IGF2BP1 Drives Macrophage Glycolysis and Fibrosis via m6A-THBS1 Axis

Study Background and Research Question

Pulmonary fibrosis (PF) is a progressive interstitial lung disease marked by accumulation of extracellular matrix and fibroblast proliferation, ultimately leading to loss of lung function. Although inflammation and immune cell dynamics are recognized contributors, the mechanistic roles of macrophage metabolic reprogramming and posttranscriptional RNA modifications in PF remain incompletely understood. Recent attention has focused on N6-methyladenosine (m6A), the most prevalent reversible mRNA modification, and its regulatory proteins, including the m6A reader insulin-like growth factor 2 mRNA binding protein 1 (IGF2BP1). The current study asks: how does IGF2BP1 influence macrophage function and fibrogenesis in pulmonary fibrosis, and through which molecular intermediates?

Key Innovation from the Reference Study

The reference study reveals a previously uncharacterized IGF2BP1/THBS1/TLR4 regulatory axis in the pathogenesis of pulmonary fibrosis. Specifically, IGF2BP1 is shown to promote macrophage M2 polarization and glycolytic activation by stabilizing thrombospondin-1 (THBS1) mRNA in an m6A-dependent manner. This stabilization enhances TLR4 signaling, leading to increased fibrotic activity. This mechanistic insight significantly extends our understanding of how epigenetic mRNA regulation intersects with metabolic and immunological pathways in fibrotic disease (Hu et al., 2025).

Methods and Experimental Design Insights

The study employs a multi-tiered experimental strategy, combining in vivo, ex vivo, and in vitro approaches:

• Mouse models of bleomycin (BLM)-induced pulmonary fibrosis, with and without IGF2BP1 knockdown, to assess lung pathology and immune cell dynamics.
• Immunohistochemistry and flow cytometry to quantify macrophage subpopulations and fibrotic markers.
• RNA immunoprecipitation and mRNA stability assays to confirm IGF2BP1 binding to THBS1 via m6A residues.
• Gain- and loss-of-function experiments manipulating THBS1 and TLR4 expression in macrophages, coupled with metabolic profiling (e.g., glycolysis markers, lactate production, ATP levels).
• Gene expression analyses (qPCR, Western blot) to quantify key markers of fibrosis, macrophage polarization, and glycolytic metabolism.

This integrative design allows for mechanistic dissection of the pathway from IGF2BP1 to downstream fibrotic phenotypes.

Core Findings and Why They Matter

• IGF2BP1 is upregulated in macrophages during pulmonary fibrosis: Elevated IGF2BP1 expression was observed in macrophages from BLM-treated mice. Knockdown of IGF2BP1 markedly reduced fibrosis severity, as shown by decreased extracellular matrix deposition, fibroblast proliferation, and Ashcroft scores.
• IGF2BP1 promotes M2 polarization and glycolysis via THBS1: Mechanistic studies demonstrated that IGF2BP1 binds and stabilizes THBS1 mRNA in an m6A-dependent fashion. THBS1 overexpression reversed the effects of IGF2BP1 knockdown, restoring M2 polarization and glycolytic activity, as evidenced by increased expression of HK2, LDHA, PKM2, and higher lactate/ATP levels.
• THBS1 interacts with TLR4 to drive macrophage phenotype: Physical interaction between THBS1 and TLR4 was confirmed. TLR4 overexpression rescued the loss of M2 polarization and glycolytic reprogramming in THBS1-knockdown cells, linking m6A regulation to innate immune signaling.
• Comprehensive attenuation of fibrotic markers: IGF2BP1 knockdown downregulated a broad spectrum of profibrotic and inflammatory markers, including TGF-β1, α-SMA, Collagen I/III, Arg1, CCL18, Ym1, CD163, IL-6, IL-1β, and TIMP1.

Taken together, these findings identify IGF2BP1 as a central node coordinating macrophage activation and metabolic reprogramming to drive pulmonary fibrosis (Hu et al., 2025).

Comparison with Existing Internal Articles

Recent internal resources have explored the role of macrophage colony stimulating factor (M-CSF) in macrophage viability, activation, and differentiation workflows. For example, one article highlights M-CSF's key function as a macrophage survival and proliferation regulator, which is foundational for modeling macrophage biology in vitro. Another resource (Optimizing Macrophage Assays) provides workflow guidance and performance benchmarks for using recombinant M-CSF to achieve reproducible macrophage expansion and activation.

However, while these internal articles focus on practical and technical aspects of macrophage culture and assay reproducibility, the reference study uniquely dissects the molecular and epigenetic mechanisms (m6A-IGF2BP1-THBS1 axis) underlying macrophage-driven fibrosis. The mechanistic link between m6A-dependent mRNA stabilization, metabolic reprogramming, and fibrotic signaling is not addressed in these practice-oriented guides, highlighting the distinct and complementary value of the reference study for researchers investigating macrophage-mediated disease pathways.

Limitations and Transferability

Despite its mechanistic depth, several limitations should be noted:

• Species and model specificity: Findings are based on mouse models of BLM-induced pulmonary fibrosis, which may not fully mirror the complexity of human disease.
• Focus on M2 polarization and glycolysis: Other macrophage metabolic states and polarization phenotypes (e.g., M1, hybrid states) were less extensively characterized.
• Therapeutic translation: While the IGF2BP1/THBS1/TLR4 axis emerges as a promising target, direct pharmacological interventions were not tested within this study.
• Contextual network complexity: The study narrows in on a specific regulatory pathway; broader transcriptional and epigenetic networks may modulate or compensate for IGF2BP1/THBS1/TLR4 perturbations in vivo.

Therefore, while the mechanistic insights are robust, their transferability to clinical or cross-species contexts requires further validation.

Protocol Parameters

• Macrophage polarization assays: Macrophages can be polarized toward M2 phenotype using IL-4/IL-13, with or without co-stimulation (reference protocols may specify 20 ng/mL IL-4 for 48 h).
• Bleomycin-induced PF model: BLM is typically administered intratracheally (1-3 units/kg) to induce fibrosis in mice, with assessment time points ranging from 7 to 28 days post-instillation.
• Gene knockdown/overexpression: Lentiviral or siRNA-mediated approaches are employed for IGF2BP1, THBS1, and TLR4 modulation; efficiency and timeline depend on vector systems and target cell type.
• Metabolic profiling: Glycolysis can be quantified by measuring glucose uptake, lactate production, ATP content, and the expression of HK2, LDHA, PKM2 (using commercial assay kits and qPCR/Western blot).
• Macrophage culture support: Incorporate validated recombinant cytokines such as M-CSF (10-100 ng/mL) to support macrophage survival and expansion, as recommended in published in vitro protocols and product datasheets.

Research Support Resources

For researchers aiming to model macrophage activation, polarization, or metabolic phenotypes in fibrotic disease workflows, it is essential to use high-purity reagents that support cell viability and experimental reproducibility. Recombinant Mouse Macrophage Colony Stimulating Factor (M-CSF) without Tag (SKU PM2021) from APExBIO is a validated reagent produced in HEK293 cells, ensuring species-specific activity for mouse models and macrophage cultures. Its documented purity and robust biological activity make it suitable for macrophage proliferation and polarization assays, which underpin studies investigating pathways like the IGF2BP1/THBS1 axis in fibrosis.