Researchers at the Hopkins School of Medicine have discovered a link between electrical stimulation and the ability to repair damaged brain matter. Focusing on an important type of brain cell called oligodendrocytes, they were able to build on previous research involving electrical stimulation and recovery of damaged brain tissue.
Oligodendrocytes are a type of auxiliary cell found in the brain. They produce the myelin sheaths that wrap around the parts of brain cells responsible for transmitting messages to other parts of the nervous system and the body. Myelin is a fatty substance that acts as an electrical insulator to improve the speed and accuracy of message transmission in the brain. It coats the axon, an elongated part of the brain cell, along which messages in the form of electrical impulses travel. Myelin is also important to brain physiology — its color is the basis of the term "white matter."
Low myelin is characteristic of many neurodegenerative disorders, including multiple sclerosis. Patients have scarred myelin sheaths, which cause electrical signals to be transmitted erratically or not at all.
Previous studies have linked light exposure to myelin production by oligodendrocytes. Rearing mice in the dark and early opening of the eyes in newborn rabbits have shown an increase in myelin synthesis. A type of cell located in the optical nerve, the region connecting the brain to the eye, is a precursor directly responsible for the formation of oligodendrocytes in the brain.
It has also been found that electrical stimulation can support white matter development, and therefore myelin production, in laboratory cells and animal models. But the researchers further investigated this connection by observing the effect of electical stimulation on the viability of oligodendrocytes and the response of neurons to electrical impulses.
They created two samples containing OPC's, the precursor cells to oligodendrocytes found in the optic nerve. The cells were allowed to grow and differentiate over three days, then electrical stimulation was applied to one sample over the course of an additional seven days. They found that after electrical stimulation, there was a significantly higher number of oligodendrocytes in the sample as compared to the sample that did not receive any electrical stimulation.
Another pair of samples was created, these containing just cortical neurons, which are basic message transmitting cells of the brain. They found that there was no substantial difference in the number of oligodendrocytes between a sample exposed to electrical stimulation and a sample that wasn't. But when the cortical neurons were combined with a sample of OPC's, electrical stimulation resulted in more than double the number of oligodendrocytes than there were without stimulation.
Their results showed that while electrical stimulation could possibly increase the number of oligodendrocytes, the presence of neurons was essential to promote a significant increase in oligodendrocyte viability. Further, they showed that electrical stimulation had no negative effect on the ability of oligodendrocytes to proliferate and differentiate into viable myelin producing cells.
Other compounds were necessary for oligodendrocyte growth including insulin, interleukin-6 and apoptosis inhibition proteins. Insulin is a hormone that controls the level of sugar in the blood, while interleukin-6 is secreted by the immune system and has been shown to have many properties including fighting pneumonia in mice. Apoptosis inhibition proteins prevent cells from undergoing apoptosis – a controlled cell death mechanism that initiates when a cell becomes severely damaged.
The next step, according to the researchers, is to investigate how electrical stimulation can be used to improve the function of basic neurons and if it can also be used to promote repair of damages brain tissue in human patients.
