Upregulation of Transforming Growth Factor-beta After Panretinal Photocoagulation

Purpose: To determine whether upregulation of transforming growth factor-beta (TGF-beta) gene expression occurs after panretinal photocoagulation (PRP). To quantitate two TGF-beta isoforms in the aqueous and vitreous humors and to localize TGF-beta 2-like immunoreactivities (TGF-beta 2-LI) and TGF-beta 2 mRNA in the retina after PRP.

Methods: PRP was performed on Brown Norway rats by using an argon-green laser. Sensory retina, aqueous and vitreous humors were collected from the rats on days 1, 3, and 7 after PRP, and semiquantitative polymerase chain reaction analyses were carried out. TGF-beta 2 in the aqueous and vitreous humors was quantitated by enzyme-linked immunosorbent assay. Localization of TGF-beta 2-LI was demonstrated by immunohistochemistry, and that of TGF-beta 2 mRNA by in situ reverse transcription-polymerase chain reaction (RT-PCR).

Results: Gene expression of both TGF-beta 1 and -beta 2 was upregulated by PRP. Expression of TGF-beta 2 was greater than that of beta 1 (12.8-fold increase versus 3.24-fold increase, respectively, compared with control level on day 3). TGF-beta 2 concentration was increased in the vitreous humor (4.37-fold increase, P < 0.01) but not in the aqueous humor (the same level compared with control) on day 1. TGF-beta 2-LI and TGF-beta 2 mRNA were detected in cells of the outer retinal layer and in retinal pigment epithelial cells adjacent to the laser burns.

Conclusions: PRP upregulates expression of TGF-beta 2 in the retina, and increased TGF-beta 2 concentrations are found in the retina and the vitreous humor. Retinal pigment epithelial cells and sensory retina around the laser burn appear to play a major role in the upregulation.