Abstract
Purpose :
Vascular remodeling and arterial-venous specification are among the critical events required for proper retinal vascularization. Here, we used mouse retina as a model system to investigate the role of laminins containing γ3 chain, an extracellular matrix (ECM) component, in vascular remodeling and arterial-venous specification.
Methods :
Laminin g3 chain deposition, artery-specific EphrinB2 expression, vein-specific EphB4 expression and astrocyte maturation state were analyzed using immunohistochemistry. Arterial branching, arterial smooth muscle coverage and vascular pruning were evaluated anatomically and quantified. Arterial Dll4 expression level was measured using quantitative fluorescent microscopy.
Results :
Morphologically, retinal arteries have smaller caliber with fewer branches. On the other hand, retinal veins have larger caliber with more branches. Atsrocytes associated with the retinal arteries and veins mature at different rates. Venous astrocytes retain PDGFRa expression, an immature astrocyte marker, through post-natal day 18 (P18). Here we asked if retinal arterial-venous identity specification is disrupted in the mice lacking laminin g3 chain (Lamc3-/-). We show that the laminin g3 chain is deposited on both arteries and veins during superficial retinal vascular plexus development (P5-P7). In the Lamc3-/- mice, retinal arteries bear twice as branches as those of WT arteries (101% increase; p=0.02). Peri-arterial vascular pruning, measured by the number of empty collagen sheaths, is significantly less extensive in the Lamc3-/- retinas than the WT (42% reduction; p=0.003). Additionally, vascular smooth muscle coverage of the arteries is reduced in the Lamc3-/- retinas (26% reduction; p=0.05). On the molecular level, arterial Dll4 expression level is significantly down-regulated (45% reduction; p=0.004) and artery-specific EphrinB2 expression is disrupted in the Lamc3-/- retinas. However, vein-specific EphB4 expression is unaffected in the retinas of these laminin mutants.
Conclusions :
Our results suggest that the laminins containing γ3 chain regulate vascular remodeling and arterial identity specification via Dll4/Notch signaling pathway during retinal angiogenesis.
This is an abstract that was submitted for the 2016 ARVO Annual Meeting, held in Seattle, Wash., May 1-5, 2016.