P41 Exploring the effect of isotretinoin on expression of acne-associated microRNAs in dermal fibroblasts

Introduction and aims Acne vulgaris is a chronic inflammatory skin condition associated with a heavy comorbidity burden. Oral isotretinoin is an effective treatment for severe acne. We have previously identified acne-associated microRNAs (miRNAs) (miR-21-3p, miR-150-5p and miR-223-3p). Increased circulating levels of the acne-associated miRNAs were increased in individuals with various degrees of scarring (mild, moderate, severe). miR-21-3p has been previously involved in wound healing and fibrotic responses driven by fibroblasts. Notably, the transcriptional and post-transcriptional response of skin fibroblasts to isotretinoin remain poorly characterized. Here, we aim to dissect the miR-21-3p-dependent effects of isotretinoin in primary skin fibroblasts. Methods In vitro, human primary dermal fibroblasts were stimulated with transforming growth factor (TGF)β and/or tumour necrosis factor (TNF), or isotretinoin. mRNA levels of fibrosis and inflammation-related genes (αSMA, FN1, IL6) and miRNAs were measured using quantitative reverse transcriptase polymerase chain reaction. miR-21 function was assessed using locked nucleic acid-oligonucleotide-mediated inhibition and levels of its targets measured by immunoblotting. Results Among acne-associated miRNAs, only miR-21-3p is expressed in fibroblasts. TGFβ-dependent myofibroblast differentiation does not affect miR-21-3p expression. However, TNF or isotretinoin treatment upregulate miR-21-3p and suppress myofibroblast markers in skin fibroblasts. Partial inhibition of miR-21-3p results in upregulation of SMAD7, TGFBRII and tissue inhibitor of metalloproteinase 3, indicating derepression of antifibrotic pathways. Conclusions These findings suggest that the extent of the antifibrotic isotretinoin effect might be controlled by miR-21-3p induction in fibroblasts. This will be further validated in vitro and in a currently recruiting clinical study measuring circulating miRNA and proinflammatory cytokine levels in 40 individuals with acne (with no/minimal or moderate/severe scarring) at baseline and following oral isotretinoin treatment.