P29 Exploring the epigenetic and transcriptional priming of keloid scar fibroblasts

Abstract Introduction and aims Keloids are a type of fibroproliferative scar that progressively grow beyond the original wound site. Currently, there are no treatments to halt or revert keloid scarring, emphasizing an unmet clinical need. Fibroblasts are presumed to be one of the main cells involved in keloid, due to their role in depositing and remodelling extracellular matrix. In normal tissue repair fibroblasts enter a resolution phase, which we hypothesize fails in keloid. Therefore, this study investigates the chromatin and transcriptional landscape of keloid fibroblasts, questioning whether manipulation of the epigenome can reverse their locked profibrotic state. Methods We performed ATAC sequencing (ATACseq) and RNA sequencing on a patient-matched pair of keloid and nonlesional fibroblasts. Bioinformatic analysis revealed differential accessible regions with multiple transcription factors and regulatory elements which we correlated to gene expression changes. Identified key candidates were manipulated in two-dimensional cell culture models and validated in keloid scar tissue. Results ATACseq analysis revealed a more accessible chromatin structure in keloid fibroblasts in areas regulating developmental, growth factor signalling and profibrotic gene signatures. This was confirmed in vitro with increased histone acetylation and methylation marks, associated with open chromatin and higher transcriptional activation. The most accessible chromatin regions in keloid fibroblasts were around the FGFR2 and TGFβR3 gene loci. Stimulation of cells with these growth factors increased signalling responsiveness in proliferation in keloid fibroblasts. Additionally, keloid cells had shown a more reticular-like cellular membrane lipid composition which can be altered in response to fibroblast growth factor 2 and transforming growth factor β stimulation. Treatment with chromatin-modifying drugs such as trichostatin A actively modulated the fibrotic morphology of keloid fibroblasts. Conclusions Keloids have a more open chromatin that is anticipated to play an active role in maintaining profibrotic signalling pathways and cell behaviours. We are currently exploring the therapeutic potential of manipulating the chromatin in keloid fibroblasts to reduce scarring.