Under inflammatory stimuli mesenteric mesothelial cells transdifferentiate into macrophages and produce pro-inflammatory cytokine IL-6

OBJECTIVE: Inflammatory stimuli inducing epithelial-to-mesenchymal transition (EMT) can transdifferentiate mesenteric mesothelial cells into macrophages. METHODS: Sprague Dawley rat mesenteric mesothelial cells were used as a model. 1 ml Freund adjuvant was injected into the peritoneal cavity of rat and GM-CSF treatment was used to induce inflammation. IL-10 and IL-6 expression were studied by immunocytochemistry and Western blot analysis both in vivo and in vitro. RESULTS: Control mesothelial cell express anti-inflammatory IL-10, but no pro-inflammatory IL-6 expression could be detected in them. By the time of inflammation, IL-6 expression increased (reached the maximum level at the fifth day of inflammation), parallel to this the IL-10 entirely disappeared from these cells. In vitro GM-CSF treatment resulted in similar changes. As the mesothelial cells started to recover (at the eighth day of inflammation) IL-6 expression decreased and IL-10 level started to increase again. CONCLUSION: These data show that under inflammatory stimuli mesothelial cells—like macrophages—can produce pro-inflammatory cytokines.