Effects of maternal Campylobacter rectus infection on murine placenta, fetal and neonatal survival, and brain development

Maternal periodontitis may cause lower birth weight in children: genetic evidence from a comprehensive Mendelian randomization study on periodontitis and pregnancy

OBJECTIVES

This study aims to comprehensively investigate the potential genetic link between periodontitis and adverse pregnancy outcomes using a two-sample Mendelian Randomization approach.

MATERIALS AND METHODS

We employed robust genetic instruments for chronic periodontitis as exposure data from the FinnGen database. Data encompassing various pregnancy stage outcomes, including pre-pregnancy conditions (irregular menstruation, endometriosis, abnormal reproductive bleeding, and female infertility), pregnancy complications (hemorrhage, spontaneous miscarriage, and abnormalities in products), and post-pregnancy factors (single spontaneous delivery, labor duration, and birth weight of the child), were obtained from the UK Biobank. The random-effects inverse-variance weighted (IVW) method was utilized to compute primary estimates while diligently assessing potential directional pleiotropy and heterogeneity.

RESULTS

Our findings indicate a negative association between periodontitis and labor duration (odds ratio [OR] = 0.999; 95% confidence interval [CI]: 0.999 to 1.000; P = 0.017). Individuals with periodontitis are more likely to deliver lower-weight infants (OR = 0.983; 95% CI: 0.972 to 0.995; P = 0.005). We found no evidence of pleiotropy or heterogeneity in aforementioned two associations. We did not observe casual links with pre-pregnancy conditions and pregnancy complications.

CONCLUSIONS

This Mendelian Randomization study underscores the genetic influence of periodontitis on specific adverse pregnancy outcomes, particularly concerning labor duration and lower birth weight deliveries.

CLINICAL RELEVANCE

Our study emphasizes the critical importance of maintaining periodontal health during pregnancy and offers genetic evidence supporting these associations. Further investigation is required to delve deeper into the specific underlying mechanisms.

Antepartum periodontitis treatment and risk of offspring screening positive for autism spectrum disorder

BACKGROUND

To evaluate if treating maternal periodontal disease, a pro-inflammatory condition, during pregnancy (intervention) compared to after pregnancy (control) reduces the likelihood of offspring screening positive for autism spectrum disorder (ASD).

METHODS

In a follow-up study to the MOTOR randomized trial, we compared rates of positive screens on the Modified Checklist for Autism in Toddlers (M-CHAT) among n = 306 two-year-old toddlers and correlated findings to maternal and cord blood pro-inflammatory interleukin-6 (IL-6).

RESULTS

Toddlers in the intervention group had decreased risk of a positive M-CHAT screen (adjusted RR = 0.53, 95% CI 0.29-0.99). Toddlers screening positive compared to negative had higher mean IL-6 in cord blood (1.58 ± 1.14 vs. 1.09 ± 0.72 p = 0.001) and maternal IL-6 change from baseline (1.30 ± 0.61 vs 0.96 ± 0.62 p = 0.03).

CONCLUSIONS

Treating periodontal disease during pregnancy reduced risk of a positive ASD screen. M-CHAT positivity was associated with increased IL-6 in maternal and cord blood.

CLINICAL TRIAL

Trial Registration numbers: Clinicaltrials.gov NCT03423836.

Role of Maternal Infections and Inflammatory Responses on Craniofacial Development

Pregnancy is a tightly regulated immunological state. Mild environmental perturbations can affect the developing fetus significantly. Infections can elicit severe immunological cascades in the mother's body as well as the developing fetus. Maternal infections and resulting inflammatory responses can mediate epigenetic changes in the fetal genome, depending on the developmental stage. The craniofacial development begins at the early stages of embryogenesis. In this review, we will discuss the immunology of pregnancy and its responsive mechanisms on maternal infections. Further, we will also discuss the epigenetic effects of pathogens, their metabolites and resulting inflammatory responses on the fetus with a special focus on craniofacial development. Understanding the pathophysiological mechanisms of infections and dysregulated inflammatory responses during prenatal development could provide better insights into the origins of craniofacial birth defects.

Mycobacterium tuberculosis-Induced Maternal Immune Activation Promotes Autism-Like Phenotype in Infected Mice Offspring

The maternal system’s exposure to pathogens during pregnancy influences fetal brain development causing a persistent inflammation characterized by elevated pro-inflammatory cytokine levels in offspring. Mycobacterium tuberculosis (Mtb) is a global pathogen that causes tuberculosis, a pandemic responsible for health and economic burdens. Although it is known that maternal infections increase the risk of autism spectrum disorder (ASD), it is not known whether Mtb infection is sufficient to induce ASD associated behaviors, immune dysregulation and altered expression of synaptic regulatory genes. The current study infected pregnant Balb/c mice with Mtb H37Rv and valproic acid (VPA) individually and in combination. Plasma cytokine profiles were measured in offspring using the Bio-plex Th17 pro mouse cytokine panel. Mtb infection increased plasma interleukin (IL)-6 and IL-17A, while tumor necrosis factor alpha (TNF-α), interferon (IFN)-γ and IL-1β were reduced when compared with saline. Mtb-induced maternal immune activation (MIA) offspring displayed increased grooming behavior. The study also revealed dysregulation in gene expression of synaptic molecules in the cerebellum. MIA rescued the VPA-induced effects on self-grooming and social interaction behaviors. Our finding therefore highlights a potential role of Mtb as a MIA agent that can potentially contribute to ASD.

