Nerve-Blood Vessel Coordination During Development Revealed

Nerve cells require a significant amount of energy and oxygen to function properly, which they receive through the blood. This is why nerve tissue is typically filled with a large number of blood vessels, which provide these essential nutrients and oxygen to the cells. However, in collaboration with international partners, researchers at the Universities of Heidelberg and Bonn have discovered a mechanism that allows these two types of cells to coexist without getting in each other's way. The findings of their research have been published in the journal Neuron.

During embryonic development, both blood vessels and neurons are formed in the brain, spinal cord, and retina. These two processes mustn't interfere with each other, but the exact mechanisms behind this process have remained unclear. 

The team began by growing human brain cells in vitro, as well as collecting and studying mouse embryos at different stages of development. They also used a variety of techniques to analyze the cells and tissues, including measuring the levels of certain molecules using qRT-PCR, detecting the presence and location of specific molecules in the tissues with in situ hybridization, and identifying the presence of certain proteins in the tissues using immunohistochemistry.

Additionally, the researchers used microscopes to examine the cells and tissues in more detail, allowing them to assess the development and function of nerve tissues at the molecular and cellular level.

By studying the formation of blood vessels in the spinal cord of mice, the researchers found that blood vessels do not grow in all directions between days 10.5 and 12.5 of development, despite the presence of growth-promoting molecules. During this time, large numbers of motor neurons migrate from their origin in the spinal cord to their final positions, forming extensions called axons that connect to various muscles.

The researchers discovered that the motor neurons use a protein called semaphorin 3C to send a "stop" message to the vascular cells, telling them to pause their growth. This protein docks onto a receptor called PlexinD1 on the vascular cells, allowing the neurons to grow without interference.

When the researchers stopped the production of semaphorin 3C in neurons or stopped the formation of PlexinD1 in vascular cells, the blood vessels formed prematurely and prevented the axons of the neurons from developing properly.

Overall, this discovery sheds light on the complex interactions between nerve cells and blood vessels and provides a deeper understanding of how these cells coexist and support each other during development. This knowledge could potentially be used to improve the development and repair of nerve tissue in the future.