Complete cardiac regeneration in a mouse model of myocardial infarction

Cardiac remodeling and subsequent heart failure remain critical issues after myocardial infarction despite improved treatment and reperfusion strategies. Recently, complete cardiac regeneration has been demonstrated in fish and newborn mice following resection of the cardiac apex. However, it remained entirely unclear whether the mammalian heart can also completely regenerate following a complex cardiac ischemic injury. We established a protocol to induce a severe heart attack in one-day-old mice using left anterior descending artery (LAD) ligation. LAD ligation triggered substantial cardiac injury in the left ventricle defined by Caspase 3 activation and massive cell death. Ischemia-induced cardiomyocyte death was also visible on day 4 after LAD ligation. Remarkably, 7 days after the initial ischemic insult, we observed complete cardiac regeneration without any signs of tissue damage or scarring. This tissue regeneration translated into long-term normal heart functions as assessed by echocardiography. In contrast, LAD ligations in 7-day-old mice resulted in extensive scarring comparable to adult mice, indicating that the regenerative capacity for complete cardiac healing after heart attacks can be traced to the first week after birth. RNAseq analyses of hearts on day 1, day 3, and day 10 and comparing LAD-ligated and sham-operated mice surprisingly revealed a transcriptional programme of major changes in genes mediating mitosis and cell division between days 1, 3 and 10 postnatally and a very limited set of genes, including genes regulating cell cycle and extracellular matrix synthesis, being differentially regulated in the regenerating hearts. We present for the first time a mammalian model of complete cardiac regeneration following a severe ischemic cardiac injury. This novel model system provides the unique opportunity to uncover molecular and cellular pathways that can induce cardiac regeneration after ischemic injury, findings that one day could be translated to human heart attack patients

Supratentorial and spinal pediatric ependymomas display a hypermethylated phenotype which includes the loss of tumor suppressor genes involved in the control of cell growth and death

Epigenetic alterations, including methylation, have been shown to be an important mechanism of gene silencing in cancer. Ependymoma has been well characterized at the DNA copy number and mRNA expression levels. However little is known about DNA methylation changes. To gain a more global view of the methylation profile of ependymoma we conducted an array-based analysis. Our data demonstrated tumors to segregate according to their location in the CNS, which was associated with a difference in the global level of methylation. Supratentorial and spinal tumors displayed significantly more hypermethylated genes than posterior fossa tumors, similar to the ‘CpG island methylator phenotype’ (CIMP) identified in glioma and colon carcinoma. This hypermethylated profile was associated with an increase in expression of genes encoding for proteins involved in methylating DNA, suggesting an underlying mechanism. An integrated analysis of methylation and mRNA expression array data allowed us to identify methylation-induced expression changes. Most notably genes involved in the control of cell growth and death and the immune system were identified, including members of the JNK pathway and PPARG. In conclusion, we have generated a global view of the methylation profile of ependymoma. The data suggests epigenetic silencing of tumor suppressor genes is an important mechanism in the pathogenesis of supratentorial and spinal, but not posterior fossa ependymomas. Hypermethylation correlated with a decrease in expression of a number of tumor suppressor genes and pathways that could be playing an important role in tumor pathogenesis

Towards establishing the effects and mechanism of action of a series of indoles in an in vitro chemosensitivity system for glioma treatment

INTRODUCTION: Substituted indoles and related structures have been shown to exhibit potent anticancer activity against breast cancer cell lines. Here, the effects of structurally similar substituted indoles against the human glial cancer cell lines, 1321N1 and U87MG, have been investigated by comparing the effects of these compounds to conventional anti cancer drugs. METHODS: Cell viability in the presence of the test compounds was measured using an MTS assay and corroborated by an ATP cell proliferation assay as well as a Trypan blue exclusion test. The significance of reactive oxygen species (ROS) in the process was determined using an Image-iT® LIVE ROS kit from Invitrogen. RESULTS: Both cell lines were treated with four commercial anticancer drugs and IC50 values were only reached at concentrations of 20 µM for cisplatin and 50 µM for gemcitabine over 48hrs on the 1321N1 cell line. However, the more malignant U87MG cell line was resistant to all the drugs, except for cisplatin where the IC50 value was reached at 300 µM after treatment for 48hrs. Similar studies were carried out with various substituted indoles and the cytotoxicity results on both cell lines showed that the IC50 value was reached within 90 minutes for the most potent compound at a concentration of 600 µM (1321N1) and 800 µM (U87MG). The idea that the mechanism of action of these compounds may work through the generation of ROS was investigated and this was confirmed over a similar time course using a suitable fluorogenic marker. Moreover, it was shown that the addition of an antioxidant (ascorbic acid) abolished the potency of the most active compound. CONCLUSION: Here, it has been demonstrated that certain substituted indoles are able to have a rapid, deleterious effect on the viability of two glioma cell lines and indicated that ROS generation may induce cell death