Gestational gut microbial remodeling is impaired in a rat model of preeclampsia superimposed on chronic hypertension

Preeclampsia is a progressive hypertensive disorder of pregnancy affecting 2%-8% of pregnancies globally. Preexisting chronic hypertension is a major risk factor associated with developing preeclampsia, and growing evidence suggests a role for the gut microbiome in the development of preeclampsia. However, neither alterations in the gut microbiome associated with preeclampsia nor the mechanisms involved are fully understood. In this study, we tested the hypothesis that normal gestational maternal gut microbiome remodeling is impaired in the Dahl salt-sensitive (Dahl S) rat model of superimposed preeclampsia. Gut microbiome profiles of pregnant Dahl S, normal pregnant Sprague-Dawley (SD), and matched virgin controls were assessed by 16S rRNA gene sequencing at baseline; during early, middle, and late pregnancy; and 1-wk postpartum. Dahl S rats had significantly higher abundance in Proteobacteria, and multiple genera were significantly different from SD rats at baseline. The pregnant SD displayed a significant increase in Proteobacteria and genera such as Helicobacter, but these were not different between pregnant and virgin Dahl S rats. By late pregnancy, Dahl S rats had significantly lower α-diversity and Firmicutes compared with their virgin Dahl S controls. β-diversity was significantly different among groups (P < 0.001). KEGG metabolic pathways including those associated with short-chain fatty acids were different in Dahl S pregnancy but not in SD pregnancy. These results reveal an association between chronic hypertension and gut microbiome dysbiosis which may hinder pregnancy-specific remodeling in the gut microbial composition during superimposed preeclampsia.

Metabolic syndrome and masticatory hypofunction: a cross-sectional study

The objective of this paper is to clarify the rate of abdominal obesity (AO), waist-to-height ratio (WHtR), metabolic syndrome (MetS) and determine the relationship with the masticatory capacity (MC) in terms of total functional tooth units (t-FTU) in a representative sample of older Spanish adults. This cross-sectional study included 544 adult subjects aged 50 or over, who were prospectively selected and who had participated in a survey conducted in a primary dental care service in a Public Oral Health Service in Spain. Anthropometric, clinical variables and t-FTUs were obtained through a calibrated and well-established protocol. Univariate and multivariate binary and multinomial logistic regression analyses were developed. With regards to the t-FTU or MC, it was poor in 60.3%, good in 17.6%, and complete in 22.1% of the sample. The univariate odss ratio (OR) for MetS and AO increased as the MC decreased and as the age group increased. With regards to gender, women presented with an OR of 5.56 (CI 95% 3.70-8.38). With regards to the WHtR-a3 (WHtR grouped into three categories), the univariate ORs were all significant for morbid obesity compared to the healthy group, with a risk of 6.86 (CI 95% 3.23-14.58) for patients with poor MC compared to those with complete MC. Masticatory hypofunctionality could be associated with the presence of MetS. Clinical relevance: The number of t-FTUs is directly related to AO.

Periodontal disease and adverse pregnancy outcomes

Periodontal diseases are considered not only to affect tooth-supporting tissues but also to have a cause-and-effect relationship with various systemic diseases and conditions, such as adverse pregnancy outcomes. Mechanistic studies provide strong evidence that periodontal pathogens can translocate from infected periodontium to the feto-placental unit and initiate a metastatic infection. However, the extent and mechanisms by which metastatic inflammation and injury contribute to adverse pregnancy outcomes still remain unclear. The presence of oral bacteria in the placenta of women with term gestation further complicates our understanding of the biology behind the role of periodontal pathogens in pregnancy outcomes. Epidemiological studies demonstrate many methodological inconsistencies and flaws that render comparisons difficult and conclusions insecure. Therefore, despite the fact that a number of prospective studies show a positive association between periodontal diseases and various adverse pregnancy outcomes, the evidence behind it is still weak. Future well-designed explanatory studies are necessary to verify this relationship and, if present, determine its magnitude. The majority of high-quality randomized controlled trials reveal that nonsurgical periodontal therapy during the second trimester of gestation does not improve pregnancy outcomes. From a biological standpoint, this can be partially explained by the fact that therapy rendered at the fourth to sixth months of pregnancy is too late to prevent placental colonization by periodontal pathogens and consequently incapable of affecting pathogen-induced injury at the feto-placental unit. Thus, interventions during the preconception period may be more meaningful. With the increase in our understanding on the potential association between periodontal disease and adverse pregnancy outcomes, it is clear that dental practitioners should provide periodontal treatment to pregnant women that is safe for both the mother and the unborn child. Although there is not enough evidence that the anti-infective therapy alters pregnancy outcomes, it improves health-promoting behavior and periodontal condition, which in turn advance general health and risk factor control.

The Role of Periodontitis and Periodontal Bacteria in the Onset and Progression of Alzheimer's Disease: A Systematic Review

The evidence of a connection between the peripheral inflammatory processes and neurodegenerative diseases of the central nervous system is becoming more apparent. This review of the related literature highlights the most recent clinical, epidemiological, and in vitro studies trying to investigate possible connections between periodontal bacteria and the onset and progression of Alzheimer's disease. This review was conducted by searching databases such as PubMed and Scopus using keywords or combinations such as Alzheimer's Disease AND periodontal or dementia AND periodontitis OR periodontal. After eliminating overlaps and screening the articles not related to these issues, we identified 1088 records and proceeded to the selection of articles for an evaluation of the associative assumptions. The hypothesis suggested by the authors and confirmed by the literature is that the bacterial load and the inflammatory process linked to periodontal disease can intensify inflammation at the level of the central nervous system, favoring the occurrence of the disease. The analysis of the literature highlights how periodontal disease can directly contribute to the peripheral inflammatory environment by the introduction of periodontal or indirect pathogenic bacteria and proinflammatory cytokines locally produced at the periodontal level following bacterial colonization of periodontal defects.

