ES were first cultured stably and successfully seven years ago, and from a week-old embryo, and after seven years of work, only 150 well-established lines have been successfully propagated (The Future, 2005, A6). In the United States, unfortunately, the Bush administration has restricted federal research funding to only 22 lines, many of which are now contaminated and of little use in productive research. This is partly because a feeder layer of cells has always been needed to get the ES cells to grow in culture and up until this year, mouse skin cells were used for this layer and the cells were nourished with fetal calf serum, thus possibly contaminating the ES with animal proteins or pathogens. However earlier this year, researchers were able to grow ES using human feeder layers, but there is still a problem with contamination from the media used. Another problem has emerged in that ES cannot be used directly for therapeutic use because they cause tumor development, so it will be necessary for scientists to discover how to get ES to differentiate into specialized cells before transplanting them into humans (A7). Mature, differentiate cells have been used to treat diseases, such as pancreatic insulin-producing beta cells to treat diabetes, and fetal brain cells to treat brain diseases (A8).
Although the public gets stirred up over the possibilities held out for stem cells in curing diseases, the scientific community is just as interested in pursuing them