Activation of both transforming growth factor-b and bone morphogenetic protein signalling pathways upon traumatic brain injury restrains pro-inflammatory and boosts tissue reparatory responses of reactive astrocytes and microglia Georgios Divolis, 1 Athanasios Stavropoulos, 1 Maria Manioudaki, 1 Anastasia Apostolidou, 1 Athanasia Doulou, 1 Ariana Gavriil, 1 Ioannis Dafnis, 2 Angeliki Chroni, 2 Christine Mummery, 3 Maria Xilouri 1 and Paschalis Sideras 1 Various ligands and receptors of the transforming growth factor-b superfamily have been found upregulated following traumatic brain injury; however, the role of this signalling system in brain injury pathophysiology is not fully characterized. To address this, we utilized an acute stab wound brain injury model to demonstrate that hallmarks of transforming growth factor-b superfamily system activation, such as levels of phosphorylated Smads, ligands and target genes for both transforming growth factor-b and bone morphogenetic protein pathways, were upregulated within injured tissues. Using a bone morphogenetic protein-responsive re- porter mouse model, we showed that activation of the bone morphogenetic protein signalling pathway involves primarily astro- cytes that demarcate the wound area. Insights regarding the potential role of transforming growth factor-b superfamily activation in glia cells within the injured tissues were obtained indirectly by treating purified reactive astrocytes and microglia with bone mor- phogenetic protein-4 or transforming growth factor-b1 and characterizing changes in their transcriptional profiles. Astrocytes responded to both ligands with considerably overlapping profiles, whereas, microglia responded selectively to transforming growth factor-b1. Novel pathways, crucial for repair of tissue-injury and blood–brain barrier, such as activation of cholesterol biosynthesis and transport, production of axonal guidance and extracellular matrix components were upregulated by transforming growth fac- tor-b1 and/or bone morphogenetic protein-4 in astrocytes. Moreover, both ligands in astrocytes and transforming growth factor- b1 in microglia shifted the phenotype of reactive glia cells towards the anti-inflammatory and tissue reparatory ‘A2’-like and ‘M0/ M2’-like phenotypes, respectively. Increased expression of selected key components of the in vitro modulated pathways and markers of ‘A2’-like astrocytes was confirmed within the wound area, suggesting that these processes could also be modulated in situ by the integrated action of transforming growth factor-b and/or bone morphogenetic protein-mediated signalling. Collectively, our study provides a comprehensive comparative analysis of transforming growth factor-b superfamily signalling in reactive astro- cytes and microglia and points towards a crucial role of both transforming growth factor-b and bone morphogenetic protein path- ways in modulating the inflammatory and brain injury reparatory functions of activated glia cells. 1 Center for Clinical Research, Experimental Surgery and Translational Research, Biomedical Research Foundation of the Academy of Athens, 11527 Athens, Greece 2 Institute of Biosciences and Applications, National Center for Scientific Research-Demokritos, 15341 Athens, Greece 3 Department of Anatomy and Embryology, Leiden University Medical Center, 2333ZC Leiden, The Netherlands Received July 26, 2019. Revised September 24, 2019. Accepted October 7, 2019. Advance Access publication October 21, 2019 V C The Author(s) (2019). Published by Oxford University Press on behalf of the Guarantors of Brain. This is an Open Access article distributed under the terms of the Creative Commons Attribution Non-Commercial License (http://creativecommons.org/licenses/by-nc/4.0/), which per- mits non-commercial re-use, distribution, and reproduction in any medium, provided the original work is properly cited. For commercial re-use, please contact journals.permissions@oup.com B BR AIN COMMUNICATIONS AIN COMMUNICATIONS doi:10.1093/braincomms/fcz028 BRAIN COMMUNICATIONS 2019: Page 1 of 20 | 1 Downloaded from https://academic.oup.com/braincomms/article/1/1/fcz028/5601596 by guest on 15 October 2021