MSCs secrete important factors, the levels of which increase upon PBMC coculture. Human MSCs and human PBMCs isolated from unrelated donors were cocultured (MSC to PBMC ratio, 1:10) for 24 hours, and cell supernatants were collected and analyzed for various secreted factors by ELISA. (A) Human MSCs secreted factors IL-6, IL-8, VEGF, and PGE₂, and the levels of each of these factors increased more than 3-fold upon hPBMC coculture (IL-6: 6-fold; IL-8: 6-fold; VEGF: 3-fold; and PGE₂: 10-fold). Bars represent cytokine levels (mean pg/mL ± SD) from 2 independent hMSC and 1 hPBMC donors. (B) Human MSCs from 3 independent donors were cultured in the presence of TNF-α and IFN-γ for 24 hours, following which PGE₂ levels in the supernatant were determined using ELISA. The results shown are from duplicate cultures performed in parallel (mean ± SD).