more specialized types of cells found throughout the human body. In recent years researchers have increasingly focused on stem cell research as a possible new source for treatments of many kinds of diseases and disorders.
The new research has uncovered differences between two basic types of stem cells. Embryonic stem cells are cells which naturally grow in the early stages of the human embryo, the beginning of an unborn fetus. The harvesting of embryonic stem cells typically involves the destruction of the fetus they are taken from, however. Although the process leading to fetus death (i.e. abortion) is still legal in most countries, the notion of destroying human embryos for scientific research has touched off a fierce ethical debate, particularly in the United States. Still, scientists initially hoped that embryonic stem cells would prove much more flexible and adaptable than the more readily available adult stem cells.
In the past several years, however, researchers have also begun to work with what are know as induced pluripotent stem cells. These stem cells resemble natural embryonic stem cells in many key respects, but are artificially produced using other cells, in order to solve the ethical problems involved with embryonic stem cell research. According to the National Institutes of Health, induced pluripotent stem cells were first produced in 2006, and have already begun to prove their usefulness in developing new drug therapies. Medical researchers also hope they will eventually prove useful in devising new methods for organ transplants, as well.
The new research, however, suggests that there are some important differences between human embryonic stem cells and induced pluripotent stem cells, which may make research more difficult after all. According to Hebrew University stem cell researcher Nissim Benvenisty, who led the study, “our findings might underline a more general phenomenon of… differences between human embryonic and induced pluripotent stem cells. Until we understand better the differences between these two types of stem cells, the optimal approach might be to model human genetic disorders using both systems, wherever possible.”
The new research suggests that the differences between induced pluripotent stem cells and embryonic stem cells may be both genetic (encoded in the DNA of the cells) and epigenetic (acquired without changing the basic DNA in the cell, although often involving the activation or deactivation of specific sequences within the DNA). In Benvenisty’s research, published in the journal Stem Cell, the team produced induced pluripotent stem cells from skin cells taken from boys suffering from an inherited mental disorder, Fragile X Syndrome, and compared them with embryonic stem cells taken from embryos who it is believed would have developed the same disorder (since their mother carried the Fragile X gene). They reported that the Fragile X-causing gene, called FMR1, was active in the embryonic cells as expected, but was inactive in the mature stem cells.
This is known as an epigenetic change (since the gene was still present, just inactive), and pointed to the likelihood of many other important differences as well. In April 2011, the most recent study by Benvenisty, co-written with Uri Ben-David, reports that there are also a range of other differences which affect the cells’ tendency to mutate and form cancerous tumors, known as tumorigenicity. Embryonic stem cells tend to be highly tumorigenic, but for unknown reasons, the induced pluripotent stem cells are not. The new results were published in the journal Nature Reviews Cancer.
Sources
European Stem Cell Consortium. EU Funded Study Sheds Light on Stem Cells.
National Institutes of Health. What Are Induced Pluripotent Stem Cells?
Nature Reviews Cancer. The Tumorigenicity of Human Embryonic and Induced Pluripotent Stem Cells.
