This year, scientists built on this work with spectacular results. Two research teams took cells from patients suffering from a variety of diseases and reprogrammed them into stem cells. Many of these diseases are difficult or impossible to study with animal models, making the need for human cell lines to study even more acute.

The transformed cells grow and divide in the laboratory, unlike most adult cells, which don't survive in culture conditions. The cells could then be induced to assume new identities, including those cell types most affected by the diseases afflicting the patients who had donated the initial cells.
The new cell lines will be major tools for understanding how diseases arise and develop, and they may also prove useful in screens for potential drugs. Eventually, if scientists can master cellular reprogramming so that it's more finely controlled, efficient and safe, patients may someday be treated with healthy versions of their own cells.

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