Alterations in the cellular component of the maternal immune system in a murine preterm delivery model

Deficiency of hydrogen sulfide production and pregnancy rate in an experimental model: Association with preterm delivery

PROBLEM

Pro-inflammatory phenomena drive preterm delivery (PTD). Hydrogen sulfide is a gasotransmitter with anti-inflammatory properties produced through the activity of the enzyme cystathionine-γ-lyase (CSE), and its impact was studied in models of normal delivery and PTD in mice.

METHOD OF STUDY

Female CSE+/+ and CSE-/- mice were mated with male CSE+/+ mice; mating was done with drinking water unsupplemented and supplemented with cysteine. The pregnancy rate was monitored. PTD was induced by the intraperitoneal injection of bacterial lipopolysaccharide (LPS) on day 14.5 of pregnancy. Mice were sacrificed for tissue collection and splenocyte isolation after 6 and 12 h. Isolated splenocytes were stimulated for the production of tumor necrosis factor-alpha (TNFα), interleukin (IL)-10 and interferon-gamma (IFNγ); TNFα and vascular endothelial growth factor (VEGF) were measured in the fetuses and the placenta.

RESULTS

The successful pregnancy rate was lower in CSE-/- mice and it was restored with cysteine supplementation. CSE deficiency was associated with higher tissue concentrations of TNFα in the fetuses, attenuated IL-10 responses and higher IFNγ production from splenocytes. CSE deficiency was not associated with PTD. Following PTD induction, CSE-/- mice did not show attenuated IL-10 responses but the production of TNFα and IFNγ was lowered over-time; placental VEGF was also increased over-time.

CONCLUSIONS

CSE deficiency has an unfavorable impact on pregnancy. H2 S deficiency through CSE does not drive PTD but mediates pro-inflammatory phenomena in fetuses.

Immune-checkpoint proteins, cytokines, and microbiome impact on patients with cervical insufficiency and preterm birth

Background

Microenvironmental factors, including microbe-induced inflammation and immune-checkpoint proteins that modulate immune cells have been associated with both cervical insufficiency and preterm delivery. These factors are incompletely understood. This study aimed to explore and compare interactions among microbiome and inflammatory factors, such as cytokines and immune-checkpoint proteins, in patients with cervical insufficiency and preterm birth. In particular, factors related to predicting preterm birth were identified and the performance of the combination of these factors was evaluated.

Methods

A total of 220 swab samples from 110 pregnant women, prospectively recruited at the High-Risk Maternal Neonatal Intensive Care Center, were collected between February 2020 and March 2021. This study included 63 patients with cervical insufficiency receiving cerclage and 47 control participants. Endo- and exocervical swabs and fluids were collected simultaneously. Shotgun metagenomic sequencing for the microbiome and the measurement of 34 immune-checkpoint proteins and inflammatory cytokines were performed.

Results

First, we demonstrated that immune-checkpoint proteins, the key immune-regulatory molecules, could be measured in endocervical and exocervical samples. Secondly, we identified significantly different microenvironments in cervical insufficiency and preterm birth, with precise cervical locations, to provide information about practically useful cervical locations in clinical settings. Finally, the presence of Moraxella osloensis (odds ratio = 14.785; P = 0.037) and chemokine CC motif ligand 2 levels higher than 73 pg/mL (odds ratio = 40.049; P = 0.005) in endocervical samples were associated with preterm birth. Combining M. osloensis and chemokine CC motif ligand 2 yielded excellent performance for predicting preterm birth (area under the receiver operating characteristic curve = 0.846, 95% confidence interval = 0.733-0.925).

Conclusion

Multiple relationships between microbiomes, immune-checkpoint proteins, and inflammatory cytokines in the cervical microenvironment were identified. We focus on these factors to aid in the comprehensive understanding and therapeutic modulation of local microbial and immunologic compositions for the management of cervical insufficiency and preterm birth.

Association of modulation of pro-inflammatory responses by dectin-2 with preterm delivery: An experimental model

PROBLEM

Pro-inflammatory responses of pathogen recognition receptors (PRR) are implicated in preterm delivery (PTD). Dectin-2 is one PRR recognizing unselective carbohydrate structures; its participation in PTD has never been studied before.

METHOD OF STUDY

In an experimental model, PTD was induced in female pregnant wild-type (WT) mice and mice with homologous deficiency for dectin-2 by the intraperitoneal injection of bacterial lipopolysaccharide (LPS) on day 14 of pregnancy. Time to delivery and fetal mortality were recorded. Challenged mice were killed for tissue collection and splenocyte isolation 6 hours later. Concentrations of tumour necrosis factor-alpha (TNFα), interleukin (IL)-1α, and IL-1β were measured.

