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* = Presenting author

P033. Drugs used in the treatment of fistulae in Crohn's disease preserve mesenchymal stem cell survival

L. Meran1, H. Rashidi2, R. Jones3, F. Rose2, K. Shakesheff2, C. Hawkey1

1Nottingham Digestive Diseases Centre, Department of Gastroenterology, Nottingham University Hospitals, Nottingham, United Kingdom; 2Tissue Engineering, STEM, Centre for Biomolecular Sciences, University of Nottingham, Nottingham, United Kingdom; 3Department of Immunology, Nottingham University Hospitals, Nottingham, United Kingdom

Background: Mesenchymal stem cells (MSCs) have the potential to enhance healing of fistulae, owing to their multilineage differentiation capacity and immunosuppressive properties, and are currently under investigation in clinical trials in patients with fistulae. However, little is known of the interaction of MSCs with drugs used in the treatment of fistulae in Crohn's disease. We demonstrate here that on exposure to antibiotics used in the management of fistulae (ciprofloxacin and metronidazole), as well as anti‑TNF α (infliximab), MSCs retain their proliferation and differentiation capacity.

Methods: Cultured human bone marrow derived MSCs were plated at a density of 5×104 cells per square centimeter in 24 well plates and allowed to adhere overnight. Cells were exposed to a range of daily doses of ciprofloxacin, metronidazole (0.1 µg/ml – 30 µg/ml) and infliximab (1 µg/ml – 500 µg/ml) for a six-week period. MSC morphology was assessed daily and differentiation capacity into adipocyte, osteocyte and chondrocyte lineages was studied after exposure to drugs. MSC survival was assessed at using Annexin‑V Apodetect assay followed by FACS analysis. Cell survival was expressed as percentages of cells that were negative for Annexin‑V and propidium iodide staining. Analyses were performed using the SPSS statistical package (version 19.0).

Results: MSCs exposed to a range of concentrations of ciprofloxacin, metronidazole and infliximab daily, consistently displayed a normal morphology as assessed by light microscopy. Following exposure of these drugs, differentiation into adipocyte, osteocyte and chondrocyte lineages was conserved. In the absence of drugs, mean survival (±SD) of MSCs was 81.8±8.6%. In the presence of ciprofloxacin, mean survival of MSCs was generally increased compared to control cells, significantly so at the highest concentration of 30 µg/ml: 90.1% (p < 0.05). By contrast, with metronidazole and infliximab there was no change in survival level, when compared to control cells at any of the concentrations used.

Conclusions: This study demonstrates that, in vitro, morphological characteristics, proliferation and differentiation capacity of MSCs is preserved in the presence of ciprofloxacin, metronidazole and infliximab. These findings are important in the consideration of the combination of MSCs with antibiotics and anti-TNF α therapy in the management of fistulating Crohn's disease, and will inform subsequent studies to optimize drug and cell delivery.