Transcriptomic Remodelling of Fetal Endothelial Cells During Establishment of Inflammatory Memory.

Inflammatory memory involves the molecular and cellular 'reprogramming' of innate immune cells following exogenous stimuli, leading to non-specific protection against subsequent pathogen exposure. This phenomenon has now also been described in non-hematopoietic cells, such as human fetal and adult endothelial cells. In this study we mapped the cell-specific DNA methylation profile and the transcriptomic remodelling during the establishment of inflammatory memory in two distinct fetal endothelial cell types - a progenitor cell (ECFC) and a differentiated cell (HUVEC) population. We show that both cell types have a core transcriptional response to an initial exposure to a viral-like ligand, Poly(I:C), characterised by interferon responsive genes. There was also an ECFC specific response, marked by the transcription factor ELF1, suggesting a non-canonical viral response pathway in progenitor endothelial cells. Next, we show that both ECFCs and HUVECs establish memory in response to an initial viral exposure, resulting in an altered subsequent response to lipopolysaccharide. While the capacity to train or tolerize the induction of specific sets of genes was similar between the two cell types, the progenitor ECFCs show a higher capacity to establish memory. Among tolerized cellular pathways are those involved in endothelial barrier establishment and leukocyte migration, both important for regulating systemic immune-endothelial cell interactions. These findings suggest that the capacity for inflammatory memory may be a common trait across different endothelial cell types but also indicate that the specific downstream targets may vary by developmental stage.

Amniotic fluid interleukin 6 and interleukin 8 are superior predictors of fetal lung injury compared with maternal or fetal plasma cytokines or placental histopathology in a nonhuman primate model.

BACKGROUND: Intra-amniotic infection or inflammation is common in early preterm birth and associated with substantial neonatal lung morbidity owing to fetal exposure to proinflammatory cytokines and infectious organisms. Amniotic fluid interleukin 8, a proinflammatory cytokine, was previously correlated with the development of neonatal bronchopulmonary dysplasia, but whether amniotic fluid cytokines or placental pathology more accurately predicts neonatal lung pathology and morbidity is unknown. We have used a pregnant nonhuman primate model of group B Streptococcus infection to study the pathogenesis of intra-amniotic infection, bacterial invasion of the amniotic cavity and fetus, and microbial-host interactions. In this nonhuman primate model, we have studied the pathogenesis of group B Streptococcus strains with differing potential for virulence, which has resulted in a spectrum of intra-amniotic infection and fetal lung injury that affords the opportunity to study the inflammatory predictors of fetal lung pathology and injury. OBJECTIVE: This study aimed to determine whether fetal lung injury is best predicted by placental histopathology or the cytokine response in amniotic fluid or maternal plasma. STUDY DESIGN: Chronically catheterized pregnant monkeys (Macaca nemestrina, pigtail macaque) at 116 to 125 days gestation (term at 172 days) received a choriodecidual inoculation of saline (n=5), weakly hemolytic group B Streptococcus strain (n=5, low virulence), or hyperhemolytic group B Streptococcus strain (n=5, high virulence). Adverse pregnancy outcomes were defined as either preterm labor, microbial invasion of the amniotic cavity, or development of the fetal inflammatory response syndrome. Amniotic fluid and maternal and fetal plasma samples were collected after inoculation, and proinflammatory cytokines (tumor necrosis factor alpha, interleukin beta, interleukin 6, interleukin 8) were measured by a multiplex assay. Cesarean delivery was performed at the time of preterm labor or within 1 week of inoculation. Fetal necropsy was performed at the time of delivery. Placental pathology was scored in a blinded fashion by a pediatric pathologist, and fetal lung injury was determined by a semiquantitative score from histopathology evaluating inflammatory infiltrate, necrosis, tissue thickening, or collapse scored by a veterinary pathologist. RESULTS: The principal findings in our study are as follows: (1) adverse pregnancy outcomes occurred more frequently in animals receiving hyperhemolytic group B Streptococcus (80% with preterm labor, 80% with fetal inflammatory response syndrome) than in animals receiving weakly hemolytic group B Streptococcus (40% with preterm labor, 20% with fetal inflammatory response syndrome) and in controls (0% preterm labor, 0% fetal inflammatory response syndrome); (2) despite differences in the rate of adverse pregnancy outcomes and fetal inflammatory response syndrome, fetal lung injury scores were similar between animals receiving the weakly hemolytic group B Streptococcus strains and animals receiving the hyperhemolytic group B Streptococcus strains; (3) fetal lung injury score was significantly correlated with peak amniotic fluid cytokines interleukin 6 and interleukin 8 but not tumor necrosis factor alpha or interleukin 1 beta; and (4) fetal lung scores were poorly correlated with maternal and fetal plasma cytokine levels and placental pathology. CONCLUSION: Amniotic fluid interleukin 6 and interleukin 8 levels were superior predictors of fetal lung injury than placental histopathology or maternal plasma cytokines. This evidence supports a role for amniocentesis in the prediction of neonatal lung morbidity owing to intra-amniotic infection, which cannot be provided by cytokine analysis of maternal plasma or placental histopathology.

