Vascular Basement Membrane Laminins Modulate Functional Zonation of Cerebral Microvessels

We investigated whether vascular basement membrane (BM) laminins influence vascular zonation by performing single-cell RNA sequencing on cerebral blood vessels from mice lacking the major vascular laminins in endothelial and smooth muscle BMs, laminin α4 ( Lama4 ^-/- ) and laminin α5 ( Tek-cre:Lama5 ^-/- ), 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 α5 in Lama4 ^-/- vessels enhances expression of junctional proteins ( Ocln , Cldn5 ) and promotes vessel contractility via increased expression of contractile molecules in mural cells. Additionally, loss of Lama4 upregulates expression of large artery markers ( Gja4 , Dll4 , Tgfb2 ) and results 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 α4/α5 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.