MSCs promote monocyte migration through TNF-α-induced secretion of CCL2. Supernatants (sups) were collected from human BM-derived MSCs that were stimulated by TNF-α (50 ng/ml) or by its vehicle for 24 hours. Thereafter, the sups were incubated with neutralizing antibodies for CCL2 or with nonrelevant isotype-matched control antibody (I.C.) for 30 minutes. The migration of monocytic cells in response to control medium (without chemokine), to recombinant human CCL2 (rhCCL2; 100 ng/ml) or to sups from TNF-α-stimulated or TNF-α nonstimulated MSCs was determined by Boyden chamber migration assays. Cells were counted under a high-power field (HPF). The findings are representatives of n = 3 independent experiments that have shown similar results.