Biphasic effect of relaxin, inhibitable by a collagenase inhibitor, on the strength of human fetal membranes

BACKGROUND: Relaxin has been proposed as a hormone involved in the collagen remodeling of the utero-placental unit.

MATERIALS AND METHODS: Human fetal membrane explants were incubated with H1 or H2 relaxin for 48 hours and stretched until rupture in a materials testing machine. Co-incubation with a synthetic collagenase inhibitor was performed in order to examine whether the effects of relaxin could be inhibited. The effects on hydroxyproline and histology were evaluated.

RESULTS: Biomechanical testing showed that H2 relaxin induced a biphasic weakening of human fetal membranes, an effect that was abolished after co-incubation with a collagenase inhibitor. H1 relaxin produced no significant effects on the biomechanical properties. The effects of H2 relaxin on the biomechanical properties were, however, not followed by changes in the hydroxyproline concentration or the histology.

CONCLUSION: H2 relaxin had an effect on human fetal membranes and this effect may be mediated through collagenases.