Scientists Use Rabies To Better Understand Bone Development

Researchers at the Hebrew University in Jerusalem have used the rabies virus in order to discover a new neural pathway from the brain, which affects bone development and density. The implications of this research could have great significance in treating osteoporosis and neural disorders.

The research, headed by Prof. Itai Bab, of the university’s bone laboratory, is published in the prestigious American science journal Proceedings of the National Academy of Sciences. Bab and his fellow researchers used a weakened version of the rabies virus for the experiment.

Although rabies usually brings about a negative connotation, since it is a lethal disease carried by wild animals, it also has the unique characteristic of following neural pathways to the brain. So the researchers monitored the virus’ path after injecting it into mice thigh bones, and discovered that it uses neural pathways which belong to the parasympathetic nervous system.

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The human nervous system uses two types of neural pathways for communication between the brain and other organs, known as the sympathetic and parasympathetic nervous systems. Up until recently, it was thought that the brain is connected to bones only through the sympathetic nervous system. However, this recent research suggests otherwise.

Understanding how the brain “talks” with the body

“The parasympathetic nervous system, alongside the sympathetic nervous system is a part of the autonomous nervous system”, explains Bab. “Both subsystems create the principal means of communication between the brain and the internal organs. Each subsystem has its own unique pathways. Researches done in the past decade have shown that bones are connected to the sympathetic nervous system, which sometimes slow down skeletal development, but there was no information on a parasympathetic pathway that reaches the skeleton”.

In the past, the same group of researchers has discovered that the activity of a certain protein (interleukin-1) also affects bone development. On this most recent research, the researchers found that the way this protein affects bone is almost identical to that of the parasympathetic nervous system. Hence, when the researchers shut down the protein’s activity in the brain, they discovered that bone development was hindered. In addition, they also found that the new neural pathway, which consists of the protein and the parasympathetic system, regulates the heartbeat.

“A new field of research”

This new discovery offers more information on the way the body builds bone density during adolescence and could offer further insight into treatment of related conditions. “Communication between the brain and the skeleton in general, and the involvement of the newly discovered neural pathway in particular, is a new field of research with very little information”, says Bab, “Our new findings show an important physiological function for the connection between interleukin-1 in the brain and the autonomous nervous system. It is probable that the new pathway has an important role in the functioning of other organs controlled by the autonomous nervous system, along with the skeleton and the heart”.

The research was conducted by Bab, alongside Prof. Raz Yirmiya, head of the laboratory for brain and behavioral research, research students Alon Bajayo and Vardit Kram and master’s degree students Arik Bar and Marilyn Bachar.

Photo by Trace Meek