Moiseeva and colleagues examined gene expression and chromatin (the DNA-protein complex in which genetic material is packaged in the nucleus) in the senescent cell populations from young and old animals. To explore the mechanism by which senescent cells block muscle regeneration, the group further profiled gene expression in the cells, and found a decrease in expression of genes related to the function of energy-producing organelles called mitochondria, and an increase in inflammatory genes, among other changes. In particular, interferon-stimulated genes (which are associated with inflammation) are upregulated in both ageing and senescence. ...the authors found changes in collagen production, which have previously been linked to fibrosis6.