Melatonin for prevention of fetal lung injury associated with intrauterine inflammation and for improvement of lung maturation.

Inflammation is associated with injury to immature lungs, and melatonin administration to preterm newborns with acute respiratory distress improves pulmonary outcomes. We hypothesized that maternally administered melatonin may reduce inflammation, oxidative stress, and structural injury in fetal lung and help fetal lung maturation in a mouse model of intrauterine inflammation (IUI). Mice were randomized to the following groups: control (C), melatonin (M), lipopolysaccharide (LPS; a model of IUI) (L), and LPS with melatonin (ML). Pro-inflammatory cytokines, components of the Hippo pathway, and Yap1/Taz were analyzed in the fetal lung at E18 by real-time RT-qPCR. Confirmatory histochemistry and immunohistochemical analyses (surfactant protein B, vimentin, HIF-1ß, and CXCR2) were performed. The gene expression of IL1ß in the fetal lung was significantly increased in L compared to C, M, and ML. Taz expression was significantly decreased in L compared to C and M. Taz gene expression in L was significantly decreased compared with those in ML. Immunohistochemical analyses showed that the expression of HIF-1ß and CXCR2 was significantly increased in L compared to C, M, and ML. The area of surfactant protein B and vimentin were significantly decreased in L than C, M, or ML in the fetal and neonatal lung. Antenatal maternally administered melatonin appears to prevent fetal lung injury induced by IUI and to help lung maturation. The results from this study results suggest that melatonin could serve as a novel safe preventive and/or therapeutic medicine for preventing fetal lung injury from IUI and for improving lung maturation in prematurity.

Biphasic Impact of Prenatal Inflammation and Macrophage Depletion on the Wiring of Neocortical Inhibitory Circuits.

The etiology of neurodevelopmental disorders is linked to defects in parvalbumin (PV)-expressing cortical interneurons and to prenatal immune challenges. Mouse models of maternal immune activation (MIA) and microglia deficits increase the postnatal density of PV interneurons, raising the question of their functional integration. Here, we show that MIA and embryonic depletion of macrophages including microglia have a two-step impact on PV interneurons wiring onto their excitatory target neurons in the barrel cortex. In adults, both challenges reduced the inhibitory drive from PV interneurons, as reported in neurodevelopmental disorders. In juveniles, however, we found an increased density of PV neurons, an enhanced strength of unitary connections onto excitatory cells, and an aberrant horizontal inhibition with a reduced lateral propagation of sensory inputs in vivo. Our results provide a comprehensive framework for understanding the impact of prenatal immune challenges onto the developmental trajectory of inhibitory circuits that leads to pathological brain wiring.

