Researchers have detected mitochondrial abnormalities, and differences in neuronal firing, in young neurons from patients with bipolar disorder by using induced pluripotent stem-cell (iPSC) technology. These stem cells are created from patient’s skin cells (fibroblasts) or from patient’s white blood cells (lymphocytes). It is possible to take skin cells or white blood cells and reverse engineer them back to the state where they have the ability to grow into different types of cells (basically back to the very early embryo state when the original template cells are just beginning to turn into different types of cells.) Then these stem cells can be grown in the lab and encouraged to become neurons. By imaging these created neurons from people with and without bipolar disorder, researchers have seen a difference in neuron firing between people who respond to lithium treatment vs those who don’t respond to treatment. This hyperexcitability activity of young neurons in bipolar disorder was selectively reversed by lithium treatment only in neurons derived from patients who also responded to lithium treatment.
Mitochondria are structures found within all cell types, and they are the organelles that help provide energy for the cells, along with other important functions. Mitochondria contain their own DNA separate from the cell’s nuclear DNA. Mitochondria DNA is mainly inherited from the egg, therefore the maternal side of the family. In one study, in about 80% of the bipolar patients, hippocampal mitochondria were smaller than even the smallest of the control subjects’ mitochondria. The hippocampus is the elongated ridges on the floor of each lateral ventricle of the brain, thought to be the center of emotion, memory, and the autonomic nervous system. Differences in expression of the genes in the mitochondria were also found between subjects and controls. Is it possible then that a greater predisposition to bipolar disorder could be influenced by the maternal family side?
Brain research is complicated because tissue is difficult and dangerous to extract, and studying brain tissue after death doesn’t give us a good picture of cause and effect across the lifetime. In post-morteum brain tissue, abnormalities could be due to a number of different environmental exposures (such as drug treatment) or trauma such as concussions that are difficult to control in living subjects. A model that does not use living subjects is difficult to create.
However, researchers have been able to use stem cell from patients to create tissue in the lab for study. They can take stem cells and “engineer” them to create many different types of tissues; in this study they use patients’s stem cells to create neurons. The hyperexcitability of the neurons is one early indicator of bipolar disorder, and this model of iPSCs in this disease might be useful in developing new therapies and drugs aimed at its clinical treatment.
Here is a link to the study in Nature:
https://www.ncbi.nlm.nih.gov/pubmed/28242870
And a link to one of the earlier studies:
https://www.nature.com/nature/journal/v527/n7576/full/nature15526.html
Genetic Discovery SF 