Maarja A Mäe1, Liqun He1,2, Sofia Nordling1,3, Elisa Vazquez-Liebanas1, Khayrun Nahar1, Bongnam Jung1, Xidan Li4, Bryan C Tan5, Juat Chin Foo6, Amaury Cazenave-Gassiot6,7, Markus R Wenk6,7, Yvette Zarb8, Barbara Lavina1, Susan E Quaggin9, Marie Jeansson1,4, Chengua Gu10, David L Silver5, Michael Vanlandewijck1,4, Eugene C Butcher3, Annika Keller8, Christer Betsholtz1,4. 1. Department of Immunology, Genetics, and Pathology, Rudbeck Laboratory, Uppsala University, Sweden (M.A.M., L.H., S.N., E.V.-L., K.N., B.J., B.L., M.J., M.V., C.B.). 2. Neurosurgery, Tianjin Medical University General Hospital, Tianjin Neurological Institute, Key Laboratory of Post-Neuroinjury Neuro-Repair and Regeneration in Central Nervous System, Ministry of Education and Tianjin City, China (L.H.). 3. Pathology, Stanford University School of Medicine, CA (S.N., E.C.B.). 4. Integrated Cardio Metabolic Center (ICMC) and Department of Medicine Huddinge, Karolinska Institutet Campus Flemingsberg, Sweden (X.L., M.J., M.V., C.B.). 5. Duke-NUS Medical School, Singapore (B.C.T., D.L.S.). 6. Singapore Lipidomics Incubator (SLING), Life Sciences Institute (J.C.F., A.C.-G., M.R.W.), National University of Singapore. 7. Biochemistry, Yong Loo Lin School of Medicine (A.C.-G., M.R.W.), National University of Singapore. 8. Neurosurgery, Clinical Neuroscience Centrum, Zürich University Hospital, Zürich University (Y.Z., A.K.). 9. Medicine, Northwestern University, Feinberg School of Medicine, Chicago, IL (S.E.Q.). 10. Neurobiology, Harvard Medical School, Boston, MA (C.G.).
Abstract
RATIONALE: Pericytes are capillary mural cells playing a role in stabilizing newly formed blood vessels during development and tissue repair. Loss of pericytes has been described in several brain disorders, and genetically induced pericyte deficiency in the brain leads to increased macromolecular leakage across the blood-brain barrier (BBB). However, the molecular details of the endothelial response to pericyte deficiency remain elusive. OBJECTIVE: To map the transcriptional changes in brain endothelial cells resulting from lack of pericyte contact at single-cell level and to correlate them with regional heterogeneities in BBB function and vascular phenotype. METHODS AND RESULTS: We reveal transcriptional, morphological, and functional consequences of pericyte absence for brain endothelial cells using a combination of methodologies, including single-cell RNA sequencing, tracer analyses, and immunofluorescent detection of protein expression in pericyte-deficient adult Pdgfbret/ret mice. We find that endothelial cells without pericyte contact retain a general BBB-specific gene expression profile, however, they acquire a venous-shifted molecular pattern and become transformed regarding the expression of numerous growth factors and regulatory proteins. Adult Pdgfbret/ret brains display ongoing angiogenic sprouting without concomitant cell proliferation providing unique insights into the endothelial tip cell transcriptome. We also reveal heterogeneous modes of pericyte-deficient BBB impairment, where hotspot leakage sites display arteriolar-shifted identity and pinpoint putative BBB regulators. By testing the causal involvement of some of these using reverse genetics, we uncover a reinforcing role for angiopoietin 2 at the BBB. CONCLUSIONS: By elucidating the complexity of endothelial response to pericyte deficiency at cellular resolution, our study provides insight into the importance of brain pericytes for endothelial arterio-venous zonation, angiogenic quiescence, and a limited set of BBB functions. The BBB-reinforcing role of ANGPT2 (angiopoietin 2) is paradoxical given its wider role as TIE2 (TEK receptor tyrosine kinase) receptor antagonist and may suggest a unique and context-dependent function of ANGPT2 in the brain.
RATIONALE: Pericytes are capillary mural cells playing a role in stabilizing newly formed blood vessels during development and tissue repair. Loss of pericytes has been described in several brain disorders, and genetically induced pericyte deficiency in the brain leads to increased macromolecular leakage across the blood-brain barrier (BBB). However, the molecular details of the endothelial response to pericyte deficiency remain elusive. OBJECTIVE: To map the transcriptional changes in brain endothelial cells resulting from lack of pericyte contact at single-cell level and to correlate them with regional heterogeneities in BBB function and vascular phenotype. METHODS AND RESULTS: We reveal transcriptional, morphological, and functional consequences of pericyte absence for brain endothelial cells using a combination of methodologies, including single-cell RNA sequencing, tracer analyses, and immunofluorescent detection of protein expression in pericyte-deficient adult Pdgfbret/ret mice. We find that endothelial cells without pericyte contact retain a general BBB-specific gene expression profile, however, they acquire a venous-shifted molecular pattern and become transformed regarding the expression of numerous growth factors and regulatory proteins. Adult Pdgfbret/ret brains display ongoing angiogenic sprouting without concomitant cell proliferation providing unique insights into the endothelial tip cell transcriptome. We also reveal heterogeneous modes of pericyte-deficient BBB impairment, where hotspot leakage sites display arteriolar-shifted identity and pinpoint putative BBB regulators. By testing the causal involvement of some of these using reverse genetics, we uncover a reinforcing role for angiopoietin 2 at the BBB. CONCLUSIONS: By elucidating the complexity of endothelial response to pericyte deficiency at cellular resolution, our study provides insight into the importance of brain pericytes for endothelial arterio-venous zonation, angiogenic quiescence, and a limited set of BBB functions. The BBB-reinforcing role of ANGPT2 (angiopoietin 2) is paradoxical given its wider role as TIE2 (TEK receptor tyrosine kinase) receptor antagonist and may suggest a unique and context-dependent function of ANGPT2 in the brain.
Authors: John C van Swieten; Bart J L Eggen; Emma Gerrits; Lucia A A Giannini; Nieske Brouwer; Shamiram Melhem; Danielle Seilhean; Isabelle Le Ber; Alwin Kamermans; Gijs Kooij; Helga E de Vries; Erik W G M Boddeke; Harro Seelaar Journal: Nat Neurosci Date: 2022-07-25 Impact factor: 28.771
Authors: Ryota L Matsuoka; Luke D Buck; Keerti P Vajrala; Rachael E Quick; Olivia A Card Journal: Cell Mol Life Sci Date: 2022-06-20 Impact factor: 9.207