1. Ovine Fetal Thymus Response to Lipopolysaccharide-Induced Chorioamnionitis and Antenatal Corticosteroids
- Author
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Kuypers, Elke, Collins, Jennifer JP, Jellema, Reint K, Wolfs, Tim GAM, Kemp, Matthew W, Nitsos, Ilias, Pillow, J Jane, Polglase, Graeme R, Newnham, John P, Germeraad, Wilfred TV, Kallapur, Suhas G, Jobe, Alan H, and Kramer, Boris W
- Subjects
Paediatrics ,Reproductive Medicine ,Biomedical and Clinical Sciences ,Perinatal Period - Conditions Originating in Perinatal Period ,Lung ,Preterm ,Low Birth Weight and Health of the Newborn ,Infectious Diseases ,Infant Mortality ,Pediatric ,Reproductive health and childbirth ,Adrenal Cortex Hormones ,Animals ,Apoptosis ,Bone Morphogenetic Protein 4 ,CD3 Complex ,Cell Proliferation ,Chorioamnionitis ,Female ,Fetus ,Forkhead Transcription Factors ,Gene Expression Regulation ,Hedgehog Proteins ,Lipopolysaccharides ,Pregnancy ,Sheep ,T-Lymphocytes ,Thymus Gland ,Time Factors ,Toll-Like Receptors ,General Science & Technology - Abstract
RationaleChorioamnionitis is associated with preterm delivery and involution of the fetal thymus. Women at risk of preterm delivery receive antenatal corticosteroids which accelerate fetal lung maturation and improve neonatal outcome. However, the effects of antenatal corticosteroids on the fetal thymus in the settings of chorioamnionitis are largely unknown. We hypothesized that intra-amniotic exposure to lipopolysaccharide (LPS) causes involution of the fetal thymus resulting in persistent effects on thymic structure and cell populations. We also hypothesized that antenatal corticosteroids may modulate the effects of LPS on thymic development.MethodsTime-mated ewes with singleton fetuses received an intra-amniotic injection of LPS 7 or 14 days before preterm delivery at 120 days gestational age (term = 150 days). LPS and corticosteroid treatment groups received intra-amniotic LPS either preceding or following maternal intra-muscular betamethasone. Gestation matched controls received intra-amniotic and maternal intra-muscular saline. The fetal intra-thoracic thymus was evaluated.ResultsIntra-amniotic LPS decreased the cortico-medullary (C/M) ratio of the thymus and increased Toll-like receptor (TLR) 4 mRNA and CD3 expression indicating involution and activation of the fetal thymus. Increased TLR4 and CD3 expression persisted for 14 days but Foxp3 expression decreased suggesting a change in regulatory T-cells. Sonic hedgehog and bone morphogenetic protein 4 mRNA, which are negative regulators of T-cell development, decreased in response to intra-amniotic LPS. Betamethasone treatment before LPS exposure attenuated some of the LPS-induced thymic responses but increased cleaved caspase-3 expression and decreased the C/M ratio. Betamethasone treatment after LPS exposure did not prevent the LPS-induced thymic changes.ConclusionIntra-amniotic exposure to LPS activated the fetal thymus which was accompanied by structural changes. Treatment with antenatal corticosteroids before LPS partially attenuated the LPS-induced effects but increased apoptosis in the fetal thymus. Corticosteroid administration after the inflammatory stimulus did not inhibit the LPS effects on the fetal thymus.
- Published
- 2012