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Low-temperature prevents side effects of an anti-cancer drug, cyclophosphamide, on organ development: a study of ex vivo organ culture model

ABSTRACT: Development of chemotherapy has led to a high survival rate of cancer patients; however, severe side effects of anti-cancer drugs, including organ hypoplasia, persists. This study examined the molecular mechanism of the side effects of cyclophosphamide (CPA), a commonly used anti-cancer drug for the treatment of leukemia, and determined how to suppress the side effects using an organ culture system. Treatment with CPA disturbed the growth of tooth germs by inducing apoptosis and suppressing cellular proliferation and differentiation. Furthermore, organs cultured at low-temperature could avoid the CPA-mediated inhibition of organ morphogenesis and differentiation. Cap analysis of gene expression of CPA-treated tooth germ revealed that the expression of genes related to the G1/S cell cycle checkpoint were down-regulated in the CPA-treated tooth germ cultured at low-temperature. In vitro analysis revealed that low-temperature impeded Rb phosphorylation and caused cell cycle arrest at the G1 phase. This can prevent the CPA-mediated cell damage of DNA replication caused by the cross-linking reaction of CPA. Our results revealed that the side effects of CPA on organ development can be avoided by maintaining a low temperature. Further, this study provides a new screening model for assessing the effects of anticancer drugs on organ development.

ORGANISM(S): Mus musculus

PROVIDER: GSE182499 | GEO | 2021/08/23

REPOSITORIES: GEO

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Project description:The tooth is derived from both the ectoderm and the neural crest (ectomesenchyme). It is often used as a model for studies of the basic mechanisms of organ development, including differentiation, cellular interaction, morphogenesis, and mineralization of extracellular matrices. In mouse, tooth development begins at embryonic day 11.5 (E11.5) by thickening of the dental epithelium, whereas mineralization of enamel and dentin in first molars starts at postnatal day 0 (P0). Tooth development entails a multistep and complex process of gene expression. Studies with genetically modified mice have contributed substantially to our understanding of genes that regulate tooth development and morphology. MicroRNAs (miRNA) are a class of non-coding RNAs that regulate gene expression at a post-transcriptional level, and are considered as important regulatory molecules during foetal development. By binding to target mRNAs, miRNA induce mRNA decay or translation repression. Recent bioinformatic predictions of miRNA targets in vertebrates indicate that hundreds of miRNAs are responsible for regulation of expression of up to 30% of the human protein-coding genes. Recent experiments has verified that miRNAs can regulate expression of hundreds of mRNAs in cultured cells. Previous study has also shown that microarrays can be used to detect physiologically relevant effects of miRNAs on expression of mRNAs in vertebrates; miRNAs have been shown to alter expression of a greater number of transcripts than previously appreciated, primarily through interaction with 3M-4UTRs. Understanding the biological function of miRNAs require knowledge of their mRNA targets. Bioinformatic approaches have been used to predict mRNA targets, among which both transcription factors and pro-apoptopic genes were prominent candidates. The precise molecular function of miRNAs remains largely unknown and a better understanding may require loss-of-function studies in vivo. It has been shown that intravenous administration of a novel class of chemically engineered oligonucleotides termed M-^SantagomirsM-^T resulted in a marked reduction of corresponding miRNA levels in most tissues. This resulted in upregulated expression of hundreds of genes predicted to be repressed by miR-122 because these genes had a miR-122 recognition motif in their 3M-4UTR region. Paradoxically, antagomir treatment also revealed a significant number of downregulated genes that may be activated by miR-122. The mechanism by which miRNAs may activate gene expression in vivo is unknown. However, it may involve an indirect effect (the suppression of a transcriptional repressor), or alternatively, miRNA may have a direct effect on gene activation (e.g. chromatin remodeling). Studies of microRNA expression profiles of the developing murine molar tooth germ have shown these to be highly dynamic, some miRNAs being abundantly expressed during the early development of the molar tooth germ, while others are highly expressed only at later developmental stages. A recent study also suggested that miRNAs modulate tooth morphogenesis and ameloblast differentiation, perhaps largely by fine tuning conserved signaling networks. The function of microRNA-214 (miR-214) is unknown, however, it has been related to normal growth and skeletal development in mice. In tooth germs miR-214 is more highly expressed during later developmental stages. It was selected as a target for silencing using anti-miR-214. Here we report effects from injections of 1-100 pmol of anti-miR-214 close to developing first mandibular molar in newborn mice. At 24 hrs, or more, after injection significant changes in gene expression, and in levels of several correspondingly encoded proteins, were found in the tooth germ.

