Systemic administration of mesenchymal stem cells (MSCs) has been shown to be safe and efficacious in humans with Crohn's disease. The aim of this study was to evaluate the safety of an intravenous (IV) infusion of adipose tissue-derived mesenchymal stem cells (ASCs) and to assess macroscopic and histological effects in the digestive tract of dogs with inflammatory bowel disease (IBD). Eleven dogs with confirmed IBD received a single ASC infusion (2 × 10(6) cells/kg bodyweight). Full digestive endoscopic evaluation was performed pre-treatment and between 90 and 120 days post-treatment with mucosal changes being assessed using a fit-for-purpose endoscopic scale. Endoscopic biopsies from each digestive section were evaluated histologically according to the World Small Animal Veterinary Association (WSAVA) Gastrointestinal Standardization Group criteria. The pre- and post-treatment canine IBD endoscopic index (CIBDEI) and histological score (HS) were calculated and compared using the Wilcoxon test. Remission was defined as a reduction of >75% of the CIBDEI and HS compared with pre-treatment. No acute reactions to ASC infusion or side effects were reported in any dog. Significant differences between pre- and post-treatment were found in both the CIBDEI (P = 0.004) and HS (P = 0.004). Endoscopic remission occurred in 4/11 dogs with the remaining dogs showing decreased CIBDEI (44.8% to 73.3%). Histological remission was not achieved in any dog, with an average reduction of the pre-treatment HS of 27.2%. In conclusion, a single IV infusion of allogeneic ASCs improved gastrointestinal lesions as assessed macroscopically and slightly reduced gastrointestinal inflammation as evaluated by histopathology in dogs with IBD.
