Epigenetic reprogramming through KDM6B drives immunofibroblast early commitment and immune properties [Mus_stromal_cells]

TLS are composed of immune cells, including lymphocytes and myeloid cells, lymphatic and blood endothelial cells, and PDPN+ stromal cells with lymphoid stromal cells (LSC) features called immunofibroblasts. These LSC play a central role in the physiology of secondary lymphoid organs. Recent studies have focused on the heterogeneity of immunofibroblast and their cell of origin, but molecular and epigenetic mechanisms involved in their commitment are still unknown. In this study, we took advantage of the combination of an in vitro model of human ASC commitment to LSC/immunofibroblasts, and an in vivo model of murine TLS induction. We highlighted in both cases an early induction of KDM6B in stromal cells associated with an early epigenetic reprogramming. The KDM6B signature was enriched in sorted pathogenic stroma from patients with autoimmune diseases. Furthermore, using a KDM6 inhibitor, we demonstrated that KDM6B was required for the acquisition of immunofibroblast phenotype and functions, including upregulation of CCL2 production and monocyte recruitment. Overall, our results shed light on epigenetic mechanisms involved in the early commitment, but also immune properties of immunofibroblasts. Balb/c mice were bred and maintained under specific pathogen-free conditions in the Biomedical Service Unit at the University of Birmingham according to Home Office and local ethics committee regulations. The submandibular glands of mice (8-12 weeks old) were intraductally cannulated with 10^8 to 10^9 plaque forming units (p.f.u.) of replication-defective adenovirus (Ad5) to induce the formation of ectopic tertiary lymphoid structure (TLS). Salivary glands were harvested (as previously shown: Nayar S, et al.; PMID: 31213547), at various time points after cannulation and gp38+ fibroblasts were sorted and used for quantification of gene expression.