Single-cell transcriptional profiling reveals PAX5-mediated naïve B cell differentiation defect in severe adenoid...

Adenoid hypertrophy significantly impacts pediatric upper airway function, but its molecular mechanisms remain elusive. This study characterizes the cellular landscape in adenoid hypertrophy using single-cell RNA sequencing (scRNA-seq).

Adenoid tissue samples were obtained from pediatric patients diagnosed with either severe hypertrophic adenoids (SHA) and mild to moderate hypertrophic adenoids (MHA). scRNA-seq was performed to generate transcriptomic profiles at single-cell resolution. Clustering and differential expression analyses were performed, with pseudotime trajectory, cell-cell communication, and copy number variation analyses.

Analysis of 45,917 single-cell transcriptomes revealed 18 distinct cell clusters with B cells predominating. SHA samples exhibited significant enrichment of naïve B cells with corresponding reduction of memory B cells, suggesting disrupted B cell differentiation. Pseudotime analysis confirmed B cell differentiation disruption in SHA, with cells accumulating at the naïve B cell stage. Notably, paired box gene 5 (PAX5), a master transcription factor essential for B cell lineage commitment but typically downregulated during terminal differentiation, was significantly upregulated in SHA. CNV analysis showed no evidence of clonal expansion or malignant transformation.

Our findings reveal that adenoid hypertrophy is characterized by impaired B cell differentiation with accumulation of naïve B cells and PAX5 overexpression, suggesting a differentiation blockade as a novel pathogenic mechanism. These insights offer potential therapeutic targets within the B cell maturation pathway, including modulation of PAX5 activity.