Study Identifies Altered Immune Signaling Pathway in Brain Cells from People with Bipolar Disorder
Researchers used iPSC-derived cortical networks from 12 bipolar disorder patients and 12 healthy controls to identify 191 dysregulated biological pathways, with the toll-like receptor (TLR) signalling pathway notably downregulated in bipolar disorder. iPSC technology allows scientists to study living human brain cells that retain each donor's genetic profile, enabling controlled comparisons not possible with post-mortem tissue. The findings suggest immune dysregulation — not just neurotransmitter imbalance — may be a core feature of bipolar disorder's biology, potentially opening new therapeutic targets.
A preprint study posted to bioRxiv used induced pluripotent stem cell (iPSC)-derived cortical networks — co-cultures of neurons and astrocytes — from 12 individuals with bipolar disorder (BD) and 12 healthy controls to investigate the molecular underpinnings of the condition. Peripheral blood mononuclear cells were reprogrammed into iPSCs using episomal vectors, then differentiated into neural progenitor cells and matured into cortical networks expressing neuronal and astrocyte markers. Whole transcriptome sequencing was performed on the Illumina NovaSeq X platform, and differential expression analysis using DESeq2 identified 191 enriched pathways in BD. Among these, the toll-like receptor (TLR) signalling pathway — a key component of innate immune response — was found to be downregulated in bipolar disorder and was selected for deeper investigation. The authors conclude that immune dysregulation, particularly within the TLR pathway, plays a significant role in BD pathophysiology, framing the immune system as a complex signalling network rather than a peripheral factor. This work adds to a growing body of evidence implicating neuroinflammation in bipolar disorder and may inform future drug development strategies targeting immune pathways.
What's missing
As a preprint, this study has not yet undergone peer review. Key limitations include the small sample size (12 per group), which limits statistical power and generalizability. The functional consequences of TLR pathway downregulation — whether causal or compensatory — are not established. Additionally, iPSC-derived cortical networks may not fully recapitulate the complexity of in vivo brain tissue, and the degree to which in vitro transcriptomic findings translate to living patients remains uncertain.
What different sources said
- bioRxivCenter
The toll-like receptor signalling pathway is altered in iPSC-derived cortical networks from people with bipolar disorder.
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