Smad translocation and growth suppression in lens epithelial cells by endogenous TGF beta 2 during wound repair

To determine whether endogenous TGF beta affects lens epithelial cells duri ng repair after an anterior capsule injury in mice, we studied translocatio n of Smad proteins, which carry the TGF beta signal from cell surface recep tors to promoters in nuclei. We immunolocalized Smads in murine lenses at i ntervals up to 8 weeks following capsular injury. Effects of injecting TGF beta neutralizing antibodies on Smad4 location and cell proliferation were examined at 24 hr after injury. Finally, we examined whether exogenous TGF beta2 induced Smad nuclear translocation in murine lenses in organ culture. Cell proliferation was quantitated by 5-bromo-2'-deoxyuridine (BrdU) label ling. In uninjured lenses, Smads were located in the cytoplasm. In injured lenses, nuclear localization of Smads was observed in cells next to the cap sular break from 8 to 24 hr after the injury, and was observed peripheral t o the break at 48 hr. Nuclear Smads then continued to be observed occasiona lly in a minority of cells. Injection of antibodies neutralizing TGF beta2, but not TGF beta1 or TGF beta3, inhibited Smad4 nuclear translocation and resulted in the appearance of BrdU-positive anterior epithelial cells. With the lenses in culture, transient nuclear localization of Smads occurred be tween 3 and 24 hr in response to continuous exposure to TGF beta2. No nucle ar translocation was seen at 48 hr. Endogenous TGF beta2 affects lens cells during wound repair after anterior capsule injury, inhibiting lens cell pr oliferation during the early phase. Nuclear translocation of Smads in lens epithelial cells is transient even with continuous exposure to TGF beta2. ( C) 2001 Academic Press.