Effects of a ceramic biomaterial on immune modulatory properties and differentiation potential of human mesenchymal stromal cells of different origin

International audienceThe aim of this study was to assess the immune modulatory properties of human mesenchymal stromal cells obtained from bone marrow (BM-MSCs), fat (ASCs) and cord blood (CB-MSCs) in presence of a hydroxyapatite and tricalcium-phosphate (HA/TCP) biomaterial as a scaffold for MSC delivery. In resting conditions, a short-term culture with HA/TCP did not modulate the anti-apoptotic and suppressive features of the various MSC types towards T, B and NK cells; in addition, when primed with inflammatory cytokines, MSCs similarly increased their suppressive capacities in presence or absence of HA/TCP. The long-term culture of BM-MSCs with HA/TCP induced an osteoblast-like phenotype with up-regulation of OSTERIX and OSTEOCALCIN, similarly to what obtained with dexamethasone and, to a higher extent, with BMP-4 treatment. MSC-derived osteoblasts did not trigger immune cell activation, but were less efficient than undifferentiated MSCs in inhibiting stimulated T and NK cells. Interestingly, their suppressive machinery included not only the activation of indoleamine-2,3 dioxygenase (IDO), which plays a central role in T cell inhibition, but also cyclooxygenase 2 (COX-2) that was not significantly involved in immune modulatory effect of human undifferentiated MSCs. As COX-2 is significantly involved in bone healing, its induction by HA/TCP could also contribute to the therapeutic activity of MSCs for bone tissue engineering