The role of microglia in early neurodevelopment and the effects of maternal immune activation.

Activation of the maternal immune system during gestation has been associated with an increased risk for neurodevelopmental disorders in the offspring, particularly schizophrenia and autism spectrum disorder. Microglia, the tissue-resident macrophages of the central nervous system, are implicated as potential mediators of this increased risk. Early in development, microglia start populating the embryonic central nervous system and in addition to their traditional role as immune responders under homeostatic conditions, microglia are also intricately involved in various early neurodevelopmental processes. The timing of immune activation may interfere with microglia functioning during early neurodevelopment, potentially leading to long-term consequences in postnatal life. In this review we will discuss the involvement of microglia in brain development during the prenatal and early postnatal stages of life, while also examining the effects of maternal immune activation on microglia and neurodevelopmental processes. Additionally, we discuss recent single cell RNA-sequencing studies focusing on microglia during prenatal development, and hypothesize how early life microglial priming, potentially through epigenetic reprogramming, may be related to neurodevelopmental disorders.

Transcriptional profiling of macaque microglia reveals an evolutionary preserved gene expression program.

Microglia are tissue-resident macrophages of the central nervous system (CNS), and important for CNS development and homeostasis. In the adult CNS, microglia monitor environmental changes and react to tissue damage, cellular debris, and pathogens. Here, we present a gene expression profile of purified microglia isolated from the rhesus macaque, a non-human primate, that consists of 666 transcripts. The macaque microglia transcriptome was intersected with the transcriptional programs of microglia from mouse, zebrafish, and human CNS tissues, to determine (dis)similarities. This revealed an extensive overlap of 342 genes between the transcriptional profile of macaque and human microglia, and showed that the gene expression profile of zebrafish is most distant when compared to other species. Furthermore, an evolutionair core based on the overlapping gene expression signature from all four species was identified. This study presents a macaque microglia transcriptomics profile, and identifies a gene expression program in microglia that is preserved across species, underscoring their CNS-tailored tissue macrophage functions as innate immune cells with CNS-surveilling properties.

Human fetal microglia acquire homeostatic immune-sensing properties early in development.

Microglia, immune cells of the central nervous system (CNS), are important for tissue development and maintenance and are implicated in CNS disease, but we lack understanding of human fetal microglia development. Single-cell gene expression and bulk chromatin profiles of microglia at 9 to 18 gestational weeks (GWs) of human fetal development were generated. Microglia were heterogeneous at all studied GWs. Microglia start to mature during this developmental period and increasingly resemble adult microglia with CNS-surveilling properties. Chromatin accessibility increases during development with associated transcriptional networks reflective of adult microglia. Thus, during early fetal development, microglia progress toward a more mature, immune-sensing competent phenotype, and this might render the developing human CNS vulnerable to environmental perturbations during early pregnancy.

Effect of Deep Margin Elevation on CAD/CAM-Fabricated Ceramic Inlays.

CLINICAL RELEVANCE: Using the deep margin elevation technique in preparations extending beyond the cemento-enamel junction appears to be beneficial in maintaining structural integrity of CAD/CAM-fabricated feldspathic ceramic inlays. SUMMARY: Objective: To evaluate the effect of deep margin elevation on structural and marginal integrity of ceramic inlays.Methods and Materials: Forty extracted human third molars were collected and randomly separated into four groups (n=10/group). In group 1 (enamel margin group), the gingival margin was placed 1 mm supragingival to the cemento-enamel junction (CEJ). In group 2 (cementum margin group), the gingival margin was placed 2 mm below the CEJ. In group 3 (glass ionomer [GI] margin group), the gingival margin was placed 2 mm below the CEJ, and then the margin elevated with GI to the CEJ. In group 4 (resin-modified glass ionomer [RMGI] margin group), the gingival margin was placed 2 mm below the CEJ, and then the margin elevated with RMGI to the CEJ. Standardized ceramic class II inlays were fabricated with computer-aided design/computer-aided manufacturing and bonded to all teeth, and ceramic proximal box heights were measured. All teeth were subjected to 10,000 cycles of thermocycling (5°C/55°C) and then underwent 1,200,000 cycles of vertical chewing simulation at 50 N of force. Ceramic restorations and marginal integrity were assessed with a Hirox digital microscope. The Fisher exact test (two-tailed) with adjusted p-values (α=0.05) and logistic regression were used for statistical analysis.Results: The cementum margin group had a significantly higher ceramic fracture rate (90%) compared to other groups (10% in enamel margin and GI margin groups, p=0.007; 0% in RMGI group, p<0.001). Logistic regression showed that with increased ceramic proximal box heights, the probability of ceramic fracture increased dramatically.Conclusion: Deep marginal elevation resulted in decreased ceramic fracture when preparation margins were located below the CEJ. There was no difference found between margin elevation with GI or RMGI. Increased heights of ceramic proximal box may lead to an increased probability of ceramic fracture.

