This trial is investigating the effect of donated bone marrow stem cells in people suffering from Crohn's disease. Mesenchymal stem cells were collected from the bone marrow of healthy volunteers and expanded in the laboratory before being administered in the trial. The trial is being conducted in in Liege, Belgium in patients who have not responded to conventional treatment. There is no control group in this trial and participants will be accessed for changes in blood cell profile and markers of the immune system. The trial is expected to run until June 2016 and enrol 20 participants.