RESULTS

Delivery was induced significantly earlier in WT than dectin-2^-/- mice; however, fetal mortality was higher among dectin-2^-/- mice. Candida albicans challenge could not lead to these changes. Sacrifice experiments showed that LPS challenge led to significant increase of TNFα, IL-1α, and IL-1β in maternal tissues of WT; this was further enhanced for TNFα and IL-1β in dectin-2^-/- mice. Pre-treatment with the prostaglandin inhibitor diclofenac delayed time to delivery of WT mice, but not of dectin2^-/- mice. TNFα stimulation of splenocytes of dectin2^-/- mice was enhanced with the addition of anti-TLR4 and decreased in the presence of lipid A.

CONCLUSIONS

Dectin-2 delays LPS-induced PTD by enhancing the production of pro-inflammatory cytokines.

Cell-Free Fetal DNA Increases Prior to Labor at Term and in a Subset of Preterm Births

Cell-free fetal DNA in the maternal circulation has been associated with the onset of labor at term. Moreover, clinical studies have suggested that cell-free fetal DNA has value to predict pregnancy complications such as spontaneous preterm labor leading to preterm birth. However, a mechanistic link between cell-free fetal DNA and preterm labor and birth has not been established. Herein, using an allogeneic mouse model in which a paternal green fluorescent protein (GFP) can be tracked in the fetuses, we established that cell-free fetal DNA (Egfp) concentrations were higher in late gestation compared to mid-pregnancy and were maintained at increased levels during the onset of labor at term, followed by a rapid decrease after birth. A positive correlation between cell-free fetal DNA concentrations and the number of GFP-positive pups was also observed. The increase in cell-free fetal DNA concentrations prior to labor at term was not linked to a surge in any specific cytokine/chemokine; yet, specific chemokines (i.e., CCL2, CCL7, and CXCL2) increased as gestation progressed and maintained elevated levels in the postpartum period. In addition, cell-free fetal DNA concentrations increased prior to systemic inflammation-induced preterm birth, which was associated with a strong cytokine response in the maternal circulation. However, cell-free fetal DNA concentrations were not increased prior to intra-amniotic inflammation-induced preterm birth, but in this model, a mild inflammatory response was observed in the maternal circulation. Collectively, these findings suggest that an elevation in cell-free fetal DNA concentrations in the maternal circulation precedes the physiological process of labor at term and the pathological process of preterm labor linked with systemic inflammation, but not that associated with intra-amniotic inflammation.

Single nucleotide polymorphisms of Toll-like receptor-4 and of autophagy-related gene 16 like-1 gene for predisposition of premature delivery: A prospective study

To investigate the impact of carriage of single nucleotide polymorphisms (SNPs) of the Toll-like receptor-4 (TLR4) and of autophagy-related gene 16-like-1 (ATG16L1) in preterm delivery (PTD).A prospective cohort of 145 pregnant women was studied. Women were prospectively followed-up until delivery. Genotyping for rs4986790 (Asp299Gly transition) and rs4986791 (Thr399Ile transition) of TLR4 and for rs2241880 of ATG16L1 was done by PCR-restriction fragment length polymorphism. The primary study endpoint was the impact of carriage of minor alleles of TLR4 on early PTD before gestational week 32. Associations with human chorionic gonadotrophin (hCG) were also analyzed. Peripheral blood mononuclear cells were isolated from 15 healthy women and stimulated for cytokine production.No difference in clinical characteristics was observed between women delivering full term and preterm. The frequency of early PTD was 25% among women carrying minor alleles of TLR4 and 6.8% among women carrying major alleles (P: .032). Odds ratios for PTD were 3.85 among women carrying the GG genotype of rs2241880 and major alleles of TLR4 and 0.26 among carriers of GG genotype and minor alleles of TLR4 (P: .030). The co-presence of GG genotype of rs2241880 and hCG above 70 U/L was an independent variable for PTD. Stimulated production of interleukin-6 was greater among women with GG genotypes of rs2241880.Minor alleles of SNPs of TLR4 predispose to early PTD. The GG genotype of rs2241880 of ATG16L1 is associated with PTD when hCG is supra-elevated.

Early changes of the heat-shock protein 60 to 70 ratio as prediction of miscarriage in pregnancy

PROBLEM

To study the balance of circulating heat shock protein (HSP)60 and HSP70 in pre-term delivery.

