'Zombie cells' accumulate in brain before cognitive loss

Zombie cells, which are unable to die or function normally, accumulate in the brain before cognitive loss, and can be targetted to prevent diseases like Alzheimer's and Parkinson's, scientists say.

These zombie, or senescent, cells are implicated in a number of age-related diseases.

"Senescent cells are known to accumulate with advancing natural age and at sites related to diseases of ageing, including osteoarthritis; atherosclerosis; and neurodegenerative diseases, such as Alzheimer's and Parkinson's," said Darren Baker, a from Mayo Clinic in the US.

"In prior studies, we have found that elimination of senescent cells from naturally aged mice extends their healthy life span," said Baker.

In the study published in the journal, the team used a model that imitates aspects of Alzheimer's disease.

"We used a mouse model that produces sticky, cobweb like tangles of tau protein in neurons and has genetic modifications to allow for senescent cell elimination," said Tyler Bussian, a student at Mayo Clinic Graduate School of Biomedical Sciences.

"When senescent cells were removed, we found that the diseased animals retained the ability to form memories, eliminated signs of inflammation, did not develop neurofibrillary tangles, and had maintained normal brain mass," said Bussian.

The team was also able to identify the specific type of cell that became senescent, Baker said.

"Two different brain cell types called 'microglia' and 'astrocytes' were found to be senescent when we looked at brain tissue under the microscope," said Bussian.

"These cells are important supporters of neuronal health and signalling, so it makes sense that senescence in either would negatively impact neuron health," he said.