Maternal microbiome and the hypertensive disorder of pregnancy, preeclampsia

Preeclampsia (PE) is a pregnancy-specific disorder that can be life threatening for both mother and baby. It is characterized by a new onset hypertension during the second half of pregnancy and affects ~300,000 women in the United States every year. There is no cure for PE, and the only effective treatment is delivery of the placenta and the fetus, which is often preterm. PE is believed to be a severe manifestation of placental dysfunction due to early angiogenic imbalances and inflammatory disturbances; however, the cause of this is unknown. The once thought "sterile" placenta now has been proposed to have a unique microbiome of its own. Under ideal conditions, the microbiome represents a balanced bacterial community that is important to the maintenance of a healthy environment. Dysbiosis of these communities may lead to inflammation that potentially contributes to adverse pregnancy outcomes, such as preterm birth and PE. Thus far, the female reproductive tract microbiome has been found to be influenced by periodontal disease, cardiometabolic complications, and maternal obesity, all of which have been identified as contributors to PE. This review will look at the maternal reproductive tract microbiome, evidence for and against, and its role in pregnancy and PE-related events as well as data from relevant mouse models that could be useful for further investigating the influence of the reproductive tract microbiome on the pathogenesis of PE.

The Clinical Importance of Campylobacter concisus and Other Human Hosted Campylobacter Species

Historically, Campylobacteriosis has been considered to be zoonotic; the Campylobacter species that cause human acute intestinal disease such as Campylobacter jejuni and Campylobacter coli originate from animals. Over the past decade, studies on human hosted Campylobacter species strongly suggest that Campylobacter concisus plays a role in the development of inflammatory bowel disease (IBD). C. concisus primarily colonizes the human oral cavity and some strains can be translocated to the intestinal tract. Genome analysis of C. concisus strains isolated from saliva samples has identified a bacterial marker that is associated with active Crohn's disease (one major form of IBD). In addition to C. concisus, humans are also colonized by a number of other Campylobacter species, most of which are in the oral cavity. Here we review the most recent advancements on C. concisus and other human hosted Campylobacter species including their clinical relevance, transmission, virulence factors, disease associated genes, interactions with the human immune system and pathogenic mechanisms.

Do Laboratory Mouse Females that Lose Their Litters Behave Differently around Parturition?

Efficiency in laboratory mouse breeding is hampered by poor reproductive performance, including the loss of entire litters shortly after birth. However, the underlying mechanisms are not yet fully understood and establishing the cause of death in laboratory mouse pups can be complicated. Newborn mouse pups are generally hidden in nests, dead pups are often eaten by the female, and the widespread practice of leaving periparturient females undisturbed complicates inspection, which may delay the discovery of pup loss. In order to efficiently prevent problems with litter loss, it is important to find key factors for survival. We investigated differences in periparturient behavior between female laboratory mice whose pups survived until weaning and females whose entire litters were lost. Video recordings of 82 primiparous females of the C57BL/6 strain or knockouts with C57BL/6 background were used. The mice were observed from 24 h before until 24 h after parturition and female behaviors coded using a pre-established ethogram. The relationship between behavior and survival was analyzed using logistic models, where litter survival was regressed on the proportion of 30-s observations with at least one occurrence of the behavior. We found that females with surviving litters performed more nest building behavior during the last 24 h before parturition (p = 0.004) and spent less time outside the nest during the entire observation period (p = 0.001). Increased litter survival was also associated with more passive maternal behaviors and the female ignoring still pups less. Females that lost their litters performed more parturition-related behaviors, suggesting prolonged labor. The results indicate that maternal behavior plays a significant role in laboratory mouse pup survival. Complications at parturition also contribute to litter mortality.

11.7 T MR Imaging Revealed Dilatation of Virchow-Robin Spaces within Hippocampus in Maternally Lipopolysaccharide-exposed Rats

PURPOSE

11.7 Tesla MRI was examined to detect Virchow-Robin spaces (VRSs) smaller than 100 μm in the rat brain. The effects of maternal exposure to lipopolysaccharide (LPS) were evaluated on basis of the number of dilated VRSs in the offspring rat brain.

METHODS

T₂-weighted MRI with an in-plane resolution up to 78 μm (repetition time = 5000 ms, echo time = 35 ms, slice thickness = 250 μm, imaging plane, coronal) was applied to identify VRSs. The dilated VRSs were counted in the rat brain at 5 and 10 weeks of age. The dams of half the number in each group were treated with LPS during pregnancy, and the remaining half was employed as control. LPS injection in gestation period was used to simulate maternal infections, the method of which was widely accepted as a rat model inducing neuropsychiatric disorders in the offspring. Effects of LPS exposure on the offspring rat brain were statistically investigated.

RESULTS

VRSs as small as 78 μm were successfully detected by the ultra high-field MRI. All dilated VRSs were observed within lacunosum molecular layer of hippocampus, and molecular and granular layers of dentate gyrus around hippocampal fissure. In juvenile rats (5 weeks of age), the number of dilated VRSs was significantly increased in the prenatal LPS exposed rat brain (12.9 ± 2.4, n = 7) than in the control (5.3 ± 1.5, n = 7, P < 0.05), while in young adult rats (10 weeks of age), there was no significant difference in the number between the prenatal LPS exposed rat brain (3.6 ± 0.9, n = 5) and the control (2.6 ± 0.4, n = 5).

