Age profoundly affects the fibrogenic response to liver injury, according to findings from a mouse model. Acute liver injury was greater in old mice (18 months old) than in middle-aged mice (9 months old). The fibrogenic response to chronic liver injury was also greater in old livers when compared with middle-aged livers. A greater number of macrophages (which are thought to have a role in fibrogenesis) were found in the younger mice and livers than in the older mice and livers, suggesting that macrophage recruitment and dynamics have a role in age-related fibrotic disease.