Urokinase-type Plasminogen Activator (uPA) and Matrix Metalloproteinase-9 (MMP-9) Expression and Activity During Early Embryo Development in the Cow

Several extracellular matrix (ECM)-degrading proteinases are hypothesised to play important roles during early mammalian development. In particular, urokinase-type plasminogen activator (uPA) and matrix metalloproteinase 9 (MMP-9) are expressed in peri-implantation mouse, sheep, and pig embryos and are implicated in the implantation process. These proteinases are not expressed in early (pre-blastocyst) mouse, sheep or pig embryos. The aim of this study was to establish the gene expression and proteolytic activity of uPA and MMP-9 in in vitro-produced (IVP) cow embryos. Using RT-PCR, mRNA transcripts for uPA and MMP-9 were detected during the first 7 days of development. To investigate the activity of these proteinases, conditioned media from various stages of development (days 2, 3, 4, 5 and 7) were assayed for uPA activity by chromogenic assay and MMP-9 activity by gelatin zymography. Both uPA and MMP-9 activities were detected in the media samples indicating the production and secretion of these proteinases. This pattern of proteinase expression is novel in comparison to the mouse where uPA and MMP-9 are only expressed from the blastocyst stage onwards. The results of this study suggest that these ECM proteinases have a role prior to implantation in the cow, in contrast to that exhibited by mouse, sheep and pig embryos.