The Role Of Subclinical Infection And Cytokines In Preterm Parturition

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1. Signature pathways identified from gene expression profiles in the human uterine cervix before and after spontaneous term parturition. The uterine cervix plays a central role in normal parturition, preterm labor, cervical insufficiency, and in functional disorders which are the most common cause of caesarean delivery at term (arrest of dilatation). Thus far, there is an incomplete understanding of the mechanisms responsible for cervical ripening, as well as those associated with cervical changes during parturition. The Branch has undertaken the application of systems biology tools to improve the understanding of these processes. A cross-sectional study was conducted to identify "signature pathways" that characterize biologic processes, based on genes differentially expressed in the uterine cervix before and after spontaneous labor. Fifty-two pathways were enriched significantly in differentially expressed genes that were previously suspected as involved in cervical dilation and remodeling, and 2 of the top 5 pathways were novel pathways involved in cervical remodeling: plasmin signaling and plasminogen activator urokinase signaling. This is the first application of systems biology to the understanding of cervical biology before and after parturition. 2. Clinical significance of the presence of amniotic fluid sludge in asymptomatic patients at high risk for spontaneous preterm delivery. Intrauterine infection has emerged as a frequent and important mechanism of disease in preterm birth and is the only pathologic process for which a firm causal link with prematurity has been established. The sonographic finding of dense aggregates of particulate matter in the amniotic fluid (AF) close to the uterine cervix has been previously described in women with an episode of preterm labor and referred to as AF sludge. We conducted a retrospective case-control study including 281 asymptomatic patients at risk for spontaneous preterm delivery who underwent transvaginal ultrasound examination between 13 and 29 completed weeks of gestation. The prevalence of AF sludge in the study population was 23.5%. Patients with sludge had a significantly higher rate of spontaneous preterm delivery at <28 weeks, <32 weeks and <35 weeks; a higher frequency of clinical chorioamnionitis, histologic chorioamnionitis and funisitis; a higher frequency of preterm premature rupture of membranes (PPROM) and lower gestational age at PPROM; and a shorter ultrasound-to-delivery interval than those without sludge. To determine the nature of AF sludge, this material was collected under sonographic guidance in patients with impending preterm delivery. Macroscopically, sludge is similar to pus and is associated with a markedly elevated white blood cell count in AF, as well as positive Gram stain and cultures. We propose that the detection of AF sludge represents a sign that microbial invasion of the amniotic cavity and an inflammatory process is in progress. Such an interpretation will strengthen the view that intra-amniotic infection is chronic and subclinical in nature. 3. Differential expression of microRNAs (miRNAs) with progression of gestation and inflammation in the human chorioamniotic membranes. miRNAs are members of a class of small, non-coding RNA molecules that have a critical role in post-transcriptional regulation of protein-coding genes. The expression of 157 miRNAs was assessed by real-time qRT-PCR. More than 95% of the miRNAs screened were expressed. Gestational age-dependent changes in expression were observed for 13 miRNAs. The expression of miR-223 and miR-338 was increased (37-fold and 24-fold, respectively)) in the presence of chorioamnionitis. Gene Ontology analysis of genes targeted by differentially expressed miRNAs revealed enrichment for specific biological process categories. This study reports, for the first time, the expression profiles of miRNA in human chorioamniotic membranes with advancing gestation and chorioamnionitis. 4. Antibiotic administration to patients with PPROM does not eradicate intra-amniotic infection. Antibiotic administration has become part of the standard of care for patients with PPROM. Yet, the natural history of intrauterine infection/inflammation during antibiotic therapy remains largely unknown. We conducted a study to determine if antibiotic administration to the mother eradicates intra-amniotic infection and/or reduces the frequency of intra-amniotic inflammation in patients with PPROM. The findings demonstrated that antibiotic administration (ceftriaxone, clindamycin, and erythromycin) rarely eradicates intra-amniotic infection in patients with PPROM, and that intra-amniotic inflammation developed in one-third of patients who did not have inflammation at admission, despite antibiotic administration. Thus, the current standard of practice neither eradicates infection, nor prevents it. 5. Dermatitis as a component of the fetal inflammatory response syndrome is associated with activation of Toll-like receptors (TLRs) in epidermal keratinocytes. A fetal inflammatory response is closely linked to preterm labor and delivery and has been associated with increased perinatal morbidity and long-term sequelae such as cerebral palsy and chronic lung disease. We have coined the term Fetal Inflammatory Response Syndrome (FIRS) to describe a condition characterized by fetal systemic inflammation and an elevation of fetal plasma interleukin-6. TLRs are essential components of the innate immune system implicated in recognizing the presence of microorganisms. The skin epidermis is not only a mechanical barrier, but also an active immune organ that participates in the protection of the host against microbial invasion. The expression of TLR-2 and TLR-4 mRNA and proteins has been demonstrated in human keratinocytes along with accessory signalling molecules. Investigators at the PRB aimed to examine histopathological features of fetal skin exposed to microbial invasion of the amniotic cavity and to assess the changes in TLR-2 and TLR-4 expression. Leukocytic infiltrates into the superficial dermis were observed in cases with chorioamnionitis. TLR-2 immunoreactivity in the skin was stronger in fetuses with chorioamnionitis than in those without this condition. This study demonstrates for the first time that fetal dermatitis can be detected and is part of FIRS. We propose that this FIRS-associated fetal dermatitis is a fetal counterpart of chorioamnionitis. 6. Microglial activation in perinatal rabbit brain induced by intrauterine inflammation: detection with 11C-(R)-PK11195 and small-animal PET. Intrauterine infection can lead to fetal systemic inflammation, which is associated with brain injury (e.g., periventricular leukomalacia) and cerebral palsy. Activated microglia have been found in cases of brain injury and can lead to oligodendrocyte damage and white matter injury. To determine if microglial activation can be detected before birth and if treatment can prevent lesions, we have developed an animal model. Rabbits with timed pregnancies underwent laparotomy and were randomly allocated to receive saline or lipopolysaccharide. Pups were scanned using small-animal Positron Emission Tomography (PET) and by MRI on postnatal day 1. There was increased brain retention of (11)C-(R)-PK11195 tracer (a marker for microglia activation) in the endotoxin-treated pups when compared with that of age-matched controls. These findings were confirmed by immunohistochemical staining. This study demonstrated that intrauterine inflammation leads to activation of microglial cells and that may be responsible for the development of brain injury and white matter damage in the perinatal period and that molecular imaging can be used to detect the presence and progress of neuroinflammation in utero.