Mesenchymal stem cells (MSC) may be a therapeutic option in diseases associated with severe inflammation or auto-immune diseases, due to their immunomodulatory and anti-inflammatory properties. A number of clinical trials are being conducted worldwide testing th efficacy of MSC, mainly isolated from bone marrow, for different conditions, such as Graft Versus host Disease, refractory Crohn's Disease, ischemic stroke, acute myocardial infarction, type I Diabetes Mellitus, or Chronic Obstructive Pulmonary Disease. Usually, the route of administration of the cells in these studies is intravenous. Local injection of MSC for fistulizing Crohn's Disease has proven efficacious. Endoscopy is a routinary technique for the evaluation of gastrointestinal and colonic conditions. The purpose of our study is to evaluate safety and efficacy of the intracolonic injection by using a colonoscope of allogeneic adipose tissue-derived MSC in patients with moderate active ulcerative colitis.