Differential Roles of TREM2+ Microglia in Anterograde and Retrograde Axonal Injury Models
Microglia are the main immune cells of the central nervous system (CNS), and they are devoted to the active surveillance of the CNS during homeostasis and disease. In the last years, the microglial receptor Triggering Receptor Expressed on Myeloid cells-2 (TREM2) has been defined to mediate several...
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| Format: | Article |
| Language: | English |
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Frontiers Media S.A.
2020-11-01
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| Series: | Frontiers in Cellular Neuroscience |
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| Online Access: | https://www.frontiersin.org/articles/10.3389/fncel.2020.567404/full |
| _version_ | 1818404194819768320 |
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| author | Gemma Manich Ariadna Regina Gómez-López Beatriz Almolda Nàdia Villacampa Mireia Recasens Kalpana Shrivastava Berta González Bernardo Castellano |
| author_facet | Gemma Manich Ariadna Regina Gómez-López Beatriz Almolda Nàdia Villacampa Mireia Recasens Kalpana Shrivastava Berta González Bernardo Castellano |
| author_sort | Gemma Manich |
| collection | DOAJ |
| description | Microglia are the main immune cells of the central nervous system (CNS), and they are devoted to the active surveillance of the CNS during homeostasis and disease. In the last years, the microglial receptor Triggering Receptor Expressed on Myeloid cells-2 (TREM2) has been defined to mediate several microglial functions, including phagocytosis, survival, proliferation, and migration, and to be a key regulator of a new common microglial signature induced under neurodegenerative conditions and aging, also known as disease-associated microglia (DAM). Although microglial TREM2 has been mainly studied in chronic neurodegenerative diseases, few studies address its regulation and functions in acute inflammatory injuries. In this context, the present work aims to study the regulation of TREM2 and its functions after reparative axonal injuries, using two-well established animal models of anterograde and retrograde neuronal degeneration: the perforant pathway transection (PPT) and the facial nerve axotomy (FNA). Our results indicate the appearance of a subpopulation of microglia expressing TREM2 after both anterograde and retrograde axonal injury. TREM2+ microglia were not directly related to proliferation, instead, they were associated with specific recognition and/or phagocytosis of myelin and degenerating neurons, as assessed by immunohistochemistry and flow cytometry. Characterization of TREM2+ microglia showed expression of CD16/32, CD68, and occasional Galectin-3. However, specific singularities within each model were observed in P2RY12 expression, which was only downregulated after PPT, and in ApoE, where de novo expression was detected only in TREM2+ microglia after FNA. Finally, we report that the pro-inflammatory or anti-inflammatory cytokine microenvironment, which may affect phagocytosis, did not directly modify the induction of TREM2+ subpopulation in any injury model, although it changed TREM2 levels due to modification of the microglial activation pattern. In conclusion, we describe a unique TREM2+ microglial subpopulation induced after axonal injury, which is directly associated with phagocytosis of specific cell remnants and show different phenotypes, depending on the microglial activation status and the degree of tissue injury. |
| first_indexed | 2024-12-14T08:36:17Z |
| format | Article |
| id | doaj.art-37cce1d9315747579833ca220f0cb889 |
| institution | Directory Open Access Journal |
| issn | 1662-5102 |
| language | English |
| last_indexed | 2024-12-14T08:36:17Z |
| publishDate | 2020-11-01 |
| publisher | Frontiers Media S.A. |
| record_format | Article |
| series | Frontiers in Cellular Neuroscience |
| spelling | doaj.art-37cce1d9315747579833ca220f0cb8892022-12-21T23:09:24ZengFrontiers Media S.A.Frontiers in Cellular Neuroscience1662-51022020-11-011410.3389/fncel.2020.567404567404Differential Roles of TREM2+ Microglia in Anterograde and Retrograde Axonal Injury ModelsGemma ManichAriadna Regina Gómez-LópezBeatriz AlmoldaNàdia VillacampaMireia RecasensKalpana ShrivastavaBerta GonzálezBernardo CastellanoMicroglia are the main immune cells of the central nervous system (CNS), and they are devoted to the active surveillance of the CNS during homeostasis and disease. In the last years, the microglial receptor Triggering Receptor Expressed on Myeloid cells-2 (TREM2) has been defined to mediate several microglial functions, including phagocytosis, survival, proliferation, and migration, and to be a key regulator of a new common microglial signature induced under neurodegenerative conditions and aging, also known as disease-associated microglia (DAM). Although microglial TREM2 has been mainly studied in chronic neurodegenerative diseases, few studies address its regulation and functions in acute inflammatory injuries. In this context, the present work aims to study the regulation of TREM2 and its functions after reparative axonal injuries, using two-well established animal models of anterograde and retrograde neuronal degeneration: the perforant pathway transection (PPT) and the facial nerve axotomy (FNA). Our results indicate the appearance of a subpopulation of microglia expressing TREM2 after both anterograde and retrograde axonal injury. TREM2+ microglia were not directly related to proliferation, instead, they were associated with specific recognition and/or phagocytosis of myelin and degenerating neurons, as assessed by immunohistochemistry and flow cytometry. Characterization of TREM2+ microglia showed expression of CD16/32, CD68, and occasional Galectin-3. However, specific singularities within each model were observed in P2RY12 expression, which was only downregulated after PPT, and in ApoE, where de novo expression was detected only in TREM2+ microglia after FNA. Finally, we report that the pro-inflammatory or anti-inflammatory cytokine microenvironment, which may affect phagocytosis, did not directly modify the induction of TREM2+ subpopulation in any injury model, although it changed TREM2 levels due to modification of the microglial activation pattern. In conclusion, we describe a unique TREM2+ microglial subpopulation induced after axonal injury, which is directly associated with phagocytosis of specific cell remnants and show different phenotypes, depending on the microglial activation status and the degree of tissue injury.https://www.frontiersin.org/articles/10.3389/fncel.2020.567404/fullIL-10 (interleukin-10)IL-6 (interleukin-6)phagocytosisproliferationneuroinflammationmicroglial clusters |
| spellingShingle | Gemma Manich Ariadna Regina Gómez-López Beatriz Almolda Nàdia Villacampa Mireia Recasens Kalpana Shrivastava Berta González Bernardo Castellano Differential Roles of TREM2+ Microglia in Anterograde and Retrograde Axonal Injury Models Frontiers in Cellular Neuroscience IL-10 (interleukin-10) IL-6 (interleukin-6) phagocytosis proliferation neuroinflammation microglial clusters |
| title | Differential Roles of TREM2+ Microglia in Anterograde and Retrograde Axonal Injury Models |
| title_full | Differential Roles of TREM2+ Microglia in Anterograde and Retrograde Axonal Injury Models |
| title_fullStr | Differential Roles of TREM2+ Microglia in Anterograde and Retrograde Axonal Injury Models |
| title_full_unstemmed | Differential Roles of TREM2+ Microglia in Anterograde and Retrograde Axonal Injury Models |
| title_short | Differential Roles of TREM2+ Microglia in Anterograde and Retrograde Axonal Injury Models |
| title_sort | differential roles of trem2 microglia in anterograde and retrograde axonal injury models |
| topic | IL-10 (interleukin-10) IL-6 (interleukin-6) phagocytosis proliferation neuroinflammation microglial clusters |
| url | https://www.frontiersin.org/articles/10.3389/fncel.2020.567404/full |
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