Perinatal immuno/inflammatory responses in the presence or absence of bovine fetal infection.

BACKGROUND: It is known that the bovine fetus can mount an immune and inflammatory reaction to infection, but it is not known whether there is a contemporaneous maternal response. Nor is it known whether the response of calves which die perinatally, with or without infection, differs from that of live perinates. Hence, the objective of this study was to determine if acute phase reactant and immunoglobulin concentrations differed between calves (and their dams) in three groups: live calves (CC; n = 21) and dead calves with (PM INF+; n = 22) or without (PM INF-; n = 89) in utero infection. In calf plasma, serum amyloid A, haptoglobin, immunoglobulins M, G1 and G2 and interleukin-6 were measured. In dam serum, SAA and Hp was measured and in amniotic and abomasal fluid, IL-6 was measured. RESULTS: Live calves had higher plasma concentrations of SAA and IL-6 than dead calves with (PM INF+) or without (PM INF-) in utero infection. Calves in the PM INF-, but not PM INF+ group, had higher Hp concentrations than calves in the CC group. Calves in the PM INF+ group had higher IgG1 concentrations than calves in the PM INF- and CC groups. Except for higher IgG1 and IgG2 concentrations, biomarker values did not differ significantly between dead calves with or without in utero infection. Live calves had higher IL-6 concentrations in abomasal fluid compared to PM INF- calves. There were no significant differences in blood biomarker concentrations between dams of the three groups of calves. Amniotic fluid IL-6 concentrations were higher from the dams of control calves than the dams of uninfected calves. CONCLUSIONS: Differences in biomarkers (higher Hp and IgG1; lower SAA and IL-6) between perinatal mortalities and live perinates probably reflect differences between these two groups in age at sampling (SAA and IL-6) and in utero infection (IgG1). Out of the six analytes measured in calves, only IgG1 and IgG2 were biomarkers of (chronic) in utero infection.

Chronic inflammation and impaired development of the preterm brain.

The preterm newborn is at significant risk of neural injury and impaired neurodevelopment. Infants with mild or no evidence of injury may also be at risk of altered brain development, with evidence impaired cell maturation. The underlying causes are multifactorial and include exposure of both the fetus and newborn to hypoxia-ischemia, inflammation (chorioamnionitis) and infection, adverse maternal lifestyle choices (smoking, drug and alcohol use, diet) and obesity, as well as the significant demand that adaptation to post-natal life places on immature organs. Further, many fetuses and infants may have combinations of these events, and repeated (multi-hit) events that may induce tolerance to injury or sensitize to greater injury. Currently there are no treatments to prevent preterm injury or impaired neurodevelopment. However, inflammation is a common pathway for many of these insults, and clinical and experimental evidence demonstrates that acute and chronic inflammation is associated with impaired brain development. This review examines our current knowledge about the relationship between inflammation and preterm brain development, and the potential for stem cell therapy to provide neuroprotection and neurorepair through reducing inflammation and release of trophic factors, which promote cell maturation and repair.

Mecp2 regulates tnfa during zebrafish embryonic development and acute inflammation.

Mutations in MECP2 cause Rett syndrome, a severe neurological disorder with autism-like features. Duplication of MECP2 also causes severe neuropathology. Both diseases display immunological abnormalities that suggest a role for MECP2 in controlling immune and inflammatory responses. Here, we used mecp2-null zebrafish to study the potential function of Mecp2 as an immunological regulator. Mecp2 deficiency resulted in an increase in neutrophil infiltration and upregulated expression of the pro- and anti-inflammatory cytokines Il1b and Il10 as a secondary response to disturbances in tissue homeostasis. By contrast, expression of the proinflammatory cytokine tumor necrosis factor alpha (Tnfa) was consistently downregulated in mecp2-null animals during development, representing the earliest developmental phenotype described for MECP2 deficiency to date. Expression of tnfa was unresponsive to inflammatory stimulation, and was partially restored by re-expression of functional mecp2 Thus, Mecp2 is required for tnfa expression during zebrafish development and inflammation. Finally, RNA sequencing of mecp2-null embryos revealed dysregulated processes predictive for Rett syndrome phenotypes.

