DNA methylation variability in pediatric aplastic anemia contributes to T cell differentiation

Aplastic anemia (AA) is caused by immune-mediated bone marrow failure and exhibits an inexplicable peak of age distribution in children. To study the specific mechanism in pediatric AA, a cohort of 76 AA children was compared with 20 age-matched healthy controls in terms of T cell characteristics and subclusters using a multi-omics approach, including flow cytometry analysis, whole genome bisulfite sequencing, and single-cell RNA sequencing. We observe increased T cell proportions and a higher Th17/Treg ratio in AA patients. In CD3+ T cells, DNA methylation analysis uncovered hypomethylated STAT3 genes in patients and implicated enrichment of Th17 cell differentiation, Th1 & Th2 cell differentiation, and PD-L1 expression & PD-1 checkpoint pathways. Single-cell RNA sequencing further confirmed that the IL-6/JAK2/STAT3 signaling pathway is involved in CD4+ T cell subset expansion (notably CD4-IL6ST-naïve and CD4-CAMK4-naïve cells). Our data showed that DNA methylation variability is associated with aberrant balance of Th17/Treg cells and T cell differentiation in children with AA, which may be related to dysregulation of the IL-6/JAK2/STAT3 signaling pathway. Our study provided new evidence that supports the 'locust’ theory in the progression of pediatric AA and possibly novel targets for immunotherapy in the future.