Age changes in the skeleton of the human lens.

The cytoskeleton of the human lens (newborn, 24 year-old and 80 year-old) was studied by morphological methods. Actin and intermediate (10 nm) filaments were identified in the epithelial cells of all the lenses. In the newborn lens intermediate filaments and chains of protein were found in cortical and nuclear fiber cells. Many intermediate filaments and protein chains in the elongated form were observed in the superficial cortical fiber cells of the 24 year-old lens. However, in the deep cortical cells the number of intermediate filaments decreased and the protein chains became more coiled and aggregated. In the nuclear region the protein chains were markedly aggregated and intermediate filaments were absent. The 80 year-old fiber cells contained only protein aggregates in the fiber cells. While the size of the chain backbone corresponds to actin, the conclusive demonstration that it is actin remains to be shown.