Marmoset monkey trophoblastic tissue growth and matrix metalloproteinase secretion in culture

Marmoset monkey blastocysts maintained in culture produced trophoblastic vesicles up to 4 mm in diameter that were subdivided into fragments and subcultured to produce new vesicles. These tissues are composed of an outer layer of trophoblast-like cells and an inner layer of endoderm-like cells, and resemble a blastocyst wall. When such vesicles were cultured in serum-free medium for 14 days, they increased in size but there was no significant difference in their protein content at the end of culture. The proliferation index, measured by BrdU incorporation, varied considerably within and between vesicles. The purpose of this investigation was to determine which matrix metalloproteinases are secreted by marmoset monkey trophoblastic tissue in vitro, and the effect of extracellular laminin on this secretion. It was determined by zymography that the vesicles secreted matrix metalloproteinase 2, but not matrix metalloproteinase 9, and that matrix metalloproteinase 2 was secreted as the proenzyme (72 kDa). Matrix metalloproteinases 1, 3 and 7 were not detectable in the culture medium. The addition of laminin (5-20 micrograms ml-1), either as a substrate or in solution in the medium, did not have a consistent effect on matrix metalloproteinase 2 secretion during the culture period. The vesicles were found to express both matrix metalloproteinases 2 and 9 in both types of cell when examined by immunohistochemistry. The expression of matrix metalloproteinase 9 in the vesicles, but the absence of its secretion, indicates that specific factors, possibly of endometrial origin, may be required for inducing secretion.