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T Yamamoto, RN Fariss, FI Hickman, G Pagan-Mercado, S Sato, JY Tsai; Pericyte Recruitment in Silver Nitrate-Induced Corneal Angiogenesis . Invest. Ophthalmol. Vis. Sci. 2002;43(13):1754.
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Purpose: In physiological vascular development, pericytes are recruited when endothelial cell networks are established. The recruitment is crucial in maintaining the functional structures of capillaries. However, it remains unknown whether the pericyte recruitment also occurs in pathological angiogenesis. In this study, utilizing two lines of transgenic mice, one expressing GFP under control of the smooth muscle alpha actin promoter (SMAA-GFP mice) and another expressing GFP with Tie2 promoter (Tie2-GFP mice), we have examined whether pericyte recruitment occurs in corneal angiogenesis. Methods: A small burn injury was induced in the center of the cornea by placing a silver nitrate stick on the cornea surface for 4 seconds. 3 days later, the cornea including sclera and limbal conjunctiva was dissected under microscope. The new vessels growing into the cornea in either SMAA-GFP or Tie2-GFP mice were directly examined by confocal microscope. Identification of endothelial cells and pericytes was also confirmed by immunostaining with CD31 and SMAA. Results: Although there were significant individual variations, new vessel growth was detected within 3 days in all cases treated with silver nitrate. All new vessels originated from limbal vessels. In Tie2-GFP mice, the GFP signal was similar in both normal and new vessels. In SMAA-GFP mice, the GFP was detected in almost all new vessels. However, the anti-SMAA signal and GFP in SMAA-GFP mice appeared to be much lower at the front edge of new vessels than the area closer to the limbus. The shape of new vessels was also different. The diameter of these new vessels away from the limbus tends to be larger than those near limbus. Conclusion: Like in physiological angiogenesis, pericytes are recruited into new vessels during cornea neovascularization induced by silver nitrate burn injury. Although the origin(s) of pericytes are not clear, capillary maturation in corneal angiogenesis appears to be accompanied by the proliferation and migration of existing pericytes.
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