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Cui Chen, Beatrice Michelini–Norris, Scott Stevens, James Rowsey, Xiao-ou Ren, Michael Goldstein, Gregory Schultz; Measurement of mRNAs for TGFβ and Extracellular Matrix Proteins in Corneas of Rats after PRK. Invest. Ophthalmol. Vis. Sci. 2000;41(13):4108-4116.
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© ARVO (1962-2015); The Authors (2016-present)
purpose. To assess the role of the transforming growth factor (TGF)β system in
formation of corneal haze after excimer laser photorefractive
keratectomy (PRK), levels of mRNAs for three TGFβ isoforms (TGFβ1,
TGFβ2, and TGFβ3), the TGFβ type II receptor (TβRII), and
extracellular matrix (ECM) genes including fibronectin (FN),
collagen I, collagen III, and collagen IV were measured in rat corneas.
methods. Corneas were graded for corneal haze at 0, 1.5, 7, 21, 42, and 91 days
after PRK. Total RNA was isolated from pooled corneas, and the levels
of mRNAs were measured using competition-based quantitative reverse
transcription–polymerase chain reaction (RT-PCR).
results. Severe corneal haze developed by day 42 and persisted to day 91. Levels
of TGFβ1 mRNA were high in rat corneas before PRK and remained
relatively constant. In contrast, levels of TGFβ2 and TGFβ3 mRNAs
were very low in normal corneas, increased 300-fold and 25-fold,
respectively, on day 21, and remained elevated on day 91. Levels of
mRNA for TβRII increased, with a peak elevation of 50-fold on day 42
after PRK. Levels of mRNAs for ECM proteins also increased. Fibronectin
mRNA was nondetectable in normal corneas but rapidly increased to 675
copies/cell on day 7 and remained elevated to day 91. Collagen III mRNA
levels peaked on day 21 with a 700-fold increase compared with a very
low level of expression in normal cornea, and then decreased on day 91.
Expression of collagen I mRNA lagged expression of collagen III mRNA
and peaked at day 42 after PRK with a 1200-fold increase over normal
cornea. In contrast, mRNA for collagen α(1)IV, a major component in
basement membranes, remained relatively stable through day 21 and then
increased slightly on days 42 and 91.
conclusions. The synchronized increase in mRNA synthesis for both the TGFβ system
and key ECM genes supports the hypothesis that TGFβ is a key growth
factor promoting stromal haze formation in corneas after PRK and
suggests that limiting TGFβ system may reduce corneal scarring after
excimer laser ablation.
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