Scientists Remove Zombie Cells to Reverse Liver Damage in Mice

UCLA researchers have identified a key mechanism behind liver aging and fatty liver disease: the accumulation of senescent "zombie" immune cells called macrophages. These dysfunctional cells stop dividing but remain active, continuously releasing inflammatory signals that damage surrounding tissue.

The breakthrough came from solving a long-standing puzzle about whether macrophages could truly become senescent. The team identified a clear molecular signature using two proteins, p21 and TREM2, that reliably marks truly senescent macrophages. Using this marker, they discovered these zombie cells increase from just 5% in young mouse livers to 60-80% in older mice.

Crucially, the researchers found that excess LDL cholesterol can push healthy macrophages into senescence. When exposed to high cholesterol levels in lab conditions, normal macrophages stopped dividing and began releasing inflammatory proteins. This suggests that high-fat, high-cholesterol diets may accelerate biological aging by promoting senescent cell accumulation not just in the liver, but potentially throughout the body.

When scientists selectively removed these zombie cells from mice, liver inflammation dropped sharply and damage was reversed, even though the animals continued eating unhealthy diets. This dramatic improvement occurred without any dietary interventions, highlighting the powerful role these cells play in age-related liver disease. The findings suggest that targeting senescent macrophages could offer a new therapeutic approach for fatty liver disease and potentially slow aspects of biological aging itself.