METHOD OF STUDY

A two-stage approach was used. At first stage, we run retrospective analysis of prospective collected clinical data, and at a second stage, we studied an animal model of pre-term delivery (PTD). Blood samples were collected for prenatal screening in 3629 women. Samples from 23 women with miscarriage before gestational week 21 and 53 well-matched comparators for age, body mass index, parity, and previous miscarriage with full-term pregnancy were depicted. Women with risk factors were excluded. HSP60 and HSP70 were measured by an enzyme immunosorbent assay. PTD was induced after injection of low dose of bacterial lipopolysaccharide; mice were killed for the measurement of HSP60 and HSP70 in blood and tissues. The study endpoint was the association of the HSP60 to HSP70 ratio to miscarriage.

RESULTS

A ratio >6 could distinguish between women who will miscarry from women with term pregnancies with sensitivity 60%, specificity 81.8%, positive predictive value 81.8%, and negative predictive value 60% (OR: 6.750, P = 0.025). Mice of the LPS-group PTD had this ratio significantly increased in maternal serum, placentas, and embryos compared to the sham-operation group. Gene expression of hsp60/70 remained in tissues unaltered.

CONCLUSION

A HSP60/HSP70 ratio equal to or more than 6 until gestational week 12 is accompanied with great likelihood for miscarriage. A similar ratio applies in an animal model of PTD induced by low-dose LPS.

Intra-amniotic administration of lipopolysaccharide induces spontaneous preterm labor and birth in the absence of a body temperature change

OBJECTIVE

Intra-amniotic infection is associated with spontaneous preterm labor. In most cases, the infection is subclinical and bacteria are detected in the amniotic cavity rather than in the chorioamniotic membranes. The aims of this study were to establish a model of intra-amniotic lipopolysaccharide (LPS)-induced preterm labor/birth that resembles the subclinical syndrome and to compare this model to two established models of LPS-induced preterm labor/birth.

METHODS

Pregnant B6 mice received an intra-amniotic, intra-uterine, or intra-peritoneal injection of LPS (100 ng/amniotic sac, 15 μg/25 μL, and 15 μg/200 μL respectively) or PBS (control). Following injection, body temperature (every two hours for a 12-h period), gestational age, and the rate of preterm labor/birth were recorded.

RESULTS

An intra-amniotic injection of LPS resulted in preterm labor/birth [LPS 80 ± 24.79% (8/10) versus PBS 0% (0/8); p = 0.001] without causing maternal hypothermia. Intra-peritoneal [LPS 100% (8/8) versus PBS 0% (0/8); p < 0.001)] and intra-uterine [LPS 100% (8/8) versus PBS 28.57 ± 33.47% (2/7); p =0 .007] injections of LPS induced preterm labor/birth; yet, maternal hypothermia was observed.

CONCLUSION

Intra-amniotic injection of LPS induces preterm labor/birth in the absence of a body temperature change, which resembles the subclinical syndrome.

Angiopoietin-2 primes infection-induced preterm delivery

Current knowledge on the participation of angiopoietin-2 (Ang-2) in the inflammatory process and on the importance of bacterial endotoxins (LPS) in the induction of preterm delivery (PTD) led us to investigate the role of Ang-2/LPS interplay in the pathogenesis of PTD. At a first stage, Ang-2 was measured at the end of the first trimester of pregnancy in the serum of 50 women who delivered prematurely; of 88 women well-matched for age and parity who delivered full-term; and of 20 non-pregnant healthy women. Ang-2 was greater in pregnant than in non-pregnant women. The time until delivery was shorter among those with Ang-2 greater than 4 ng/ml (odds ratio for delivery until week 34; p: 0.040). To further investigate the role of Ang-2 for PTD, an experimental model of PTD induced by the intraperitoneal injection of LPS in mice was used. Ang-2 was administered intraperitoneally before LPS on day 14 of pregnancy. When Ang-2 was administered before the LPS diluent, all mice delivered full-term. However, administration of Ang-2 prior LPS accelerated further the time until delivery. Sacrifice experiments showed that the effect of Ang-2 was accompanied by decrease of the penetration of Evans Blue in the embryos and by increase of its penetration in maternal tissues. In parallel, the concentration of tumour necrosis factor-alpha in the maternal circulation, in fetal tissues and in the placentas was significantly decreased. Results indicate that Ang-2 accelerated the phenomena of PTD induced by LPS. This is related with deprivation of fetal perfusion.