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How macrophages repair brain bleeding

When small blood vessels in the brain rupture, this carries the risk of hemorrhagic stroke and brain microbleeds. Furthermore, previous studies have shown a relationship between ruptures to blood vessels and neurodegenerative diseases, which can lead to cognitive decline.

New research from Southwest University in China has shown how macrophages help with the repair broken blood vessels. Prior to the study, biologists were unsure about how the brain deals with broken blood vessels and how capable the immune system is with dealing with such incidents.

For the study, the researchers used zebrafish, which are transparent and thus provide an ideal research model. The workings of the zebrafish were assessed using a multi-photon laser, with the laser causing tiny breaks to small blood vessels in the brains of the fish. The focus was on how the fish responded to vascular injury. A special microscope and time-lapse photography was used to assess what was happening.

Here it was found that around 30 minutes after the injury, macrophages (a type of white blood cell) reached the site of the rupture and proceeded to ‘clean up’ cellular debris and engulf any pathogens. The macrophages also used two extensions to re-connect the broken blood vessel; here the cells secreted molecules with adhesive properties.

Speaking with Laboratory Roots, lead scientist Chi Liu said: “We confirmed that the macrophage mediates this repair through direct physical adhesion and generation of mechanical traction forces. This is a previously unexpected role of macrophages.”

The work was also replicated on the fin of a zebrafish. Since macrophages are found in the tissues of most organisms, including people, the researchers think a similar reaction occurs with the human brain should an injury occur. It is hoped that understanding the mechanism more fully will lead to ways to optimize the immune response to ruptured blood vessels.

The outcome of the study has been published in the journal Immunity. The research paper is titled “Macrophages Mediate the Repair of Brain Vascular Rupture through Direct Physical Adhesion and Mechanical Traction.”

Written By

Dr. Tim Sandle is Digital Journal's Editor-at-Large for science news. Tim specializes in science, technology, environmental, and health journalism. He is additionally a practising microbiologist; and an author. He is also interested in history, politics and current affairs.

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