Other improvements over the last paper include the reduced use of animal products in laboratory procedures and better evidence that the cell lines matched the patients' cells and did not have a parthenogenetic origin, where unfertilized eggs can divide on their own.
Hwang and colleagues report that the cells are chromosomally normal, self-renewing and "pluripotent" ?meaning they have the ability to form the three major types of cells in the early embryo that give rise to all other cells in the body. For example, the stem cells can differentiate into cells that display characteristics of skin and retina cells, muscle cell bundles, bone matrix cells and cells of the gastrointestinal and respiratory lining.
One of the next preclinical steps, according to the authors, is to evaluate, in the lab, differentiated patient-specific human embryonic stem cell lines for immune-system tolerance, therapeutic efficacy and safety. Initial laboratory experiments showed immune system compatibility between the stem cell lines and the cells of people who supplied each line's nuclear DNA, suggesting that the patient's body might tolerate the cells after transplantation.
The authors caution that work with human embryonic stem cells and studies of stem cells in animal model systems indicate that serious abnormalities in human development would result if the cells were used in reproductive cloning. Any attempts at reproductive cloning would be dangerous and should not be attempted under any conditions.
W.S. Hwang, B.C. Lee, S.K. Kang, D.K. Kwon, S.W. Park, H.S. Kwon, C.K. Lee, C. Ahn, S.H. Paek, S.K. Oh, H.S. Kim and S.Y. Moon at Seoul National University in Seoul, Korea; S.I. Roh, S.J. Kim, J.B. Lee and J.M. Kim at MizMedi Hospital in Seoul, Korea; S.S. Chang and J.J. Koo at Hanna Women's Clinic in Seoul, Korea; H.S. Y