Mesenchymal Stromal Cell Therapy in Crohn's Disease.

Background: Mesenchymal stromal cells (MSC) are multipotent adult stem cells with immunomodulatory properties. They uniquely express HLA class I antigen at a low level, and do not express HLA class II. Hence, for allogeneic administration, donor to recipient matching is not required; yet a prolonged chimeric state does not occur. Contrary to haematopoietic stem cell transplantation, cytotoxic drug therapy is not required to harvest, or administer, cells. Key Messages: MSC are obtained from marrow, adipose tissue or placenta. In our centre, MSC are isolated from a 10 ml donor marrow aspirate, by virtue of their adherence to plastic. They are expanded in culture, cryopreserved, and subjected to strict quality controls before release for intravenous administration. These activities occur in a dedicated, nationally accredited, laboratory. Initial observations of allogeneic MSC efficacy were in graft-versus-host disease. Both autologous and allogeneic MSC have since been evaluated in biologic refractory luminal and fistulising Crohn's disease (CD). Data from early-phase studies have suggested efficacy for luminal disease when allogeneic MSC were given intravenously and also suggested efficacy for fistulising disease when either allogeneic or autologous MSC were administered into fistulas. MSC treatment is not reported to have caused serious adverse events. Although in vitro criteria for defining MSC exist, a major challenge lies in how to define MSC for clinical use. MSC function in vivo is likely to be dependent upon donor immunological characteristics, and widely varying manufacturing processes between laboratories. MSC dose, frequency of administration, stage of disease, and presence of concomitant immunosuppression also require to be defined.

Conclusions: MSC therapy may have future utility in CD, but considerable work is first required to determine appropriate phenotypic and functional characteristics of administered cells.