Inflammation in maternal obesity and gestational diabetes mellitus.

BACKGROUND: The prevalence of maternal obesity is rising rapidly worldwide and constitutes a major obstetric problem, increasing mortality and morbidity in both mother and offspring. Obese women are predisposed to pregnancy complications such as gestational diabetes mellitus (GDM), and children of obese mothers are more likely to develop cardiovascular and metabolic disease in later life. Maternal obesity and GDM may be associated with a state of chronic, low-grade inflammation termed "metainflammation", as opposed to an acute inflammatory response. This inflammatory environment may be one mechanism by which offspring of obese women are programmed to develop adult disorders. METHODS: Herein we review the evidence that maternal obesity and GDM are associated with changes in the maternal, fetal and placental inflammatory profile. RESULTS: Maternal inflammation in obesity and GDM may not always be associated with fetal inflammation. CONCLUSION: We propose that the placenta 'senses' and adapts to the maternal inflammatory environment, and plays a central role as both a target and producer of inflammatory mediators. In this manner, maternal obesity and GDM may indirectly program the fetus for later disease by influencing placental function.

Differences in visceral fat and fat bacterial colonization between ulcerative colitis and Crohn's disease. An in vivo and in vitro study.

Crohn's disease (CD) is notably characterized by the expansion of visceral fat with small adipocytes expressing a high proportion of anti-inflammatory genes. Conversely, visceral fat depots in ulcerative colitis (UC) patients have never been characterized. Our study aims were a) to compare adipocyte morphology and gene expression profile and bacterial translocation in omental (OM) and mesenteric (MES) adipose tissue of patients with UC and CD, and b) to investigate the effect of bacterial infection on adipocyte proliferation in vitro. Specimens of OM and MES were collected from 11 UC and 11 CD patients, processed and examined by light microscopy. Gene expression profiles were evaluated in adipocytes isolated from visceral adipose tissue using microarray and RTqPCR validations. Bacteria within adipose tissue were immuno-detected by confocal scanning laser microscopy. Adipocytes were incubated with Enterococcus faecalis and cells counted after 24 h. Morphology and molecular profile of OM and MES revealed that UC adipose tissue is less inflamed than CD adipose tissue. Genes linked to inflammation, bacterial response, chemotaxis and angiogenesis were down-regulated in adipocytes from UC compared to CD, whereas genes related to metallothioneins, apoptosis pathways and growth factor binding were up-regulated. A dense perinuclear positivity for Enterococcus faecalis was detected in visceral adipocytes from CD, whereas positivity was weak in UC. In vitro bacterial infection was associated with a five-fold increase in the proliferation rate of OM preadipocytes. Compared to UC, visceral adipose tissue from CD is more inflamed and more colonized by intestinal bacteria, which increase adipocyte proliferation. The influence of bacteria stored within adipocytes on the clinical course of IBD warrants further investigations.

Lipopolysaccharide-induced injury is more pronounced in fetal transgenic ErbB4-deleted lungs.

Pulmonary ErbB4 deletion leads to a delay in fetal lung development, alveolar simplification, and lung function disturbances in adult mice. We generated a model of intrauterine infection in ErbB4 transgenic mice to study the additive effects of antenatal LPS administration and ErbB4 deletion during fetal lung development. Pregnant mice were treated intra-amniotically with an LPS dose of 4 µg at E17 of gestation. Lungs were analyzed 24 h later. A significant influx of inflammatory cells was seen in all LPS-treated lungs. In heterozygote control lungs, LPS treatment resulted in a delay of lung morphogenesis characterized by a significant increase in the fraction of mesenchyme, a decrease in gas exchange area, and disorganization of elastic fibers. Surfactant protein (Sftp)b and Sftpc were upregulated, but mRNA of Sftpb and Sftpc was downregulated compared with non-LPS-treated controls. The mRNA of Sftpa1 and Sftpd was upregulated. In ErbB4-deleted lungs, the LPS effects were more pronounced, resulting in a further delay in morphological development, a more pronounced inflammation in the parenchyma, and a significant higher increase in all Sftp. The effect on Sftpb and Sftpc mRNA was somewhat different, resulting in a significant increase. These results imply a major role of ErbB4 in LPS-induced signaling in structural and functional lung development.

