Acute inflammatory response of glial cell co-culture to magnesium material

Abstract text (incl. figure legends and references)

Biodegradable Mg materials show good cytocompatibility and as an element, it is vital to all tissues including the brain. Mg ions play an important role in brain homeostasis and Mg deficiency has even been linked to low-grade neuroinflammation. Therefore, Mg materials could be used for biodegradable implant applications such as regenerative nerve electrodes [1] and drug-releasing implants [2]. Therefore, it is important to have an understanding of the foreign body response towards Mg material. In the brain, the microglia and astrocytes are the key players in the inflammatory response. Here, we used a co-culture of microglia (HMC3 cell line) and astrocytes (SV-40 immortalized line) in which, astrocytes were seeded directly onto Mg discs and the microglia were seeded on an insert. The cell proliferation was measured by a modified MTT-DMSO assay and the gene expression was analysed using qPCR at 24 h and 72 h post seeding. Both cell types proliferated in the presence of Mg, although there was a reduction in proliferation when compared to the control and the microglia (56% reduction) were more affected than the astrocytes (20% reduction). The astrocyte activation markers (FN1, TNC, NES, VIM) were not upregulated in response to Mg at the tested timepoints. Microglial IL-6 expression was upregulated in the co-culture at 24 h and it was reduced to normal levels at 72 h. Moreover, anti-inflammatory and protective factors - TGFb and GDNF - were upregulated in microglia at 72 h. The anti-apoptotic factor BCL2 was significantly downregulated in microglia at 24 h (-7.14) and the levels improved at 72 h (-1.65). The Mg concentration levels measured by ICP-OES revealed that the concentration in the supernatant increased up to 6 mM over 72 h of degradation. Overall, the results suggest a balanced inflammatory response of the glial co-culture to Mg material.

[1] Augello et al. 2015, doi:10.1016/B978-1-78242-078-1.00012-8

[2] Unbehau et al. 2020, doi:10.1016/j.actbio.2020.08.043