Genetic Modulation of Hypoxia Signaling: The Protective Role of HIF1A in Multiple Sclerosis Progression

Multiple sclerosis (MS) is a chronic neuroinflammatory disease characterized by substantial heterogeneity in clinical outcomes. While many patients transition from a relapsing–remitting phase to progressive disability, others remain relatively stable over decades. A central driver of long-term disability is “smoldering inflammation”, a compartmentalized immune process localized at the edges of chronic lesions. However, the biological determinants underlying this process remain poorly understood .

Recent advances in human genetics provide a powerful framework for identifying molecular mechanisms that influence disease trajectories. The study analyzed here investigates how genetic variation in inflammation-related pathways—particularly those linked to iron metabolism—modulates long-term disability in MS.

Genetic Discovery: Identification of a Protective HIF1A Variant
Using a discovery–replication design across two large cohorts totaling 2,817 MS patients, the study identified a significant association between disease course and a variant in the HIF1A gene. Specifically, the minor allele (rs11621525 A) was associated with a more favorable disease trajectory, characterized by reduced disability accumulation over more than 20 years .

The effect was robust:

Discovery cohort: Odds ratio ~1.75

Replication cohort: Significant association confirmed

The HIF1A gene encodes hypoxia-inducible factor 1-alpha, a transcription factor central to cellular adaptation to hypoxia and metabolic stress. This finding positions hypoxia signaling as a key axis in MS progression.

Linking Genetics to Imaging: Reduced Smoldering Inflammation
To translate genetic findings into biological relevance, the authors integrated advanced neuroimaging data. A hallmark of smoldering inflammation—paramagnetic rim lesions (PRLs)—was quantified using high-resolution MRI.

Carriers of the protective HIF1A allele exhibited:

Reduced PRL volume (but not number)

Indicating attenuated chronic inflammatory activity at lesion edges

As illustrated in the imaging workflow (Figure on page 6), PRLs represent iron-laden, microglia-rich lesion borders, a key substrate of progressive MS .

These findings directly link genetic variation to in vivo markers of chronic neuroinflammation, strengthening causal interpretation.

Fluid Biomarkers: Evidence of Reduced Axonal Injury
The study further evaluated neurofilament light chain (NFL), a well-established biomarker of axonal damage. Results showed that carriers of the protective allele had:

Lower plasma NFL levels

Lower CSF NFL levels

These reductions indicate less ongoing neuroaxonal injury, reinforcing the hypothesis that the HIF1A variant mitigates neurodegeneration .

Importantly, these effects were detectable early in disease and independent of relapse activity, suggesting a direct influence on chronic pathological processes rather than acute inflammation.

Neuropathological Validation: Reduced Microglial Activation and Iron Deposition
Post-mortem spinal cord analyses provided mechanistic validation at the tissue level. Individuals carrying the protective allele demonstrated:

Reduced microglia/macrophage activation (CD68+)

Decreased acute axonal injury (BAPP-positive axons)

Lower iron accumulation in chronic lesions

The histological comparison (Figure on page 10) highlights reduced inflammatory burden in both lesional and non-lesional tissue .

Additionally, cortical iron rim lesions—strongly associated with disability—were absent in carriers of the protective genotype. This suggests a systemic modulation of iron-driven neurotoxicity.

Cellular Mechanisms: Context-Dependent Regulation of HIF1A
A major innovation of this study lies in its integration of single-nucleus RNA sequencing and spatial transcriptomics. These analyses revealed that the genetic variant exerts cell-type-specific and context-dependent effects on gene expression.

Key findings include: Increased HIF1A expression in several CNS cell types
Reduced expression in a specific immune subset: monocyte-derived dendritic cells (moDCs) within chronic lesion rims

Localization of these cells to active lesion edges, as shown in spatial maps

This “dynamic eQTL” effect suggests that the protective allele selectively dampens hypoxia-driven inflammatory responses in critical microenvironments.

Biological Interpretation: The Hypoxia–Inflammation Axis in MS
HIF1A is a master regulator of the cellular response to hypoxia and metabolic stress. In chronic MS lesions, a state of “virtual hypoxia” arises due to mitochondrial dysfunction and increased energy demand.

The study proposes that:

Dysregulated HIF1A signaling sustains chronic inflammation

Genetic variation can modulate this axis, influencing disease severity

This aligns with broader evidence linking hypoxia signaling to immune activation and neurodegeneration across diseases .

Conclusion: Implications for Precision Medicine and Therapeutics

This study provides compelling evidence that a common genetic variant in HIF1A: Reduces smoldering inflammation

Limits axonal injury

Improves long-term clinical outcomes in MS

By integrating genetics, imaging, biomarkers, pathology, and transcriptomics, the research establishes a multi-scale model of disease modulation.

Crucially, these findings highlight HIF1A and its downstream pathways as promising therapeutic targets. Interventions aimed at modulating the hypoxia–inflammation axis could offer new strategies to halt or slow MS progression—an area of significant unmet clinical need.

Disclaimer: This blog post is based on the provided research article and is intended for informational purposes only. It is not intended to provide medical advice. Please consult with a healthcare professional for any health concerns.

References:
Giordano, A., Stridh, P., Preziosa, P. et al. A HIF1A variant impacts long-term disability and smoldering inflammation in multiple sclerosis. Acta Neuropathol 151, 12 (2026). https://doi.org/10.1007/s00401-026-02984-w