Proinflammatory Cytokines Found in Amniotic Fluid Induce Collagen Remodeling, Apoptosis, and Biophysical Weakening of Cultured Human Fetal Membranes1

Abstract

The mechanisms by which fetal membranes (FM) rupture during the birth process are unknown. We have recently reported that FM weaken, at least in part, because of a developmental process of extracellular matrix remodeling and apoptosis. We now hypothesize that cytokines that normally increase in amniotic fluid at term induce FM collagen remodeling and apoptosis with concomitant weakening. Full-thickness FM fragments were cultured with (0-100 ng/ml) or without tumor necrosis factor (TNF) or interleukin 1, beta (IL1B). Physical properties were then examined with specially adapted industrial rupture strength testing equipment. Cultured FM were also evaluated for evidence of collagen remodeling and apoptosis. Cytokine-treated FM exhibited a dose-dependent decrease in strength and work to rupture. Compared with controls, the highest TNF dose caused maximal decrease in FM rupture strength (13.2 +/- 1.2 N versus 3.8 +/- 1.5 N; P = 0.0003) and work to rupture (0.035 +/- 0.005 J versus 0.005 +/- 0.002 J; P< 0.0001). The highest IL1B dose also decreased rupture strength (12.9 +/- 3.2 versus 4.6 +/- 1.1 N; P = 0.0027) and work to rupture (0.018 +/- 0.005 J versus 0.005 +/- 0.002 J; P < 0.01). Matrix metalloproteinase 9 (MMP9) protein increased, tissue inhibitor of matrix metalloproteinase 3 (TIMP3) protein decreased, and poly (ADP-ribose) polymerase (PARP1) cleavage increased with increasing TNF or IL1B doses (all P < 0.05), suggesting collagen remodeling and apoptosis. TNF and IL1B cause significant weakening of cultured FM. Both cytokines induce biochemical markers in the FM in a manner characteristic of the weak zone of FM overlying the cervix. TNF and or IL1B may be involved in the development of the weak zone of the FM.

Weakening and Rupture of Human Fetal Membranes – Biochemistry and Biomechanics

“…Thus we conclude that MMP-9 plays a major role in FM remodeling, weakening and rupture. Our work also demonstrates that MMP-9 levels are an excellent marker for FM strength (El-Khwad et al, 2005Kumar et al, 2006; R.M. Moore et al, 2009b) [Fig.…”

Endocrine immune interactions in human parturition

“…Increased PGE2 production in the amnion could diffuse through the chorion and decidua to stimulate myometrial cell prostaglandin production and hence contractility (Slater et al, 1999, Smith, 2007. The fetus and placenta may also jointly trigger fetal membrane rupture, since prostaglandins, TNF-α and corticotrophin releasing hormone (CRH) (which also rise in the amniotic fluid towards term (Alvi et al, 1999, Laatikainen et al, 1988) all stimulate the production of MMP-9, which weakens the membranes and thus facilitates membrane rupture (Kumar et al, 2006, Young et al, 2002.…”

Progesterone inhibits in vitro fetal membrane weakening

“…To address these shortcomings, we developed an in vitro explant model system in which human fetal membrane rupture strength, which is the major parameter of clinical interest, and concomitant (and presumably causative) biochemical changes within the fetal membrane can be measured accurately. [8][9][10] Using this system, we found that cytokines such as tumor necrosis factor-a (TNF) and interleukin 1ß, which induce tissue level inflammation, and thrombin, which causes changes that are associated with abruption and bleeding, markedly weaken full-thickness fetal membrane. 4,9,11,12 Concomitant with weakening, these agents induce biochemical and histologic tissue changes that mimic those seen in the physiologic weak zone (fetal membrane rupture initiation site) in the fetal membrane region overlying the cervix.…”