In ENTRAIN thirteen partners from the academic and private sector with complementary scientific background have joined forces. They have acquired a large number of tools and methods to explore the biology of brain endothelial cells and macrophages. Investigating key aspects of endothelial-macrophage interaction, they trained 14 Early Stage Researchers (ESRs) in experimental and translational research. Work was structured according to the direction of the interaction. WP1 focused on effects of endothelial cells on macrophages. WP2 took a reverse perspective and looked at macrophage effects on the blood-brain. Finally, WP3 aimed for pharmacological tools to modulate the mutual interaction. In a very fruitful kick-off meeting in Barcelona in October 2019 we have reinforced our close collaborations and coordinated the first steps for implementing the project. Due to the corona pandemic, the 2nd network meeting took place as an online meeting in May 2020. Also, the summer school was held as an online course (23.8. – 01.09.2021); it included the public symposium “Brain Vasculature & Immune System” that was very successfully organized by the ESRs. Finally, we were able to meet in person in Lübeck (20.02. – 24.02.2022) for a scientific update and a technical workshop. The ESRs had an additional technical workshop in Amsterdam (17.05. – 22.05.2022) before we met with scientific guests and invited speakers in Budapest for the Final Symposium of the consortium (28.09. – 30.09.2022). To compensate for restricted traveling, we established a monthly online seminar consisting of project report and journal club as well as an introductory lecture by one of the PIs. ENTRAIN ran for four years from 01.05.2019 until 30.04.2023.
The consortium ENTRAIN has made important discoveries. In WP1 “Endothelial checkpoints of macrophage function”, Kristina Berve, UNIBERN, has investigated the sex-dependent effects of angiopoietin-2 on CNS-resident macrophages and inflammatory myeloid cells. Sai Kiran Samawar Reddy, WWU, investigates how the basement membrane proteins laminin α4 and α5 impact on the immigration of myeloid cells into the inflamed CNS. Adria Dalmau Gasull, UKLFR, has established an imaging mass cytometry protocol to detect epigenetic markers in glial cells of the CNS. To explore the apicobasal polarisation of brain endothelial cells when orchestrating the immigration of immune cells into the CNS, Jacqueline Hammer, ETHZ, has set up proteomics tools and cell culture models of the blood-brain barrier. The cell biology work has been performed in close cooperation with VUMC. In WP2 “Modulation of endothelial function by macrophages”, Cathrin Hansen, VUMC, has explored the role of lipid mediators in the regulation of endothelial function and inflammation during MS and aging. Ana Rita Bras, IEM HAS, has characterized anatomical contacts between endothelial cells and brain macrophages by employing high-end imaging techniques. Tizibt Bogale, UNIBS, explored the role of α-synuclein in shaping the interaction between endothelial cells and brain macrophages. Martina Glavan, INSERM, employed advanced imaging techniques to analyse the role of perivascular macrophages in the pathogenesis of aneurysms. Joe Kelk, IRFMN, focused on the role of perivascular macrophages in models of ischemic stroke and characterized morphological aspects of these cells. Ümit Özorhan, UZL, investigated whether microglia and perivascular macrophages determine vessel density in a model of small vessel disease. In WP3 “Endothelial-macrophage interaction as a therapeutic target”, Arya Lekshmi Nair, MIM, has established a human neurovascular unit on-a-chip model to promote pharmacological studies. In a parallel endeavour, Ying-Chieh Wu has reconstituted in vitro blood-brain barrier models with cells derived from patient iPSCs. Dimitrios Spyropoulos, UZL, has studied the role of G protein signalling as a target of potential drugs that restore the blood-brain barrier. Last but not least, Sara Figuerola, CSIC, explored the interaction between perivascular macrophages and brain endothelial cells as a drug target focusing on exosomes.
Overall, the work in ENTRAIN has characterized the close interaction of brain macrophages and brain endothelial cells at a genetic, morphological, and functional level. New facets of the interaction have been identified. The consortium could elucidate some of the mechanisms underlying the joint dysfunction of endothelial cells and macrophages in brain diseases. The results suggest strategies for harnessing the new findings to improve blood-brain barrier function and to counteract inflammation and neurodegeneration. In addition, work in the consortium laid the foundation for new in vitro models of the interaction between blood-brain barrier and brain macrophages that will be commercialized.
