Induction of matrix metalloproteinases and collagenolysis in chick embryonic membranes before hatching

The membranes surrounding the chick embryo undergo striking morphological c hanges before hatching, which include structural degradation of the allanto ic membrane, The fibrillar collagen content of the membranes declined by em bryonic day (ED) 20 (the day of hatching). By ED 19, a 55-kDa matrix metall oproteinase (MMP) activity appeared in the extraembryonic fluid, and by ED 20 there was substantial 55-kDa MMP activity in embryonic membrane extracts . Reverse transcription-polymerase chain reaction was employed to clone a p artial cDNA representing the chicken homologue of MMP-13, a 55- to 57-kDa e nzyme. MMP-13 mRNA dramatically increased in abundance in embryonic membran es by ED 19, reaching a peak on ED 20. Introduction of the MMP inhibitor ba timastat into the extraembryonic fluid prevented the structural changes in the embryonic membranes before hatching. We conclude that, like mammalian f etal membranes, chick embryonic membranes undergo terminal remodeling befor e hatching, in part as a result of increased MMP activity. The chicken egg system represents a novel in vivo model for exploring biochemical events le ading to embryonic membrane remodeling prior to birth and to test inhibitor s of MMPs for their ability to prevent collagenolysis and fetal membrane ru pture.