POS0481 DEFINING DISTINCT RESIDENT AND MIGRATORY FIBROBLAST POPULATIONS FROM SKIN BIOPSIES IN SYSTEMIC SCLEROSIS

Background Recent studies using single cell RNA sequencing have delineated distinct subpopulations of fibroblasts in skin and other organs. To improve understanding functional differences between fibroblast subpopulations, we developed a novel technique to selectively isolate “migratory” fibroblasts, non-migratory “resident” from heathy control (HC) SSc skin. Objectives compare migratory resident populations dermal systemic sclerosis by their differential gene or protein expression, through assays fibrotic potential. Methods Forearm punch biopsies were collected dcSSc(n=3), healthy skin(n=3). Migratory first isolated standard explant culture, then the residual biopsy fragments underwent collagenase digestion yield population that retained fragments. These further expanded for use at passage 3-6. Functional characterisation included 3-D collagen gel contraction, scratch-wound assays. Expression pro-collagen I (Col1), CTGF αSMA was compared western blot. Bulk RNAseq on each performed. Statistical analysis carried out Rsoftware “tidyverse”. Criteria significant expression fold change ≥1.5, adjusted p-value (FDR) <0.05 Results Compared with HC, all showed hallmark phenotype increased faster migration, overexpression Col1, HC. However, attenuated reduced levels fibroblasts. performed confirmed 5579 significantly differentially expressed genes whereas no HC compared, understand disease-related two populations. 739 overexpressed (including ASPM, TRIP3), 745 upregulated population. The CCL2, CXCL8, ICAM1. Many typically associated (such as SERPINE1, COMP), not different but elevated both populations, suggesting these reflect more generic phenotype. Conclusion exhibit transcriptional are much less apparent biopsies. Further work is required precise contribution pathogenesis, how they might be targeted therapeutically. Our findings also highlight conventional culture techniques may ignore important importance detailed such better pathobiology SSc. Table 1. most highest Significantly Fold Adjusted p value GPR1 5.99 0.01 CCL2 38.66 <0.0001 PPME1 4.86 0.011 CXCL8 24.36 0.0001 KIF20A 4.34 0.015 ICAM1 15.38 CENPF 4.31 0.018 EGR1 15.19 0.0002 STC2 4.18 EGR2 12.77 ASPM 3.88 0.02 IFI44L 11.5 0.002 TRIB3 3.60 CXCL6 11.43 HAPLN1 3.36 0.039 PDGF-D 10.14 0.0003 CCNB2 3.29 0.025 OAS3 8.94 0.0009 KIF14 3.24 0.027 IFIT1 8.58 0.004 Disclosure Interests Kristina Clark: None declared, Alice Cole: Xu Shiwen: Voon Ong: Christopher D Buckley Employee of: founder Mestag Therapeutics https://mestagtherapeutics.com/ , P Denton: declared.