Vascular Basement Membrane Laminins Modulate  Functional Zonation of Cerebral Microvessels [RNA-seq]
We investigated whether vascular basement membrane (BM) laminins influence vascular zonation by performing single-cell RNA sequencing (scRNAseq) on cerebral blood vessels from Lama4-/- mice - lacking the major vascular laminin ?4 in endothelial and smooth muscle BMs - and wild-type littermates. Our dataset expands existing cerebral vascular transcriptomic profiles and reveals that Lama4-/- endothelial cells exhibit increased arterial marker expression and reduced postcapillary venule identity. In vitro and in vivo studies indicate that compensatory upregulation of laminin ?5  in Lama4-/- vessels enhances expression of junctional proteins (Ocln, Cldn5) and promotes vessel contractility via increased expression of contractile genes in pericytes, which reside within the endothelial BM. Additionally, loss of Lama4 upregulates expression of large artery markers (Gja4, Dll4, Edn1,Tgfb2) and resulted in elevated autotaxin (Enpp2) levels, a key enzyme in lysophosphatidic acid production implicated in stroke. Accordingly, Lama4-/- mice exhibit worsened stroke outcomes, driven not by immune infiltration or junctional defects, but by increased vascular permeability likely mediated by autotaxin and/or activation of resident myeloid cells. Our data suggest that laminin ?4/?5 ratios in vascular BMs regulate functional zonation between arterioles, capillaries and postcapillary venules by modulating metabolic pathways in endothelial and mural cells, and indirectly influencing resident myeloid cells. Overall design: Transient focal ischemia using the intraluminal filament model was performed on 12 week-old male mice. The left middle cerebral artery was occluded for 60 min and reperfusion was for 24h; ipsilateral (IL) brain hemispheres represent stroke samples and contralateral (CL) hemispheres were used as non-stroke controls.