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M Joseph Costello, Ashik Mohamed, Kurt O Gilliland, Jamie L Wenke, Kevin L Schey; Non-human primate lenses display the cortical remodeling zone. Invest. Ophthalmol. Vis. Sci. 2014;55(13):733.
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© ARVO (1962-2015); The Authors (2016-present)
In 2009 a lens fiber cell remodeling zone was reported to be 40 µm thick at about 100 µm from the lens surface where cell membranes were highly modified. This remodeling zone has been described only in the human lens cortex. In 2013 ultrastructural details showed that cells became extensively interdigitated, then sorted out their membrane topology and cytoplasm to produce cells destined to become the compacted cells of lens adult nucleus. The goal of this study was to determine if the remodeling zone occurs in non-human primate lenses and how it may be correlated to cellular compaction.
Macaque monkey lenses (9-13y) were fixed in 10% buffered formalin for 24-48h followed by fixation in 4% paraformaldehyde in cacodylate buffer for 48h. After storage at 4°C in cacodylate buffer, fixed lenses were Vibratome sectioned into 200 µm thick slices and further processed for transmission electron microscopy as described previously. Fixed lenses were also stained with fluorescent wheat germ agglutinin and visualized with fluorescence confocal or bright field light microscopy.
Thin sections prepared near the equatorial plane revealed the capsule, epithelium, elongating fiber cells and classical fiber cells with flattened hexagonal cross-sections. About 80-100 µm deep in the cortex, fiber cells lost their classical shape and developed complex interdigitations similar to ball-and-socket interdigitations. The cells were remodeled within a narrow band about 50 µm thick where radial cell columns were not visible. Fiber cells became more uniform by 150 µm deep and radial cell columns were again detectable. A reversal of heavy metal staining occurred across the remodeling zone as reported for human lenses: cytoplasm stained light and membranes dark in the outer cortex and the opposite in the deep cortex. The dense cytoplasm in the deep cortex was maintained into the nucleus and was consistent with high refractive index and dense packing of crystallins. Minor compaction was observed in the deep cortex and outer nucleus suggesting that the observed dramatic cellular changes in the remodeling zone occurred even if the cells were not extremely compacted.
The remodeling zone in the outer cortex of macaque monkey lenses was observed at nearly the same location and with similar cellular modifications as in adult human lenses. The limited compaction in these lenses may indicate their similarity to young adult human lenses.
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