Summary of differential methylation by source of variation.

<p>*Strand specific methylation.</p><p>Summary of differential methylation by source of variation.</p

Comparison of differential methylation in parental strains and allele-specific methylation in F1 crosses.

<p>(A) Venn diagram showing the number of CpGs tested for differential methylation in the parental strains ONLY or for allele-specific methylation ONLY (grey areas) and the fraction of CpGs tested for BOTH (intersection, blue). The light blue area shows the number of CpGs significantly differentially methylated between the parentals AND/OR showing allele-specific methylation. Areas are not proportional. CpGs on the X chromosome and the mitochondrial chromosome have been excluded. (B) Overlap of differential methylation between the parental strains and allele specific methylation in the F1s. In total, 52,410 out of the 1,705,718 CpG dinucleotides analysed in both the parentals and the F1s (intersection, blue in (A)) showed significant differential methylation. The Venn diagram shows the fraction of CpGs that were differentially methylated between the parents ONLY (purple), between the alleles in the F1s ONLY (orange) or in BOTH (green). The theoretical distribution of frequencies assuming random overlap between the parental and the F1 data sets are shown in italics (<i>X²</i> = 135276.2, <i>P</i><4.9×10⁻³²⁴). The overlap of the two sets is >15 fold higher than expected by chance. (C) Frequency of CpGs with a SNP within 50 base pairs for CpGs showing differential methylation between the parentals only (purple), the F1 alleles only (orange) and both (green) compared to all CpGs analysed in the parentals and the F1s (blue) and the whole genome (red).</p

Hierarchical clustering and principal component analysis of CpG methylation profiles obtained in the F1 reciprocal crosses.

<p>Dendrograms showing the results of clustering the CpG methylation profiles obtained in each of the F1 animals before (A) and after (C) phasing the read data by parental genotype. The prefix of the phased F1 profiles in (C) denotes the reciprocal cross (bnxshr, shrxbn) and the suffix the genotype of the phased read set (bn = Brown Norway, shr = Spontaneously Hypertensive Rat). Numbers after the reciprocal cross prefix denote biological replicates. Profiles were clustered by the Ward's method using the pairwise euclidean distance between the profiles as the distance metric. Panels B and D show the projection of methylation profiles onto the 1^st principal component (PC). Replicates for each cross-genotype combination are separated along the y-axis. The prefix of the label denotes the reciprocal cross (bnxshr, shrxbn), the suffix denotes the parental genotype (bn, shr). While the 1^st PC does not separate crosses in the unphased data it provides complete separation by parental genotype in the phased data. Only CpGs with at least 5× coverage in each replicate/phased read set were included in the analysis and CpG positions affected by SNPs/indels were removed prior to clustering and principal component analysis.</p

Differential CpG methylation between the BN and SHR strains.

<p>A) Dendrogram showing the clustering the CpG methylation profiles obtained in four BN and four SHR rats. B) Projection of methylation profiles onto the first principal component. Numbers after the strain label denote biological replicates.</p

Correlation of CpG cytosine meth-QTL linkage and difference in CpG methylation between parental strains.

<p>Methylation data were obtained from PCR amplification of bisulfite-treated DNA followed by Sanger or Illumina sequencing in parental and RI strains. CpGs were classified according to linkage type (<i>cis</i>, <i>trans</i>, no significant linkage) and LOD scores were plotted against the absolute value of the difference in methylation between parental strains. No linkage refers to CpGs for which permutation-based p≥0.05. Correlation was assessed by Pearson <i>r</i> value. The cluster of CpGs with >80% difference in methylation are all from a single amplicon selected because of high differential methylation in the parental strains.</p