title: Hypoxia-induced epigenetic modifications are associated with cardiac tissue fibrosis and the development of a myofibroblast-like phenotype.
abstract: Ischemia caused by coronary artery disease and myocardial infarction leads to aberrant ventricular remodeling and cardiac fibrosis. This occurs partly through accumulation of gene expression changes in resident fibroblasts, resulting in an overactive fibrotic phenotype. Long-term adaptation to a hypoxic insult is likely to require significant modification of chromatin structure in order to maintain the fibrotic phenotype. Epigenetic changes may play an important role in modulating hypoxia-induced fibrosis within the heart. Therefore, the aim of the study was to investigate the potential pro-fibrotic impact of hypoxia on cardiac fibroblasts and determine whether alterations in DNA methylation could play a role in this process. This study found that within human cardiac tissue, the degree of hypoxia was associated with increased expression of collagen 1 and alpha-smooth muscle actin (ASMA). In addition, human cardiac fibroblast cells exposed to prolonged 1% hypoxia resulted in a pro-fibrotic state. These hypoxia-induced pro-fibrotic changes were associated with global DNA hypermethylation and increased expression of the DNA methyltransferase (DNMT) enzymes DNMT1 and DNMT3B. Expression of these methylating enzymes was shown to be regulated by hypoxia-inducible factor (HIF)-1α. Using siRNA to block DNMT3B expression significantly reduced collagen 1 and ASMA expression. In addition, application of the DNMT inhibitor 5-aza-2'-deoxycytidine suppressed the pro-fibrotic effects of TGFβ. Epigenetic modifications and changes in the epigenetic machinery identified in cardiac fibroblasts during prolonged hypoxia may contribute to the pro-fibrotic nature of the ischemic milieu. Targeting up-regulated expression of DNMTs in ischemic heart disease may prove to be a valuable therapeutic approach.
authors.affiliation: School of Medicine & Medical Science, UCD Conway Institute, University College Dublin, Belfield, Dublin 4, Ireland.
authors.forename: Chris J
authors.initials: CJ
authors.lastname: Watson
authors.forename: Patrick
authors.initials: P
authors.lastname: Collier
authors.forename: Isaac
authors.initials: I
authors.lastname: Tea
authors.forename: Roisin
authors.initials: R
authors.lastname: Neary
authors.forename: Jenny A
authors.initials: JA
authors.lastname: Watson
authors.forename: Claire
authors.initials: C
authors.lastname: Robinson
authors.forename: Dermot
authors.initials: D
authors.lastname: Phelan
authors.forename: Mark T
authors.initials: MT
authors.lastname: Ledwidge
authors.forename: Kenneth M
authors.initials: KM
authors.lastname: McDonald
authors.forename: Amanda
authors.initials: A
authors.lastname: McCann
authors.forename: Osama
authors.initials: O
authors.lastname: Sharaf
authors.forename: John A
authors.initials: JA
authors.lastname: Baugh
mesh_terms: D000368:Aged; D015153:Blotting, Western; D002478:Cells, Cultured; D003094:Collagen / Q000235:genetics / Q000378:metabolism; D000076123:DNA (Cytosine-5-)-Methyltransferase 1; D004248:DNA (Cytosine-5-)-Methyltransferases / Q000037:antagonists & inhibitors / Q000235:genetics / Q000378:metabolism; D019175:DNA Methylation; D057890:Epigenomics; D005260:Female; D005355:Fibrosis / Q000209:etiology* / Q000378:metabolism / Q000473:pathology; D005434:Flow Cytometry; D006321:Heart / Q000503:physiopathology*; D006801:Humans; D000860:Hypoxia / Q000150:complications* / Q000503:physiopathology; D007124:Immunoenzyme Techniques; D008297:Male; D058628:Myofibroblasts / Q000378:metabolism / Q000473:pathology*; D010641:Phenotype; D012333:RNA, Messenger / Q000235:genetics; D034741:RNA, Small Interfering / Q000235:genetics; D060888:Real-Time Polymerase Chain Reaction; D020133:Reverse Transcriptase Polymerase Chain Reaction; D016212:Transforming Growth Factor beta / Q000235:genetics / Q000378:metabolism; D000097584:DNA Methyltransferase 3B
chemical_list: D003094:Collagen; D000076123:DNA (Cytosine-5-)-Methyltransferase 1; D004248:DNA (Cytosine-5-)-Methyltransferases; D012333:RNA, Messenger; D034741:RNA, Small Interfering; D016212:Transforming Growth Factor beta; D000097584:DNA Methyltransferase 3B; C000619380:DNMT1 protein, human