Dysregulated glial phenotypes and neuro-immune communication in neurodegenerative diseases
1Neuron Glia Biology in Health and Disease, Research Institute for Medicines (iMed.ULisboa), Faculty of Pharmacy, Universidade de Lisboa;
2Department of Biochemistry and Human Biology, Faculty of Pharmacy, Universidade de Lisboa, Lisbon, Portugal.
Amyotrophic Lateral Sclerosis (ALS) is the third most common neurodegenerative disease. ALS is strongly linked with neuron-glia deregulated communication, neuroinflammatory processes and miRNA dysregulation. To better understand such complex pathological interplay we used the SOD1G93A (mSOD1) mouse model at the presymptomatic (4-6 week-old) and symptomatic (12-14-week-old) stages. Loss of motor neurons (MNs), a hallmark of ALS disease, was only observed at the symptomatic stage in both spinal cord and cortical tissue homogenates (1, 2) and was accompanied by the expression of astrocyte aberrant markers. Only in the spinal cord, we observed downregulated glia interplay in the presymptomatic stage that preceded the inflammatory status at the symptomatic one. Depressed decrease of MFG-E8 and Arginase 1, as well as upregulation of miRNA(miR)-155, were observed as early and sustained markers, previously to the increase of miR-146a and miR-124. To identify the contribution of neural cells to such deregulated expression of miRNAs, we used mSOD1 NSC-34 MNs (3). Data showed that miR-124 is expressed by ALS MNs and is part of their extracellular vesicles (EVs) that when transferred to microglia cause heterogeneous activated phenotypes (4). Using 2 days in vitro (DIV) and 16 DIV mSOD1 spinal microglia (5), we certified early miR-155 elevation and MFG-E8 decrease, together with late miR-146a and miR-124 upregulation (unpublished). Activated microglia was not a feature in ALS cortical brain, but a downregulation of miR-146a was noticed in its atypical astrocytes (2), which showed to acquire early phenotypic aberrancies when isolated from 7 day-old mSOD1 mice, contrasting with those from the spinal cord (unpublished). To translate our findings to human cells, we directly converted ALS patient fibroblasts into induced astrocytes (iAstro). All of the iAStro from patients showed a neurotoxic phenotype over mouse HB9/GFP-positive MNs. Differential dysregulation of GFAP, Cx43, miR-155 and miR-146a was manifested by iAst subsets. In sum, new targets were discovered and astrocytes were shown to comprise heterogeneous populations with distinct properties that also depend from their anatomical region in ALS disease. Importantly, transdifferentiated astrocytes are highlighted as a powerful tool to uncover ALS pathological mechanisms, to stratify patients, and to test therapies toward precision medicine.
Funded by Fundação para a Ciência e a Tecnologia to D.B. (PTDC/MED-NEU/31395/2017 and LISBOA-01-0145-FEDER-031395), as well as by private donation from Santa Casa da Misericórdia de Lisboa (SCML) to D.B (ALS Research Grant ELA-2015-002).
1. Cunha et al. Mol Neurobiol 2018: 55; 4207-4224.
2. Gomes et al. Mol Neurobiol (in press, doi: 10.1007/s12035-018-1220-8).
3. Vaz et al. Mol Neurobiol 2015: 51; 864-877.
4. Pinto et al. Front Neurosci 2017: 11.
5. Caldeira et al. Front Cell Neurosci 2014: 8; 152.