Scientists from UC Santa Barbara have discovered how human embryonic stem cells either divide and renew or become transformed into virtually any cell within the body. Through their research, they have shown that the micro RNA, miR-145, a single-stranded RNA that decreases gene expression, lowers the activity of three key ingredients in embryonic stem cells. The researchers believe that their discovery may help improve the efficiency methods currently used to reprogram differentiated cells into embryonic stem cell-like cells. The study was reported in a recent issue of the journal Cell.

"We have found an element in the cell that controls 'pluripotency,' that is the ability of the human embryonic stem cell to differentiate or become almost any cell in the body," says senior author Kenneth S. Kosik, M.D., professor in the Department of Molecular, Cellular and Developmental Biology. "The beauty and elegance of stem cells is that they have these dual properties," says Dr. Kosik. "On the one hand, they can proliferate -- they can divide and renew. On the other hand, they can also transform themselves into any tissue in the body, any type of cell in the body." And he adds, "The heart of the matter is that before this paper, we knew that if you want to maintain a pluripotent state and allow self-renewal of embryonic stem cells, you have to sustain levels of transcription factors. We also knew that stem cells transition to a differentiated state when you decrease those factors. Now we know how that happens a little better." The researchers believe that their findings will impact cancer research, since tumor stem cells are responsible for tumor growth. In addition, the discovery is also expected to help with the prevention and treatment of other diseases and injuries.

In addition to Dr. Kosik, the research team included James Thomson, who is widely considered the "father of stem cell biology" as a result of his pioneering work in the isolation and culture of non-human primate and human embryonic stem cells. These cells gave researchers unprecedented access to the human body's cellular components, opening the door to applications in basic research, drug discovery and transplantation. 

News Release: Scientists shed light on inner workings of human embryonic stem cells  www.sciencedaily.com  May 7, 2009