Amniochorion gelatinase-gelatinase inhibitor imbalance in vitro: A possible infectious pathway to rupture.

OBJECTIVE:
    To estimate the effect of lipopolysaccharide on gelatinases and tissue inhibitors of matrix metalloproteinase 2 (gelatinase inhibitor) balance in human fetal membranes.

METHODS:
    Amniochorionic membranes in organ explant were stimulated with 1000 ng/mL lipopolysaccharide for 24 hours after a 48-hour preincubation period. Quantitative competitive polymerase chain reaction (PCR) was performed to quantitate messenger ribonucleic acids for gelatinase A and B (matrix metalloproteinase 2 and 9) and tissue inhibitor of metalloproteinase 2. Protein levels were assayed by enzyme linked immunosorbant assay (ELISA). The molar ratio between gelatinases and tissue inhibitor of metalloproteinase 2 was calculated. Statistical evaluation was done by Mann-Whitney U test.

RESULTS:
    Lipopolysaccharide stimulation produced 3.6 x 106 versus 366 transcripts of gelatinase A and B compared with only 5.9 x 104 (P=.009) and three transcripts (P=.006) respectively in the control. Lipopolysaccharide stimulation released 210 compared with 7 ng/mL of gelatinase A and B proteins compared with 120 (P=.01) and 4.6 ng/mL (P=.3) in controls respectively. Control amniochorion produced 5.7 x 105 transcripts of tissue inhibitor of metalloproteinase 2 whereas lipopolysaccharide stimulation produced 4.1 x 105 transcripts (P=.69). Lipopolysaccharide reduced the release of this inhibitor from 114 ng/mL to 68 ng/ml (P=.007). The molar ratio between gelatinases and tissue inhibitor of metalloproteinase 2 increased from a balanced ratio of 1:1 to 3.1:1 after 1000 ng/mL of lipopolysaccharide.

CONCLUSION:
     Lipopolysaccharide increases the expression and release of gelatinases and decreases its inhibitor, shifting the balance in favor of gelatinase activity leading to membrane degradation predisposing to premature rupture of membrane.