Can microRNAs Predict Steroid Response in Childhood Asthma?

While inhaled corticosteroids (ICS) remain the cornerstone of long-term asthma management in children, clinical response varies widely. Recent molecular research is increasingly pointing toward regulatory RNA molecules as potential mediators of treatment response, and a new analysis from the Childhood Asthma Management Program (CAMP) explores whether circulating microRNAs (miRNAs) may influence ICS responsiveness in children with asthma, particularly in the context of vitamin D status.

For context, miRNAs act post-transcriptionally by binding to messenger RNA and reducing protein translation, thereby fine-tuning cellular signaling pathways. Because they circulate in blood and reflect changes in immune and inflammatory activity, they have emerged as promising biomarkers for treatment response and disease phenotypes. This study examines how baseline circulating miRNA profiles interact with vitamin D levels to influence long-term ICS treatment outcomes.

Study Design and Molecular Analysis

Investigators conducted a stratified analysis using data from the CAMP randomized controlled trial, which enrolled 1,041 children with mild-to-moderate asthma and compared long-term treatments including budesonide, nedocromil, and placebo. For the current analysis, researchers focused on 187 children randomized to budesonide therapy, with serum samples collected prior to treatment initiation and lung function monitored for up to four years.

Baseline circulating miRNAs were quantified using small RNA sequencing from serum samples collected before treatment initiation. Participants were then stratified according to vitamin D status, categorized as insufficient (≤30 ng/mL) or sufficient (>30 ng/mL). The primary clinical outcome was the change in pre-bronchodilator forced expiratory volume in 1 second (FEV₁) percent predicted over a four-year follow-up period, used as a measure of response to inhaled corticosteroid therapy.

To explore the biological mechanisms underlying these associations, gene expression profiling was conducted in lymphoblastoid B-cell lines derived from 22 CAMP participants six years after trial completion. Selected miRNA findings were evaluated in an independent cohort from the Genetics of Asthma in Costa Rica Study to assess the reproducibility of the observed associations.

Key Molecular Signals Linked to ICS Response

The analysis identified 12 circulating miRNAs associated with improvement in FEV₁ among vitamin D-insufficient participants, whereas no significant miRNA associations were observed in children with sufficient vitamin D levels.

Two miRNAs showed particularly strong effects. Higher expression of hsa-miR-125a-5p was associated with a greater improvement in FEV₁ percent predicted (β = 6.52, p = 0.005), indicating a more favorable response to inhaled corticosteroid therapy. In contrast, elevated expression of hsa-miR-181a-5p was associated with a smaller improvement in FEV₁ percent predicted (β = −8.32, p = 0.02), suggesting a diminished ICS response. Together, these opposing associations highlight how specific circulating miRNAs may differentially relate to measured changes in FEV₁ over the course of treatment.

Overall, 11 miRNAs demonstrated significant interaction with vitamin D levels, suggesting that vitamin D modifies the relationship between miRNA expression and corticosteroid responsiveness.

Immune Pathways Connecting Vitamin D and Corticosteroid Action

Functional experiments helped clarify the molecular context of these findings. Gene expression profiling revealed 220 genes differentially expressed in dexamethasone-treated cells and 212 genes altered with vitamin D exposure, many of which participate in immune regulation and inflammatory signaling.

Network analyses linked key miRNAs to pathways regulating:

• Hematopoiesis
• Leukocyte differentiation
• Cytokine signaling
• NF-κB–mediated inflammatory responses

These pathways converge on immune cell development and function, suggesting that vitamin D may influence corticosteroid efficacy by reshaping immune cell differentiation through miRNA-mediated gene regulation.

Predicting Treatment Response

The study also evaluated the predictive value of miRNA biomarkers. A logistic regression model combining miR-125a-5p and miR-181a-5p demonstrated strong ability to distinguish high from low ICS responders in vitamin D-insufficient children, achieving an area under the ROC curve (AUROC) of 0.86. In contrast, predictive performance was poor among children with sufficient vitamin D levels, highlighting the importance of vitamin D status in this regulatory network.

Clinical Perspective

These findings suggest that circulating miRNAs may serve as molecular intermediaries linking vitamin D biology to corticosteroid responsiveness in childhood asthma. If validated in larger cohorts, miRNA profiling—particularly in vitamin D-insufficient patients—could eventually help identify children most likely to benefit from ICS therapy or guide adjunctive interventions such as vitamin D optimization.

Reference:

Jiang M, Zhang Y, Liu T, et al. Circulating miRNAs and childhood asthma ICS response: a stratified analysis in the intervention arm of an RCT with vitamin D effect modification. Thorax. 2025;80(11):788-795. doi:10.1136/thorax-2024-222618