CONCLUSION

The results of the present study suggested that maternal infection might cause dilatation of VRSs through neural damages especially in the dentate gyrus of the offspring rats. Thus, ultra high-field MRI can offer a promising diagnostic tool capable of determining the location of neonatal brain damage caused by maternal infections.

Adverse pregnancy outcomes (APOs) and periodontal disease: pathogenic mechanisms

AIM

To evaluate the evidence on potential biological pathways underlying the possible association between periodontal disease (PD) and adverse pregnancy outcomes (APOs).

MATERIAL & METHODS

Human, experimental and in vitro studies were evaluated.

RESULTS

Periodontal pathogens/byproducts may reach the placenta and spread to the foetal circulation and amniotic fluid. Their presence in the foeto-placental compartment can stimulate a foetal immune/inflammatory response characterized by the production of IgM antibodies against the pathogens and the secretion of elevated levels of inflammatory mediators, which in turn may cause miscarriage or premature birth. Moreover, infection/inflammation may cause placental structural changes leading to pre-eclampsia and impaired nutrient transport causing low birthweight. Foetal exposure may also result in tissue damage, increasing the risk for perinatal mortality/morbidity. Finally, the elicited systemic inflammatory response may exacerbate local inflammatory responses at the foeto-placental unit and further increase the risk for APOs.

CONCLUSIONS

Further investigation is still necessary to fully translate the findings of basic research into clinical studies and practice. Understanding the systemic virulence potential of the individual's oral microbiome and immune response may be a distinctly different issue from categorizing the nature of the challenge using clinical signs of PD. Therefore, a more personalized targeted therapy could be a more predictive answer to the current "one-size-fits-all" interventions.

Adverse pregnancy outcomes (APOs) and periodontal disease: pathogenic mechanisms

AIM

To evaluate the evidence on potential biological pathways underlying the possible association between periodontal disease (PD) and adverse pregnancy outcomes (APOs).

MATERIAL & METHODS

Human, experimental and in vitro studies were evaluated.

RESULTS

Periodontal pathogens/byproducts may reach the placenta and spread to the foetal circulation and amniotic fluid. Their presence in the foeto-placental compartment can stimulate a foetal immune/inflammatory response characterized by the production of IgM antibodies against the pathogens and the secretion of elevated levels of inflammatory mediators, which in turn may cause miscarriage or premature birth. Moreover, infection/inflammation may cause placental structural changes leading to pre-eclampsia and impaired nutrient transport causing low birthweight. Foetal exposure may also result in tissue damage, increasing the risk for perinatal mortality/morbidity. Finally, the elicited systemic inflammatory response may exacerbate local inflammatory responses at the foeto-placental unit and further increase the risk for APOs.

CONCLUSIONS

Further investigation is still necessary to fully translate the findings of basic research into clinical studies and practice. Understanding the systemic virulence potential of the individual's oral microbiome and immune response may be a distinctly different issue from categorizing the nature of the challenge using clinical signs of PD. Therefore, a more personalized targeted therapy could be a more predictive answer to the current "one-size-fits-all" interventions.

Interferon-gamma inhibits the neuronal differentiation of neural progenitor cells by inhibiting the expression of Neurogenin2 via the JAK/STAT1 pathway

Interferon-gamma (IFN-γ) is one of the critical cytokines released by host immune cells upon infection. Despite the important role(s) of IFN-γ in host immune responses, there has been no in vivo study regarding the effects of IFN-γ on brain development, and the results from many in vitro studies are controversial. In this study, the effects of IFN-γ on embryonic neurogenesis were investigated. Treatment of E14.5 mouse neural progenitor cells (NPCs) with IFN-γ resulted in a decrease in the percentage of TuJ1-positive immature neurons but an increase in the percentage of Nestin-positive NPCs. Similar results were obtained in vivo. Treatment of NPCs with a JAK inhibitor or the knockdown of STAT1 expression abrogated the IFN-γ-mediated inhibition of neurogenesis. Interestingly, the expression of one of proneural genes, Neurogenin2 (Neurog2) was dramatically inhibited upon IFN-γ treatment, and cells overexpressing Neurog2 did not respond to IFN-γ. Taken together, our results demonstrate that IFN-γ inhibits neuronal differentiation of NPCs by negatively regulating the expression of Neurog2 via the JAK/STAT1 pathway. Our findings may provide an insight into the role of IFN-γ in the development of embryonic brain.

Identification and Characterization of a Putative Chemotaxis Protein, CheY, from the Oral Pathogen Campylobacter rectus

Campylobacter rectus is an understudied oral bacterium that contributes to periodontitis. Processes that contribute to the disease-causing capabilities of pathogens, such as chemotaxis, are largely unknown in C. rectus. The aim of this study was to better understand C. rectus chemotaxis, by examining the C. rectus genome for the presence of a cheY gene. CheY proteins play a part in chemotaxis by acting as two-component response regulators. Significantly, CheY proteins from several pathogens, including the related species Campylobacter jejuni, have been shown to contribute to bacterial virulence. Degenerate PCR, RT-PCR, sequence analyses, and structural modeling showed that C. rectus encodes a gene (Cr-CheY) which shares significant homology with previously characterized CheY proteins. Functional studies of a recombinant form of the protein supports a likely role of Cr-CheY in C. rectus chemotaxis. Cr-CheY is the first CheY characterized from the oral campylobacters.

