MS Brains Harbor Senescent Radial Glia Cells That Drive Smoldering Inflammation
Scientists identify a novel disease-associated radial glia-like cell population in progressive MS brains with epigenetically dysregulated interferon signaling.
Résumé
Researchers used direct reprogramming to convert skin fibroblasts from progressive multiple sclerosis (PMS) patients into induced neural stem cells (iNSCs), preserving the epigenetic memory of the donor cells. Whole-genome bisulfite sequencing revealed PMS-specific hypomethylation at lipid metabolism and interferon signaling genes. Single-cell multi-omics uncovered a novel disease-associated radial glia-like cell (DARG) subpopulation marked by senescence and heightened interferon responsiveness. PMS iNSCs also induced paracrine senescence in healthy control cells, an effect reversed by the senolytic drug ABT-263 (navitoclax). Post-mortem brain analysis confirmed DARGs in chronic active MS lesions, spatially co-localizing with inflammatory glia, suggesting they sustain smoldering neuroinflammation and represent a previously unrecognized therapeutic target.
Résumé détaillé
Progressive multiple sclerosis (PMS) is defined by relentless neurodegeneration driven by a smoldering inflammatory process that current therapies fail to adequately address. Understanding the cellular and epigenetic drivers of this chronic inflammation is critical for developing new treatments. This study takes a uniquely integrated approach, combining epigenomics, bulk and single-cell transcriptomics, spatial transcriptomics, and functional cell biology to dissect PMS pathology at unprecedented resolution.
The team directly reprogrammed skin-derived fibroblasts from PMS patients and healthy controls into induced neural stem cells (iNSCs) using a protocol specifically chosen to preserve epigenetic memory—unlike iPSC reprogramming, which erases age-related methylation marks. Whole-genome bisulfite sequencing (WGBS) of parental fibroblasts and matched iNSC lines identified a PMS-specific pattern of DNA hypomethylation at genes governing lipid metabolism and interferon (IFN) signaling, indicating that the inflammatory predisposition is epigenetically encoded in patient cells before reprogramming and faithfully retained in the derived iNSCs.
Bulk RNA sequencing confirmed strong transcriptional upregulation of senescence and IFN pathways in PMS iNSCs, with key differentially expressed genes including ISG15, IFIT1, IFIT2, OASL, and SERPINE1. Gene regulatory network analysis identified IRF2 as a central hub interacting with CDKN2A, CDKN1C, IRF1, and CGAS, linking cellular senescence and innate immune activation. Experimental validation showed PMS iNSCs had shortened telomeres, elevated SA-β-galactosidase activity, reduced proliferation, and increased p16Ink4a, p21, and GDF15 protein levels. Critically, treatment with the senolytic ABT-263 (navitoclax) reversed these senescence markers and blocked paracrine senescence induction in co-cultured healthy control cells, demonstrating a causal and targetable role for senescent cells in propagating the inflammatory state.
Single-cell multi-omics analysis revealed a previously undescribed DARG subpopulation within PMS iNSC cultures, characterized by a radial glia-like transcriptional identity combined with potent IFN responsiveness and hallmarks of cellular senescence. Specific transcription factors were identified as drivers of this unique state. Validation in post-mortem PMS brain tissue using single-nucleus and spatial transcriptomics datasets confirmed the existence of analogous DARG populations in vivo, specifically enriched within chronically active demyelinating lesions and spatially co-localizing with inflammatory microglia and astrocytes. Developmental trajectory analysis showed the in vitro iNSC-derived DARGs align with those found in PMS brain tissue, supporting their biological relevance.
These findings establish DARGs as a novel cellular axis in PMS pathology with the capacity to sustain smoldering neuroinflammation through IFN-driven, senescence-associated secretory programs. The study opens therapeutic avenues targeting DARG senescence and IFN dysregulation in progressive MS, while the direct reprogramming model provides a powerful epigenetically faithful platform for future drug discovery.
Principales conclusions
- PMS patient fibroblasts and iNSCs carry epigenetic hypomethylation at IFN signaling and lipid metabolism genes, encoding inflammatory predisposition.
- A novel disease-associated radial glia-like cell (DARG) subpopulation was identified in PMS iNSCs exhibiting senescence and heightened IFN responsiveness.
- PMS iNSCs induce paracrine senescence in healthy control cells; senolytic ABT-263 treatment reverses this effect and reduces inflammatory signaling.
- DARGs were confirmed in post-mortem PMS brains within chronic active lesions, co-localizing spatially with inflammatory microglia and astrocytes.
- IRF2 was identified as a central transcriptional hub linking cellular senescence genes (CDKN2A, CDKN1C) and innate immune activation (CGAS, IRF1) in PMS.
Méthodologie
The study used direct reprogramming of PMS patient and healthy control fibroblasts into iNSCs to preserve epigenetic memory, followed by whole-genome bisulfite sequencing, bulk RNA-seq, and single-cell multi-omics. Post-mortem PMS brain tissue was analyzed using single-nucleus and spatial transcriptomics to validate in vitro findings in human disease tissue.
Limites de l'étude
The study relies on post-mortem brain tissue for in vivo validation, limiting causal inference in living patients, and sample sizes for epigenomic analysis are modest. The direct reprogramming model, while epigenetically informative, may not fully recapitulate the complex in vivo CNS microenvironment, and the functional role of DARGs in smoldering inflammation requires further in vivo validation.
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