Dr. Wendie Trubow explains senescent cells, which are cells that stop dying when they should. Instead of being replaced, they become "cellular zombies" that poison neighboring healthy cells, spreading the damage and accelerating aging.
Chapters
What are senescent cells? Every cell in our body is designed to do a particular job for a particular period of time, at which point it runs to the end of its lifespan and is supposed to die. We call it autophagy, that is self-eating. It's supposed to die and fall apart and be replaced by a new cell. But a small percentage of cells hit that endpoint, and instead of dying, they basically become cellular zombies. They stop doing what they're supposed to do. They start kicking out anti-growth, anti-healing, anti-repair chemicals into their environment. They become the living dead of the cellular world. The problem is those anti-growth, anti-healing chemicals that they kick out poison healthy cells and turn them into these cellular zombies. And so as we age, we start accumulating these.