Abstract
Abstract: :
Purpose: Human lens epithelial cell (LEC) lines express Fas and are sensitive to apoptosis induced by Fas-activating antibody. Primary human LECs from anterior capsulotomy specimens express Fas but are resistant to apoptosis induced by Fas-activating antibody. The aim of this study was to determine why primary LECs are resistant to Fas-mediated apoptosis. Methods: Anterior capsulotomy specimens were pinned out in culture (DMEM + 10%FCS) and LECs were allowed to migrate from the capsule forming a pericapsular halo. Cultures were treated with anti-Fas IgM (Upstate) or control IgM (500ng/ml) with the capsule present or after the capsule and adherent cells had been removed. Apoptosis in the pericapsular halo was then measured by Hoechst staining and cell counting (%intact vs apoptotic nuclei) in standard fields. The role of lens capsular extracellular matrix in regulating sensitivity to apoptosis was investigated by culturing the human LEC line HLE-B3 on tissue culture (TC) plastic, pig lens capsule, soluble collagen IV (BD Biosciences) or laminin (Calbiochem) for 1-14 days. Cultured HLE-B3 cells were treated with anti-Fas or control IgM (500ng/ml) and apoptosis was measured as above. Results: Primary LECS in the pericapsular halo were resistant to apoptosis induced by Fas-activating antibody as long as the capsule and adherent cells were present (<5% apoptotic cells after 48 hours treatment). Sensitivity to Fas-mediated apoptosis in the cells in the pericapsular halo was increased by removal of the capsule (36% apoptotic cells). HLE B3 cells cultured on TC plastic for up to 4 days were sensitive to apoptosis induced by anti-Fas antibody (40% apoptotic after 24 hours of antibody treatment). Culture on pig lens capsule rendered HLE B3 cells insensitive to Fas-mediated apoptosis such that there was no significant difference between control and anti-Fas treated cells. Culture of HLE B3 cells on collagen IV, but not laminin, provides partial protection against Fas-mediated apoptosis. Conclusions: Interaction of LECs with lens capsule confers protection against Fas-mediated apoptosis. Short range factors produced by LECs cultured on lens capsule may confer protection on neighbouring LECs not on the capsule. One component of the lens capsule important for providing protection against Fas-mediated apoptosis is collagen IV.
Keywords: apoptosis/cell death • posterior capsular opacification (PCO) • cataract