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. 2015 Sep;213(3):387.e1-10.
doi: 10.1016/j.ajog.2015.05.007. Epub 2015 May 12.

An animal model for chorioamnionitis at term

Valeria Dell'Ovo  1 , Jason Rosenzweig  2 , Irina Burd  2 , Nana Merabova  1 , Nune Darbinian  1 , Laura Goetzl  3
Affiliations

An animal model for chorioamnionitis at term

Valeria Dell'Ovo et al. Am J Obstet Gynecol. 2015 Sep.

Abstract

Objective: The purpose of this study was to develop an animal model for intrapartum inflammation at term to investigate the interactions between maternal and fetal inflammatory responses and adverse neurologic outcome.

Study design: Lipopolysaccharide (160, 320, or 640 μg/kg) was administered intraperitoneally to day 20 term-pregnant Sprague Dawley rat dams 2, 4, and 6 hours before sample collection. Maternal outcomes included dam core temperature and plasma interleukin 6 (IL-6). Fetal outcomes included plasma IL-6, brain IL-6 messenger RNA expression, and brain IL-6 protein expression. Primary cortical cell cultures were prepared to examine neuronal morphologic condition. Neurite counts were obtained with the use of automated Sholl analysis.

Results: Maternal plasma IL-6 levels peaked 2 hours after lipopolysaccharide stimulus and rapidly resolved, except for an observed low level persistence at 6 hours with 640 μg/kg. Fetal plasma and placental IL-6 expression also peaked rapidly but only persisted in placental samples. Fetal brain IL-6 RNA and protein expression was significantly higher than control litters at 6 hours after the exposure to both 320 μg/kg (P ≤ .05) and 640 μg/kg (P ≤ .01). Cortical cells from fetuses that were exposed for 6 hours to maternal systemic inflammation showed reduced neurite number and neurite length (P < .001) with increasing lipopolysaccharide dose.

Conclusion: Our results demonstrate that fetal brain injury follows isolated systemic maternal inflammation and that fetal brain inflammation lags after maternal stimulus, which creates a potential 4-hour clinical window for therapeutic intervention.

Keywords: brain injury; cerebral palsy; chorioamnionitis.

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Figures

FIGURE 1
FIGURE 1. Dose-dependent effect of lipopolysaccharide on dam core temperature
Lipopolysaccharide dose effect on dam core temperature was monitored up to 6 hours at 640 μg/kg (dotted/-dashed line), 320 μg/kg (dashed line), 160 μg/kg (dotted line), and 0 μg/kg (continuous line). Data are expressed as mean ± SD (n = 2-6 animals per time point). One-way analysis of variance with Least Significant Difference Post-Hoc test was performed with repeated measures taken into account; a probability value of ≤ .05 was set as a significance threshold. The single asterisk indicates a probability value of ≤ .05; the double asterisk indicates a probability value of ≤ .01 vs control. The apostrophe indicates minutes.
FIGURE 2
FIGURE 2. Time-course of maternal and fetal plasma IL-6 levels after exposure to increasing doses of LPS
LPS was injected at time 0 hours at the doses of 640 μg/kg (squared bars), 320 μg/kg (vertical line bars), 160 μg/kg (horizontal line bars), and 0 μg/kg (open bars). Data are expressed as mean ± SD. One-way analysis of variance with Least Significance Difference Post-Hoc test was performed; a probability value of ≤ .05 was set as a significance threshold. A, Values that were obtained at time 0 hours before LPS administration were below the lowest limit of detection of the assay in maternal plasma (mean sensitivity = 21 pg/mL). At 2 hours, 320 μg/kg and 640 μg/kg was associated with increased IL-6 compared with control (P < .05). At 4 and 6 hours, only 640 μg/kg significantly increased compared with control (P < .05). Control group dams had constant basal IL-6 levels at all time points. B, Values at 2 and 4 hours increased at all doses compared with controls (P<.05); there was no significant difference in fetal response by dose. At 6 hours, fetal levels were comparable with controls at all doses. Control fetuses had constant basal IL-6 levels at all time points.
FIGURE 3
FIGURE 3. Time-course of placental and fetal brain IL-6 RNA levels after dam exposure to increasing doses of LPS
Representative gel of amplicons that were obtained from A, placenta tissue or B, fetal brain 2 hours after maternal LPS injections. In each gel, products that were obtained from amplification reactions with IL-6 primers are shown on the left; products that were obtained with β-actin primers are shown on the right. Lanes are labeled c(controls) and i, ii, iii (160, 320 and 640 μg/kg LPS), respectively. Graphs depict IL-6 RNA expression levels in placenta and fetal brain relative to expression at 0 hours with LPS doses of 640 μg/kg (squared bars), 320 μg/kg (vertical line bars), 160 μg/kg (horizontal line bars) and 0 μg/kg (open bars). Data are expressed as mean ± SD. One-way analysis of variance with Least Significant Difference Post-Hoc test was performed; a probability value of ≤ .05 was set as a significance threshold. A, The single asterisk indicates a probability value of ≤ .05; the double asterisk indicates a probability value of ≤ .01 vs saline solution; the triple asterisk indicates no significance compared with 640 μg at 2 hours or 160 μg at 6 hours. B, The single asterisk indicates a probability value of ≤ .05 vs saline solution. C, Distribution of fold IL-6 expression normalized to β-actin in individual pup brains from the 640 μg and control groups is shown.
FIGURE 4
FIGURE 4. IL-6 protein expression in fetal brains 6 hours after maternal LPS injection
Representative protein blots from control, 320 μg/kg, and 640 μg/kg with control (GAPDH). Relative fluorescent intensity normalized to GAPDH shown from individual pup brains. One-way analysis of variance with Least Significant Difference Post-Hoc test was performed; a probability value of ≤ .05 was set as a significance threshold.
FIGURE 5
FIGURE 5. LPS dose-dependent reduction in neurite sprouting by automated Sholl analysis
A, A representative neuron is shown from primary neuronal cultures at each dose with an overlay, B, to demonstrate quantification of neurite length. Categories of neurite length by LPS dose are shown. C, Ordinal-by-ordinal analysis was performed for categories of neurite length (P = .0006). The number of neurites per cell body is shown. One-way analysis of variance with Least Significant Difference Post-Hoc test was performed; a probability value of ≤ .05 was set as a significance threshold. The number of neurites per cell body was significantly related to dose (overall analysis of variance: P < .001). Post-hoc pairwise analysis compared with control: P < .06 vs 160 μg/kg; P < .001 vs 320 μg/kg; P < .001 vs 640 μg/kg.
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References

    1. Rosenbaum P, Paneth N, Leviton A, et al. A report: the definition and classification of cerebral palsy April 2006. Dev Med Child Neurol. 2007;109(suppl):8–14. - PubMed
    1. Himmelmann K, Uvebrant P. The panorama of cerebral palsy in Sweden: XI, changing patterns in the birth-year period 2003-2006. Acta paediatr. 2014;103:618–24. - PubMed
    1. Fairhurst C. Cerebral palsy: the whys and hows. Arch Dis Child Educ Pract Ed. 2012;97:122–31. - PubMed
    1. Soleimani F, Vameghi R, Biglarian A. Ante-natal and intrapartum risk factors for cerebral palsy in term and near-term newborns. Arch Iran Med. 2013;16:213–6. - PubMed
    1. Grether JK, Nelson KB. Maternal infection and cerebral palsy in infants of normal birth weight. JAMA. 1997;278:207–11. - PubMed

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