MicroRNAs(miRNAs)aresmallnon-codingRNAmoleculesthatplayacrucialroleinpost-transcriptionalgeneregulation.Theyareinvolvedinvariousbiologicalprocesses,includingtheregulationofepithelial–mesenchymaltransition(EMT)andmesenchymal–epithelialtransition(MET).EMTisaprocesswhereepithelialcellslosetheirpolarityandcell–celladhesion,gainingmigratoryandinvasivepropertiestobecomemesenchymalcells,whichisessentialinembryonicdevelopment,woundhealing,andcancermetastasis.Conversely,METisthereverseprocesswheremesenchymalcellsreverttoanepithelialphenotype,importantintissuehomeostasisandorganogenesis.miRNAsregulatethesetransitionsbytargetingkeytranscriptionfactors(e.g.,SNAIL,TWIST,ZEB)andsignalingpathways(e.g.,TGF-β,Wnt,Notch)thatcontrolEMTandMET.DysregulationofthesemiRNAscanleadtopathologicalconditions,suchasfibrosisandcancerprogression.UnderstandingtheroleofmiRNAsinEMTandMETprovidesinsightsintopotentialtherapeuticstrategiesfordiseasesinvolvingabnormalcellularplasticity.
