Current status of mesenchymal stem cell therapy and bone marrow transplantation in IBD.

Cellular therapy is a promising new approach to address unmet medical needs in patients with IBD, mainly Crohn's disease (CD). Two series have reported autologous hematopoietic stem cell transplantation (HSCT) for CD. The largest one is a phase I study from Chicago including 24 patients with active CD refractory to conventional therapies. All patients went into remission with a CD Activity Index (CDAI) <150. The percentage of clinical relapse-free survival was 91% at 1 year, 63% at 2 years, 57% at 3 years, 39% at 4 years and 19% at 5 years. The percentage of patients in remission (CDAI <150), steroid-free or medication-free at any post-transplantation evaluation interval remained ≥70, ≥80 and ≥60%, respectively. In Europe and Canada, a currently ongoing randomized trial hopes to answer the question of whether autologous HSCT adds any benefit to the effect of immunosuppression used during mobilization. Although promising, HSCT for CD is still experimental and its toxicity leaves this option for a considerably reduced number of refractory patients in whom the disease is not amenable to surgical resection. A more recently developed, less aggressive approach involves the use of mesenchymal stem cells (MSCs). Successful pre-clinical studies using MSCs in models of autoimmunity, inflammation or tissue damage have paved the way for clinical trials. Two phase I studies on autologous bone marrow-derived MSCs for the treatment of active refractory CD have been published recently; one using systemic administration in patients with luminal CD and the other assessing the effects of local injection of MSCs for the treatment of fistulizing CD, showing that application of autologous MSCs is feasible, well tolerated and might produce clinical benefits.