DEVELOPMENT OF THE EMBRYO
7:30 AM-10:00 AM
(148) EXPRESSION AND SECRETION OF MATRIX METALLOPROTEINASE-9 IN DEVELOPING MOUSE PERI-IMPLANTATION BLASTOCYSTS.
Martinez-Hernandez, Maria1, Baiza-Gutman, Luis1, Armant, D1, 1 Departments of Obstetrics & Gynecology and Anatomy & Cell Biology, Detroit, MI
ABSTRACT- Once the blastocyst contacts the endometrium, invasion of the endometrium commences, in part through the action of proteinases secreted by the embryo. Matrix metalloproteinase-9 (MMP-9) is a cation-dependent collagenolytic enzyme expressed by the trophoblast during blastocyst implantation. The aim of this study was to determine temporal changes in cellular distribution, secretion and mRNA levels of MMP-9 during mouse in vitro blastocyst development and the role of trophoblast interactions with extracellular matrix in MMP-9 expression. Mouse embryos were cultured from gestation day (GD) 4 to GD 8 under mineral oil in drops of Ham-F10 medium supplemented with 0.1% of BSA. The levels of MMP-9 mRNA increased progressively from GD 4 to GD 8. MMP-9 was detected by immunocitochemistry in the cytoplasm of trophoblast cells on GD 5 and GD 6 and on the apical surface of trophoblast cells on GD 7 before outgrowth. A major gelatinase of 106 kDa corresponding to pro-MMP-9 was detected by electrophoresis and zymography of the embryo culture medium. Pro-MMP-9 secretion increased slightly on GD 7 and sharply on GD 8. When the embryos were exposed to fibronectin, a decrease in MMP-9 mRNA levels was observed, whereas laminin or collagen IV stimulated MMP9 secretion. In conclusion, MMP-9 was synthesized and stored in trophoblast cells between GD 4 and GD 6, followed by its release into the medium on GD 7 and GD 8 as trophoblast cells began to outgrow. The changes in MMP9 synthesis and secretion were dependent on an endogenous developmental program modulated by interaction with the extracellular matrix. Supported by NIH grants HD367664 and AA12057 to D.R.A, and by scholarships to M. G. M. and L. B. from CONACyT and DGAPA-UNAM.
KEY WORDS: Blastocyst implantation, Metalloproteinase-9, Trophoblast, Mouse embryo