Study conducted by Duijveistein and coworkers documented that 6 weeks after mesenchymal stem cells treatment, three patients required surgery due to disease worsening. Similar results were noticed in another clinical trial. In this study, autologous mesenchymal stem cells, derived from marrow aspirate and propogated for 2-3 weeks with fibrinogen depleted human platelet lysate, were adminestered to inflammatory bowel disease patients. Twelve patients received single mesenchymal stem cells intravenous infusion of 2,5 or 10 millioncells/kg and serious adverse events were seen in seven patients. Aggravation of disease was noticed in five patients while adverse events in other two patients were possibly related to infusion of mesenchymal stem cells.