Microglia-Mediated Ependymal Injury in Bacille Calmette-Guérin-Induced Meningitis Is Attenuated by Sodium Butyrate with Restoration of Hmgcs2 Expression

Background: Tuberculous meningitis (TBM) is the most severe form of central nervous system tuberculosis, associated with high mortality and neurological sequelae. Microglia-driven neuroinflammation is a key contributor to TBM pathogenesis; however, its specific effects on ependymal cells—critical for cerebrospinal fluid dynamics and barrier function—and potential therapeutic strategies remain unclear. Methods: A murine TBM model was established by tail vein injection of BCG. Although the virulence of BCG, an attenuated strain of Mycobacterium bovis, is different from that of clinically isolated human Mycobacterium tuberculosis, its induced phenotypes such as periventricular inflammatory infiltration, microglia activation, and ependymal dysfunction highly reproduce the key histopathological features of human TBM. Primary ependymal cells were cultured and treated either directly with BCG or indirectly with conditioned medium from BCG-stimulated BV2 microglial cells (BCG+BV2-CM). Transcriptomic profiling was conducted via RNA sequencing, with validation by qPCR and Western blot. Functional outcomes, including ciliary morphology and apoptosis, were assessed using immunofluorescence and flow cytometry. The therapeutic effect of sodium butyrate (NaB) was evaluated through pretreatment experiments. Results: BCG infection induced characteristic TBM pathology, with persistent bacteria in the brain and lungs, ventricular inflammation, and pulmonary damage. Transcriptomic analysis showed that direct BCG treatment altered the expression of 1036 genes in ependymal cells, whereas BCG+BV2-CM treatment induced 3558 differentially expressed genes, highlighting microglia’s role in amplifying ependymal injury. Integrated analysis identified 64 consistently dysregulated genes across in vitro and in vivo models, enriched in immune and metabolic pathways. BCG challenge significantly downregulated Hmgcs2, leading to ciliary shortening and increased apoptosis. Sodium butyrate treatment restored Hmgcs2 expression, preserved ciliary structure, and reduced apoptosis. Conclusion: Microglia profoundly exacerbate transcriptional dysregulation in ependymal cells during TBM. Sodium butyrate confers protection against BCG-induced ependymal damage by upregulating Hmgcs2, revealing a novel therapeutic target for tuberculous meningitis.