STAT3 and fibrosis: Multiple signalling pathways have been demonstrated to positively regulate cardiac fibrosis, including transforming growth factor β (TGF‐β)/small mothers against decapentaplegic proteins 2 and 3 (Smad2/3), Janus kinase 2 (Jak2)/signal transducer and activator of transcription 3 (Stat3) signalling pathways.4