6B). M?CC differentiated on bsa HTC produce very little amounts of immunregulatory IL-10 while M?CC on coll and coll/HA do not. In M?CC differentiated on coll/lsHA and coll/hsHA the amount of released IL-10 is increased (coll/lsHA < coll/hsHA) but still at low levels (Fig. 6C). Figure 6. Late cytokine response of M?CC differentiated on aECM. Monocytes were differentiated into M?CC on bsa, coll or different aECMs. On day 6 of differentiation, cytokine response and NF-��B activation were evaluated ... In summary, we observe for M?CC differentiated on coll/hsHA consistently reduced secretion of the early inflammatory mediators IL-8, IL-1�� and TNF�� (except MCP-1) while IL-6 release is unaffected on all aECMs.
On day 6, we find that in fully matured M?CC on coll/hsHA the release of the pro-inflammatory cytokines IL-12, TNF�� and RANTES is reduced while levels of the immunoregulatory cytokine IL-10 are increased. Since gene expression of inflammatory cytokines is regulated by the transcription factor NF-��B,28 we analyzed the NF-��B expression in M?CC and found nearly 50% reduced protein expression levels of NF-��B in M?CC on coll/hsHA compared with bsa control (Fig. 6D). Discussion Bioengineered aECMs have been shown to modulate cellular responses, i.e., of fibroblasts and mesenchymal stroma cells, and were highlighted as functional coating to improve biomaterial integration and healing.2,810,29 In this study we tested for immunmodulatory effects of different aECMs composed of a collagen matrix and native HA or HA artificially sulfated at low or high levels on the differentiation of monocytes into macrophages induced by a cytokine cocktail mimicking conditions of a sterile inflammation.
The cytokine cocktail was composed of MCP-1, IL-6, and IFN�� which were shown by different studies to attract monocytes in sterile wounds and to prime and activate them.16,17,19-22 Here, we demonstrate that treatment of human monocytes with the cytokine cocktail containing MCP-1, IL-6 and IFN�� stimulates their activation and differentiation in vitro. During the differentiation process into macrophages, monocytes acquire new properties and functions; i.e., they gain adhesive properties, enlarge in size and express a different set of surface markers.30 Likewise, after stimulation with the cytokine cocktail for six days, monocytes were increased in size and displayed macrophage specific surface markers such as CD16, CD71 and HLA-DR indicating their differentiation into macrophages.
30,31 However, they did not properly adhere and spread on the underlying substrate. Adhesion is regarded as a critical factor for monocyte survival and differentiation in vitro and loss of adherence is often associated with cell death.30,32 Apoptosis rate of monocytes treated with the cytokine cocktail was not increased compared with those stimulated with GM-CSF and M-CSF, respectively Batimastat (data not shown).