In this interview, Dr. Tilman explains the functions of iPSC-derived microglia and their relevance to conditions like Alzheimer’s 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 progenitor cells in the yolk sac throughout embryonic development. They help maintain the homeostasis of neurons and other glial cells while contributing to inflammatory responses.
Microglia can occur in varied levels of activation:
- Resting or Surveying State: 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 CNS homeostasis, responding to injury, and regulating the brain's immune system.
Microglia provide various essential functions:
- Immune defense: Microglia constantly monitor the CNS environment 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 within the CNS.
- Neuroprotection and repair: Microglia secrete neurotrophic factors and other useful molecules to support neuronal survival and repair.
How are microglia implicated in neurodegenerative diseases?
The dysregulation of microglial activity has been linked to a variety of neurological diseases, including Alzheimer's, Parkinson's, Multiple Sclerosis, and psychiatric disorders.
Microglia play a role in neurodegeneration through various processes, including impaired 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, which causes additional degeneration.
What role does microglia play in Alzheimer’s Disease (AD)?
Microglia are thought to play a key role in the development of AD. They are often found in an activated state surrounding beta-amyloid plaques in the brain, which is a hallmark of the disease.
Human genetics also show that microglia play a critical role in the etiology of AD. Most of the 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, synapse loss, and a failure to update accumulated proteins and toxic cell debris.
How are iPSC microglia cells manufactured?
At Axol, we manufacture them to ISO 9001 standards to assure excellent quality and consistency at 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 have differentiated over 30 iPSC lines to successfully generate microglia, including healthy, patient-derived, and gene-edited cells.
What assays can you run using microglia?
Microglia can be used in a variety of applications, including monoculture chemical screening and co-culture with neurons and astrocytes. We have various optimized assays that have been extensively used, and we are always willing to design new assays on request.
Key assays 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 microglia cells?
The first step is to ensure that all iPSCs are of high quality and have passed our internal quality control checks. This includes karyotyping and confirming the presence of pluripotency markers through flow cytometry.
Once differentiated into microglia, we implement rigorous quality control across 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 |
| Post-thaw Viability |
Record result |
| Viable Cell Count** |
Record result |
| Markers by ICC |
Presence of markers: IBA1, TMEM119, P2RY12, CX3CR1 |
*7 day broth incubation
**Counted using CountessTM Automated Cell Counter
All cells come with a complete Certificate of Analysis and are officially approved by HPSCreg® to assure ethical and biological compliance for your peace of mind.
What about functional QC for microglia cells?
We have been exploring functional QC (fQC) as the next step in the quality chain, which involves examining the usability and performance of cells in biologically relevant experiments. We anticipate that this new standard will increase trust in our cells' physiological relevance and improve translational power in advanced in vitro models.
How easy is it to use axoCellsTM microglia ourselves?
axoCells iPSC-derived microglia are straightforward to culture and assay-ready within seven days after thawing. User manuals are provided, and all necessary media can be sourced from Axol to ensure consistency with the in-house data. Technical support is always available for any issues or specific questions.
About Jessica Tilman
Jessica Tilman, Scientific Group Leader, plays a crucial role in developing microglia-based products and implementing service programs. She completed her Ph.D. at Imperial College London, where she researched the macrophage phenotype in chronic obstructive pulmonary disease.
Dr. Tilman now works in the Cellular Science group at Axol Bioscience, focusing on microglia differentiation, manufacturing optimization, cell health, characterization, and drug development.
She is also actively involved in custom service initiatives, evaluating substances on healthy and diseased cell lines.
2024 is shaping up to be “the year of iPSCs"