Schematic representation of miRNAs influencing the occurrence of PCOS. MiR-320a is significantly downregulated in CCs, resulting in decreased steroidogenesis due to dysregulation of RUNX2 and CYP11A1/CYP19A1. In GCs, both miR-93 and miR-21 are upregulated and positively correlated with free testosterone and the androgen index, whereas miR-483 and miR-145 are downregulated. MiR-483 directly targets the IGF1 mRNA, leading to decreased cell proliferation. IRS1 mRNA is a direct target of miR-145, leading to inhibition of the MAPK/ERK signalling pathway, resulting in decreased cell proliferation. Abbreviations—RUNX2: runt-related transcription factor 2; CYP11A1: cytochrome P450 family 11 subfamily A member 1; CYP19A1: cytochrome P450 family 19 subfamily A member 1; IGF1: insulin-like growth factor 1; IRS1: insulin receptor substrate 1; MAPK: mitogen-activated protein kinase; ERK: extracellular signal-regulated kinase; GCs: granulosa cells; CCs: cumulus cells. (Created with BioRender.com, accession date: 29 May 2021).