Biswas Saptarshi, Bachay Galina, Chu Julianne, Hunter Dale D, Brunken William J
Department of Ophthalmology, State University of New York Upstate Medical University, Syracuse, New York; Department of Ophthalmology, State University of New York Downstate Medical Center, Brooklyn, New York; Center for Vision Research, Syracuse, New York.
Department of Ophthalmology, State University of New York Downstate Medical Center, Brooklyn, New York.
Am J Pathol. 2017 Sep;187(9):2112-2127. doi: 10.1016/j.ajpath.2017.05.016. Epub 2017 Jul 8.
Retinal vascular diseases are among the leading causes of acquired blindness. In recent years, retinal microglia have been shown to influence vascular branching density and endothelial cell proliferation. However, how microglial recruitment and activation are regulated during development remains unclear. We hypothesized that microglial recruitment, activation, and down-stream signaling are modulated by components of the mural basement membrane. We used a reverse genetic approach to disrupt laminin expression in the vascular basement membrane and demonstrate that microglia respond to the mural basement membrane in an isoform-specific manner. Microglial density is significantly increased in the laminin γ3-null (Lamc3) retinal superficial vascular plexus and consequently the vascular branching density is increased. Microglia also respond to astrocyte-derived matrices and become hyperactivated in the Lamc3 retina or when tested in vitro with cell-derived matrix. Pharmacological activation of microglia in the wild-type retina produced an Lamc3-like vascular phenotype, whereas pharmacological blocking of microglial activation in the Lamc3 retina rescued the wild-type vascular phenotype. On the molecular level, microglial transforming growth factor-β1 expression is down-regulated in the Lamc3 retina, and SMAD signaling decreased in endothelial cells with a consequent increase in endothelial proliferation. The reverse effects were seen in the Lamb2 retina. Together, our results demonstrate a novel mechanism by which laminins modulate vascular branching and endothelial cell proliferation during retinal angiogenesis.
视网膜血管疾病是后天性失明的主要原因之一。近年来，已证实视网膜小胶质细胞会影响血管分支密度和内皮细胞增殖。然而，在发育过程中，小胶质细胞的募集和激活是如何被调控的仍不清楚。我们推测，小胶质细胞的募集、激活及下游信号传导受壁层基底膜成分的调节。我们采用反向遗传学方法破坏血管基底膜中层粘连蛋白的表达，并证明小胶质细胞以亚型特异性方式对壁层基底膜作出反应。在层粘连蛋白γ3基因敲除（Lamc3）小鼠的视网膜浅层血管丛中，小胶质细胞密度显著增加，因此血管分支密度也增加。小胶质细胞也会对星形胶质细胞衍生的基质作出反应，并在Lamc3视网膜中或在体外与细胞衍生基质一起检测时变得过度激活。在野生型视网膜中对小胶质细胞进行药理激活会产生类似Lamc3的血管表型，而在Lamc3视网膜中对小胶质细胞激活进行药理阻断则可挽救野生型血管表型。在分子水平上，Lamc3视网膜中小胶质细胞转化生长因子-β1的表达下调，内皮细胞中的SMAD信号传导减少，从而导致内皮细胞增殖增加。在Lamb2视网膜中则观察到相反的效果。总之，我们的结果证明了一种新的机制，即层粘连蛋白在视网膜血管生成过程中调节血管分支和内皮细胞增殖。
