Researchers have improved neuronal reprogramming by manipulating mitochondria

Replacing lost neurons is a sacred grail for neuroscience. The new promising approach is to transform glomerular cells into new neurons. Improving the efficiency of this conversion or re-programming after a brain injury is an important step towards the development of reliable regenerative drug therapy. Researchers from Helmholtz Zentrum M મchen and Ludwig Maximilians University Munich (LMU) have identified an obstacle to efficient transformation: cell metabolism. By expressing neuron-rich mitochondrial proteins at an early stage of the direct reprogramming process, the researchers achieved four times higher conversion rates and simultaneously increased the speed of reprogramming.

Neurons (nerve cells) have very important functions in the brain such as information processing. Many diseases of the brain, injuries and neurodegenerative processes, are characterized by loss of neurons that have not changed. Regenerative medicine approaches therefore aim to convert neurons into functional neurons through transplantation, stem cell differentiation, or direct conversion of endogenous neuronal cell types.

Researchers at Helmholtz Zentrum Manchen and LMU are at the forefront of direct transformation of globular cells into neurons, which they have found to be the origin. The glioma is the most abundant cell type in the brain and is spread by injury. Currently, researchers are able to convert glial cells into neurons – but many cells die during the process. This means that only a few glial cells are converted into functional nerve cells, disabling the process.

Exploring new approaches

Gaddafi and his team explored potential barriers to the transformation process and took a new approach: while most studies focus directly on the genetic aspects of neuronal reprogramming, they decided to study the role of mitochondria and cell metabolism in this process. His previous work with Helmholtz Zentrum Machin, in collaboration with Marcus Conrad’s group, was inspired by the fact that cells die due to over-reactive oxygen-oxygen species in the conversion process.

“We hypothesized that if we could help reprogram the metabolism of glial cells toward the metabolism of neurons, this conversion could improve efficiency,” explains Gianluca Russo, the study’s first author. Looking at their previous data, the researchers focused on the cell’s powerhouse, the mitochondria. The group compared their proteins in rat neurons and astrocytes (a specific type of glial cell) by studying their proteins in collaboration with a group of prototyping experts at the mitochondria Ca. Surprisingly, they found that the mitochondria of neurons and astrocytes differ in about 20 percent of their proteins. This means that mitochondrial proteins are different in every five between astrocytes and neurons.

Reprogrammed neurons activate mitochondrial proteins rich in late-stage neurons

“Knowing how different the mitochondrial proteins of neurons are from astrocytes, we needed to see if the converted neurons from astrocytes actually receive the mitochondrial protome of the neuron,” says Giacomo Masherdotti, co-author of the study. In the standard reprogramming process, glial cells, such as astrocytes, are converted into neurons in a few days and develop into functional neurons in two weeks. “It was surprising that the cells showed mitochondrial proteins, which are typical for neurons, only after a week, the regenerative process is relatively late. Most cells die before this time, so this can be a barrier. Those cells that failed to re-program, still expressed mitochondrial proteins rich in astrocytes. ”

With this new understanding, the researchers hypothesized that failure to turn on neuronal mitochondrial proteins could block the conversion process.

Improving and accelerating the conversion by metabolism

To overcome this obstacle, the group used CRISPR / KS9 technology in cooperation with the groups of Stephen Striker and Wolfgang Wurst at the Helmholtz Zentrum Machine. With new gene activation tools developed by this group, neuron-rich mitochondrial proteins can be activated in the neurons of astrocytes at an early stage of the reprogramming programming process. By manipulating just one to two mitochondrial proteins, the researchers found four times more reconstructed neurons. On top of that, neurons appear and mature rapidly, as revealed by continuous live imaging.

“I was amazed that changing the expression of a few mitochondrial proteins really speeds up reprogramming,” says Magdalena Gates, lead author of the study. “This shows just how important the cell-type-specific differences of mitochondrial proteins are. And indeed, with our proteom experts at Helholholtz Munich, we are looking for more organizer differences between cell types that reach 70 percent. This will pave the way for the brain in vivo.” To repair reprogrammed neurons that look like endogenous neurons even after injury. ”