Purpose. The rapid and synchronous loss of organelles is a characteristic feature of lens fiber cell differentiation that results in the formation of a central, organelle-free zone (OFZ). In the present study, we examined the role of lysosomes in this process. Methods. Living lens slices were incubated with acridîne orange (AO) and viewed on a confocal microscope. AO accumulates in lysosomes, where low pH causes a red shift in the emission spectrum of the dye. Slices were also processed for immunofluorescence with LEP-100, an antibody raised against a lysosomal glycoprotein. Results. Lysosomes were most concentrated beneath the basal membranes of epithelial and fiber cells. There was also a marked accumulation at the sutures. Lysosomes were evenly distributed throughout the remainder of the cytoplasm, although at a lesser concentration. Time-lapse microscopy of AOstained lenses revealed saltatory motion of lysosomes. This was particularly evident in the epithelial cells. At E18, when the OFZ is well defined, the number of lysosomes was reduced in the deep fiber cells, such that, at the border of the OFZ, lysosomes were very sparse. Lysosomes were not observed in fiber cells within the OFZ. Conclusions. The distribution of lysosomes revealed by this study does not suggest a direct role for these organelles in the formation of the OFZ. However, the presence of lysosomes near the basal membranes and at the sutures may imply a role in cell signaling and/or macromolecular processing at the lens surface. The intracellular transport of lysosomes observed in living preparations indicates the presence of previously uncharacterized cytoplasmic transport mechanisms.
|Journal||Investigative Ophthalmology and Visual Science|
|State||Published - Dec 1 1997|