Molecular characterization of soluble factors from human menstrual effluent that induce epithelial to mesenchymal transitions in mesothelial cells.

We have studied menstrual effluent in order to identify soluble menstrual factors that induce epithelial to mesenchymal transitions (EMT) in mesothelial cells. A variety of molecules, such as nitric oxide and its reaction products, proteases (i.e. matrix metalloproteinases, plasmin) and proteins and/or peptides (i.e. growth factors: b-fibroblast growth factor, epidermal growth factor, hepatocyte growth factor, transforming growth factor-beta; cytokines: interleukin 1 beta, tumour necrosis factor-alpha [TNF-alpha]) may be involved in this process. We have demonstrated that TNF-alpha is involved in EMT, whereas the other molecules are not. Biochemical analysis has shown that the inducing menstrual factors are heat-labile molecules, are uncharged at neutral pH, have a molecular weight between 50-70 kDa (or are bound in complexes of that size) and are eluted in the albumin fraction during gel filtration chromatography. Further analysis of this fraction by using proteomics and mass spectrometry has led to the identification of alpha-enolase and haemoglobin whose inhibition partially prevents EMT. When antibodies against TNF-alpha, alpha-enolase and haemoglobin are combined, EMT is almost completely inhibited. Thus, the candidates for soluble menstrual factors that induce mesothelial EMT are TNF-alpha, alpha-enolase and haemoglobin.