Stem Cell Sunrise

It’s one of nature’s great migrations: neural stem cells spreading through the embryo as they form the brain and nervous system. But unlike the migrations of monarch butterflies or humpback whales, this was never a spectacle we could film.

That’s now changed. Twenty-two years ago, researchers discovered the mature brain retains some neural stem cells. They can be isolated and grown on a microscope slide. First they bunch into a “neurosphere” (blue). Then they start migrating, forming different cell types as they go: neurons (for thinking), and the glia that look after them.

Viewing the spectacle by fluorescence microscopy is not only beautiful, it also helps researchers figure out how to use neural stem cells to repair a damaged brain.

Image courtesy of Lovelace and Chan-Ling
(University of Sydney)

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Neural Networks

Neurons – the brain’s thinking cells – are masters of communication. The secret is their long wiry axons (blue), designed to transmit messages at speeds of up to 120 metres per second.

It may be a message to retrieve a memory from another brain cell, an “ouch that was sharp” coming from a skin sensory cell, or a command from a motor neuron to move a muscle. Wired together by axons, our 100 billion neurons form the most complex circuit in the universe – one that allows us to think.

In this image we see axons from hundreds of newly formed brain cells wiring together. The orange stain shows newly deposited myelin, an insulator that coats the axons like plastic around a wire.

Image courtesy of Morley (University of Western Sydney), Woolley and Gilmour (University of New South Wales).

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Brain cells from skin

Believe it or not, these neurons (green) and glia (red), have been made from “reprogrammed” skin cells (blue).

In 2007, Japanese researchers took a skin cell from an adult and reprogrammed it by adding four genes. The cell regained the youthful properties of a stem cell. Known as an “induced pluripotent stem cell”, it could make any other type of cell, including brain cells. It was a Nobel prize-winning discovery.

Researchers now study the brain cells of a person with Huntington’s or Alzheimer’s disease simply by scraping off a few of their skin cells and converting them into neurons. The technique is helping researchers understand these diseases and find new treatments.

Image courtesy of Wolvetang and Naylor (AIBN, University of Queensland)

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Reach for the Stars

Neurons do our thinking. But they rely on their support team, the glia and particularly astrocytes. Named for their star-shaped appearance, astrocytes provide nutrients and keep the place clean so that the process of transmitting signals takes place smoothly.

Astrocytes also do repairs. After an injury they start to proliferate, extending their starry tips into the wound. The astrocytes shown here (green) are reaching for each other across the gaping chasm of a wound in order to fill it.

Researchers are testing whether magnetic pulses applied in a technique known as “transcranial magnetic stimulation” can help speed up this healing process.

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Image courtesy of Rodger, Bates and Penstone (University of Western Australia)