Project description:In a systemic effort to survive environmental stress, organ systems fluctuate and adapt to overcome external pressures. The evolutionary drive back towards homeostasis, makes it difficult to determine if an organism experienced a toxic exposure to stress, especially in early prenatal and neonatal periods of development. Previous studies indicate that primary human teeth may provide historical records of experiences related to stressors during that early time window. To assess the molecular effects of early life adversity on enamel formation, we used a limited bedding and nesting (LBN) mouse model of early life adversity (ELA), to assess changes in enamel organ gene expression and enamel mineralization. Enamel of postnatal day 12 (P12) weight-matched ELA mice was more mineralized as compared control enamel. RNAseq showed 724 genes significantly upregulated in ELA enamel organs as compared to controls, and 574 significantly downregulated genes (DESeq2 p-value <= 0.05). Transcripts expressing the enamel matrix proteins amelogenin (Amelx) and enamelin (Enam) were among the top 4 most differentially expressed genes. The most significantly enriched GO and Reactome pathway was Extracellular Matrix Organization, while the most significantly enriched KEGG Pathways were Butanoate metabolism and Synthesis and Degradation of Ketone Bodies. qPCR analysis of weight-matched ELA and control enamel organs confirmed that expression of the ameloblast-specific proteins Amelx and Enam were highly upregulated in ELA mice. When evaluating molecular mechanisms for amelogenin upregulation, we found significantly increased expression of Dlx3, while transcripts for clock genes Per1 and Nrd1, which have also positively associated with amelogenin expression, were downregulated. These findings suggest that the developing enamel organs are sensitive to the pressures of early life adversity and produce structural biomarkers in tooth enamel mineral to reflect these changes. Together these results support the possibility that tooth enamel may contain biomarkers of cellular effects associated with systemic early life adversity.

Project description:The organ development is dictated by the genes preferentially expressed in tissue or cell types uniquely. The clarification of gene expression profile and identification of specific genes in organ provide detailed understanding of organogenesis. Toward this purpose, the genome-wide analysis is a growing powerful tool for understanding development processes in organogenesis. Tooth is composed from enamel, dentin and cementum and these tissues are identical from other organs. The tooth-forming cell types are therefore unique and have complexed organization. The mechanisms of signal induction during tooth development is complicated because of the function of each cell types are still unclear. Previously, we performed the CAGE (Cap Analysis of Gene Expression) using mouse tooth germ to identify the genes preferentially expressed in tooth. The CAGE has advantage in quantification because it counts short reads of 5’ end without the bias of transcript length. Single-cell RNA-sequence (scRNA-seq) is a suitable tool revealing gene expression of each cells. The fundamental question of this study is how we can identify the tooth-specific and cell-type specific genes. In this study, we approach this using combination of scRNA-seq and CAGE (Cap Analysis of Gene Expression) as bioinformatics analyses. We obtained the scRNA-seq datasets of 12,212 cells from postnatal-day (P) 1 mouse molars, and the CAGE-seq datasets from P1 molars. scRNA-seq analysis revealed the spatio-temporal expression of tooth-related genes and CAGE determined whether these genes are truly tooth-specific or are expressed in ubiquitously. Furthermore, we identified candidate genes as novel tissue- and cell type- specific markers. Our results show that the integration of scRNA-seq and CAGE-seq improves the highlight genes important for tooth development from numerous gene profiles. These findings contribute resolving the mechanism of tooth development and establish the basis of tooth regeneration in future.

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Low-temperature prevents side effects of an anti-cancer drug, cyclophosphamide, on organ development: a study of ex vivo organ culture model

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