Excess placental secreted frizzled-related protein 1 in maternal smokers impairs fetal growth
Alice Wang, … , Saira Salahuddin, S. Ananth Karumanchi
Alice Wang, … , Saira Salahuddin, S. Ananth Karumanchi
Published September 28, 2015
Citation Information: J Clin Invest. 2015;125(11):4021-4025. https://doi.org/10.1172/JCI80457.
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Brief Report Reproductive biology

Excess placental secreted frizzled-related protein 1 in maternal smokers impairs fetal growth

Abstract

Maternal cigarette smoking during pregnancy remains one of the most common and preventable causes of fetal growth restriction (FGR), a condition in which a fetus is unable to achieve its genetically determined potential size. Even though epidemiologic evidence clearly links maternal cigarette smoking with FGR, insight into the molecular mechanisms of cigarette smoke–induced FGR is lacking. Here, we performed transcriptional profiling of placentas obtained from smoking mothers who delivered growth-restricted infants and identified secreted frizzled-related protein 1 (sFRP1), an extracellular antagonist of endogenous WNT signaling, as a candidate molecule. sFRP1 mRNA and protein levels were markedly upregulated (~10-fold) in placentas from smoking mothers compared with those from nonsmokers. In pregnant mice, adenovirus-mediated overexpression of sFRP1 led to FGR, increased karyorrhexis in the junctional zone, and decreased proliferation of labyrinthine trophoblasts. Consistent with our hypothesis that placental WNT signaling is suppressed in maternal smokers, we found that exposure to carbon monoxide analogs led to reduced WNT signaling, increased SFRP1 mRNA expression, and decreased cellular proliferation in a trophoblast cell line. Moreover, administration of carbon monoxide analogs to pregnant mice in late gestation led to FGR. In summary, our results indicate that the increased placental expression of sFRP1 seen in smokers impairs fetal growth by inhibiting WNT signaling and trophoblast proliferation.

Authors

Alice Wang, Zsuzsanna K. Zsengellér, Jonathan L. Hecht, Roberto Buccafusca, Suzanne D. Burke, Augustine Rajakumar, Emily Weingart, Paul B. Yu, Saira Salahuddin, S. Ananth Karumanchi

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Figure 3

Effect of carbon monoxide analogs on canonical WNT transcriptional activity, sFRP1 expression, trophoblast proliferation, and fetal growth.

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Effect of carbon monoxide analogs on canonical WNT transcriptional activ...
(A) Luciferase activity of the canonical WNT reporter in HTR cells transfected with the TOPFLASH TCF reporter plasmid after exposure to varying concentrations of CO-RM2, inactivated CO-RM2 (iCO-RM2), and 10% cigarette smoke extract (CSE) for a period of 24 hours. The normalized value of unstimulated control was arbitrarily set at 100%. Bars represent mean values of 3 different experiments; error bars indicate SEM. P < 0.001 by ANOVA, *P < 0.05 for 50 μM CO-RM2 versus DMSO control by t test, #P < 0.05 for 100 μM CO-RM2 versus control by t test, +P < 0.05 for 200 μM CO-RM2 versus DMSO control by t test. (B) Relative quantification of SFRP1 mRNA levels measured by qRT-PCR in HTR cells after exposure to CO-RM2 for a period of 24 hours. Data are presented as scatter plot (mean ± SEM). SFRP1 expression was increased after exposure to 100 μM CO-RM2 compared with that after exposure to DMSO control (P < 0.05 by t test). (C) Dose-dependent reduction of [3H] thymidine incorporation in serum-starved HTR cells after exposure to varying concentrations of CO-RM2. Inactivated CO-RM2 had no effect of [3H] thymidine incorporation. Experiments were performed twice, in triplicate (mean ± SEM). (D) Fetal weights on E18 were decreased in CD1 pregnant mice injected on E15 with CO-RM2 (n = 5 litters, 63 fetuses) as compared with those injected with 1% DMSO vehicle (n = 5 litters, 67 fetuses). Data are presented as a box plot (25th–75th percentile), with horizontal bars representing median values and whiskers representing minimum and maximum values (*P < 0.001 versus mice injected with DMSO vehicle by t test).