Single and Compound Knock-outs of MicroRNA (miRNA)-155 and Its Angiogenic Gene Target CCN1 in Mice Alter Vascular and Neovascular Growth in the Retina via Resident Microglia

J Biol Chem. 2015 Sep 18;290(38):23264-81. doi: 10.1074/jbc.M115.646950. Epub 2015 Aug 4.


The response of the retina to ischemic insult typically leads to aberrant retinal neovascularization, a major cause of blindness. The epigenetic regulation of angiogenic gene expression by miRNAs provides new prospects for their therapeutic utility in retinal neovascularization. Here, we focus on miR-155, a microRNA functionally important in inflammation, which is of paramount importance in the pathogenesis of retinal neovascularization. Whereas constitutive miR-155-deficiency in mice results in mild vascular defects, forced expression of miR-155 causes endothelial hyperplasia and increases microglia count and activation. The mouse model of oxygen-induced retinopathy, which recapitulates ischemia-induced aberrant neovessel growth, is characterized by increased expression of miR-155 and localized areas of microglia activation. Interestingly, miR-155 deficiency in mice reduces microglial activation, curtails abnormal vessel growth, and allows for rapid normalization of the retinal vasculature following ischemic insult. miR-155 binds to the 3'-UTR and represses the expression of the CCN1 gene, which encodes an extracellular matrix-associated integrin-binding protein that both promotes physiological angiogenesis and harnesses growth factor-induced abnormal angiogenic responses. Single CCN1 deficiency or double CCN1 and miR-155 knock-out in mice causes retinal vascular malformations typical of faulty maturation, mimicking the vascular alterations of miR-155 gain of function. During development, the miR-155/CCN1 regulatory axis balances the proangiogenic and proinflammatory activities of microglia to allow for their function as guideposts for sprout fusion and anastomosis. Under ischemic conditions, dysregulated miR-155 and CCN1 expression increases the inflammatory load and microglial activation, prompting aberrant angiogenic responses. Thus, miR-155 functions in tandem with CCN1 to modulate inflammation-induced vascular homeostasis and repair.

Keywords: angiogenesis; extracellular matrix protein; inflammation; microRNA (miRNA); retina.

Publication types

  • Research Support, N.I.H., Extramural
  • Research Support, Non-U.S. Gov't

MeSH terms

  • 3' Untranslated Regions / genetics
  • Animals
  • Cysteine-Rich Protein 61 / genetics
  • Cysteine-Rich Protein 61 / metabolism*
  • Ischemia / genetics
  • Ischemia / metabolism
  • Ischemia / pathology
  • Mice
  • Mice, Knockout
  • MicroRNAs / genetics
  • MicroRNAs / metabolism*
  • Microglia / metabolism*
  • Microglia / pathology
  • Retina / metabolism*
  • Retina / pathology
  • Retinal Neovascularization / genetics
  • Retinal Neovascularization / metabolism*
  • Retinal Neovascularization / pathology
  • Retinal Vessels / metabolism*
  • Retinal Vessels / pathology


  • 3' Untranslated Regions
  • CCN1 protein, mouse
  • Cysteine-Rich Protein 61
  • MicroRNAs
  • Mirn155 microRNA, mouse