In this interview, Dr. Tilman explains the functions of iPSC-derived microglia and their relevance to conditions such as Alzheimer’s disease and other neurodegenerative diseases.
Can you please explain what microglia are?
Microglia are the primary immune cells found in the brain and spinal cord. They are tissue-resident macrophages that emerge from precursor cells in the yolk sac during embryonic development. They help maintain homeostasis of neurons and other glial cells while contributing to inflammatory responses.
Microglia can occur in different activation levels:
- Rest or survey condition: In the absence of pathology, microglia continuously scan the environment.
- Activated state: In response to injury or disease, microglia respond by altering their activity, releasing inflammatory mediators and phagocytic activity.
What is the function of microglial cells?
Microglia are critical for maintaining central nervous system homeostasis, responding to injury, and regulating the brain’s immune system.
Microglia provide several essential functions:
- Immune defense: Microglia continuously monitor the environment of the central nervous system and respond to injury or disease by removing damaged cells, pathogens, and debris via phagocytosis.
- Synaptic pruning: Microglia help refine neural circuits during development by removing unnecessary synapses.
- Regulation of inflammation: Microglia release cytokines and other signaling molecules to modulate inflammation in the central nervous system.
- Neuroprotection and repair: Microglia secrete neurotrophic factors and other beneficial molecules to support the survival and repair of neurons.
How are microglia involved in neurodegenerative diseases?
The dysregulation of microglial activity has been linked to a variety of neurological diseases, including Alzheimer’s disease, Parkinson’s disease, multiple sclerosis, and psychiatric disorders.
Microglia play a role in neurodegeneration through several processes, including reduced phagocytosis of cell debris and pathogenic proteins such as beta-amyloid and TAU and persistent activation.
Activated microglia release pro-inflammatory mediators and are thought to aid in the growth of protein aggregates, causing additional degeneration.
What role do microglia play in Alzheimer’s disease (AD)?
Microglia are believed to play a key role in the development of AD. They are often found in an activated state around beta-amyloid plaques in the brain, which is a hallmark of the disease.
Human genetics also shows that microglia play a crucial role in the etiology of AD. Most genes identified as risk factors for Alzheimer’s disease, including TREM2, APOE, and CD33, are highly and sometimes selectively expressed in microglia.
Dysfunctional microglia can cause excessive inflammation, loss of synapses, and the inability to update accumulated proteins and toxic cell waste.
How are iPSC microglia cells manufactured?
At Axol we produce them according to ISO 9001 standards to ensure excellent quality and consistency on a large scale.
Can you generate microglia from patient donors?
Reprogrammed iPSC cells from donor samples (blood or skin fibroblasts) can be differentiated to produce microglia that retain the donor’s phenotypic characteristics. We differentiated more than 30 iPSC lines to successfully generate microglia, including healthy, patient-derived and gene-edited cells.
What tests can you perform with microglia?
Microglia can be used in a variety of applications, including chemical screening in monoculture and co-culture with neurons and astrocytes. We have several optimized tests that are widely used and we are always willing to design new tests upon request.
Important tests using microglia include:
- Phagocytosis (pH-labeled baits, such as beta-amyloid, dead neurons, myelin basic protein, and S. aureus)
- Chemotaxis
- Cytokine release
How does Axol ensure quality control for iPSC-derived microglial cells?
The first step is to ensure that all iPSCs are of high quality and have passed our internal quality checks. This includes karyotyping and confirming the presence of pluripotency markers by flow cytometry.
Once differentiated by microglia, we implement strict quality controls on the following parameters:
Source: Axol Bioscience
| Test | Specification |
|---|---|
| Flow cytometry | Presence of lineage-specific markers and absence of pluripotency marker |
| Sterility* | Growth not detected |
| Mycoplasma | Not detected |
| Viability after the thaw | Register result |
| Viable cell count** | Register result |
| Markings by ICC | Presence of markers: IBA1, TMEM119, P2RY12, CX3CR1 |
*7 days of broth incubation
** Counted using CountessTM Automated Cell Counter
All cells come with a complete certificate of analysis and are officially approved by HPSCreg® to ensure ethical and organic compliance for your peace of mind.
What about functional QC for microglial cells?
We explored functional QC (fQC) as the next step in the quality chain, examining the usability and performance of cells in biologically relevant experiments. We expect that this new standard will increase confidence in the physiological relevance of our cells and improve translational power in advanced in vitro models.
How easy is it to use axoCellsT.M microglia themselves?
axoCells iPSC-derived microglia are easy to culture and ready for testing within seven days after thawing. User manuals are provided and all necessary media can be sourced from Axol to ensure consistency with internal data. Technical support is always available for any problems or specific questions.
About Jessica Tilman
Jessica Tilman, Scientific Group Leader, plays a critical role in developing microglia-based products and implementing service programs. She completed her Ph.D. at Imperial College London, where she investigated the macrophage phenotype in chronic obstructive pulmonary disease.
Dr. Tilman now works in the Cellular Science group at Axol Bioscience, focusing on microglia differentiation, production optimization, cell health, characterization and drug development.
She is also actively involved in tailor-made initiatives, where substances are assessed on healthy and diseased cell lines.