Expression and activation of STAT3 in ischemia-induced retinopathy.
OBJECTIVE
Signal transducer and activator of transcription protein-3 (STAT3) is a transcription factor that participates in many biological processes, including tumor angiogenesis. The expression and activation of Stat3 in the mouse model of ischemia-induced retinal neovascularization was investigated to evaluate the possible role of STAT3 in retinal vascular disease.


METHODS
Retinal neovascularization was induced in mice pups by exposure to hyperoxia. Gene microarrays were used to identify genes whose expression in the retina is altered at postnatal day (P)12 and P18. The relative levels of Stat3 mRNA were determined by semiquantitative RT-PCR. Stat3 protein levels and the levels of the activated form of Stat3 (pStat3) at P12, P15, P18, and P22 were determined by immunoblot analysis. Stat3 and pStat3 were demonstrated by immunofluorescence in retinal sections at P12, P15, and P18.


RESULTS
In a series of microarray experiments, increased Stat3 mRNA levels in the retina were detected at P18. This result was validated by RT-PCR and demonstrated that Stat3 and pStat3 protein levels also increase during the development of neovascularization. Stat3 partially colocalized with blood vessels at the peak of neovascularization. pStat3 colocalized completely with blood vessels in both experimental samples and age-matched controls. pStat3 staining increased notably in the neovascular vessels at P15 and P18 and was more strongly associated with the epiretinal vessels than with inner retinal vessels. It was not detected in larger blood vessels, such as those of the optic nerve.


CONCLUSIONS
The level of Stat3 expression increased, and pStat3 was observed in association with retinal neovascularization. Activated Stat3 was preferentially localized to neovascular retinal vessels. These data suggest that STAT3 may have a role in proliferative retinopathy.
Mechoulam
Hadas
H
F. M. Kirby Center for Molecular Ophthalmology, Scheie Eye Institute, University of Pennsylvania School of Medicine, Philadelphia, Pennsylvania 19104, USA.
Pierce
Eric A
EA
D000818:Animals; D000831:Animals, Newborn; D015153:Blotting, Western; D004195:Disease Models, Animal; D019084:Fluorescent Antibody Technique, Indirect; D018507:Gene Expression Regulation, Developmental / Q000502:physiology*; D018496:Hyperoxia / Q000150:complications; D007511:Ischemia / Q000150:complications*; D051379:Mice; D008810:Mice, Inbred C57BL; D020411:Oligonucleotide Array Sequence Analysis; D012333:RNA, Messenger / Q000378:metabolism; D015861:Retinal Neovascularization / Q000209:etiology / Q000378:metabolism* / Q000473:pathology; D012171:Retinal Vessels / Q000378:metabolism* / Q000473:pathology; D020133:Reverse Transcriptase Polymerase Chain Reaction; D050796:STAT3 Transcription Factor / Q000235:genetics* / Q000378:metabolism
D012333:RNA, Messenger; D050796:STAT3 Transcription Factor; C494087:Stat3 protein, mouse