[Properties of the chorioamnios zone inducing premature membranes rupture]

Premature membrane rupture (PMR) is one of the most serious public health problems in the world, ocurring in 10% of all pregnancies. PMR has important adverse effects on maternofetal morbidity-mortality, as it has been estimated that it accounts on the whole for 70% and 40% of neonatal morbidity and mortality, respectively. PMR treatment is empirical, as its aetiology is unknown and its physiopathogenic description has just been initiated. This work analyzes the possibility of documenting functional differences in human chorio-amnios, comparing the zone where rupture most frequently occurs in PMR with some other distant chorio-amnionic zones and with equivalent zones of fetal membranes obtained from nine month pregnancies which have not undergone labor. The membrane zone which was nearest to the cervical os was identified and marked to be analyzed later for extracellular matrix metalloprotease (MMP) activity, histology and topographical MMP distribution. The MMP expression was quantitatively determined in explant culture media from membrane fragments using specific immuno-enzymatic essays (ELISA) and zymography. In addition, immuno-histochemistry methods were used to reveal MMP expression in the different tissues. This methods allowed us to show the existence of a decreasing MMP activity gradient, with the greatest value corresponding to the zone nearest to the cervical os in the membranes obtained from PMR cases. In membranes obtained from cesarean operations no characteristic pattern was documented and values were always lower than those obtained for PMR tissues. We conclude that there is a chorio-amnionic zone in which connective tissue degradation is specifically induced and which coincides with the membrane zone in contact with the cervical os.