Inflammation recapitulates the ontogeny of lymphoid stromal cells.

Stromal cells in lymphoid tissues regulate lymphocyte recruitment and survival through the expression of specific chemokines and cytokines. During inflammation, the same signals recruit lymphocytes to the site of injury; however, the "lymphoid" stromal (LS) cells producing these signals remain poorly characterized. We find that mouse inflammatory lesions and tumors develop gp38(+) LS cells, in recapitulation of the development of LS cells early during the ontogeny of lymphoid organs and the intestine, and express a set of genes that promotes the development of lymphocyte-permissive tissues. These gp38(+) LS cells are induced by a robust pathway that requires myeloid cells but not known Toll- or NOD-like receptors, the inflammasome, or adaptive immunity. Parabiosis and inducible genetic cell fate mapping experiments indicate that local precursors, presumably resident fibroblasts rather that circulating precursors, massively proliferate and give rise to LS cells during inflammation. Our results show that LS cells are both programmed during ontogeny and reinduced during inflammation.

Fetal wound healing using a genetically modified murine model: the contribution of P-selectin.

PURPOSE: During early gestation, fetal wounds heal with paucity of inflammation and absent scar formation. P-selectin is an adhesion molecule that is important for leukocyte recruitment to injury sites. We used a murine fetal wound healing model to study the specific contribution of P-selectin to scarless wound repair. METHODS: Linear excisional wounds were created on the dorsa of E15.5 and E17.5 gestation fetuses in wild-type and P-selectin (-/-) mice (term = 19 days). Wounds were harvested at various time-points after wounding and analyzed using histology and immunohistochemistry. RESULTS: The E15.5 wounds in both wild-type and P-selectin (-/-) fetuses healed scarlessly and with minimal inflammation, whereas E17.5 wounds healed with fibrosis and inflammation. However, the scars of the P-selectin (-/-) wounds appeared slightly different than wild-type. There were significantly more inflammatory cells in E17.5 wild-type wounds 6 hours after injury (P < .001), but the difference was no longer significant by 24 hours. Finally, reepithelialization was slower in the E15.5 knockout wounds compared to their wild-type counterparts. CONCLUSIONS: Absence of P-selectin delays inflammatory cell recruitment and reepithelialization of fetal wounds; however, scar formation still occurs in late gestation wounds. The contribution of specific molecules to fetal wound healing can be elucidated using murine knockout or transgenic models.

The transcription factors c-rel and RelA control epidermal development and homeostasis in embryonic and adult skin via distinct mechanisms.

Determining the roles of Rel/NF-kappaB transcription factors in mouse skin development with loss-of-function mutants has been limited by redundancy among these proteins and by embryonic lethality associated with the absence of RelA. Using mice lacking RelA and c-rel, which survive throughout embryogenesis on a tumor necrosis factor alpha (TNF-alpha)-deficient background (rela(-/-) c-rel(-/-) tnfalpha(-/-)), we show that c-rel and RelA are required for normal epidermal development. Although mutant fetuses fail to form tylotrich hair and have a thinner epidermis, mutant keratinocyte progenitors undergo terminal differentiation to form an outer cornified layer. Mutant basal keratinocytes are abnormally small, exhibit a delay in G(1) progression, and fail to form keratinocyte colonies in culture. In contrast to the reduced proliferation of mutant keratinocytes during embryogenesis, skin grafting experiments revealed that the mutant epidermis develops a TNF-alpha-dependent hyperproliferative condition. Collectively, our findings indicate that RelA and c-rel control the development of the epidermis and associated appendages during embryogenesis and regulate epidermal homeostasis in a postnatal environment through the suppression of innate immune-mediated inflammation.

