Lefty is expressed in mouse endometrium in estrous cycle and peri-implantation period

BACKGROUND: Reproductive tissues are unique structures that exhibit cyclic stromal remodelling during menstrual cycles in humans. Ebaf/lefty participates in tissue remodelling of human endometrium by induction of matrix metalloproteases (MMP). METHODS: We describe the temporal expression and spatial distribution of lefty and tissue remodelling events in mouse endometrium. RT-PCR and real-time PCR were used to identify mRNA expression and western blots to analyse Lefty protein. Immunolocalization was performed with specific antibodies and horseradish peroxidase staining. RESULTS: Lefty was expressed in endometrium throughout the estrous cycle. Expression of MMP (MMP-2, -3, -7 and -14) was higher at estrus, metestrus and/or diestrus while collagen content of endometrium decreased in these phases. During pregnancy, lefty levels were higher on days 3-5 and were minimal by day 9. Similarly, expression of endometrial MMP was higher on days 3 and 5 of pregnancy and was low on day 9. During pregnancy, loss of collagen was initiated on day 3, persisted to day 5, and led to a significantly reduced collagen on day 9. Immunoreactive lefty decorated basal laminae, and was associated with extracellular matrix in stroma. CONCLUSIONS: Regulated expression and spatial distribution of lefty in mouse endometrium confines its biological impact on tissues that undergo remodelling during estrous cycle and pregnancy.