Reactive astrocyte nomenclature, definitions, and future directions
Carole Escartin, Elena Galea, András Lakatos, James P O'Callaghan, Gabor C Petzold, Alberto Serrano-Pozo, Christian Steinhäuser, Andrea Volterra, Giorgio Carmignoto, Amit Agarwal, Nicola J Allen, Alfonso Araque, Luis Barbeito, Ari Barzilai, Dwight E Bergles, Gilles Bonvento, Arthur M Butt, Wei-Ting Chen, Martine Cohen-Salmon, Colm Cunningham, Benjamin Deneen, Bart De Strooper, Blanca Díaz-Castro, Cinthia Farina, Marc Freeman, Vittorio Gallo, James E Goldman, Steven A Goldman, Magdalena Götz, Antonia Gutiérrez, Philip G Haydon, Dieter H Heiland, Elly M Hol, Matthew G Holt, Masamitsu Iino, Ksenia V Kastanenka, Helmut Kettenmann, Baljit S Khakh, Schuichi Koizumi, C Justin Lee, Shane A Liddelow, Brian A MacVicar, Pierre Magistretti, Albee Messing, Anusha Mishra, Anna V Molofsky, Keith K Murai, Christopher M Norris, Seiji Okada, Stéphane H R Oliet, João F Oliveira, Aude Panatier, Vladimir Parpura, Marcela Pekna, Milos Pekny, Luc Pellerin, Gertrudis Perea, Beatriz G Pérez-Nievas, Frank W Pfrieger, Kira E Poskanzer, Francisco J Quintana, Richard M Ransohoff, Miriam Riquelme-Perez, Stefanie Robel, Christine R Rose, Jeffrey D Rothstein, Nathalie Rouach, David H Rowitch, Alexey Semyanov, Swetlana Sirko, Harald Sontheimer, Raymond A Swanson, Javier Vitorica, Ina-Beate Wanner, Levi B Wood, Jiaqian Wu, Binhai Zheng, Eduardo R Zimmer, Robert Zorec, Michael V Sofroniew, Alexei Verkhratsky
Reactive astrocytes are astrocytes undergoing morphological, molecular, and functional remodeling in response to injury, disease, or infection of the CNS. Although this remodeling was first described over a century ago, uncertainties and controversies remain regarding the contribution of reactive astrocytes to CNS diseases, repair, and aging. It is also unclear whether fixed categories of reactive astrocytes exist and, if so, how to identify them. We point out the shortcomings of binary divisions of reactive astrocytes into good-vs-bad, neurotoxic-vs-neuroprotective or A1-vs-A2. We advocate, instead, that research on reactive astrocytes include assessment of multiple molecular and functional parameters-preferably in vivo-plus multivariate statistics and determination of impact on pathological hallmarks in relevant models. These guidelines may spur the discovery of astrocyte-based biomarkers as well as astrocyte-targeting therapies that abrogate detrimental actions of reactive astrocytes, potentiate their neuro- and glioprotective actions, and restore or augment their homeostatic, modulatory, and defensive functions.