FILE - In this Friday, July 30, 2010 file photo, Dr. Paolo Macchiarini looks on during a press conference where he announced that his surgical team successfully transplanted the windpipes of two cancer patients with an innovative procedure that uses stem cells to allow a donated trachea to regenerate tissue and create an organ that is biologically close to the original, Florence, Italy. Sweden's Karolinska Institute said on Friday, Aug. 28, 2015 that Macchiarini, a leading stem cell scientist accused of unethical behavior, has been cleared of scientific misconduct though he sometimes acted without due care. (AP Photo/Lorenzo Galassi, File)