10. 2014年4月14日 07:06:36
In the early 2000s, Charles and Martin Vacanti conducted studies that led them to the idea that stem cells could be spontaneously created when ordinary tissues are stressed via mechanical injury or increased acidity.
The technique for producing STAP cells was subsequently developed by Obokata at the Brigham and Women's Hospital (BWH), while she was studying under Charles Vacanti, and then at the RIKEN Center for Developmental Biology in Japan. In 2008, while working at Harvard Medical School, she verified at the request of Charles Vacanti that some of the cultured cells she was working with shrank to the size of stem cells after being squeezed through a capillary tube. She went on to test the effects of various stimuli on cells. After perfecting her technique, Obokata was able to show that white blood cells from newborn mice could be transformed into cells that behaved much like stem cells. She repeated the experiment with other cell types including brain, skin, and muscle cells with the same result.
Initially Obokata's findings were met with skepticism, even among her coworkers. "Everyone said it was an artefact – there were some really hard days", she recalled. The manuscript describing the work was rejected multiple times before its eventual publication in the journal Nature. A series of experiments, first turning a mouse embryo green by fluorescently tagging STAP cells, then video taping the transformation of T-cells into pluripotent cells, finally convinced skeptics that the results were real.
In February 2014, Vacanti said he believes the team now has evidence the same technique can be used to get stem cells from human skin cells. Early evidence suggest that the technique has also generated stem cells from human dermal fibroblasts and that there is a parallel process going on when the stem cells are generated from skin tissue.
Investigation into disputed claims
In the months after the Nature paper was released, most scientists who tried to duplicate Obokata's results failed and suspicion arose that her results were due to error or fraud. An investigation into alleged irregularities was launched by RIKEN on 15 February 2014. The allegations question the use of seemingly duplicated images in the papers, and report failure to reproduce her results in other prominent stem-cell laboratories. Nature also announced they are investigating. Several stem-cell scientists defended Obokata or reserved their opinion while the investigation was ongoing. To address the problem of reproducibility in other laboratories, Obokata published some technical 'tips' on the protocols on 5 March while promising the detailed procedure will be published in due course.
On 11 March, Teruhiko Wakayama, one of Obokata's coauthors urged all the researchers involved to withdraw the articles, citing many "questionable points". Charles Vacanti said he opposed their retraction and posted details about how to create STAP cells on his own website.
On 14 March, RIKEN released an interim report of the investigation. Out of the six items being investigated, the committee concluded that there was inappropriate handling of data on two items, but did not judge the mishandling as research misconduct. On 1 April, RIKEN concluded that Obokata had enganged in "research misconduct", falsifying data on two occasions. The co-authors were cleared of misconduct, but bore "grave responsibility" for not verifying the data themselves. Obokata maintained her innocence and said she would fight the decision.