Neural stem cells of the developing rodent brain perform self-renewal and also produce cells that are destined to become neurons. The stem cells receive direction as to how frequently they reproduce and what cell type they create. The signals that send those directions have been unclear, however. This new work shows how important blood vessels are in this process.
"We found that blood vessels play a vital role in telling neural stem cells when and how to reproduce," explained the lead author of the work, Mathew Tata of the UCL Institute of Ophthalmology. "We examined neural stem cell behaviour in the brainstem of mice lacking the blood vessel protein NRP1, because this part of the brain is particularly important to control fundamental processes such as breathing and heart rate.”
The researchers used genetically altered mice in their work. “Preventing blood vessel growth in the neurogenic areas of the brainstem interfered with normal neuron production, causing neural stem cells to lose their ability to reproduce. As a result the stem cells disappeared from the brainstem before its growth was complete, so mice lacking NRP1 ended up with smaller brainstems," said Tata.
The investigators have shown that blood vessels play critical roles not only in supplying the developing brain with oxygen, but also in stem cell signaling and how stem cells are regulated.
"Blood vessels are best known for their important function in supplying oxygen and nutrients to the brain," said senior author Christiana Ruhrberg, also of the UCL Institute of Ophthalmology. "However, the most intriguing finding of this study was that blood vessels did not regulate neural stem cell behavior in the brainstem simply through their role in brain oxygenation or keeping brain tissue healthy. We found that blood vessels also provide important signals that allow stem cells to reproduce for a longer period of time, before they permanently become nerve cells that cannot multiply."
Sources: AAAS/Eurekalert! via UCL News, PNAS