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

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. RNA-seq analysis was performed on ASC coming from 3 different donors. ASC were committed or not into immunofibroblasts by TNF/LT treatment.

三级淋巴结构（Tertiary Lymphoid Structures, TLS）由免疫细胞（含淋巴细胞与髓系细胞）、淋巴及血管内皮细胞，以及具备淋巴样基质细胞（LSC）特征的podoplanin阳性（PDPN+）基质细胞——即免疫成纤维细胞——构成。此类LSC在次级淋巴器官的生理过程中发挥核心调控作用。
近期研究多聚焦于免疫成纤维细胞的异质性及其细胞起源，但参与其定向分化的分子与表观遗传机制仍未阐明。本研究结合人源脂肪源性基质细胞（ASC）定向分化为LSC/免疫成纤维细胞的体外模型，与小鼠TLS诱导的体内模型开展实验。我们在两类模型中均观察到，基质细胞内会早期诱导赖氨酸去甲基化酶6B（KDM6B）表达，并伴随早期表观遗传重编程。KDM6B特征基因集在自身免疫病患者分选获得的致病性基质细胞中显著富集。此外，通过使用KDM6抑制剂，我们证实KDM6B是免疫成纤维细胞表型与功能获得所必需的关键因子，其功能包括上调趋化因子配体2（CCL2）的表达与促进单核细胞招募。
综上，本研究结果不仅揭示了参与免疫成纤维细胞早期定向分化的表观遗传机制，同时阐明了免疫成纤维细胞的免疫特性。本研究对来自3名不同供者的ASC开展了RNA测序（RNA-seq）分析：通过肿瘤坏死因子/淋巴毒素（TNF/LT）处理，可将ASC定向诱导为免疫成纤维细胞，或维持其未分化状态。