It is unclear what causes bipolar disorder - a condition characterized by dramatic changes in mood. But researchers from the University of Michigan Medical School have created the first stem cell model for bipolar disorder, which they say could uncover the origins of the condition and open the door to new treatments.
The research team recently published their study in the journal Translational Psychiatry.
To reach their findings, the investigators obtained skin samples from people with bipolar disorder, alongside skin samples from individuals without the condition.
By exposing small samples of skin cells to carefully controlled conditions, the researchers turned them into induced pluripotent stem cells (iPSCs). These are stem cells that have the potential to be turned into any other type of cell. The team then turned the iPSCs into neurons.
They measured gene expression of the iPSCs and then re-evaluated gene expression once the stem cells became neurons.
From this, the team found significant differences between the stem cells taken from bipolar patients and those taken from individuals without the condition.
Bipolar patients 'express more genes for calcium signaling'
The stem cell lines were made from the skin of bipolar patients.
Image credit: University of Michigan Medical School
The researchers found that the neurons from bipolar patients expressed more genes for membrane receptors and ion channels than the neurons from non-bipolar patients - particularly genes for receptors and channels involved in sending and receiving calcium signals between cells.
Since calcium signals play a significant role in neuron development and function, the investigators say their findings suggest that genetic differences in early brain development may contribute to the development of bipolar and other mental health conditions later in life.
When the researchers exposed the neurons to lithium - a chemical that bipolar patients often use to regulate their mood - signaling patterns changed.
The researchers explain that lithium changes how calcium signals are sent and received, so these new cell lines will allow them to determine the mechanisms behind this in cells specific to bipolar patients.
The team also found that the neurons from bipolar patients were "addressed" differently during development than those from non-bipolar patients, meaning signaling could be misdirected. They say this could affect brain development.
Furthermore, the researchers found differences in microRNA expression - small RNA fragments that play an important role in "reading" genes - in the cells of bipolar patients. The teams says this discovery supports the idea that bipolar disorder develops from a "combination of genetic vulnerabilities."
In the video below, the researchers talk about their findings:
Potential for personalized bipolar treatment
Bipolar disorders affects approximately 5.7 million adults in the US every year.
At present, the condition can be treated with various medications, such as mood stabilizers, antidepressants and antipsychotics. But like most drugs, not all patients respond to them in the same way and many are left with uncontrolled symptoms.
Study author Melvin McInnis, of the Department of Psychiatry at the University of Michigan Medical School, says this stem cell model could lead to personalized treatment for bipolar disorder.
"We're very excited about these findings. But we're only just beginning to understand what we can do with these cells to help answer the many unanswered questions in bipolar disorder's origins and treatment.
For instance, we can now envision being able to test new drug candidates in these cells, to screen possible medications proactively instead of having to discover them fortuitously."
The researchers are already in the process of creating more stem cell lines from other bipolar patients. They plan to share their cell lines with other investigators to enable future research of bipolar disorder, and they hope to create a way to use the lines to screen drugs for the condition.
Medical News Today recently reported on a study detailing the discovery of two new genetic regions connected to bipolar disorder.