The brain uses an intricate system to recognize, engulf, and destroy dead cells to stop them from clogging up connections and damaging the surrounding tissue. This process plays a huge role in patients with brain injuries, neurodegenerative disease, and other disorders. For the first time ever, scientists at the Yale School of Medicine have recorded a video of dead neurons being removed in mice brains, revealed in a study published in Science Advances.
The video below shows a short timelapse of a dead neuron (in red) being targeted and surrounded by the brain's immune cells, called microglia. Over the course of 24 hours, the microglia fragment the dead neuron and consume its contents, clearing it from blocking the activity of the surrounding neurons.
Capturing this amazing process has not been easy. Cell death in the brain is unpredictable and takes place very quickly, so imaging it occurring is no easy feat. To combat this, the team at Yale developed methods to directly target single brain cells and induce death by targeting them with photochemical or viral agents. They were then able to image the entire process as the brain recognized the dead cell and recruited immune cells to engulf them for removal.
Understanding this process, called apoptosis, is incredibly important for researchers. “If you were to stop collecting garbage in New York City, you wouldn’t be able to get in. There would be debris everywhere,” said Dr Eyiyemisi Damisah, assistant professor of neurosurgery at Yale School of Medicine in a statement. Much like a city covered in garbage, the brain cannot function with too many dead cells left lying around.
It is hoped that both the new methods used to target single cells for death and the new understanding of brain apoptosis will translate into helping human disease in the future. Research into brain disease struggles with applying results from mouse models, like those used in this study, to humans – but understanding apoptosis may have massive implications on neurodegenerative and inflammatory diseases.
“Cell death is very common in diseases of the brain,” said Dr Damisah. “And understanding the process might yield insights on how to address cell death in an injured brain from head trauma to stroke and other conditions.”
Dr Jaime Grutzendler, of Yale's Grutzlendler lab, added: “Following injury to the brain, you need to understand what the cells are doing and what molecules are involved in order to develop new strategies to treat the condition. And if we can remove dying cells efficiently, can we prevent age-related neurodegeneration?”