Here we investigated the role of paracrine fac tors secreted by human M1 and M2 macrophages on primary adult human dermal fibroblasts with re spect to proliferation, myofibroblast formation, collagen synthesis and degradation, as well as synthesis neverless of various cytokines. Because of the plasticity of macrophages, we also set out to investigate the influence of paracrine fac tors secreted by M1 macrophages followed by paracrine factors secreted by M2 macrophages on HDFs. Results Characterization of macrophages after M1 or M2 polarization Primary human macrophages responded to LPS IFNG or IL4 IL13, resulting in M1 or M2 polarization, respectively. M1 polarized macrophages adopted a den dritic like morphology with large filopodia while M2 polarized macrophages showed a rounded and or spindle shaped morphology, which was comparable with the morphology of unstimulated macrophages.

The three macrophage subsets showed compared to the reference gene tyrosine 3 monooxygenase tryptophan 5 monooxygenase activation protein, zeta polypeptide, a high expression of CD68, which is a general marker for macrophages. M1 macrophages had a lower CD68 expression than M2 polarized or unstimulated mac rophages. Inhibitors,Modulators,Libraries CD14, a co receptor for toll like re ceptor 4, is involved in LPS recognition and is upregulated by M1 polarized macrophages compared to M2 or unstimulated macrophages. Macrophages stimulated for 48 h with LPS IFNG showed an upregulation of the inflammatory genes inter leukin 1 beta, IL6 and CCL2 compared to M2 po larized and unstimulated macrophages.

A similar upregulation of CD40, a protein involved in the activation of antigen presenting cells, was seen after LPS IFNG stimulation. Inhibitors,Modulators,Libraries Macrophages stimulated with Inhibitors,Modulators,Libraries IL4 IL13 showed Inhibitors,Modulators,Libraries an upregulated gene expression of C type lectin domain family 10, member A and mannose receptor, C type 1 compared to M1 polarized or unstimulated macrophages. CCL18 tended to be upregulated in IL4 IL13 stimulated macro phages while interleukin 1 receptor, type II, which acts as a decoy receptor for the type I interleukin 1, showed Inhibitors,Modulators,Libraries a higher expression in IL4 IL13 and unstimulated macro phages than M1 polarized macrophages. M1 macrophages secreted significantly more CCL2 compared to M2 and unstimulated macrophages. M2 and M1 macro phages secreted more CCL18 compared to unstimulated macrophages, but no significant differences in secretion were seen between M1 and M2.

M1 macro phages secreted more pro inflammatory cytokines and che mokines compared to M2 and unstimulated macrophages. M2 macrophages secreted fibroblast Imatinib clinical trial growth fac tor 2, which was significant different compared to M1 and unstimulated macrophages. Overall, our results indicate that M1 polarized macro phages were pro inflammatory while M2 polarized mac rophages were non inflammatory and unstimulated macrophages adopted a M2 intermediate phenotype.