The role of iPSC-derived microglia in research and drug discovery

In this interview, Dr. Tilman explains the functions of iPSC-derived microglia and their relevance to diseases such as Alzheimer's and other neurodegenerative diseases.

Can you please explain what microglia are?

Microglia are the primary immune cells in the brain and spinal cord. They are tissue-bound macrophages that arise from precursor cells in the yolk sac during embryonic development. They help maintain the homeostasis of neurons and other glial cells while contributing to inflammatory responses.

Microglia can occur in different degrees of activation:

• Resting or observing 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 and releasing inflammatory mediators and phagocytic activities.

What is the function of microglia cells?

Microglia are critical for maintaining CNS homeostasis, responding to injury, and regulating the brain's immune system.

Microglia perform several important functions:

• Immune defense: Microglia constantly monitor the CNS environment and respond to injury or disease by removing damaged cells, pathogens and debris through phagocytosis.
• Synaptic pruning: Microglia help refine neuronal circuits during development by removing unnecessary synapses.
• Regulation of inflammation: Microglia release cytokines and other signaling molecules to modulate inflammation in the CNS.
• Neuroprotection and repair: Microglia secrete neurotrophic factors and other beneficial molecules to support the survival and repair of nerve cells.

What role do microglia play in neurodegenerative diseases?

Disturbed microglial activity is associated with numerous neurological diseases, including Alzheimer's, Parkinson's, multiple sclerosis and psychiatric disorders.

Microglia play a role in neurodegeneration through several processes, including impaired phagocytosis of cellular debris and pathogenic proteins such as beta-amyloid and TAU, as well as sustained activation.

Activated microglia release pro-inflammatory mediators and probably contribute to the growth of protein aggregates that lead to further degeneration.

What role do microglia play in Alzheimer's disease (AD)?

Microglia are thought to play a key role in the development of Alzheimer's disease. They are often found in an activated state around beta-amyloid plaques in the brain, a hallmark of the disease.

Human genetics also shows that microglia play a crucial role in the etiology of Alzheimer's disease. 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.

Microglial dysfunction can lead to excessive inflammation and synapse loss, as well as a failure to renew accumulated proteins and toxic cellular debris.

How are iPSC microglia cells produced?

At Axol, we manufacture them to ISO 9001 standards to ensure 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 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 tests can you do with microglia?

Microglia can be used in a variety of applications, including chemical screening of monocultures and co-culture with neurons and astrocytes. We have several optimized assays that have been widely used and are always ready to develop new assays upon request.

The most 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 microglia cells derived from iPSCs?

The first step is to ensure that all iPSCs are of high quality and have passed our internal quality controls, including karyotyping and confirmation of the presence of pluripotency markers by flow cytometry.

Once the microglia are differentiated, we perform strict quality control based on the following parameters:

Source: Axol Bioscience

*7 days broth incubation
**Counted with CountessTM Automated Cell Counter

All cells are supplied with a full certificate of analysis and are officially approved by HPSCreg^® to ensure ethical and biological compliance for your peace of mind.

What about the functional quality control of microglial cells?

We are exploring functional quality control (fQC) as the next step in the quality chain, assessing the usability and performance of cells in biologically relevant experiments. We expect this new standard to increase confidence in the physiological relevance of our cells and improve translational performance in advanced in vitro models.

How easy is it to use axoCells^TM Microglia themselves?

Microglia derived from axoCells iPSCs are easy to culture and ready for testing within seven days of thawing. User manuals are provided and all required media can be purchased from Axol to ensure consistency with internal data. If you have any problems or specific questions, technical support is always available.

About Jessica Tilman

Jessica Tilman, scientific group leader, plays a key role in the development of microglia-based products and implementation of service programs. She completed her PhD at Imperial College London, where she researched the macrophage phenotype in chronic obstructive pulmonary disease.

Dr. Tilman now works in the Cell Science group at Axol Bioscience, focusing on microglial differentiation, manufacturing optimization, cell health, characterization and drug development.

In addition, she is actively involved in customer-specific service initiatives and evaluates substances on healthy and diseased cell lines.