Bi-directional relationship between pregnancy and periodontal disease

During pregnancy profound perturbations in innate and adaptive immunity impact the clinical course of a number of infectious diseases, including those affecting periodontal tissues. Conversely, it has been suggested that periodontal infections may increase the risk of adverse pregnancy outcomes. In this review, a summary of the literature associated with the bidirectional relationship between pregnancy and periodontal disease as well as the possible mechanisms behind this interaction were examined.

A randomized controlled trial of pre-conception treatment for periodontal disease to improve periodontal status during pregnancy and birth outcomes

Background

Evidence has suggested that periodontal disease is associated with an increased risk of various adverse pregnancy and birth outcomes. However, several large clinical randomized controlled trials failed to demonstrate periodontal therapy during pregnancy reduced the incidence of adverse pregnancy and birth outcomes. It has been suggested that the pre-conception period may be an optimal period for periodontal disease treatment rather than during pregnancy. To date, no randomized controlled trial (RCT) has examined if treating periodontal disease before pregnancy reduces adverse birth outcomes. This study aims to examine if the pre-conception treatment of periodontal disease will lead to improved periodontal status during late pregnancy and subsequent birth outcomes.

Methods/Design

A sample of 470 (235 in each arm of the study) pre-conception women who plan to conceive within one year and with periodontal disease will be recruited for the study. All participants will be randomly allocated to the intervention or control group. The intervention group will receive free therapy including dental scaling and root planning (the standard therapy), supragingival prophylaxis, and oral hygiene education. The control group will only receive supragingival prophylaxis and oral hygiene education. Women will be followed throughout their pregnancy and then to childbirth. The main outcomes include periodontal disease status in late pregnancy and birth outcomes measured such as mean birth weight (grams), and mean gestational age (weeks). Periodontal disease will be diagnosed through a dental examination by measuring probing depth, clinical attachment loss and percentage of bleeding on probing (BOP) between gestational age of 32 and 36 weeks. Local and systemic inflammatory mediators are also included as main outcomes.

Discussion

This will be the first RCT to test whether treating periodontal disease among pre-conception women reduces periodontal disease during pregnancy and prevents adverse birth outcomes. If the effect of pre-pregnancy periodontal treatment is confirmed, this intervention could be recommended for application in low- or middle-income countries to improve both oral health and maternal and child health.

Trial registration

This trial is registered with Chinese Clinical Trial Registry (ChiCTR): ChiCTR-TRC-12001913.

Identification and Characterization of an Invasion Antigen B Gene from the Oral Pathogen Campylobacter rectus

The oral bacterium, Campylobacter rectus, is an etiological agent of periodontitis. The virulence genes of C. rectus are largely unknown. The aim of this study was to query C. rectus for the presence of an invasion antigen B (ciaB) gene, which is needed for cell invasion by the related species Campylobacter jejuni. PCR and PCR-walking identified a ciaB from C. rectus. In silico analyses of C. rectus 314 ciaB (Cr-ciaB) revealed an ORF of 1,830 base pairs. The Cr-CiaB protein shared significant sequence identity (BLASTx and phylogeny) with CiaB from related campylobacters. Cr-CiaB is predicted to lack membrane helices, signal peptides, and localizes to the cytoplasm; which are consistent with CiaB proteins. Expression of Cr-ciaB was confirmed with RT-PCR; and potential ciaB genes were detected in eight additional strains of C. rectus. Cr-ciaB is the first CiaB identified from the oral campylobacters.

Viral infection, inflammation and schizophrenia

Schizophrenia is a severe neurodevelopmental disorder with genetic and environmental etiologies. Prenatal viral/bacterial infections and inflammation play major roles in the genesis of schizophrenia. In this review, we describe a viral model of schizophrenia tested in mice whereby the offspring of mice prenatally infected with influenza at E7, E9, E16, and E18 show significant gene, protein, and brain structural abnormalities postnatally. Similarly, we describe data on rodents exposed to bacterial infection or injected with a synthetic viral mimic (PolyI:C) also demonstrating brain structural and behavioral abnormalities. Moreover, human serologic data has been indispensible in supporting the viral theory of schizophrenia. Individuals born seropositive for bacterial and viral agents are at a significantly elevated risk of developing schizophrenia. While the specific mechanisms of prenatal viral/bacterial infections and brain disorder are unclear, recent findings suggest that the maternal inflammatory response may be associated with fetal brain injury. Preventive and therapeutic treatment options are also proposed. This review presents data related to epidemiology, human serology, and experimental animal models which support the viral model of schizophrenia.

Toll-like receptor 4 mediates intrauterine growth restriction after systemic Campylobacter rectus infection in mice

