Results obtained in huge number of clinical trials indicate that local application of autologous and allogeneic bone marrow-mesenchymal stem cells and adipose tissue-mesenchymal stem cells are simple, safe, and beneficial therapy for the treatment of perianal fistulas in Chron’s disease patients with no adverse effects. On contrary, adverse effects have been reported in three of nine improved clinical trials that investigated therapeutic potential of intravenously injected mesenchymal stem cells.