Wound healing is a complex process involving the immune system. Unfortunately, some parts of the immune system deteriorate as we get older.
For example, ageing affects the function of white blood cells (shown above) called macrophages (big eaters). These cells play key immune roles, especially in wound repair. They chomp their way through debris at a wound site, and help to promote tissue reconstruction by producing a growth factor that boosts the cells that make connective tissue and collagen. Meanwhile, in broken bones, macrophages secrete chemicals that attract stem cells to the injured site. Ageing also appears to alter these important interactions between macrophages and stem cells.