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Studies on the regulation of lens growth during development and aging have led to the identification of external signals that may be provided during the whole life span by surrounding tissues, retina, vitreous, or iris. These signals may be positive— i.e., they may be involved in triggering cell division and cell elongation—or negative—i.e., they can prevent cell division in order to keep the growth of the lens under control. In addition, they should be aimed at some precise area of the lens epithelium or fibers, since lens growth depends on stimulation of cells at the lens periphery. They should also be able to cross the lens capsule, which completely surrounds the lens. It has been proposed that polypeptide growth factors can fulfill this function in the eyes. The purpose of this chapter is to show, on the basis data obtained in our laboratory as well as in other laboratories, that a family of growth factors— fibroblast growth factors (FGF, formerly called EDGF)—can control lens growth. |
