Intravitreal injection of plasminogen kringle 5, an endogenous angiogenic inhibitor, arrests retinal neovascularization in rats

Diabetologia. 2001 Jun;44(6):757-65. doi: 10.1007/s001250051685.


Aims/hypothesis: Plasminogen kringle 5 is an endogenous angiogenic inhibitor. The purpose of the present study was to explore the potential application of kringle 5 in the treatment of retinal neovascularization.

Methods: Plasminogen kringle 5 was expressed in E. coli and affinity-purified. Its anti-angiogenic activity was determined in cultured primary human capillary endothelial cells. Retinal neovascularization was induced in newborn rats by exposure to hyperoxia and then normoxia. Kringle 5 was intravitreally injected into the rat model. Retinal neovascularization was visualized by fluorescein angiography on flat-mounted retina and quantified by counting preretinal vascular cells.

Results: Plasminogen kringle 5 inhibited primary endothelial cells but not retinal neuronal cells, suggesting cell type-specific inhibition. The oxygen-induced retinopathy rat model showed an over-expression of vascular endothelial growth factor, preretinal neovascularization and haemorrhage. Intravitreal injection of kringle 5 before the development of neovascularization resulted in fewer neovascular tufts and pre-retinal vascular cells than in control rats with PBS injection (p < 0.01). Moreover, injection of kringle 5 after the development of neovascularization inhibited the increase in the preretinal vascular cells (p < 0.05). These results suggest that kringle 5 both prevents the development and arrests the progression of retinal neovascularization. The injection of kringle 5 did not result in any detectable inflammatory response in the retina or histological toxicity to retina neurons and pre-existing vessels.

Conclusion/interpretation: These observations suggest that intravitreal delivery of angiogenic inhibitors could have therapeutic benefits in neovascular diseases of the retina.

Publication types

  • Research Support, Non-U.S. Gov't
  • Research Support, U.S. Gov't, P.H.S.

MeSH terms

  • Angiogenesis Inhibitors / administration & dosage*
  • Angiogenesis Inhibitors / pharmacology
  • Animals
  • Capillaries / cytology
  • Capillaries / drug effects
  • Cell Count
  • Cells, Cultured
  • Endothelium, Vascular / cytology
  • Endothelium, Vascular / drug effects
  • Humans
  • Hypoxia / pathology
  • Injections
  • Kringles*
  • Neovascularization, Pathologic / pathology*
  • Neovascularization, Pathologic / prevention & control*
  • Oligopeptides / pharmacology
  • Oxygen
  • Peptide Fragments / administration & dosage*
  • Peptide Fragments / metabolism
  • Peptide Fragments / pharmacology
  • Plasminogen / metabolism*
  • Rats
  • Rats, Inbred BN
  • Rats, Sprague-Dawley
  • Recombinant Proteins / administration & dosage
  • Recombinant Proteins / pharmacology
  • Reference Values
  • Retina / drug effects
  • Retina / pathology
  • Retinal Diseases / chemically induced
  • Retinal Vessels / drug effects*
  • Retinal Vessels / pathology
  • Vitreous Body


  • Angiogenesis Inhibitors
  • Oligopeptides
  • Peptide Fragments
  • Recombinant Proteins
  • arginyl-glycyl-aspartic acid
  • Plasminogen
  • Oxygen