Conditions

Stroke Repair Mechanism Discovered; Nerve Cells Regrow From 'Support Cell' Astrocytes

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The support cells in the brain go to work rebuilding dead or damaged neurons, offering clues for treating other neurological diseases. Internet Archive Book Images

Scientists from Lund University and Karolinska Institutet in Sweden have discovered a mechanism by which the brain repairs itself following a stroke. In a new study published in the journal Science, the researchers explain how support cells known as “astrocytes” help rebuild damaged nerve cells, or neurons.

Strokes result from a bleeding or blockage inside the brain, leading to the damage or potential death of surrounding neurons. It’s for this reason stroke victims may lose sensory, cognitive, or motor function. The cells that once carried oxygen to the brain can no longer perform their base function, impairing the abilities the brain once enjoyed. The new findings could ultimately lead to manual production of neurons if scientists can activate the mechanism that essentially “turns on” the astrocytes.

“This is the first time that astrocytes have been shown to have the capacity to start a process that leads to the generation of new nerve cells after a stroke,” said Zaal Kokaia, Professor of Experimental Medical Research at Lund University, in a statement.

Kokaia and his colleagues from Karolinska Institutet first discovered almost a decade ago that stroke victims’ brains recover from the injury with help of the brain’s own stem cells. The new findings illuminate what actually is bridging those stem cells to the recovery. In an injured mouse’s brain, the astrocytes that would normally receive no signal to convert into nerve cells now receive that signal. But, as Kokaia explains, the findings extended further.

“Interestingly,” he said, “even when we blocked the signaling mechanism in mice not subjected to a stroke, the astrocytes formed new nerve cells.” This meant the nerve cells weren’t just reacting to the stroke, suggesting they could be harnessed through direct manipulation — in other words, by a curious scientist — to repair damage incurred by other diseases.

For starters, Kokaia points to Parkinson’s and Huntington’s disease. Given the initial success with astrocytes’ conversion into nerve cells, the team believes the root principle may uphold the theory for these two neurological diseases and others. Further tests are needed to determine how effective the new neurons will be at contributing to spontaneous recovery.

“One of the major tasks now is to explore whether astrocytes are also converted to neurons in the human brain following damage or disease,” Kokaia said, adding the typical origin for nerve cells is an area called the striatum — a walnut-sized structure buried deep in the core of the brain, responsible for fine-motor functions and complex social interactions. If the new mechanism can translate into human models, that would mean stroke patients in addition to disease sufferers more generally would find benefit from neuron manipulation.

Each year almost 130,000 Americans die from strokes, or roughly one out of every 19 deaths. The total cost burden of these strokes, combined with the more than 650,000 strokes that aren’t fatal, amounts to $36.5 billion, a total that can only increase unless the general public can reduce its blood pressure and cholesterol. By eliminating risk factors, people help themselves reduce future risks, as one of the greatest risk factors for stroke is having already suffered one.

The National Stroke Association calls stroke recovery a “lifelong process.” Even with extensive mental, physical, and emotional training, not everyone returns to their normal selves. However, new findings suggest your likelihood will probably be higher than previous generations’.

Source: Magnusson J, Göritz C, Tatarishvili J, et al. A latent neurogenic program in astrocytes regulated by Notch signaling in the mouse. Science. 2014.

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