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1998 - President Bill Clinton requests a National Bioethics Advisory Commission to study the question of stem cell research.
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2000 - The National Institutes of Health (NIH) issues guidelines for the use of embryonic stem cells in research, specifying that scientists receiving federal funds can use only extra embryos that would otherwise be discarded. President Clinton approves federal funding for stem cell research but Congress does not fund it.
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July 18, 2006 - The Senate votes 63-37 to loosen President Bush's limits on federal funding for embryonic stem-cell research.
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June 20, 2007 - President Bush vetoes the Stem Cell Research Enhancement Act of 2007, his third veto of his presidency.
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January 23, 2009 - The FDA approves a request from Geron Corp. to test embryonic stem cells on eight to 10 patients with severe spinal cord injuries. This will be the world's first test in humans of a therapy derived from human embryonic stem cells. The tests will use stem cells cultured from embryos left over in fertility clinics.
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March 9, 2009 - President Barack Obama signs an executive order overturning an order signed by President Bush in August 2001 that barred the National Institutes of Health from funding research on embryonic stem cells beyond using 60 cell lines that existed at that time.
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September 9, 2010 - A three-judge panel of the U.S. Court of Appeals for the D.C. Circuit grants a request from the Justice Department to lift a temporary injunction issued August 23, 2010, that blocked federal funding of stem cell research.
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October 8, 2010 - The first human is injected with cells from human embryonic stem cells in a clinical trial sponsored by Geron Corp.
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April 29, 2011 - The U.S. Court of Appeals for the District of Columbia lifts an injunction, imposed last year by a federal judge, banning the Obama administration from funding embryonic stem-cell research.
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May 11, 2011 - Stem cell therapy in sports medicine is spotlighted after New York Yankee pitcher Bartolo Colon is revealed to have had fat and bone marrow stem cells injected into his injured elbow and shoulder while in the Dominican Republic.
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February 13, 2012 - Early research published by scientists at Cedars-Sinai Medical Center and Johns Hopkins University show that a patient's own stem cells can be used to regenerate heart
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May 2013 - Scientists make the first embryonic stem cell from human skin cells by reprogramming human skin cells back to their embryonic state, according to a study published in the journal, Cell.
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April 2014 - For the first time scientists are able to use cloning technologies to generate stem cells that are genetically matched to adult patients,according to a study published in the journal,Cell Stem Cell.
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October 2014 - Researchers say that human embryonic stem cells have restored the sight of several nearly blind patients -- and that their latest study shows the cells are safe to use long-term. According to a report published in The Lancet, the researchers transplanted stem cells into 18 patients with severe vision loss as a result of two types of macular degeneration.