The profitability of automatic milking on Dutch dairy farms.

Several studies have reported on the profitability of automatic milking based on different simulation models, but a data-based study using actual farm data has been lacking. The objective of this study was to analyze the profitability of dairy farms having an automatic milking system (AMS) compared with farms using a conventional milking system (CMS) based on real accounting data. In total, 62 farms (31 using an AMS and 31 using a CMS) were analyzed for the year 2003 in a case control study. Differences between the years 2002 and 2003 also were analyzed by comparing a subgroup of 16 farms with an AMS and 16 farms with a CMS. Matching was based on the time of investment in a milking system (same year), the total milk production per year, and intensity of land use (kg/ha). Results from 2003 showed that the farms with an AMS used, on average, 29% less labor than farms with a CMS. In contrast, farms using a CMS grew faster (37,132 kg of milk quota and 5 dairy cows) than farms with an AMS (-3,756 kg milk quota and 0.5 dairy cows) between 2002 and 2003. Dairy farmers with a CMS had larger (euro7,899) revenues than those with an AMS. However, no difference in the margin on dairy production was detected, partly because of numerically greater (euro6,822) variable costs on CMS farms. Dairy farms were compared financially based on the amount of money that was available for rent, depreciation, interest, labor, and profit (RDILP). The CMS farms had more money (euro15,566) available for RDILP than the AMS farms. This difference was caused by larger fixed costs (excluding labor) for the AMS farms, larger contractor costs (euro6,422), and larger costs for gas, water, and electricity (euro1,549). Differences in costs for contractors and for gas, water, and electricity were statistically significant. When expressed per full-time employee, AMS farms had greater revenues, margins, and gross margins per full-time employee than did CMS farms. This resulted in a substantially greater (but not statistically significant) RDILP per full-time employee (euro12,953) for AMS farms compared with CMS farms. Depreciation and interest costs for automatic milking were not available but were calculated based on several assumptions. Assuming larger purchase costs and a shorter depreciation time for AMS than for CMS, costs for depreciation and interest were larger for AMS farms than for CMS farms. Larger fixed costs should be compensated for by the amount of labor that has become available after introducing the milking robot. Therefore, farm managers should decide whether the extra time acquired by automatic milking balances against the extra costs associated with an AMS.

Effects of histone deacetylation inhibition on neuronal differentiation of embryonic mouse neural stem cells.

Neural stem cells (NSCs) are multipotent cells that have the capacity for self-renewal and for differentiation into the major cell types of the nervous system, i.e. neurons, astrocytes and oligodendrocytes. The molecular mechanisms regulating gene transcription resulting in NSC differentiation and cell lineage specification are slowly being unraveled. An important mechanism in transcriptional regulation is modulation of chromatin by histone acetylation and deacetylation, allowing or blocking the access of transcriptional factors to DNA sequences. The precise involvement of histone acetyltransferases and histone deacetylases (HDACs) in the differentiation of NSCs into mature functional neurons is still to be revealed. In this in vitro study we have investigated the effects of the HDAC inhibitor trichostatin A (TSA) on the differentiation pattern of embryonic mouse NSCs during culture in a minimal, serum-free medium, lacking any induction or growth factor. We demonstrated that under these basic conditions TSA treatment increased neuronal differentiation of the NSCs and decreased astrocyte differentiation. Most strikingly, electrophysiological recordings revealed that in our minimal culture system only TSA-treated NSC-derived neurons developed normal electrophysiological membrane properties characteristic for functional, i.e. excitable and firing, neurons. Furthermore, TSA-treated NSC-derived neurons were characterized by an increased elongation and arborization of the dendrites. Our study shows that chromatin structure modulation by HDACs plays an important role in the transcriptional regulation of the neuronal differentiation of embryonic NSCs particularly as far as the development of functional properties are concerned. Manipulation of HDAC activity may be an important tool to generate specific neuronal populations from NSCs for transplantation purposes.