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Purpose: The damaging effects of oxidative stress and transforming growth factor-beta (TGFbeta)-induced transdifferentiation of lens epithelial cells have both been implicated independently in the etiology of cataract. The aim of this study was to investigate whether the presence of antioxidant systems in the lens influences the ability of lens epithelial cells to respond to TGFbeta., Methods: Whole lenses from young rats were cultured with or without TGFbeta in the presence or absence of reduced glutathione (GSH). Lens epithelial explants from weanling rats were used to investigate the effects of GSH and catalase on TGFbeta-induced cataract-related changes. Lenses were monitored for opacification for three to four days, photographed, and then processed for routine histology. Explants were assessed by phase contrast microscopy, enzyme-linked immunosorbent assay (ELISA) of alpha-smooth muscle actin (alphaSMA), and/or immunolocalization of alphaSMA and Pax6, markers for transdifferentiation and normal lens epithelial phenotype, respectively., Results: In cultured lenses, GSH strongly suppressed TGFbeta-induced opacification and subcapsular plaque formation. In explants, both GSH and catalase suppressed changes typically associated with TGFbeta-induced transdifferentiation including wrinkling of the lens capsule, cell-surface blebbing, apoptotic cell loss, induction of alphaSMA, and loss of Pax6 expression., Conclusions: This study suggests that antioxidant systems present in the normal lens, which protect the epithelium against the damaging effects of reactive oxygen species, may also serve to protect it against the potentially cataractogenic effects of TGFbeta. Taken together with other recent studies, it also raises the possibility that TGFbeta may induce cataract-related changes in lens epithelial cells via release of hydrogen peroxide.

Purpose: Many patients whose sight is initially restored by cataract surgery eventually suffer secondary loss of vision because of posterior capsule opacification (PCO; after-cataract), a condition in which lens epithelial cells left behind at surgery become aberrant and migrate into the light path. The aim of this study was to determine whether dexamethasone (DEX), an anti-inflammatory agent widely used before and after cataract surgery, influences the behavior of lens cells under conditions relevant to PCO development., Methods: An established rat PCO model was used in which explanted epithelial cells attached to the lens capsule are exposed sequentially to TGFbeta2 and FGF-2. Cultures with or without DEX (100 nM), and appropriate controls, were maintained for up to 30 days and assessed by light and scanning electron microscopy or immunolocalization of PCO markers (alpha-smooth muscle actin or fibronectin) or a marker for lens epithelial cell phenotype (Pax-6)., Results: In the absence of DEX, explants become multilayered and plaques that express PCO markers form. Cells tend to gather up into the plaques, leaving the surrounding lens capsule denuded. Changes in lens cell behavior with addition of DEX included rapid formation of long, needle-like cells, less extracellular matrix deposited on explant surface, and plaques surrounded by a monolayer of migratory cells. Immunolocalization confirmed that the latter were not normal lens epithelial cells., Conclusions: Lens cell behavior in this PCO model was significantly affected by inclusion of DEX, highlighting the possibility that its use as an anti-inflammatory at the time of cataract surgery may influence PCO development.

Purpose: While cataract surgery initially benefits most patients, many suffer secondary loss of vision because of posterior capsule opacification (PCO). Lens epithelial cells left behind at surgery become aberrant and migrate into the light path. TGF-beta (TGFbeta) appears to play a key role in this process by inducing the cells to undergo an epithelial-mesenchymal transition. Paradoxically, it also typically induces them to undergo apoptotic death. The present study was undertaken to investigate the hypothesis that FGF plays a role in PCO formation by promoting the survival of abnormal cells with PCO-like characteristics., Methods: Rat lens epithelial explants were cultured for one day with TGFbeta2 (25-100 pg/ml) then in control medium with or without FGF-2 (5-100 ng/ml) for up to 31 days, with assessment by light and scanning electron microscopy and immunolocalization., Results: Survival of TGFbeta treated cells was promoted by FGF-2 but not by EGF, PDGF, IGF, or HGF. In the absence of FGF virtually all cells were lost from explants within 5 days. However, when FGF was included cells remained viable throughout culture. These cells, which no longer expressed the lens epithelial marker Pax6, exhibited immunoreactivity for non-lens cell proteins associated with PCO (alpha-smooth muscle actin, type I collagen, and fibronectin) and also beta-crystallin. FGF inclusion also promoted ECM production, multilayering, and plaque formation, features of PCO known to contribute to visual loss., Conclusions: This study points to a key role for FGF in the etiology of PCO and suggests that FGF inhibitors may be useful in preventing PCO.

Purpose: Culturing rat lenses with transforming growth factor-beta (TGFbeta) results in the formation of anterior, opaque subcapsular plaques which exhibit many of the features of human subcapsular cataract. The present study was undertaken to determine whether this process is influenced by the presence of fibroblast growth factor (FGF), a normal component of the lens environment in situ., Methods: Rat lenses were cultured for 4-8 days with TGFbeta-2, alone or in combination with FGF-2, PDGF-AA, or the growth factor inhibitors poly(4-styrenesulfonic acid) (PSS) and suramin. Responses were assessed by monitoring opacification, by routine histology and immunolocalization of markers for fibrotic change (a-smooth muscle actin, fibronectin, and type I collagen), or by measuring DNA accumulation in the epithelial region., Results: Supplementing TGFbeta at a barely cataractogenic dose with 2.5-30 ng/ml FGF-2 resulted in a very strong opacification response. The exceptionally large plaques that formed were similar histologically to those induced by TGFbeta alone at higher concentrations and showed immunoreactivity for all markers. PDGF at a concentration equivalent to FGF in terms of proliferative potential did not demonstrate this effect. Addition of either PSS or suramin reduced the opacification response induced by a cataractogenic dose of TGFbeta alone., Conclusions: FGF has been identified as a factor capable of exacerbating the cataractogenic effects of TGFbeta. Thus FGF inhibitors, as well as TGFbeta inhibitors, have the potential to protect the lens against TGFbeta-induced cataractous changes.