Membrane-type 1 matrix metalloproteinase is induced in decidual stroma without direct invasion by trophoblasts

Membrane-type 1 matrix metalloproteinase (MT1-MMP) in endometrium and decidua may greatly affect attachment of the embryo to the epithelium, invasion of the trophoblast into the stroma, and extracellular matrix remodelling in the endometrium and decidua. We investigated the expression of this enzyme in normally cycling endometrium and in decidua associated with normal and tubal pregnancies at both the gene and protein level. Localization of expression (but not the overall level of expression), differed between endometrium and decidua parietalis and tubal pregnancy decidua. MT1-MMP mRNA was expressed mainly in epithelium and only faintly in stroma throughout the menstrual cycle, while in decidua parietalis and tubal pregnancy decidua, this mRNA was expressed predominantly in stromal cells. MT1-MMP protein was detected in the epithelium alone throughout the menstrual cycle, while in decidua parietalis and tubal pregnancy decidua, it was detected in stromal cells as well as the epithelium. Since decidua showed altered expression in the absence of trophoblastic contact, trophoblast invasion may not directly affect MT1-MMP gene expression.