Project description:DNA methylation is an important epigenetic control mechanism that has been shown to be associated with gene silencing through the course of development, maturation and aging. However, only limited data are available regarding the relationship between methylation and gene expression in human development. We analyzed the methylomes and transcriptomes of three human fetal liver samples (gestational age 20-22 weeks) and three adult human liver samples. Genes whose expression differed between fetal and adult numbered 7,673. Adult overexpression was associated with metabolic pathways and, in particular, cytochrome P450 enzymes, while fetal overexpression reflected enrichment for DNA replication and repair. Analysis for DNA methylation using the Illumina Infinium 450K HumanMethylation BeadChip showed that 42% of the quality filtered 426,154 methylation sites differed significantly between adult and fetal tissue (q≤0.05). Differences were small; 69% of the significant sites differed in their mean methylation beta value by ≤0.2. There was a trend among all sites toward higher methylation in the adult samples with the most frequent difference in beta being 0.1. Characterization of the relationship between methylation and expression revealed a clear difference between fetus and adult. Methylation of genes overexpressed in fetal liver showed the same pattern as seen for genes that were similarly expressed in fetal and adult liver. In contrast, adult overexpressed genes showed fetal hypermethylation that differed from the similarly expressed genes. An examination of gene region-specific methylation showed that sites proximal to the transcription start site or within the first exon with a significant fetal-adult difference in beta (>0.2) showed an inverse relationship with gene expression. Nearly half of the CpGs in human liver show a significant difference in methylation comparing fetal and adult samples. Sites proximal to the transcription start site or within the first exon that show a transition from hypermethylation in the fetus to hypomethylation or intermediate methylation in the adult are associated with inverse changes in gene expression. In contrast, increases in methylation going from fetal to adult are not associated with fetal-to-adult decreased expression. These findings indicate fundamentally different roles for and/or regulation of DNA methylation in human fetal and adult liver.

Project description:Fetal cartilage fully regenerates following injury while in adult mammals cartilage injury leads to osteoarthritis (OA). OA is characterized by cartilage breakdown and joint inflammation and associated with significant pain and socioeconomic costs. As no clinically satisfactory treatment is available to date, disease-modifying therapies aimed to achieve cartilage regeneration are urgently required. The inherent regeneration potential of fetal individuals may hold answers to this unmet need. Therefore, to characterize the differences in fetal and adult response to cartilage injury, we carried out histology and comprehensive proteome analyses on fetal (day 80/150-day gestation) and adult cartilage samples one (fetal samples) and three (adult and fetal samples) days after surgical induction of a full-thickness cartilage lesion. In addition, proteins secreted by inflamed fetal MSCs in vitro were compared with the in vivo response to injury to evaluate their therapeutic potential. Histology of synovial samples revealed the presence of neutrophils one day post injury (p.i.) and an influx of macrophages into the subsynovial tissue on day 3 p.i. in fetal samples. In contrast, adult synovial samples showed invasion of neutrophils on day 3 p.i. Activation and migration of Iba1+- macrophages of the synovial lining was observed both in fetal and adult animals. Comparative mass spectrometry revealed 57 proteins significantly up-regulated (> 2FC, FDR<0.05), and 67 proteins significantly down-regulated (<-2 FC) upon injury in adults. Neutrophil-related proteins and acute phase proteins were the two major upregulated protein groups in adult cartilage following injury compared to fetal sheep. In contrast, several immunomodulating proteins and growth factors were significantly higher expressed in the fetus than the adult. Comparison of the in vitro MSCs with the in vivo fetal proteome revealed shared upregulation of 17 proteins, which were considered to be of potential therapeutic interest. The results of this study support our molecular understanding of successful fetal cartilage healing and new therapeutic strategies to induce regeneration in adult articular cartilage by modulating the inflammatory environment. The shared protein upregulation in fetal cartilage in vivo and in fetal MSCS during in vitro inflammation supports the possible therapeutic potential of these factors in specific and fetal MSCs in general.

Project description:DNA methylation is an important epigenetic control mechanism that has been shown to be associated with gene silencing through the course of development, maturation and aging. However, only limited data are available regarding the relationship between methylation and gene expression in human development. We analyzed the methylomes and transcriptomes of three human fetal liver samples (gestational age 20-22 weeks) and three adult human liver samples. Genes whose expression differed between fetal and adult numbered 7,673. Adult overexpression was associated with metabolic pathways and, in particular, cytochrome P450 enzymes while fetal overexpression reflected enrichment for DNA replication and repair. Analysis for DNA methylation using the Illumina Infinium 450K HumanMethylation BeadChip showed that 42% of the quality filtered 426,154 methylation sites differed significantly between adult and fetal tissue (q≤0.05). Differences were small; 69% of the significant sites differed in their mean methylation beta value by ≤0.2. There was a trend among all sites toward higher methylation in the adult samples with the most frequent difference in beta being 0.1. Characterization of the relationship between methylation and expression revealed a clear difference between fetus and adult. Methylation of genes overexpressed in fetal liver showed the same pattern as seen for genes that were similarly expressed in fetal and adult liver. In contrast, adult overexpressed genes showed fetal hypermethylation that differed from the similarly expressed genes. An examination of gene region-specific methylation showed that sites proximal to the transcription start site or within the first exon with a significant fetal-adult difference in beta (>0.2) showed an inverse relationship with gene expression. Nearly half of the CpGs in human liver show a significant difference in methylation comparing fetal and adult samples. Sites proximal to the transcription start site or within the first exon that show a transition from hypermethylation in the fetus to hypomethylation or intermediate methylation in the adult are associated with inverse changes in gene expression. In contrast, increases in methylation going from fetal to adult are not associated with fetal-to-adult decreased expression. These findings indicate fundamentally different roles for and/or regulation of DNA methylation in human fetal and adult liver.

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Expression data from human fetal and adult neutrophils

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