Transcriptomic and glycobiological profiling of synovial fibroblasts in rheumatoid arthritis: the role of sialylation in fibroblast-macrophage crosstalk

Cil, Caglar (2026) Transcriptomic and glycobiological profiling of synovial fibroblasts in rheumatoid arthritis: the role of sialylation in fibroblast-macrophage crosstalk. PhD thesis, University of Glasgow.

Abstract

Rheumatoid arthritis (RA) is a chronic autoimmune disease in which synovial fibroblasts (SFs) and macrophages perpetuate inflammation and tissue destruction. While immune cell directed therapies are effective, treatment resistance underscores the importance of stromal contributions. Glycosylation, particularly sialylation, has emerged as a key regulatory mechanism in stromal-immune crosstalk.

Here, we investigated the role of sialylation in shaping SF function and macrophage responses. Bulk RNA sequencing of human RA synovia revealed TNF-α driven remodelling of glycosylation pathways, with upregulation of ST3GAL family members, indicating a pro–α2-3 bias in inflamed fibroblasts. Single-cell RNA-seq mapped these alterations to discrete fibroblast subsets and linked them to lectin receptor expression in tissue-resident macrophages, including Siglecs and Galectins.

Using an in vitro desialylation model, we demonstrated that selective removal of α2-3 sialic acids reprogrammed SFs toward a pro-inflammatory phenotype, enhancing cytokine secretion. Conditioned media from these fibroblasts induced M1-like polarisation of bone marrow derived macrophages, with increased Il1b, Nos2, CD80/CD86, and pathway enrichment for TNF and NF-κB signalling, In contrast, broad α2-3/α2-6 cleavage elicited mixed macrophage responses, while less α2-3 linked sialic acid removal had minimal effects. Protein-level analyses confirmed increased PD-L1 in macrophages exposed to desialylated fibroblast supernatants.

These findings identify stromal sialylation as a molecular checkpoint regulating joint inflammation. Loss of α2-3 sialylation above certain thresholds functions as a pro-inflammatory switch in SFs, amplifying macrophage activation and sustaining chronic inflammation. Targeting stromal glycosylation offers a potential therapeutic avenue and biomarker strategy in RA.

• Item Type: Thesis (PhD)
• Qualification Level: Doctoral
• Additional Information: Supported through the YLSY Abroad Scholarship Program, Turkish Ministry of National Education.
• Subjects: Q Science > QR Microbiology > QR180 Immunology; Q Science > QR Microbiology > QR355 Virology
• Colleges/Schools: College of Medical Veterinary and Life Sciences > School of Infection & Immunity
• Funder's Name: Turkish Ministry of National Education
• Supervisor's Name: Pineda, Dr. Miguel, Kurowska-Stolarska, Dr Mariola and Otto, Professor Thomas
• Date of Award: 2026
• Depositing User: Theses Team
• Unique ID: glathesis:2026-85712
• Copyright: Copyright of this thesis is held by the author.
• Date Deposited: 23 Jan 2026 14:51
• Last Modified: 25 Jan 2026 09:04
• Thesis DOI: 10.5525/gla.thesis.85712
• URI: https://theses.gla.ac.uk/id/eprint/85712