Inflammatory Cell Tissue Extravasation Pathways Can Be Regulated by Adherent Stem Cells by Inhibiting Selectin Ligand and Adhesion Receptor Expression On T Cells and Activated Endothelium.

Abstract 3631

Poster Board III-567

MultiStem is an adult bone marrow derived stem cell product with immune-modulatory activity that falls within a class of adherent stem cell platforms emerging as modalities for allogeneic therapy for modulation of GVHD. Despite initial preclinical and clinical success there remains significant need for mechanistic understanding of stromal cell interaction with inflammatory cells, particularly relating to biodistribution and the microenvironments encountered after intravenous administration. Successful GVHD treatment or prophylaxis regimens will likely by optimized by a better appreciation of adherent stem cell interactions with GVHD initiating T cells in the tissue microenvironment or in secondary lymphoid tissues. In this study we evaluated interactions of MultiStem with activated peripheral blood cells as well as activated endothelial cells using in vitro co-culture systems that permit cross-talk via soluble factors. In co-culture experiments with activated T cells we observed that MultiStem strongly inhibits gene expression of Fut7, the enzyme responsible for expression of Lewis antigen (CD15s). The resultant lack of CD15s expression on the cell surface of activated T cells was shown to result in their reduced ability to bind to endothelium activated with TNFa, relative to T cells activated in the absence of MultiStem. Furthermore, we found that co-culture of MultiStem with endothelial cells prevents upregulation of E-selectin, V-CAM, and to a lesser degree, I-CAM, to the cell surface of endothelial cells upon activation with TNF-α or interleukin-1α. Inhibition of E-selectin expression by co-culture with MultiStem was not caused by increased cleavage of E-selectin from the cell surface. Instead, MultiStem modulates cell surface induction through decreasing transcription of V-CAM, E-selectin and ICAM. This reduction in cell surface adhesion molecule expression results in decreased neutrophil binding to endothelial cells compared with untreated controls. This activity does not appear to be common to all bone marrow derived adherent stem cells as mesenchymal stem cells (MSC) are unable to modulate V-CAM, E-selectin or I-CAM cell surface upregulation upon activation with TNF-α. These results suggest MSC and MultiStem have distinct secretion profiles. These novel observations indicate that, in addition to immunomodulation activity, MultiStem has unique potential to deter GVHD by impacting various arms of the extravasation process of GVHD pathology causing inflammatory cells.