Aging-associated transcriptional programs in T cells signify constituents of TGF-β signaling for immunosenescence.

BACKGROUND: Immunosenescence, particularly the altered ratio of naïve and memory T cells, contributes to a diminished immune reserve and impaired adaptive immunity in aging and frail populations. The role of TGF-β signaling pathway-a critical hallmark of organismal senescence and T-cell exhaustion-in terminally differentiated effector memory T (Temra) cells remains elusive. We devised single-cell and bulk-cell RNA sequencing (RNA-seq) datasets to identify age-group-specific transcriptional regulatory networks in T cells and elucidate the roles of TGF-β signaling constituents associated with immunosenescence in Temra. RESULTS: Analysis of scRNA-seq data from peripheral T cells across healthy human age groups revealed young-specific regulons controlled by FOXP1, TCF7, LEF1, and IKZF1 and old-specific regulons governed by EOMES, TBX21, RUNX3, and NFATC2. Transcription factor (TF)-binding-motif enrichment analysis implicated TGF-β signaling pathway components ZEB2 and TGFBR3 as pivotal target genes coregulated by multiple TFs, potentially facilitating T-cell terminal differentiation and exhaustion. Pseudotime analysis and bulk-cell RNA-seq further corroborated these regulons, validating their association with T-cell self-renewal capacity (young-specific) or effector/terminal differentiation (old-specific). In terms of aging, multiple TGF-β signaling activation components, including TGFB1, TGFBR1, SMAD3, ZEB2, and TGFBR3, were significantly upregulated in CD8 + Temra cells relative to CD8 + naïve T cells. CONCLUSIONS: Our study used systematic approaches for delineating age-dependent transcriptional networks for T-cell-associated immunosenescence. We identified multiple components of the TGF-β signaling pathway as potential biomarkers of Temra, which are strongly associated with senescence features including impaired differentiation plasticity, high cytotoxicity, and inflammatory chemotaxis capacity.