Vascular basement membrane laminins contribute to the functional integrity of the blood vessels
Tushar Deshpande 1 *, Jula Huppert 1 *†, Sai-Kiran Samawar 1 , Kishan Kapupara 1 , Sharang Ghavampour 1§ , Jian Song 1 , Ralf Adams 2 , Hyun-Woo Jeong 2 , Lydia Wachsmuth 3 , Cornelius Faber 3 , Lingzhang Meng 1 , Jens Soltwisch 4 , Melanie-Jane Hannocks 1 , Rupert Hallmann 1 and Lydia Sorokin 1
The neurovascular unit (NVU) is the interconnection between the blood vessels and the surrounding neurons and is constituted by several cell layers, including endothelium, perivascular cells, astrocytes, and neurons, but also acellular layers that are mainly basement membranes (BMs). BMs underlie endothelium, encase pericytes and smooth muscle cells and mark the pial border and, as such, are in contact with several cellular layers of the NVU. Laminins are essential components of vascular BMs, but little is known about their contribution to the NVU. In the brain, laminin α4 and α5 occur in endothelial and mural BMs. To define their contribution to NVU integrity, we analysed blood vessel enriched, neuron depleted samples from laminin α4 knock out (Lama4 -/- ) and endothelial-specific laminin α5 knock out (Tek-cre:Lama5 -/- ) mice using single cell RNA sequencing. The data was clustered into endothelial, mural and myeloid cell types and unsupervised clustering revealed several sub-types of each category that were altered in the laminin knock out mice. Lama4 -/- endothelium showed enhanced large artery and reduced postcapillary venule sub-clusters. Accordingly, mural cells of Lama4 -/- mice presented augmented contractile gene signatures. Although devoid of laminin expression, resident myeloid cells exhibited an activated phenotype in Lama4 -/- . Analysis of Tek-cre:Lama5 -/- samples exhibited the opposite molecular and cellular phenotype to Lama4 -/- , with enhanced postcapillary venule marker expression and reduced contractile nature of perivascular cells. However myeloid cell populations were not altered in Tek-cre:Lama5 -/- samples compared to WT controls. Our data suggest direct and indirect roles for vascular laminins in the intercommunication between the endothelium, mural cells and myeloid populations associated with the arterial wall, all of which are required for the functional integrity of the NVU.
1 Institute of Physiological Chemistry and Pathobiochemistry and Cells-in-Motion Interfaculty Centre (CiMIC), University of Muenster, Germany;
2 Department of Tissue Morphogenesis, Max-Planck-Institute for Molecular Biomedicine, Muenster, Germany.
3 Clinical Radiology, University of Muenster, Germany;
4 Institute of Hygiene, University of Muenster, Germany