Stimulus-triggered acquisition of pluripotency

Stimulus-triggered acquisition of pluripotency (also known as STAP) was a proposed method of generating pluripotent stem cells by subjecting ordinary cells to certain types of stress, such as the application of a bacterial toxin, submersion in a weak acid, or physical trauma. The technique gained prominence in January 2014 when research by Haruko Obokata et al. was published in Nature. Over the following months, all scientists who tried to duplicate her results failed, and suspicion arose that Obokata's results were due to error or fraud. An investigation by her employer, RIKEN, was launched. On 1 April 2014, RIKEN concluded that Obokata had falsified data to obtain her results. On 4 June 2014, Obokata agreed to retract the papers. On August 5, 2014, Yoshiki Sasai—Obokata's supervisor at RIKEN and one of the coauthors on the STAP cell papers—was found dead at a RIKEN facility after an apparent suicide by hanging. Stimulus-triggered acquisition of pluripotency (also known as STAP) was a proposed method of generating pluripotent stem cells by subjecting ordinary cells to certain types of stress, such as the application of a bacterial toxin, submersion in a weak acid, or physical trauma. The technique gained prominence in January 2014 when research by Haruko Obokata et al. was published in Nature. Over the following months, all scientists who tried to duplicate her results failed, and suspicion arose that Obokata's results were due to error or fraud. An investigation by her employer, RIKEN, was launched. On 1 April 2014, RIKEN concluded that Obokata had falsified data to obtain her results. On 4 June 2014, Obokata agreed to retract the papers. On August 5, 2014, Yoshiki Sasai—Obokata's supervisor at RIKEN and one of the coauthors on the STAP cell papers—was found dead at a RIKEN facility after an apparent suicide by hanging. STAP would have been a radically simpler method of stem cell generation than previously researched methods as it requires neither nuclear transfer nor the introduction of transcription factors. Haruko Obokata claimed that STAP cells were produced by exposing CD45+ murine spleen cells to certain stresses including an acidic medium with a pH of 5.7 for half an hour. Following this treatment, the cells were verified to be pluripotent by observing increasing levels of Oct-4 (a transcription factor expressed in embryonic stem cells) over the following week using an Oct4-GFP transgene. On average only 25% of cells survived the acid treatment, but over 50% of those that survived converted to Oct4-GFP+CD45− pluripotent cells. The researchers also claimed that treatment with bacterial toxins or physical stress were conducive to the acquisition of pluripotent markers. STAP cells injected into mouse embryos grew into a variety of tissues and organs found throughout the body. According to the researchers, the chimaeric mice ' to be healthy, fertile, and normal' after one-to-two years of observation. Additionally, these mice produced healthy offspring, thereby demonstrating germline transmission which is 'a strict criterion for pluripotency as well as genetic and epigenetic normality.' STAP cells were supposedly able to differentiate into placental cells, meaning they would be more potent than embryonic stem cells or induced pluripotent stem cells (iPS). It was not clear why ordinary cells do not convert into stem cells when subjected to similar stimuli under ordinary conditions, such as acidity in the body; Obokata et al. suggested that in vivo inhibitory mechanisms may block conversion to pluripotency. Research is underway to generate stimulus-triggered acquisition of pluripotency (STAP) cells using human tissue: in February 2014, Charles Vacanti and Koji Kojima (Harvard researchers originally involved in the discovery and publication of STAP) claimed to have preliminary results of STAP cells generated from human fibroblasts, but concomitantly cautioned that these preliminary results require further analysis and validation. In the early 2000s, Charles Vacanti and Martin Vacanti conducted studies that led them to the idea that stem cells - spore-like cells - could be spontaneously recovered from ordinary tissues that are stressed via mechanical injury or increased acidity. The technique for producing STAP cells was subsequently studied by Obokata at the Brigham and Women's Hospital (BWH), while she was studying as a post doc 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 mechanically injured in a capillary tube. She went on as directed, to test the effects of various stimuli on cells. After modifying the 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 as an article (together with a shorter jointly-written 'letter') within the journal Nature. A series of experiments, first turning a mouse embryo green by fluorescently tagging STAP cells, then videotaping the transformation of T-cells into pluripotent cells, finally convinced skeptics that the results were real. In the months after the two Nature papers were released, all 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 questioned the use of seemingly duplicated images in the papers, and reported failure to reproduce her results in other prominent stem-cell laboratories. Nature also announced that they were 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 that the detailed procedure would 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 a 'revised protocol' for creating STAP cells on his own website, which was taken down after he resigned his BWH post.