Comparison of antibacterial and immunological properties of Mesenchymal Stem/Stromal cells from equine Bone Marrow, Endometrium and Adipose tissue

Equine Mesenchymal stem/stromal cells (MSCs) are multipotent cells that are widely used for treatment of musculoskeletal injuries, and there is significant interest in expanding their application to non-orthopedic conditions. MSCs possess antibacterial and immunomodulatory properties which may be relevant for combatting infection, however, comparative studies using MSCs from different origins have not been carried out in the horse, and this was the focus of the present study. Our results showed that MSC-conditioned media attenuated the growth of Escherichia coli, and that this effect was, on average, more pronounced for endometrium (EM)- and adipose tissue (AT)- than for bone marrow (BM)-derived MSCs. In addition, the antimicrobial Lipocalin-2 was expressed at mean higher levels in EM- compared to AT- and BM-MSCs, and the bacterial product lipopolysaccharide (LPS) stimulated its production by all three MSC types. We also show that MSCs express IL-6, IL-8, MCP-1, CCL5 and TLR4, and that, in general, these cytokines were induced in all cell types by LPS. Low expression levels of the macrophage marker CSF1-R were detected in BM- and EM-MSCs, but not in AT-MSCs. Altogether, these findings suggest that equine MSCs from endometrium, adipose tissue and bone marrow have both direct and indirect antimicrobial properties which may vary between MSCs from different origins and could be exploited towards improvement of regenerative therapies for horses.