IL-10 is highly expressed in the uterus and placenta and is implicated in controlling inflammation-induced pathologies of pregnancy. To investigate the role of IL-10 in regulating preterm labor, the response of IL-10 null mutant mice to low-dose LPS in late gestation was evaluated. When IL-10 null mutant C57BL/6 (IL-10−/−) and control (IL-10+/+) mice were administered LPS on day 17 of pregnancy, the dose of LPS required to elicit 50% preterm fetal loss was 10-fold lower in IL-10−/− mice than in IL-10+/+ mice. Surviving fetuses in IL-10−/− mice exhibited fetal growth restriction at lower doses of LPS than IL-10+/+ mice. Marked elevation of LPS-induced immunoactive TNF-α and IL-6 was evident in the serum, uterus, and placenta of IL-10−/− mice, and TNF-α and IL-6 mRNA expression was elevated in the uterus and placenta, but not the fetus. Serum IL-1α, IFN-γ, and IL-12p40 were increased and soluble TNFRII was diminished in the absence of IL-10, with these changes also reflected in the gestational tissues. Administration of rIL-10 to IL-10−/− mice attenuated proinflammatory cytokine synthesis and alleviated their increased susceptibility to preterm loss. Exogenous IL-10 also protected IL-10+/+ mice from fetal loss. These data show that IL-10 modulates resistance to inflammatory stimuli by down-regulating proinflammatory cytokines in the uterus and placenta. Abundance of endogenous IL-10 in gestational tissues is therefore identified as a critical determinant of resistance to preterm labor, and IL-10 may provide a useful therapeutic agent in this common condition.

Interleukin 10 (IL10) is a potent immune-regulating cytokine and inhibitor of inflammatory cytokine synthesis. To evaluate the anti-inflammatory role of IL10 in pregnancy, the response of genetically IL10-deficient mice to low-dose lipopolysaccharide (LPS)-induced abortion was examined. When IL10-null mutant C57Bl/6 (Il10(-/-)) and control (Il10(+/+)) mice were administered low-dose LPS on Day 9.5 of gestation, IL10 deficiency predisposed to fetal loss accompanied by growth restriction in remaining viable fetuses, with an approximately 10-fold reduction in the threshold dose for 100% abortion. After LPS administration, inflammatory cytokines tumor necrosis factor-alpha (TNFA) and IL6 were markedly increased in serum, uterine, and conceptus tissues in Il10(-/-) mice compared with Il10(+/+) mice, with elevated local synthesis of Tnfa and Il6 mRNAs in the gestational tissues. IL1A and IL12p40 were similarly elevated in serum and gestational tissues, whereas interferon gamma (IFNG) and soluble TNFRII content were unchanged in the absence of IL10. Recombinant IL10 rescued the increased susceptibility to LPS-induced fetal loss in Il10(-/-) mice but did not improve outcomes in Il10(+/+) mice. IL10 genotype also influenced the responsiveness of mice to a TNFA antagonist, etanercept. Fetal loss in Il10(-/-) mice was partly alleviated by moderate or high doses of etanercept, whereas Il10(+/+) mice were refractory to high-dose etanercept, consistent with attenuation by IL10 status of TNFA bioavailability after etanercept treatment. These data show that IL10 modulates resistance to inflammatory stimuli by downregulating expression of proinflammatory cytokines TNFA, IL6, IL1A, and IL12, acting to protect against inflammation-induced pathology in the implantation site.

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A precisely regulated sequence of molecular and cellular changes occurs in the female reproductive tract in early pregnancy to facilitate development of the embryo and its successful implantation. Cytokine–leukocyte networks are integral in the tissue remodelling and immuno-regulatory processes underpinning successful implantation. Seminal factors are implicated in activating expression of cytokine genes and inflammatory leukocyte recruitment in the uterus, but whether semen-induced effects extend to the oviduct to influence blastocyst development has not been examined. The aim of this study was to quantitate the expression of mRNA encoding epidermal growth factor (EGF), granulocyte-macrophage colony-stimulating factor (GM-CSF), heparin-binding epidermal growth factor-like growth factor (HB-EGF), insulin-like growth factor (IGFII), leukaemia inhibitory factor (LIF), tumour necrosis factor (TNFα), transforming growth factor (TGFα) and TGFβ from oviducts collected from mice at oestrus and on day 1 of pregnancy, after mating with intact, seminal plasma deficient (svx) and vasectomised (vas) mice. Total RNA was extracted, DNAse treated, reverse transcribed into cDNA, and quantified by real-time PCR using SYBR Green chemistry. All cytokine-specific primers were designed using GenBank sequences and data were normalised to β-actin mRNA expression. Expression of LIF mRNA was induced following mating with intact or vas males, but not svx males, showing that LIF mRNA is induced by factors present in seminal plasma. mRNAs encoding EGF, GM-CSF, HB EGF, IGFII, TNFα, TGFα and TGFβ were all detected in oviduct cDNA collected from oestrus and day 1 mice. These data support the proposal that cytokine-leukocyte networks shown previously to be operative in the uterus extend to the oviduct, and are influenced by exposure to seminal plasma at mating. The cytokines expressed in the oviduct during early pregnancy are likely to be key regulators of embryo growth and development.

The immune-deviating and anti-inflammatory cytokine interleukin-10 (IL-10) is expressed throughout pregnancy in the decidual and placental tissues. Mice with a null mutation in the IL-10 gene mice are fertile with no reduction in litter size, although fetal growth trajectories and placental structure are altered. IL-10 is known to terminate inflammatory responses and to limit inflammation-induced tissue pathology by inhibiting macrophage synthesis of tumor necrosis factor-α (TNFα). To investigate the anti-inflammatory role of IL-10 in pregnancy, the susceptibility of null mutant mice to low dose LPS-induced miscarriage and preterm labour has been evaluated. When IL-10 null mutant C57Bl/6 (IL-10–/–) and control (IL-10+/+) mice were given low dose E.coli LPS on d10 of pregnancy, IL-10 deficiency was associated with greater fetal loss with fewer mated IL-10–/– mice carrying viable fetuses at day 18 and increased rate of fetal resorption. In mice treated with LPS on day 17, preterm delivery within 24 h occurred in a higher proportion of IL-10–/– mice than IL-10+/+ mice. LPS induced very high and sustained TNFα and IL-6 content in serum, uterine and placental tissue in IL-10–/– mice, associated with upregulated mRNA expression of both cytokines in gestational tissues. These data show that IL-10 modulates placental resistance to inflammatory stimuli by down-regulating expression of the pro-inflammatory cytokines TNFα and IL-6. We conclude that IL-10 has a dual role in pregnancy, acting to regulate placental morphogenesis and fetal growth trajectory, and to protect against inflammation-induced miscarriage and preterm labour.