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P050. Intraperitoneally injected mesenchymal stromal cells home significantly more often to the intestines in colitis mice compared to healthy controls

I. Molendijk1, J.M. Perez Galarza2, E.S. de Jonge-Muller1, A.E. van der Meulen-de Jong1, W.E. Fibbe2, D.W. Hommes3, M. van Pel2, H.W. Verspaget1, 1Leiden University Medical Center, Gastroenterology and Hepatology, Leiden, Netherlands, 2Leiden University Medical Center, Immunohematology and Blood Transfusion, Leiden, Netherlands, 3University of California Los Angeles, Digestive Diseases, Los Angeles, United States

Background

Mesenchymal stromal cells (MSCs) are multipotent cells with immunomodulatory and tissue regenerative properties. Therefore, they may be useful in the treatment of inflammatory bowel disease (IBD). Whether or not MSCs need to home to and engraft at the site of inflammation to exert their beneficial effect in colitis needs to be elucidated. We compared the homing and engraftment capacity of MSCs and prestimulated MSCs in experimental colitis.

Methods

MSCs were isolated from bone marrow of wild type BALB/c mice and transduced with a firefly-luciferase and GFP construct. The week before infusion, some MSCs were prestimulated with interferongamma to give iMSCs. TNBS-colitis was induced in BALB/c mice and 2×106 transduced (i)MSCs were injected intraperitoneally. (i)MSCs were visualized in vivo by bioluminescence imaging (BLI). At sacrifice, 3 days after injection of the cells, inguinal lymph nodes (ILNs), mesenteric lymph nodes (MLNs), spleen, small intestine (SI) and colon were also imaged by BLI. Organs were imbedded in paraffin for immunohistochemistry.

Results

A 5.5 fold higher amount of injected MSCs and 4 fold higher amount of injected iMSCs was traceable by BLI in the abdomen of mice with colitis compared to control mice without colitis 2 days after infusion of the cells (p < 0.0001 and p = 0.0029). A similar difference was observed a day later [p = 0.0005 (MSCs); p = 0.0048 (iMSCs)]. BLI at sacrifice 3 days after (i)MSC injection showed the same trend in colon, SI and MLN. Nineteen days after infusion of the (i)MSCs BLI-signal was completely disappeared in the mice that were not sacrificed at day 3. Colons and SI stained for GFP showed spherical (i)MSC formations situated in the fat surrounding the serosal site of the intestines. In these spheres macrophage were found close to (i)MSCs. No (regulatory) lymphocytes were observed inside the spheres, whereas in the surrounding area some CD3 and FoxP3 positivity was found. Furthermore, collagen deposition and some proliferation was observed in these (i)MSC-spheres.

Conclusion

The amount of traceable injected (i)MSCs in the abdomen was significantly higher in mice with colitis compared to healthy controls. (i)MSCs were more likely to cluster around the intestines when colitis was present. No difference in homing or engraftment was observed between MSCs and iMSCs.