Campylobacter rectus is associated with fetal exposure and low birthweight in humans. C. rectus also invades placental tissues and induces fetal intrauterine growth restriction (IUGR) in mice, along with overexpression of Toll-like receptors (TLR4), suggesting that TLR4 may mediate placental immunity and IUGR in mice. To test this hypothesis we examined the effect of in vitro TLR4 neutralization on trophoblastic proinflammatory activity and studied the IUGR phenotype in a congenic TLR4-mutant mouse strain after in vivo C. rectus infection. Human trophoblasts were pretreated with TLR4 neutralizing antibodies and infected with C. rectus; proinflammatory cytokine production was assessed by cytokine multiplex assays. Neutralizing TLR4 antibodies significantly impaired the production of proinflammatory cytokines in trophoblastic cells after infection in a dose-dependent manner. We used a subcutaneous chamber model to provide a C. rectus challenge in BALB/cAnPt (TLR4(Lps-d) ) and wild-type (WT) females. Females were mated with WT or TLR4(Lps-d) males once/week; pregnant mice were infected at (E)7.5 and sacrificed at (E)16.5 to establish IUGR phenotypes. Maternal C. rectus infection significantly decreased fetal weight/length in infected WT when compared with sham WT controls (P < 0.05, analysis of variance). However, infected TLR4(Lps-d -/-) mice did not show statistically significant differences in fetal weight and length when compared with WT controls (P > 0.05). Furthermore, heterozygous TLR4(Lps-d +/-) fetuses showed IUGR phenotype rescue. We conclude that TLR4 is an important mediator of trophoblastic proinflammatory responses and TLR4-deficient fetuses do not develop IUGR phenotypes after C. rectus infection, suggesting that placental cytokine activation is likely to be mediated by TLR4 during low birthweight/preterm birth pathogenesis.

The viral theory of schizophrenia revisited: abnormal placental gene expression and structural changes with lack of evidence for H1N1 viral presence in placentae of infected mice or brains of exposed offspring

Researchers have long noted an excess of patients with schizophrenia were born during the months of January and March. This winter birth effect has been hypothesized to result either from various causes such as vitamin D deficiency (McGrath, 1999; McGrath et al., 2010), or from maternal infection during pregnancy. Infection with a number of viruses during pregnancy including influenza, and rubella are known to increase the risk of schizophrenia in the offspring (Brown, 2006). Animal models using influenza virus or Poly I:C, a viral mimic, have been able to replicate many of the brain morphological, genetic, and behavioral deficits of schizophrenia (Meyer et al., 2006, 2008a, 2009; Bitanihirwe et al., 2010; Meyer and Feldon, 2010; Short et al., 2010). Using a murine model of prenatal viral infection, our laboratory has shown that viral infection on embryonic days 9, 16, and 18 leads to abnormal expression of brain genes and brain structural abnormalities in the exposed offspring (Fatemi et al., 2005, 2008a,b, 2009a,b). The purpose of the current study was to examine gene expression and morphological changes in the placenta, hippocampus, and prefrontal cortex as a result of viral infection on embryonic day 7 of pregnancy. Pregnant mice were either infected with influenza virus [A/WSN/33 strain (H1N1)] or sham-infected with vehicle solution. At E16, placentas were harvested and prepared for either microarray analysis or for light microscopy. We observed significant, upregulation of 77 genes and significant downregulation of 93 genes in placentas. In brains of exposed offspring following E7 infection, there were changes in gene expression in prefrontal cortex (6 upregulated and 24 downregulated at P0; 5 upregulated and 14 downregulated at P56) and hippocampus (4 upregulated and 6 downregulated at P0; 6 upregulated and 13 downregulated at P56). QRT-PCR verified the direction and magnitude of change for a number of genes associated with hypoxia, inflammation, schizophrenia, and autism. Placentas from infected mice showed a number of morphological abnormalities including presence of thrombi and increased presence of immune cells. Additionally, we searched for presence of H1N1 viral-specific genes for M1/M2, NA, and NS1 in placentas of infected mice and brains of exposed offspring and found none. Our results demonstrate that prenatal viral infection disrupts structure and gene expression of the placenta, hippocampus, and prefrontal cortex potentially explaining deleterious effects in the exposed offspring without evidence for presence of viral RNAs in the target tissues.

Effects of prenatal infection on brain development and behavior: a review of findings from animal models

Epidemiological studies with human populations indicate associations between maternal infection during pregnancy and increased risk in offspring for central nervous system (CNS) disorders including schizophrenia, autism and cerebral palsy. Since 2000, a large number of studies have used rodent models of systemic prenatal infection or prenatal immune activation to characterize changes in brain function and behavior caused by the prenatal insult. This review provides a comprehensive summary of these findings, and examines consistencies and trends across studies in an effort to provide a perspective on our current state of understanding from this body of work. Results from these animal modeling studies clearly indicate that prenatal immune activation can cause both acute and lasting changes in behavior and CNS structure and function in offspring. Across laboratories, studies vary with respect to the type, dose and timing of immunogen administration during gestation, species used, postnatal age examined and specific outcome measure quantified. This makes comparison across studies and assessment of replicability difficult. With regard to mechanisms, evidence for roles for several acute mediators of effects of prenatal immune activation has emerged, including circulating interleukin-6, increased placental cytokines and oxidative stress in the fetal brain. However, information required to describe the complete mechanistic pathway responsible for acute effects of prenatal immune activation on fetal brain is lacking, and no studies have yet addressed the issue of how acute prenatal exposure to an immunogen is transduced into a long-term CNS change in the postnatal animal. Directions for further research are discussed.

