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CHARACTERIZATION OF COLLAGENASE–1 (MMP–1) AND STROMELYSIN–1 (MMP–3) IN OVINE CORPORA LUTEA.
Smith, Michael1, Smith, George2, Kojima, Freddie1, Ricke, William1, 1 2
ABSTRACT- The matrix metalloproteinases (MMPs) are regulators of extracellular matrix (ECM) remodeling. Although luteal formation and regression are accompanied by extensive ECM remodeling, very little is known about the identification, localization and activity of MMPs in corpora lutea. Therefore, our objective was to characterize mRNA and protein expression for ovine collagenase–1 (MMP–1) and stromelysin–1 (MMP–3) during the luteal phase. We previously reported that MMPs–1 and 3 were immunolocalized to specific luteal cell types. MMP–1 was immunolocalized predominantly to large luteal cells (LLCs) on days 2, 4, 10, and 15 post estrus (day 0 = estrus) and putative endothelial cells on day 15 post estrus. MMP–3 was immunolocalized to LLCs but also to other cell types. In the present experiment, corpora lutea were collected from ewes on days 2, 4, 10, and 15 of the estrous cycle (day 0 = estrus; n = 5 to 10 per time point). Northern blot analysis confirmed MMP–1 and 3 expression within ovine luteal tissue. Transcript sizes for MMP–1 and 3 were 1.9 and 2.0 kb (respectively), which are consistent with transcript sizes reported in other species. Relative levels of MMP–1 mRNA in ovine corpora lutea did not differ at above time points examined. However, expression of MMP–3 mRNA was increased (P < 0.05) on day 4 relative to all other days evaluated. Concentrations of MMP–1 and 3 in corpora lutea were measured via enzyme–linked immunosorbent assays. Luteal concentrations of MMP–1 and 3 were greater (P < 0.05) during early luteal development (day 2) than all other days examined (days 4, 10, and 15). Our results indicate that MMP–1 and 3 mRNA and protein are expressed in ovine corpora lutea throughout the luteal phase. The higher amounts of MMP–1 and 3 detected on day 2 post estrus suggests that these enzymes may play key roles in regulating the ECM microenvironment during luteal development. Supported by USDA 98–35203–6282 (MFS) and USDA 98–35203–6226 (GWS).
KEY WORDS: Corpus Luteum, Matrix Metalloproteinase, Extracellular Matrix