Dedifferentiation of iris epithelial cells

Abstract

Electron and phase-contrast microscopic observations demonstrated that depigmentation of iris epithelial cells in vivo after lentectomy is preceded by alterations of cell shape and increases in microfilaments and microtubules in the periphery of the cell. Extensive cell processes are formed, with tips branching into fine strands that contain melanosomes. The macrophages invading the iris epithelium incorporate pieces of such strands, which are composed of cell membrane, cytoplasmic matrix, and melanosomes. Individual melanosomes are also taken up by macrophages. Some of the strands of iris cell processes seem to degenerate within the intercellular space. Thus, depigmentation of iris epithelial cells is accompanied by loss of a substantial part of the cell surface and cytoplasmic matrix of iris epithelial cells. Measurements of the absolute volume of whole iris epithelial cells, their cytoplasm, and their nuclei were conducted at various stages of depigmentation. These measurements reveal an extensive increase in the volume of the cytoplasm preceding activation of the cell surface and a significant reduction in cytoplasmic volume during the phase of extensive depigmentation. In the case of the nuclear volume, the extensive increase which occurs in parallel with that of the cytoplasmic volume is not followed by a significant change during the depigmentation phase.