Altered gene expression in murine placentas in an infection-induced intrauterine growth restriction model: a microarray analysis

The biological mechanisms leading to incomplete intrauterine growth are not completely elucidated and few studies have investigated infection-mediated growth restriction. In this investigation we report the alterations induced by maternal infectious challenge in placental gene expression patterns using a murine model. Pregnant dams were challenged at day E7.5 with the oral human pathogen Campylobacter rectus to elicit fetal growth restriction. At embryonic day E16.5 placentas were collected to compare placental gene expression patterns from normal fetuses of unchallenged dams and growth restricted fetuses from infected dams. Differential gene expression patterns were determined using Agilent Oligo array (G4121A) with a false discovery rate of P<0.05 and pathway analyses were performed. Seventy-four genes were differentially expressed during infection-mediated growth restriction with 9 genes significantly up-regulated, indicating that the effects of maternal infection on gene expression were predominantly suppressive. Pathway analyses indicated that 46 of the 65 genes that were significantly down-regulated were associated with placental/fetal development, and 26 of those were imprinted genes. Among the 9 genes that were up-regulated, 4 are involved in oxygen supply to the fetus and the development of the vascular system. Microarray analysis demonstrated that in the pregnant mouse model, maternal infection that induced growth restriction was associated with down-regulated placental expression of critical growth and developmental related genes, including many imprinted genes. These findings may have significant implications for our understanding of the mechanisms underlying infection-associated human fetal growth restriction and the role of differential placental expression of imprinted genes in fetal growth.

Characterization of the invasive and inflammatory traits of oral Campylobacter rectus in a murine model of fetoplacental growth restriction and in trophoblast cultures

Campylobacter species (C. jejuni, C. fetus) are enteric abortifacient bacteria in humans and ungulates. Campylobacter rectus is a periodontal pathogen associated with human fetal exposure and adverse pregnancy outcomes including preterm delivery. Experiments in pregnant mice have demonstrated that C. rectus can translocate from a distant site of infection to the placenta to induce fetal growth restriction and impair placental development. However, placental tissues from human, small-for-gestational age deliveries have not been reported to harbor C. rectus despite evidence of maternal infection and fetal exposure by fetal IgM response. This investigation examined the temporal relationship between the placental translocation of C. rectus and the effects on fetal growth in mice. BALB/c mice were infected at gestational day E7.5 to examine placental translocation of C. rectus by immunohistology. C. rectus significantly decreased fetoplacental weight at E14.5 and at E16.5. C. rectus was detected in 63% of placentas at E14.5, but not at E16.5. In in vitro trophoblast invasion assays, C. rectus was able to effectively invade human trophoblasts (BeWo) but not murine trophoblasts (SM9-1), and showed a trend for more invasiveness than C. jejuni. C. rectus challenge significantly upregulated both mRNA and protein levels of IL-6 and TNFalpha in a dose-dependent manner in human trophoblasts, but did not increase cytokine expression in murine cells, suggesting a correlation between invasion and cytokine activation. In conclusion, the trophoblast-invasive trait of C. rectus that appears limited to human trophoblasts may play a role in facilitating bacterial translocation and placental inflammation during early gestation.

Increased TLR4 expression in murine placentas after oral infection with periodontal pathogens

Maternal periodontitis has emerged as a putative risk factor for preterm births in humans. The periodontitis-associated dental biofilm is thought to serve as an important source of oral bacteria and related virulence factors that hematogenously disseminate and affect the fetoplacental unit; however the underlying biological mechanisms are yet to be fully elucidated. This study hypothesized that an oral infection with the human periodontal pathogens Campylobacter rectus and Porphyromonas gingivalis is able to induce fetal growth restriction, placental inflammation and enhance Toll-like receptors type 4 (TLR4) expression in a murine pregnancy model. Female Balb/C mice (n = 40) were orally infected with C. rectus and/or P. gingivalis over a 16-week period and mated once/week. Pregnant mice were sacrificed at embryonic day (E) 16.5 and placentas were collected and analyzed for TLR4 mRNA levels and qualitative protein expression by real-time PCR and immunofluorescence. TLR4 mRNA expression was found to be increased in the C. rectus-infected group (1.98 +/- 0.886-fold difference, P < 0.01, ANOVA) compared to controls. Microscopic analysis of murine placentas showed enhanced immunofluorescence of TLR4 in trophoblasts, mainly in the placental labyrinth layer. Also, combined oral infection with C. rectus and P. gingivalis significantly reduced the overall fecundity compared to controls (16.7% vs. 75%, infected vs. non-infected mice respectively, P = 0.03, Kaplan-Meier). The results supported an enhanced placental TLR4 expression after oral infection with periodontal pathogens. The TLR4 pathway has been implicated in the pathogenesis of preterm births; therefore the abnormal regulation of placental TLR4 may give new insights into how maternal periodontitis and periodontal pathogens might be linked to placental inflammation and preterm birth pathogenesis.

Demographic, clinical, and microbial aspects of chronic and aggressive periodontitis in Colombia: a multicenter study

BACKGROUND

The microbial profile of periodontal disease varies among different human populations. This study evaluated the demographic, clinical, and microbiologic aspects of periodontitis in a multigeographic sample in Colombia.

METHODS

Three hundred twenty-five patients with chronic periodontitis (CP), 158 patients with aggressive periodontitis (AgP), and 137 healthy-gingivitis controls from five regions of the country were studied. Clinical, microbial, and sociodemographic data were collected. Microbiologic identification was performed using polymerase chain reaction 16S rRNA gene on pooled subgingival samples, and the presence of Gram-negative enteric rods was evaluated by culture. Bivariate and multivariate logistic regression analyses were conducted.

RESULTS

Porphyromonas gingivalis occurred in 71.5% of individuals with periodontitis, Tannerella forsythensis occurred in 58.5%, Campylobacter rectus occurred in 57.5%, Actinobacillus actinomycetemcomitans occurred in 23.6%, and enteric rods occurred in 34.5%. P. gingivalis was more common in CP and AgP than controls. A. actinomycetemcomitans was increased in AgP compared to controls and patients with CP. T. forsythensis, C. rectus, and Eikenella corrodens had a low presence in the West Pacific and Central regions, and enteric rods were increased in the Central region (P <0.05). Other sociodemographic factors were not associated with these microorganisms.

