Photocoagulation-induced retinal gliosis is inhibited by systemically expressed soluble TGF-beta receptor type II via adenovirus mediated gene transfer.

Retinal gliosis is one of the major causes of visual dysfunction due to the loss of the retinal regular structure and function in various diseases, including diabetic retinopathy, retinal detachment, and glaucoma. Transforming growth factor-beta (TGF-beta) is assumed to play an important role in this disease process. In the present study, we determined whether the systemically expressed extracellular domain of the TGF-beta type II receptor by adenovirus-mediated gene delivery could inhibit experimental retinal gliosis both in vitro and in vivo. Cultured bovine retinal glial cells, Müller cells, were stimulated by recombinant TGF-beta and the expression of the glial marker, glial fibrillary acidic protein (GFAP), was evaluated by immunohistochemistry, semiquantitative RT-PCR, and Western blotting. In cultured Müller cells, TGF-beta stimulated the GFAP expression in a dose-dependent fashion, and the conditioned medium from 293 cells transfected with adenovirus encoding for a soluble form TGF-beta type II receptor (AdT beta-ExR) inhibited the expression of GFAP stimulated by exogenous TGF-beta (p < 0.05). In this process, Smad4 protein, which plays a key role in intracellular signaling after cell surface receptors, actually translocated from cytosol to nucleus with TGF-beta stimulation. The conditioned medium from AdT beta-ExR also inhibited the cytosol-nuclear translocation of Smad4. For in vivo studies, AdT beta-ExR was injected into the femoral muscles of Brown Norway rats and retinal photocoagulation was subsequently carried out. Immunohistochemical studies revealed that GFAP was strongly expressed around the photocoagulation spots after 12 days and these phenomena were inhibited by AdT beta-ExR. Western blotting of total retinal extract demonstrated the same results as those observed after immunohistochemistry. Our results suggest that TGF-beta plays a pivotal role in the pathologic processes in retinal gliosis, and that the systemically expressed soluble TGF receptor by gene delivery may thus have a potential therapeutic value by inhibiting excessive retinal gliosis in various ocular diseases.