Scientists have moved a step closer to the goal of creating stem cells perfectly matched to a patient’s DNA in order to treat diseases, they announced on Thursday, creating patient-specific cell lines out of the skin cells of two adult men. The advance, described online in the journal Cell Stem Cell, is the first time researchers have achieved “therapeutic cloning” of adults. Therapeutic cloning means producing embryonic cells genetically identical to a donor, usually for the purpose of treating disease. But it is also the first step in reproductive cloning — a technique that has set off controversy. In 2005, the United Nations called on countries to ban it, and the United States prohibits the use of federal funds for either reproductive or therapeutic cloning.