I COME from a family with dodgy knees. My dad, 79, has had two complete knee replacements and my sister needs one at the age of just 54. My left knee hurts when I walk downstairs and clicks when I bend it – classic signs of the age-related disease osteoarthritis, caused by wear and tear on the cartilage cushioning the joint.
By the time I get to the knee-replacement stage, however, I might not need to go under the knife. Instead, I hope to be able to swallow a few pills every so often and feel my knee pain disappear.
Osteoarthritis isn’t just down to wear and tear, but also an accumulation of some nasty cells, which attack the knee joint from within. They are called senescent cells – old or run-down cells that have reached the end of their lives or suffered irreversible damage. They ought to die and yet they don’t, instead lurking in tissue, causing trouble.
Senescent cells are normally cleared out by the immune system, though that goes wrong during ageing and they accumulate, dripping poison into their surroundings and turning other cells rogue. They are a leading cause of numerous age-related conditions, not just in the knees but also in the heart, liver, muscles and brain.
No surprise, then, that researchers have been eyeing senescent cells for many years as a juicy target for efforts to slow, halt or even reverse ageing. Now, we have numerous drugs in the pipeline and some tantalising results from human trials. There is even hope that, by taking out senescent cells, other causes of ageing will evaporate too.