The human fetal membranes: a target tissue for relaxin

Area of Science:

• Reproductive biology
• Endocrinology
• Biochemistry

Background:

• Fetal membrane remodeling is critical for childbirth.
• The role of hormones in this process is not fully understood.

Purpose of the Study:

• To investigate the paracrine role of human decidual relaxin (Rlx) in fetal membrane collagen remodeling.
• To identify specific Rlx receptors in fetal membranes.
• To examine the effects of Rlx and other hormones on enzyme release involved in collagen breakdown.

Main Methods:

• Binding assays using radiolabeled porcine Rlx to detect Rlx receptors in fetal membranes.
• In vitro studies with cultured amnion/chorion cells to measure enzyme release (plasminogen activator, collagenase, beta-glucuronidase).
• Analysis of amniotic fluid for enzyme activity in relation to membrane rupture.

Main Results:

• Specific Rlx receptors were identified in human fetal membranes.
• Rlx stimulated the release of plasminogen activator and collagenase from cultured cells.
• Hormones like PRL, hCG, estrogen, and progesterone also influenced enzyme release, with varying effects based on tissue source (cesarean section vs. term delivery).
• Increased collagenase activity was detected in amniotic fluid after spontaneous membrane rupture.

Conclusions:

• Human fetal membranes are responsive to decidual paracrine hormones (Rlx, PRL, prostaglandin F2 alpha) and other hormones (estrogen, progesterone, hCG).
• These hormones modulate enzymes essential for collagen degradation.
• This hormonal regulation plays a role in the timing of fetal membrane rupture.