Discovery and Characterization of Human Amniochorionic Membrane Microfractures

Abstract

This study obtained visual evidence of novel cellular and extracellular matrix-level structural alterations in term and preterm human fetal amniochorionic membranes. Amniochorions were collected from term cesarean (not in labor) or vaginal (labor) deliveries, preterm premature rupture of membranes, and spontaneous preterm birth. To determine the effect of oxidative stress on membranes at term or preterm labor, term not in labor samples in an organ explant culture in vitro were exposed to cigarette smoke extract. Tissues were imaged using multiphoton autofluorescence and second harmonic generation microscopy. Images were analyzed using ImageJ and IMARIS software. Three-dimensional microscopic analysis of membranes revealed microfractures that were characterized by amnion cell puckering, basement membrane degradation, and tunnels that extended into the collagen matrix with migrating cells. Numbers of microfractures were similar at term regardless of labor status; however, morphometric measures (width and depth) were higher in term labor membranes. Oxidative stress induced higher numbers of microfractures in term not in labor membranes, with morphometry resembling that seen in term labor membranes. Preterm premature rupture of the membranes had the highest number of microfractures compared to membranes from term and other preterm births. Microfractures are structural alterations indicative of areas of tissue remodeling during gestation. Their increase at preterm and in response to oxidative stress may indicate failure to reseal, predisposing membranes to rupture.

Proliferative, Migratory, and Transition Properties Reveal Metastate of Human Amnion Cells

“…14 As previously reported by us, microfractures develop during membrane growth in gestation because of shedding of senescent or apoptotic cells, characterized by degradation of basement membranes and ECM collagen. 14,25 However, these microfractures do not threaten pregnancy status or membrane integrity because they are healed by tissue and collagen remodeling. This process is aided by reactive oxygen radicalemediated signaling and localized inflammation similar to what is documented in wound healing.…”

“…In vitro, TNIL membranes exposed to OS inducers, increased microfractures, and their morphometry were similar to those seen in TL. 14 Similarly, microfractures were more frequent in pPROM and PTB with intact membranes than gestational ageematched membranes from preeclampsia. 25 We postulate that microfractures are areas of membrane remodeling and are increased in response to OS at term or preterm.…”

“…9,10 Both human and animal models suggest that development of senescence and senescence-associated inflammation are progressive events that peak at term as the membranes reach their longevity. 10e13 Senescent membranes fail to remodel, 14 lose their structural integrity, and generate various inflammatory signals that can cause transition of a quiescent uterus to an active (in labor) status. Thus, membranes can alternatively support pregnancy or promote labor.…”

“…Multiphoton microscopy of membranes showed amnion cell shedding and/or puckering, basement membrane and ECM degradation, and migration of cells through tunnels in the ECM. 14 These structures are collectively called microfractures, and TL microfractures are distinct from those in TNIL. Microfractures are more frequent in TL than TNIL membranes from cesarean sections.…”

Preterm prelabor rupture of the membranes: A disease of the fetal membranes

“…Recently, we examined fetal membrane cellular and collagen structures using nonlinear microscopy from term and preterm labor revealed development of microfractures in fetal membranes 123 . In this study, the combined methods of multi-photon autofluorescence (MPAM) and second harmonic generation (SHG) were applied to investigate the multilayered 3-dimensional micro-organization of human fetal membranes without the use of exogenous contrast agents.…”