Macrophage Migration Inhibitory Factor Elicits an Angiogenic Phenotype in Human Ectopic Endometrial Cells and Triggers the Production of Major Angiogenic Factors via CD44, CD74, and MAPK Signaling Pathways

Abstract

Context: An active angiogenesis is required for ectopic endometrial tissue growth. Our previous studies led to the identification of macrophage migration inhibitory factor (MIF), which is markedly elevated in active, vascularized, and early-stage endometriotic lesions, as a potent mitogenic factor for endothelial cells. Objective: Our objective was to study the mechanisms by which MIF may stimulate angiogenesis in ectopic endometrial implantation sites. Design: Primary cultures of ectopic endometrial cells were exposed to MIF, and the release of major angiogenic factors with targeted disruption of MIF signaling pathways was assessed. Patients: Patients were women found to have endometriosis during laparoscopy. Setting: The study was conducted at a hospital and reproduction research laboratory. Interventions: Biopsies were removed from endometriotic lesions. Main Outcome Measures: Vascular endothelial cell growth factor (VEGF), IL-8, and monocyte chemotactic protein-1 (MCP-1) mRNA and protein levels and expression and small interfering RNA silencing of MIF CD74/CD44 receptor complex and phosphorylation of ERK and p38 MAPKs were evaluated. Results: MIF markedly up-regulated VEGF, IL-8, and MCP-1 expression in endometriotic cells. Such an effect was abolished by (S,R)-3-(4-hydroxyphenyl)-4,5-dihydro-5-isoxazole acetic acid methyl ester (ISO-1), a specific inhibitor of MIF, and significantly down-regulated after specific small interfering RNA silencing of CD44 or CD74. MIF treatment strongly activated ERK and p38 MAPKs, and specific inhibitors of both pathways completely blocked basal and MIF-induced VEGF, IL-8, and MCP-1 synthesis. Conclusions: These results show for the first time that MIF exerts a potent indirect angiogenic effect by interacting with ectopic endometrial cells and inducing the secretion of major angiogenic factors via CD44, CD74, and MAPK signaling pathways and provide evidence for a possible new mechanism underlying endometriosis development and pathophysiology.