Heterogeneity in localization of isoforms of TGF-beta in human retina, vitreous, and choroid

The purpose of this work was to investigate further the immunohistochemical localization of transforming growth factor (TGF)-beta 1 to photoreceptors, which we had previously observed, to elucidate the cell types of origin for TGF-beta 1, and to determine sites of localization for TGF-beta 2 and beta 3 in the posterior segment of the human eye.

Streptavidin-peroxidase immunohistochemistry was used to localize TGF-beta antibodies in sections from cryopreserved human posterior segments from six adult donors. Two recently described polyclonal antibodies to TGF-beta 1 (anti-CC[1-30] and anti-LC[1-30]) and antibodies against TGF-beta 2 and beta 3 were employed in this study. Other studies suggest that anti-LC(1-30) antibody recognizes pre-pro-TGF-beta 1 and therefore sites of production, while anti-CC(1-30) recognizes secreted forms of TGF-beta 1.

Regional labeling of choriocapillaris was observed in all eyes using anti-LC(1-30) (anti-pre-pro-beta 1). Anti-CC(1-30) (anti-secr-beta 1) was localized predominantly in photoreceptor inner and outer segments in all eyes. Outer segment localization appeared identical to anti-opsin localization, indicating that this form of TGF-beta 1 is most likely intracellular. TGF-beta 2 was observed predominantly in the connective tissue of long ciliary arteries in choroid and in photoreceptor outer segments in all eyes. TGF-beta 3 was observed in isolated individual cells in choroid and retina. Vitreous hyalocytes were the only cell type examined that were immunoreactive for all four forms of TGF-beta studied.

The heterogeneity in localization of TGF-beta s in the human posterior eye suggests that TGF-beta s are produced, used, and degraded locally. TGF-beta 1 produced by the choriocapillaris may be stored or used by photoreceptors.