The search for viable alternatives to replace the embryonic stem cells that are derived from the inner cell mass of an early stage embyo, will continue. A summary of the three main types of stem cells includes: embryonic stem cells that are found in blastocyst (an early stage embryo), adult stem cells that are found throughout the body after embryonic development and they divide to replace dying cells and regenerate damaged tissue, and induced pluripotent stem cells, also called iPS cells that are derived from an adult somatic cell using genes and viruses. The most recent discovery in the field of stem cell research adds to the growing list cells biospsied from human testicles and grown in laboratory cultures; these cell lines are called “human adult germline stem cells.”

Shinya Yamanaka of Kyoto University in Japan and colleagues first demonstrated in 2006 that adult mouse skin cells could be reprogrammed into something similar with embryonic stem cells by the introduction of four specific genes. Researchers have then managed to generate induced pluripotent stem cells using the technique pioneered by Yamanaka. But the method used genes and viruses: to get the genes into the cells, researchers had to use retroviruses, which involved inserting their viral DNA into a cell’s chromosome and pose a risk of cancer.

But researchers have tried to improve this method by developing a safer way of obtaining stem cells from common skin cells without using harmful viruses that can cause cancer. Last month researchers at the Massachusetts General Hospital and Harvard Medical School in Boston managed to reprogram adult skin cells into embryonic-like stem cells using adenoviruses. The adenovirus doesn’t integrate into the genome, so the cells aren’t altered genetically, the researchers explained.

Scientists believe that just like the ordinary stem cells, the new types of cells could be cultured into any desired tissue, from heart muscle cells and blood cells to brain cells.

Last week, the Japanese team led by Shinya Yamanaka, of Kyoto University and the Gladstone Institute of Cardiovascular Disease found a new way to reprogram cells without viruses. The Japanese scientists delivered the reprogramming genes into mouse cells with the help of plasmids (small and stable circles of DNA). “Plasmids are safe and cheap, because they can be produced in large quantities in a laboratory, and preserved in a frozen state. It is considered a new generation of iPS cells,” Yamanaka said.

Yamanaka’s team said they plan to try their method using human cells. If the new method can be applied to human cells, it may offer a safer way to test cell therapy to treat Parkinson’s or other degenerative diseases. Japanese scientists are confident that the method will be successful when applied to human cells as well.

Scientists say it is important to continue exploring all these methods, including embryonic stem cell research. They believe that the discoveries in the field of stem cell research will at least improve the quality of life. The research will be most beneficial in improving the understanding of the disease and providing targets for drug testing.