Background: Single-cell transcriptomic studies have showed diverse fibroblast populations in systemic sclerosis (SSc). Our previous imaging mass cytometry data demonstrated that these fibroblast populations exhibit unique spatial distributions within SSc-affected tissue. However, comprehensive in situ transcriptional profiling at single-cell resolution has not yet been achieved.

Objectives: We aimed to profile the fibroblasts, cellular niches, cellular communications, and their association with disease progression in SSc.

Methods: To spatially phenotype the cell populations at single cell level, we analyzed the SSc skin tissue using cyclic in situ hybridization (cISH), an imaging-based spatial transcriptomic approach. We employed spatially-informed transcriptomic profiling to identify fibroblast populations based on both the transcriptomic profiles and their microenvironment by BANKSY algorithm.

Results: Our spatially-informed transcriptomic profiling identified nine fibroblast populations, several of which showed altered frequencies in SSc, including COL8A1+ fibroblasts. BANKSY-based clustering identified two SFRP2-expressing and two CCL19-expressing fibroblasts, separated by their spatial localization within the tissue. These populations not only occupied in the unique cellular niches but also exhibited distinct biological functions. The SFRP2+ fibroblast located in reticular dermis (RetD) demonstrated higher extracellular matrix producing capabilities compared to their counterpart in papillary dermis. Additionally, cellular interaction and spatially-informed ligand-receptor analysis revealed enhanced leukocyte recruitment to the cellular niches containing SFRP2+ RetD, CCL19+ non-perivascular, and COL8A1+ fibroblasts. Notably, macrophage-interacting COL8A1+ fibroblasts were more abundant in patients with progressive skin fibrosis and more accurately predicted future progression in LASSO models than overall COL8A1+ fibroblast frequency alone.

Conclusion: Our cISH-based spatial transcriptomic approach further profiled dysregulated fibroblasts populations and their functionally distinct cellular niches in systemic sclerosis. The amount of COL8A1+ fibroblast and its immune interaction may serve as a potential biomarker for future progression of skin fibrosis.

REFERENCES: NIL.

Acknowledgements: NIL.

Disclosure of Interests: Yi-Nan Li: None declared , Tim Filla: None declared , Andrea-Hermina Györfi Boehringer Ingelheim, Minrui Liang: None declared , Veda Devakumar: None declared , Alexandru Micu: None declared , Hongtao Chai: None declared , Christina Bergmann: None declared , Ann-Christin Pecher: None declared , Jörg Henes: None declared , Pia Moinzadeh: None declared , Suzan Al-Gburi: None declared , Thomas Krieg: None declared , Alexander Kreuter: None declared , Jiucun Wang: None declared , Georg Schett: None declared , Bernhard Homey: None declared , Sascha Dietrich: None declared , Jörg Distler Active Biotech, Anamar, ARXX, AstraZeneca, Bayer Pharma, Boehringer Ingelheim, Calliditas, Celgene, Galapagos, GSK, Inventiva, Janssen, Kyverna, Novartis, Pfizer, Quell Therapeutics, UCB, Anamar, ARXX, BMS, Bayer Pharma, Boehringer Ingelheim, Cantargia, Celgene, CSL Behring, Exo Therapeutics, Galapagos, GSK, Incyte, Inventiva, Kiniksa, Kyverna, Lassen Therapeutics, Mestag, Sanofi-Aventis, RedX, UCB, ZenasBio, Alexandru-Emil Matei: None declared.

© The Authors 2025. This abstract is an open access article published in Annals of Rheumatic Diseases under the CC BY-NC-ND license ( http://creativecommons.org/licenses/by-nc-nd/4.0/ ). Neither EULAR nor the publisher make any representation as to the accuracy of the content. The authors are solely responsible for the content in their abstract including accuracy of the facts, statements, results, conclusion, citing resources etc.