Enhanced inflammatory response in neural tubes of embryos derived from diabetic mice exposed to a teratogen.

Exposure of embryos to the teratogen cyclophosphamide (CP) and maternal diabetes is linked to pathogenesis of neural tube defects during development. Maternal diabetes aggravates the teratogen-induced inflammatory reaction leading to increased risk of neural tube defects in mouse embryos. The inflammatory reaction in the developing neural tube has been characterized by the presence of activated amoeboid microglia/brain macrophages and altered expression levels of cytokines. Although there were no obvious anomalies observed in the neural tubes of embryos from CP-treated non-diabetic mice, the frequency of neural tube defects was increased significantly in embryos of CP-treated diabetic mice. Moreover, there were more activated amoeboid microglia in the forebrain of CP-treated diabetic embryos compared to that in CP-treated non-diabetic mice. The expression of cytokines such as tumor necrosis factor-alpha (TNF-alpha) and transforming growth factor-beta1 (TGF-beta1) in the fetal brain of normal and diabetic embryos was induced in the neural tubes after CP treatment. Furthermore, the mRNA expression levels of both genes were increased markedly in the neural tube of CP-treated diabetic embryos compared to that of CP-treated non-diabetic embryos as measured by quantitative real-time PCR. Immunohistochemically, more TNF-alpha- and TGF-beta1-positive cells, which included neurons and amoeboid microglia, were detected in CP-treated diabetic embryos than in CP-treated normal embryos. Maternal diabetes aggravates teratogen-induced inflammation, which is characterized in the developing neural tube by increased amoeboid microglia and enhanced expression of inflammatory cytokines. Although a definite link has yet to be elucidated, it is suggested that the increased rate of neural tube defects observed in CP-treated diabetic embryos may be due to upregulation of proinflammatory cytokines caused by maternal diabetes.

Micronutrients and intrauterine infection, preterm birth and the fetal inflammatory response syndrome.

Prematurity is the leading cause of perinatal morbidity and mortality worldwide. Intrauterine infection has emerged as a major cause of premature labor and delivery. It has been estimated that 25% of all preterm deliveries occur to mothers who have microbial invasion of the amniotic cavity, although these infections are mostly subclinical in nature. This article describes the pathways leading to intrauterine infection, microbiology, frequency and clinical consequences of infection. The pathophysiology of the fetal inflammatory response syndrome is reviewed, as is its relationship to long-term handicap, such as cerebral palsy and bronchopulmonary dysplasia. A possible role for two micronutrients, vitamins C and E, in the prevention of the preterm prelabor rupture of membranes and the consequences of fetal inflammation is considered. Research needs are listed.

Endotoxin-induced interleukin 1 expression in testicular macrophages is accompanied by downregulation of the constitutive expression in Sertoli cells.

Interleukin-1alpha (IL-1alpha) is constitutively produced by Sertoli cells in adult rat testes. We demonstrate here that adult rats initiate expression of IL-1alpha and IL-1beta in testicular macrophages and decrease plasma testosterone by 60%, 2 h after administration of endotoxin. The macrophage activation was accompanied by downregulation of IL-1alpha mRNA expression in Sertoli cells. Despite increased tissue concentrations of IL-1alpha and IL-1beta immunoreactive protein, the level of bioactive IL-1 in the testis remained unchanged. Testes from prepubertal rats responded similarly to endotoxin, but lacked constitutive expression of IL-1alpha. We conclude that endotoxin-induced inflammation involves the testis by local macrophage activation and cytokine secretion. The paracrine mechanisms regulating IL-1 bioactivity in the testis are unknown but may represent a means to protect germ cells from noxious effects of inflammation.

