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Yi Zhang, Gregory I. Liou, Adrash K. Gulati, Rashid A. Akhtar; Expression of Phosphatidylinositol 3–Kinase during EGF-Stimulated Wound Repair in Rabbit Corneal Epithelium. Invest. Ophthalmol. Vis. Sci. 1999;40(12):2819-2826.
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purpose. To investigate the effect of epidermal growth factor (EGF) on the
induction of phosphatidylinositol 3-kinase (PI 3–kinase) gene
expression during rabbit corneal epithelial wound repair.
methods. Epithelial wounds (6 mm in size) were created in rabbit corneas and EGF
(2 μg) applied every 8 hours to one eye, and the other eye served as
a control. The wound repair was monitored by staining the tissue with
fluorescein followed by photography. The wound area was quantified with
a computer program. At different time intervals, the rabbits were
killed and the corneal epithelium used for estimation of PI 3–kinase
activity, western blot analysis, or reverse transcription–polymerase
chain reaction (RT–PCR). For in situ hybridization, the whole corneas
were sectioned and the sections processed with PI 3–kinase mRNA
results. In the untreated eye, the epithelial wound progressively healed in a
time-dependent manner, with 75% of the wound closed at 48 hours post
wounding. Application of EGF to the corneal epithelium further
stimulated wound repair at all time intervals, and the wound was
completely closed at 48 hours. Analysis of PI 3–kinase showed a
time-dependent increase in its enzyme activity that was maximally
increased at 36 hours, the time when the wound was nearly closed.
Western blot analysis revealed increased amounts of PI 3–kinase
protein during the course of wound repair. Analysis of RT–PCR products
from epithelial tissues, taken at different times during wound repair,
showed increased PI 3–kinase expression that was maximum at 48 hours
post wounding. A visible increase in PI 3–kinase gene expression was
also detected by in situ hybridization during the course of the wound
repair. This expression was increased maximally by EGF at 48 hours post
conclusions. The results indicate a temporal correlation between increased
activation and expression of PI 3–kinase and the epithelial wound
repair. Topical application of EGF further stimulates the activity and
expression of PI 3–kinase. It is suggested that PI 3–kinase and its
products may play a role in EGF-induced cell proliferation during
corneal epithelial wound repair.
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