Hello,

Primary microglia isolated from murine neonates retain substantially the characteristic amoeboid morphology of the microglia.

https://www.sciencellonline.com/mouse-microglia-490.html

A protocol for culture.

https://bio-protocol.org/e1989

From Jove, a visual protocol:

https://www.jove.com/t/57065/characterization-isolation-mouse-primary-microglia-density-gradient

This protocol allows to drive primary rat microglia into a highly ramified form, which is common in the brain.

https://www.jove.com/t/57122/isolation-culture-rodent-microglia-to-promote-dynamic-ramified

BV2 microglia are easy to culture, with either DMEM or RPMI supplemented with full serum. As described in the SI of our previous work:

http://www.rsc.org/suppdata/c5/sc/c5sc03855c/c5sc03855c1.pdf

Their morphology is comparable to mouse 264.7 cells, with fewer arborizations, and BV2 are about 2-3x the size of RAW 264.7 cells. Compared with primary cells, they look much more “featureless” (generally ovoid in shape). Only a small fraction show amoeboid shapes, and they almost never occur in ramified form in resting state.

If you are interested in BV2 differentiation, here’s a paper that can be consulted.

https://www.frontiersin.org/articles/10.3389/fncel.2019.00019/full

BV2 under LPS stimulation:

https://pubs.acs.org/doi/full/10.1021/acs.jafc.8b00437?rel=12408&utm_source=Axial&utm_medium=Partner&utm_campaign=Newsletter0718

Dear Nai-Kei Wong,

Thank you for the information.

What might be the reason for the difference compared to the primary cells regarding their ramified morphology at resting sate? Do you have any idea?

Regarding the differences between microglia cell lines and primary microglia in vitro and in vivo, I recommend the following paper by Butovsky et al. Identification of a unique TGF-β–dependent molecular and functional signature in microglia. https://www.nature.com/articles/nn.3599

Microglia cell lines and isolated microglia do not display the same transcriptional profile or functions as those in vivo. Signals from neuronal cell types are required. Morphologically, isolated mouse microglia adopt an amoeboid, macrophage-like shape, while microglia in co-culture with cortical neurons gradually adopt an intermediate to ramified phenotype, in our hands. I haven't worked with BV2s, but I suspect they would look more like monocyte or macrophages, and would not be very useful if your readout is morphology.

Dear Dr. Colleen,

Thank you very much for the response and really appreciate it. I will go the paper. As you mentioned, during the resting stages of the monoculture, BV2 cells possess macrophage like morphology. I thought that as a problem with the cell conditions. Now I can understand that the microglia are behaving differently in monocultures than in the in-vivo systems. Thank you again for the great explanation.

You are welcome, I am happy to help!

The morphological changes almost certainly are tied to molecular differences in gene expression profile, as well as the fact that in vivo, microglia resides in a mixed cell environment replete with trophic and signaling factors, whereas in vivo, cells are grown in generic or artificial culture environment.

A recent paper in Neuron discusses key factors regulating microglial ramifications (downloadable). Article Microglial Ramification, Surveillance, and Interleukin-1β Re...

You can also take a look at older works discussing microglial morphological regulation.

https://www.karger.com/Article/PDF/51020

Article In vitro model of microglial deramification: Ramified microg...

https://www.frontiersin.org/articles/10.3389/fncel.2018.00106/full

Dear Dr Wong,

Thank you very much again for the great explanation.