Standardization of mesenchymal stromal cell therapy for perianal fistulizing Crohn's disease

Local administration of mesenchymal stromal cells (MSCs) into the fistula tract seems to improve patient outcome in perianal fistulas due to Crohn's disease (CD). In this paper we propose a standardized and validated protocol for the local administration of MSCs for CD perianal fistulas to be able to reliably assess efficacy.

A working group consisting of gastroenterologists and surgeons with expertise in the treatment of perianal CD developed a consensus perianal fistula treatment protocol for local MSC treatment of perianal fistulizing CD. The treatment protocol was validated during a trial of allogeneic bone marrow-derived MSCs for the treatment of refractory perianal Crohn's fistulas.

Localization and classification of perianal fistulas with MRI and rectoscopy is of crucial importance prior to surgical intervention with local therapy administration. Examination under anesthesia is necessary to incise and drain abscesses when present. Optimization of medical treatment when active luminal CD is present, is the first step before embarking on surgery and local therapy administration. In addition, strictures preventing the surgeon from adequately performing the surgical procedure have to be endoscopically dilated. Curettage of the fistula tract has an important role as long-standing CD perianal fistulas close poorly without removal of their epithelial lining. To diminish bacterial contamination of the fistula, the internal opening has to be closed. The origin of the fistula is the internal opening, therefore, efficacy of MSCs is presumably the highest when they are injected into the tissue around the internal opening.

In this article, we propose a standardized method of local MSC administration for perianal fistulizing CD. The use of this standardized and validated protocol for the administration of local treatment of CD perianal fistulas will allow reliable comparison of the efficacy of local therapies in future.