Institution: | 1.Department of Surgery, Harvard Medical School, Massachusetts General Hospital, 15 Parkman Street, Boston, MA, 02114, USA ;2.Gastrointestinal Unit, Department of Medicine, Harvard Medical School, Massachusetts General Hospital, 55 Fruit Street, Boston, MA, 02114, USA ;3.Department of Pathology, Harvard Medical School, Massachusetts General Hospital, Boston, MA, 02114, USA ;4.Harvard Stem Cell Institute, Cambridge, MA, 02138, USA ; |