Stress-induced ATP release from and growth modulation of human lens and retinal pigment epithelial cells.

ATP release has been shown to occur following stimulation in several cellular systems. This study was undertaken to determine if lens and retinal epithelial cells release ATP in response to physiological stresses and to elucidate a possible role for ATP. Analysis of human aqueous humour samples showed a mean ATP level of 37.8+/-7.7 nM. Hyper-osmotic stress induced a dose- and time-dependent release of ATP. Both cell types were found to proliferate in serum-free medium, and the addition of ATP and adenosine at concentrations as low as 0.1 nM inhibited growth. Gene profiling also demonstrated the presence of the ectonucleotidases CD39 and CD73 and the A1 adenosine receptor on both cell types.

Ex vivo canine lens capsular sac explants.

BACKGROUND: Lens capsular sac explants from human cadaver eyes were used to investigate posterior capsular opacification (PCO). The purpose of this study was to characterize a similar model using canine tissue and to determine whether transferrin (Tf), transforming growth factor beta-2 (TGF-beta2), and insulin-like growth factor-1 (IGF-1) are secreted by lens epithelial cells (LEC) of these ex vivo sacs. METHODS: The lens from canine eyes was removed by extracapsular cataract extraction, the lens sac dissected free, pinned to a petri dish, and cultured in either serum-supplemented or serum-free medium. Morphologic characteristics and growth rate to confluence on the posterior capsule were studied by phase-contrast microscopy. Vimentin, alpha smooth muscle actin, and panTGF-beta expression by LEC were determined by immunohistochemistry. Tf, TGF-beta2, and IGF-1 levels were measured by ELISA in the supernatant of sacs cultured in serum-free medium. RESULTS: The mean time to confluence of LEC onto the posterior capsule was 5.4+/-1.1 days (n=22) and 14.7+/-3.7 days (n=14) for sacs in serum-supplemented and serum-free medium, respectively. Following development of confluence, explants displayed opacification and light scatter from cellular proliferation and capsular contraction. Confluent LEC expressed vimentin, alpha smooth muscle actin, and TGF-beta2, and both Tf and TGF-beta2 were secreted into the culture supernatant. CONCLUSION: Canine lens sac explants have characteristics virtually identical to those of human origin, and appear to be a useful alternative tissue source for this model when human cadaver eyes are unavailable. Tf and TGFbeta-2, but not IGF-1, are secreted by LEC in explanted lens sacs and may influence the proliferation and metaplasia of LEC during the development of PCO.