Integrated Transcriptomic Analysis Identifies a Candidate INHBA/Activin A-Associated Macrophage-MuSC Communication Axis in Human Skeletal Muscle Ageing.

Skeletal muscle ageing is accompanied by impaired regeneration and remodelling of the multicellular niche, yet how age-related immune changes relate to altered muscle stem cell (MuSC) states in humans remains unclear. Here, we integrated bulk RNA-sequencing, scRNA-seq and an independent older adult cohort analysis to characterize age-associated changes in human skeletal muscle and identify candidate macrophage-MuSC signalling interactions. Bulk transcriptomic analysis revealed inflammatory activation, reduced mitochondrial and metabolic programmes, and increased macrophage-associated signatures in aged muscle. Single-cell analysis resolved distinct myeloid and MuSC states. Among aged myeloid populations, inflammatory macrophages exhibited the highest SenMayo score, whereas donor-level pseudobulk analysis identified age-related early-primed MuSCs (epMuSC) remodelling involving inflammatory, interferon-related, and extracellular matrix-associated programmes. Ligand-target modelling prioritized inhibin subunit beta A (INHBA)/Activin A as a candidate signal linking inflammatory macrophages to the aged epMuSC programme. This prediction was further supported by an independent older adult human muscle scRNA-seq cohort showing concordant INHBA expression in inflammatory macrophages and Activin receptor expression in epMuSCs. In primary human MuSCs, Activin A induced Activin-responsive genes and suppressed myogenic regulators, and these effects were attenuated by SB431542, a small-molecule inhibitor of ALK4/5/7 signalling. Together, these findings support a candidate INHBA-associated, cell state-resolved communication framework between inflammatory macrophages and epMuSC remodelling in aged human muscle, providing a potential link between immune remodelling and altered regenerative cell states.