Hello scientists friends,
I recently think a lot if research in microglia cell models are actually valuable. Everyone who works with microglia knows, that they are very problematic cells to research if they are isolated as primary culture. They are problematic to grow without astrocytes, they may react to media ingredients very sensitively giving different results, and they stick so hard to the plastic surface its always a pain to stick them out. Especially when you need a lot of cells that are in good condition for instance for flow cytometry. Not to mention that lots of mice has to be sacrifice to get enough of primary microglia cells for good results.
Luckily we have lots of microglia cell models available, however recently I can see a lot of criticism about usage model microglia cells, as they react differently to stimulation as compared to primary microglia. Recently I have found SIM-A9 cells interesting, as it is the cell line that immortalized itself spontaneously and is very easy to manage. But again I start to concern if the results obtained from them will be meaningful and possible to publish in a good journal.
What are your experiences and thoughts?
Thank you for your time and knowlegle.
Dear Dr. Urszula Kozlowska
Microglia research is rapidly developing and in future I hope we will be in a better position to understand microglia biology. The development of better cell culture models, as well as the development of activation protocols that are more relevant for neurodegenerative disorders may develop in the future.
As you rightly mentioned, it is a major challenge to provide dissociated microglia with the mix of environmental cues that they receive in vivo. Microglia has to be cultured in the presence of astrocyte-conditioned medium or on an astrocyte feeder layer that support microglia survival.
One approach which I think is to use 3D cell culture models in which one may use different CNS cells. One could provide a 3D matrix with CNS microenvironmental cues or to coat the plastic or glass substrate with a surface that mimics the natural physicochemical properties that enhance microglia homeostasis.
Microglial cell lines are available from mouse, rat, macaque and human origin. The major advantage of cell lines include their ease of maintenance and their abundant availability due to their unrestricted proliferative capacity. However, there are many disadvantages such as immortalization may alter the microglial phenotype resulting in cell lines that differ genetically and functionally from primary microglia. Transcriptomics have revealed key molecular differences between in vivo microglia and microglial cell lines. When microglia are removed from the brain and put into a plastic dish, they lose the brain-specific signals which is a part of their identity. Since the use of conventional cell culture conditions cannot replicate the complex milieu of the brain, microglial cell lines could be considered as poor representation of their in vivo counterparts.
When one chooses a microglial cell line, there are several factors one should take into consideration such as authenticity, species, method of immortalization, functional characteristics, and medium requirements.
To summarize, I would mention that microglial cell lines can be used to complement but not replace in vivo microglia.
Regards,
Malcolm Nobre
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