Gene expression in human monocyte-derived macrophages: effect of loss of MYC or USF1

Macrophage function declines with age, however the underlying mechanisms remain poorly understood. Here, we report that MYC and USF1 are key in driving age-related macrophage functional decline in humans, including reduction in phagocytosis and chemotaxis. We show downregulation with age of MYC and USF1 in human monocyte-derived macrophages (MDMs) and crucially, that knockdown of MYC or USF1 in young MDMs modelled the age-related functional changes. Transcriptomic analysis of these young knockdown MDMs revealed alteration in expression of genes crucial to these functions, as well as those linked to adhesion and extracellular matrix formation. Concordant dysregulation of these genes was also seen in older MDMs. Finally, we show that morphology and F-actin content were altered with loss of MYC or USF1, similarly to that seen in ageing. Together, these results define MYC and USF1 as key drivers of MDM age-related functional decline and identify downstream targets to improve macrophage function in ageing. Overall design: To investigate the role of MYC and USF1 in monocyte-derived macrophage (MDM) functional decline with age, we knocked these genes down individually in young MDMs by siRNA transient transfection. This was done in MDMs isolated from blood of six healthy young donors that were differentiated for 7 days in M-CSF. Cell were then transfected for 72 hours and either left unstimulated (M0) or were stimulated for a further 24 hours with LPS and IFN? (MLPS+IFNy). We then performed gene expression profiling using data obtained from RNA sequencing on knockdown vs control in the M0 and MLPS+IFNy phenotypes.