CONCLUSIONS

Geographic regions do not influence the microbiota, but the microbiota may vary by geographic region. P. gingivalis, T. forsythensis, and C. rectus are the most prevalent periodontophatic microorganisms in Colombia. A. actinomycetemcomitans was more common in AgP, and a large percentage of the population studied had enteric rods in the subgingival plaque.

Exploring the relationship between periodontal disease and pregnancy complications

BACKGROUND

Increasing evidence suggests that maternal gingivitis and periodontitis may be a risk factor for preterm birth and other adverse pregnancy outcomes.

TYPES OF STUDIES REVIEWED

To clarify the possible mechanisms behind the association between periodontal disease and preterm delivery, the authors reviewed studies of the effect of infection with periodontal pathogens in animal models on pregnancy outcomes including fetal growth, placental structural abnormalities and neonatal health. After the first report, in 1996, of a potential association between maternal periodontal disease and delivery of a preterm/low-birth-weight infant in humans, many case control and prospective studies were published. This review summarizes these, as well as early studies involving periodontal intervention to reduce risk.

RESULTS

Although there are some conflicting findings and potential problems regarding uncontrolled underlying risk factors, most of the clinical studies indicate a positive correlation between periodontal disease and preterm birth. Recent studies also have shown that there are microbiologic and immunological findings that strongly support the association. The studies indicate that periodontal infection can lead to placental-fetal exposure and, when coupled with a fetal inflammatory response, can lead to preterm delivery. Data from animal studies raise the possibility that maternal periodontal infections also may have adverse long-term effects on the infant's development.

CLINICAL IMPLICATIONS

Education for patients and health care providers regarding the biological plausibility of the association and the potential risks is indicated, but there is insufficient evidence at this time for health care policy recommendations to provide maternal periodontal treatments for the purpose of reducing the risk of adverse pregnancy outcomes.

Evidence of Periopathogenic Microorganisms in Placentas of Women With Preeclampsia

BACKGROUND

Periodontal disease is a chronic inflammatory infectious disease that may act as a focus of infection. Preeclampsia is a pregnancy-specific hypertensive disorder that often leads to maternal morbidity and mortality. Acute atherosis, the placental lesion of preeclampsia, shares many histopathological features with atherosclerosis. Recently, chronic infection was linked to the initiation of atherosclerosis. Oral pathogens have been detected in atherosclerotic plaques, where they may play a role in the development and progression of atherosclerosis. The purpose of the present study was to explore the possibility that periopathogenic bacteria may translocate into the placental tissues of women with preeclampsia.

METHODS

Samples were taken from 16 placentas obtained from cesarean sections of women with preeclampsia and from 14 age-matched healthy pregnant women. Polymerase chain reaction was used to detect Actinobacillus actinomycetemcomitans, Fusobacterium nucleatum ssp., Porphyromonas gingivalis, Prevotella intermedia, Tannerella forsythensis, and Treponema denticola.

RESULTS

Eight of the 16 (50%) placenta specimens were positive for one or more periopathogenic bacteria in the preeclampsia group, compared to only two of the 14 samples (14.3%) from controls. Bacterial counts were statistically significantly higher in the preeclampsia group for all of the periopathogenic bacteria examined (P <or=0.0055). Although all of the target periopathogenic bacteria were found in the preeclampsia group, only three (P. gingivalis, T. forsythensis, and T. denticola) were found in the control group.

CONCLUSION

The significant presence of periopathogenic microorganisms or their products in human placentas of women with preeclampsia may suggest a possible contribution of periopathogenic bacteria to the pathogenesis of this syndrome.

Bacterial infection promotes DNA hypermethylation

Maternal oral infection, caused by bacteria such as C. rectus or P. gingivalis, has been implicated as a potential source of placental and fetal infection and inflammatory challenge, which increases the relative risk for pre-term delivery and growth restriction. Intra-uterine growth restriction has also been reported in various animal models infected with oral organisms. Analyzing placental tissues of infected growth-restricted mice, we found down-regulation of the imprinted Igf2 gene. Epigenetic modification of imprinted genes via changes in DNA methylation plays a critical role in fetal growth and development programming. Here, we assessed whether C. rectus infection mediates changes in the murine placenta Igf2 methylation patterns. We found that infection induced hypermethylation in the promoter region-P0 of the Igf2 gene. This novel finding, correlating infection with epigenetic alterations, provides a mechanism linking environmental signals to placental phenotype, with consequences for development.

Periodontal disease and systemic conditions: a bidirectional relationship

For decades, physicians and dentists have paid close attention to their own respective fields, specializing in medicine pertaining to the body and the oral cavity, respectively. However, recent findings have strongly suggested that oral health may be indicative of systemic health. Currently, this gap between allopathic medicine and dental medicine is quickly closing, due to significant findings supporting the association between periodontal disease and systemic conditions such as cardiovascular disease, type 2 diabetes mellitus, adverse pregnancy outcomes, and osteoporosis. Significant effort has brought numerous advances in revealing the etiological and pathological links between this chronic inflammatory dental disease and these other conditions. Therefore, there is reason to hope that the strong evidence from these studies may guide researchers towards greatly improved treatment of periodontal infection that would also ameliorate these systemic illnesses. Hence, researchers must continue not only to uncover more information about the correlations between periodontal and systemic diseases but also to focus on positive associations that may result from treating periodontal disease as a means of ameliorating systemic diseases.