A fetal systemic inflammatory response is followed by the spontaneous onset of preterm parturition.

OBJECTIVE: There is no evidence for the participation of the human fetus in the mechanisms responsible for the onset of preterm labor. We propose that preterm labor in the setting of infection results from the actions of proinflammatory cytokines secreted as part of the fetal and/or maternal host response to microbial invasion. The objective of this study was to determine whether a systemic fetal inflammatory response, defined as an elevation of fetal plasma interleukin-6 concentrations, has a temporal relationship with the commencement of labor. STUDY DESIGN: After informed consent was obtained, amniocentesis and cordocentesis were performed in 41 patients with preterm premature rupture of membranes who were not in labor on admission. Amniotic fluid was cultured for both aerobic and anaerobic bacteria, as well as for mycoplasmas. Fetal plasma interleukin-6 was assayed by a sensitive and specific immunoassay. Statistical analyses included contingency tables and survival analysis with time-dependent Cox regression hazard modeling. RESULTS: Microbial invasion of the amniotic cavity was present in 58.5% (24/41) of patients. Fetuses with fetal plasma interleukin-6 concentrations > 11 pg/mL had a higher rate of spontaneous preterm delivery within 48 and 72 hours of the procedure than those with fetal plasma interleukin-6 levels < or = 11 pg/mL (88% vs 29% and 88% vs 35%, respectively; P < .05 for all comparisons). Moreover, patients with initiation of labor and delivery within 48 hours of the procedure had a higher proportion of fetuses with plasma interleukin-6 values > 11 pg/mL than patients delivered > 48 hours (58% [7/12] vs 8% [1/13], respectively; P < .05). Survival analysis indicated that fetuses with elevated fetal plasma interleukin-6 levels had a shorter cordocentesis-to-delivery interval than those without elevated fetal plasma interleukin-6 concentrations (median 0.8 days [range 0.1 to 5] vs median 6 days [range 0.2 to 33.6], respectively; P < .05). Time-dependent Cox regression hazard modeling indicated that fetal plasma interleukin-6 level was the only covariate significantly associated with the duration of pregnancy after we adjusted for gestational age, amniotic fluid interleukin-6 level, and the microbiologic state of the amniotic cavity (P < .01). CONCLUSION: A systemic fetal proinflammatory cytokine response is followed by the onset of spontaneous preterm parturition in patients with preterm premature rupture of membranes.

Secretion of tumor necrosis factor during fetal and neonatal development of the mouse: ontogenic inflammation.

Inflammation plays an important role in homeostasis of the body. We therefore can assume that an inflammatory state occurs during ontogenesis of animals. To address this problem, we examined the ability of tumor necrosis factor (TNF), one of the inflammatory mediators, to be secreted by mouse cells during development. We cultured cells prepared from various parts of fetuses (10-19 days of gestation) and postnatal brains by collagenase digestion and assayed the secreted TNF activity by the L-929 cytotoxicity test. We found TNF activity by fetal cells without any stimulation. The spontaneous secretion of TNF was relatively high at around 13-15 days of gestation. The secretion was enhanced by lipopolysaccharide (LPS), showing that fetal cells are in an activated state for TNF secretion. These TNF activities were neutralized completely by rabbit anti-murine TNF antibody. Spontaneous and LPS-enhanced secretion by postnatal brain cells reached a peak around 7 days after birth, and thereafter declined rapidly. This time course was well correlated to the increase in the weight of brain. The producing cells were negative in macrophage marker surface antigen, and heterogeneous in relation to adherence and phagocytic activity, showing that TNF is secreted by various types of cells in the fetal body. These results suggest the presence of an inflammation-like state during ontogenesis. We consider that this "ontogenic inflammation" may be the prototype of inflammation, which can regulate homeostasis of the adult body.