Abstract

ABSTRACT Background and Objective Despite achieving complete peripheral B cell deletion after over 6 months of rituximab therapy, a clinically significant minority of neuromyelitis optica spectrum disorder (NMOSD) patients experience breakthrough relapses, yet the underlying mechanism remains unclear. Our study aims to explore the underlying mechanism—the contribution of the MALAT1/miR‐30b‐5p/BAFF axis activation in monocytes to NMOSD disease attacks and relapses resistant to rituximab therapy. Methods To investigate immune dysregulation in NMOSD, we established clinical groups comprising peripheral blood mononuclear cells (PBMCs) and serum from NMOSD patients: onset cases (PBMCs: n = 10; serum: n = 23) and rituximab‐treated cases subdivided into remission (n = 26) and rituximab‐refractory relapse (n = 13), along with healthy controls (n = 15). To profile the MALAT1/miR‐30b‐5p/BAFF axis and inflammatory mediators, we quantified MALAT1, miR‐30b‐5p, BAFF, and cytokine levels using qPCR, ELISA, and Western Blot and validated molecular interactions via dual‐luciferase reporter assays. To characterize cellular heterogeneity, single‐cell RNA sequencing (scRNA‐seq) was performed on PBMCs from two rituximab‐refractory relapsed NMOSD patients, two rituximab‐remission NMOSD patients, and two healthy controls. For mechanistic validation, THP‐1 cells were transfected with MALAT1 overexpression constructs or miR‐30b‐5p mimics, followed by functional assessments to determine their roles in monocyte activation and cytokine production. Results Significant activation of the MALAT1/miR‐30b‐5p/BAFF axis was observed in NMOSD patients at disease onset compared to healthy controls. Moreover, this axis correlated with rituximab‐refractory NMOSD, featuring monocyte‐specific MALAT1 upregulation and elevated serum BAFF in rituximab‐refractory relapse patients.