The utility of iPSC-derived microglia for research and drug discovery
We are joined by Project Manager, Jessica Tilman. Jess is deeply involved in both microglia-based product development and delivery of service projects.
Dr Tilman completed her PhD at Imperial College where she studied the macrophage phenotype in chronic obstructive pulmonary disease. At Axol Bioscience she works in the cellular science group, with a focus on microglia differentiation, manufacturing optimization and research into cell health, characterization and drug discovery. Jess regularly participates in custom service projects, testing compounds on healthy and disease lines.
For starters, can you please explain, what are microglia?
Microglia are the main immune cell found in the brain and spinal cord. They are a tissue resident macrophage which originate from progenitor cells in the yolk sac during embryonic development and contribute to homeostatic maintenance of neurons and other glial cells as well as contributing to inflammatory responses.
Microglia can exist in various states 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 essential for maintaining CNS homeostasis, responding to injury, and modulating the brain’s immune environment.
Key functions:
- Immune defence – microglia constantly monitor the CNS environment and respond to injury or disease by removing damaged cells, pathogens and debris via phagocytosis
- Synaptic pruning – during development, microglia help refine neural circuits by removing unnecessary synapses
- Regulation of inflammation – microglia release cytokines and other signalling 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?
Dysregulation of microglial activity is implicated in several neurological diseases including Alzheimer’s, Parkinson’s, Multiple Sclerosis and several psychiatric disorders. Various mechanisms are responsible for the role of microglia in neurodegeneration, including reduced phagocytosis of cell debris and pathogenic proteins such as beta-amyloid and TAU, but also a sustained state of activation. Activated microglia release pro-inflammatory mediators and are believed to aid in the propagation of protein aggregated, driving further degeneration.
What’s the involvement of microglia with Alzheimer’s Disease (AD)?
Microglia are thought to have a key role in the development of AD, often found in an activated state surrounding beta-amyloid plaques in the brain, which is a hallmark of the disease. Human genetics also demonstrate a crucial role for microglia in the pathogenesis of AD. Most genes identified as risk factors for AD are highly and sometimes selectively expressed in microglia, including TREM2, APOE and CD33. Dysfunctional microglia can drive excess inflammation, synapse loss and inability to update aggregated proteins and harmful cell debris.
How are iPSC cells manufactured?
At Axol we manufacture them to ISO 9001 standards to ensure high quality and consistency, at scale.
Can you generate microglia from patient donors?
Yes, definitely. Reprogrammed iPSC cells from donor samples (blood or skin fibroblasts) can be differentiated to produce microglia that retain the phenotypic characteristics of the donor. 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 for multiple applications including monoculture compound screening and in co-culture with neurons and astrocytes. We have several optimised assays which have been used extensively and are always open to developing new assays upon request.
Key assays:
- Phagocytosis (pHrodo labelled bait including beta-amyloid, dead neurons, myelin basic protein, S. aureus and more)
- Chemotaxis
- Cytokine release
How does Axol ensure quality control for iPSC-derived cells?
The first step is to ensure all iPSCs are high-quality and have passed our internal QC, including Karyotyping and the presence of pluripotency markers by flow cytometry. After differentiation to microglia, we utilize rigorous QC across the following parameters:
| 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 full Certificate of Analysis and are officially certified by HPSCreg®, to ensure ethical and biological conformity for your peace of mind.
How easy is it to use axoCells ourselves?
Our cells are simple to culture and are assay-ready 7 days post-thaw. User guides are available and all media can be purchased from Axol to ensure the cells are consistent with the data we have generated in-house. Technical support is always available should you encounter any issues or have specific questions.
