Purchase this article with an account.
Saptarshi Biswas, Galina Bachay, Dale d Hunter, William J Brunken; Laminins Containing β2 and γ3 Chains Regulate Retinal Angiogenesis by Modulating Microglial Activation-Dependent TGF-β Pathway. Invest. Ophthalmol. Vis. Sci. 2015;56(7 ):52.
Download citation file:
© ARVO (1962-2015); The Authors (2016-present)
Microglia play important role in retinal angiogenesis by secreting pro- or anti-angiogenic cytokines. Here, we investigated the role of the laminins containing β2 and γ3 chains, an extracellular matrix (ECM) component, in activation of retinal microglia, and the effect of microglial activation state on retinal vascular development.
Microglial density and activation were studied anatomically. Microglial expression of TGF-β1 and endothelial expression of phospho-SMAD3 was analyzed at the vascular front and in the remodeling zone. Mitotic endothelial cell density was analyzed using immunohistochemistry and 3D reconstruction. Pharmaceutical manipulations of microglial activation were performed by intraperitoneal injection of bacterial cell wall lipopolysaccharide (LPS) or minocycline.
Previously, we showed that in Lamb2-/- mice endothelial proliferation is decreased and vasculature is hypobranched; the opposite effects were seen in Lamc3-/- mice. Here we ask if the TGF-β pathway is involved in the laminin knockout phenotype. In the superficial vascular plexus, microglial TGF-β1 expression is down-regulated in the laminin γ3-/- animals. Concomitantly, the number of phospho-SMAD3 positive endothelial cells is decreased. Microglial TGF-β1 expression and number of phospho-SMAD3 positive endothelial cells are increased in the laminin β2-/- retina. LPS-induced microglial activation, in WT retina, increased endothelial cell proliferation resulting in a denser vascular plexus that phenocopies the effects of laminin γ3 deletion on retinal vasculature. Moreover, microglial TGF-β1 expression level is also decreased in the LPS treated wild type retina compared to the saline treated control. In contrast, blocking microglial activation with minocycline in the laminin γ3-/- retina decreased endothelial cell proliferation, restoring the wild type vascular phenotype. LPS-induced activation of microglia in the laminin β2-/- pups increased endothelial cell proliferation resulting in a denser retinal vasculature proper compared to the saline treated control.
Our results suggest that the laminins containing the β2 and γ3 chains differentially regulate activation-dependent microglial TGF-β1 expression and endothelial cell proliferation via downstream TGF-β signals. β2 laminins have pro-angiogenic effects and γ3 laminins have anti-angiogenic ones.
This PDF is available to Subscribers Only