Altered decorin and Smad expression in human fetal membranes in PPROM

Abstract

Humans with Ehlers-Danlos syndrome, a subtype of which is caused by abnormal decorin expression, are at increased risk of preterm birth due to preterm premature rupture of fetal membranes (PPROM). In the mouse model, the absence of decorin leads to fetal membrane abnormalities, preterm birth, and dysregulation of decorin's downstream pathway components, including the transcription factor p-Smad-2. However, the role of decorin and p-Smad-2 in idiopathic human PPROM is unknown. Fetal membranes from 20-25 pregnancies per group were obtained as a cross-sectional sample of births at one institution between January 2010 and December 2012. The groups were term, preterm without PPROM, and preterm with PPROM. Immunohistochemical analysis of fetal membranes was performed for decorin and p-Smad-2 using localization and quantification assessment. Decorin expression is developmentally regulated in fetal membranes and is decreased in preterm birth with PPROM compared to preterm birth without PPROM. In preterm with PPROM samples, the presence of infection is associated with significant decorin downregulation compared to preterm with PPROM samples without infection. The preterm with PPROM group exhibited decreased p-Smad-2 staining compared to both the term controls and the preterm-without-PPROM group. Our findings suggest that dysregulation of decorin and its downstream pathway component p-Smad-2 occurs in fetal membranes during the second trimester in pathological pregnancies, thus supporting a role for decorin and p-Smad-2 in the pathophysiology of fetal membranes and adverse pregnancy outcomes. These findings may lead to the discovery of new targets for the diagnosis and treatment of PPROM.

Keywords: PPROM; Smad; decorin; fetal membranes; preterm birth.

FIG. 1

Decorin expression in human fetal membranes during the course of gestation. A) Immunohistochemical staining of decorin increases during the course of gestation in fetal membranes after PPROM between 16 and 34 wk of gestation. B) Immunohistochemical staining of decorin increases during the course of gestation in fetal membranes without PPROM between 26 and 31 wk of gestation. Original magnification ×40; bar = 20 μm.

FIG. 2

A) Immunohistochemical analysis of decorin expression in fetal membranes at full term, preterm − PPROM, and preterm + PPROM. Decorin expression is decreased in fetal membranes with preterm + PPROM. This decrease is significant when infection is present. Original magnification ×40; bar = 20 μm. B) Schematic of amnion/chorion fibroblast layer used for quantitative analysis of decorin staining, excluding the epithelial layer of amnion and the trophoblast layer.

FIG. 3

A) Quantitative analysis of immunofluorescence showing a significant in decrease in decorin signal in preterm + PPROM fetal membranes compared to preterm − PPROM (P = 0.0037) and full term and preterm − PPROM (P = 0.0091). There is no difference between full-term fetal membranes and the preterm + PPROM group. Statistical analysis by ANOVA with Sidak post hoc t-test, n = 20–25 per experimental group. Mean ± SD. Error bars = SD. PPROM = preterm premature rupture of fetal membranes. B) Quantitative analysis of immunofluorescence showing a significant in decrease in decorin signal in preterm + PPROM fetal membranes with infection compared to preterm + PPROM without infection (P = 0.0026). Statistical analysis by t-test, n = 20–25 per experimental group. Mean ± SD. Error bars = SD. PPROM = preterm premature rupture of fetal membranes. * = statistical significance.

FIG. 4

Immunohistochemical comparison of p-Smad-2 expression in full-term, preterm − PPROM, and preterm + PPROM fetal membranes. There is decreased decorin signal in the preterm + PPROM group compared to the preterm − PPROM group and the full-term group. P-Smad-2 staining was localized more to the trophoblast layer (thin arrows) than the fibroblast layer of the amnion/chorion (thick arrows). Original magnification ×40; bar = 20 μm. n = 20–25 per experimental group. PPROM = preterm premature rupture of fetal membranes.