title: MicroRNA-7 inhibition rescues age-associated loss of epidermal growth factor receptor and hyaluronan-dependent differentiation in fibroblasts.
abstract: Age-related defects in fibroblast differentiation were previously shown to be associated with impaired hyaluronan synthase 2 (HAS2) and epidermal growth factor receptor (EGFR) function, with both required for normal fibroblast functionality. In fibroblasts, transforming growth factor-beta 1 (TGF-β1)-dependent phenotypic activation uses two distinct but co-operating pathways that involve TGF-β receptor (TGF-βR)/Smad2 activation and HA-mediated CD44-EGFR co-localization and signalling through extracellular signal-regulated kinase 1/2 (ERK1/2). The HA-mediated CD44-EGFR pathway was found to be compromised with in vitro aging, through loss of EGFR expression and a reduced movement of CD44 throughout the cellular membrane. Here, we also investigate the involvement of microRNAs (miRNAs) in age-related loss of differentiation, through investigation of miRNA-7 (miR-7) regulation of the HA-mediated EGFR-signalling pathway. The transcription of miR-7 was found to be upregulated in aged cells. In young cells, age-related loss of differentiation could be mimicked through transfection of pre-miR-7, and in aged cells, could be reversed through transfection of locked nucleic acids (LNA) targeting miR-7. Additionally, miR-7 was found to be involved in the regulation of CD44 membrane motility, which was downregulated in instances of miR-7 upregulation, and partially restorable through either miR-7 inhibition or HAS2 overexpression. The altered dynamics of CD44 in the cell membrane demonstrated a further action of miR-7 in regulating the HA-dependent CD44/EGFR pathway. We explain this novel mechanism of age-associated functional consequence due to miR-7 upregulation and demonstrate that it is reversible; highlighting miR-7 as a potential target for restoring the healing capabilities in chronic wounds in the elderly.
authors.affiliation: Institute of Nephrology, Institute of Molecular & Experimental Medicine, School of Medicine and Cardiff Institute of Tissue Engineering & Repair, University of Cardiff, Heath Park, Cardiff, CF14 4XN, UK.
authors.forename: Adam C
authors.initials: AC
authors.lastname: Midgley
authors.forename: Timothy
authors.initials: T
authors.lastname: Bowen
authors.forename: Aled O
authors.initials: AO
authors.lastname: Phillips
authors.forename: Robert
authors.initials: R
authors.lastname: Steadman
mesh_terms: D020413:3' Untranslated Regions / Q000235:genetics; D001483:Base Sequence; D002454:Cell Differentiation / Q000187:drug effects* / Q000235:genetics; D002462:Cell Membrane / Q000187:drug effects / Q000378:metabolism; D016922:Cellular Senescence / Q000187:drug effects* / Q000235:genetics; D015536:Down-Regulation / Q000187:drug effects / Q000235:genetics; D066246:ErbB Receptors / Q000235:genetics / Q000378:metabolism*; D005347:Fibroblasts / Q000166:cytology* / Q000187:drug effects / Q000378:metabolism; D014453:Glucuronosyltransferase / Q000378:metabolism; D006801:Humans; D018960:Hyaluronan Receptors / Q000378:metabolism; D000076002:Hyaluronan Synthases; D006820:Hyaluronic Acid / Q000494:pharmacology*; D035683:MicroRNAs / Q000037:antagonists & inhibitors* / Q000235:genetics / Q000378:metabolism; D008969:Molecular Sequence Data; D009841:Oligonucleotides / Q000494:pharmacology; D011401:Promoter Regions, Genetic / Q000235:genetics; D012333:RNA, Messenger / Q000235:genetics / Q000378:metabolism; D053773:Transforming Growth Factor beta1; D015854:Up-Regulation / Q000187:drug effects / Q000235:genetics
chemical_list: D020413:3' Untranslated Regions; D066246:ErbB Receptors; D014453:Glucuronosyltransferase; D018960:Hyaluronan Receptors; D000076002:Hyaluronan Synthases; D006820:Hyaluronic Acid; D035683:MicroRNAs; D009841:Oligonucleotides; D012333:RNA, Messenger; D053773:Transforming Growth Factor beta1; C549242:MIRN7-1 microRNA, human; C477371:locked nucleic acid; C101754:HAS2 protein, human
keywords: epidermal growth factor receptor; fibroblast; hyaluronan; microRNA-7; transforming growth factor-β1; wound-healing