This trial aims to investigate the safety of using mesenchymal stem cells obtained from donated bone marrow in the treatment of chronic diabetic leg ulcers. The trial is being conducted by the Sheba Medical Centre and plans to enrol 20 patients with chronic diabetic leg ulcers which have proved difficult to heal and are smaller than 10 cm². During one sitting, all the participants will receive multiple injections of donated mesenchymal stem cells in the affected limb as well as in the ulcer bed. Participants will be monitored for complications and for ulcer. The trial is expected to conclude in 2013.