Lens Differentiation in Vertebrates: A Review of Cellular and Molecular Features

Chapter 3 – The Lens: Development, Proteins, Metabolism and Cataract

Publisher Summary This chapter provides an overview of molecular characterization and the distribution and biological activities of fibroblast growth factor (FGF) in various tissues FGF in the pituitary plays a nonmitogenic role in the maintenance of prolactin and thyrotropin responsiveness, while the same molecule in macrophages may promote wound healing and in the corpus luteum angiogenesis It is based on the diverse biological activities of somatostatin in brain, hypothalamus, stomach, and pancreas and the wide distribution of numerous neuropeptides in both the central nervous system and the gastrointestinal tract The concept is equally applicable to FGF and perhaps other growth factors that show a wide distribution in many tissues The results presented in the chapter suggest that heretofore unidentified biologic activities may be related if not identical to acidic and basic FGFs These would include ovarian growth factor, macrophage-derived growth factor, cartilage growth factor, tumor angiogenic factor, eye-derived growth factor, retina-derived growth factor, corpus luteum angiogenic peptide, follicular angiogenic factor, adrenal vascularizing factor, and endothelial cell growth factors

Molecular characterization of fibroblast growth factor: distribution and biological activities in various tissues.

Identification of the cytoskeletal proteins in lens-forming cells, a special epithelioid cell type☆

Lentropin, a factor present in the vitreous humor of the eye, stimulates lens fiber differentiation from chicken embryo lens epithelial cells in vitro. Lentropin has been partially purified but has not been isolated in sufficient quantity or purity for direct comparison with other growth and differentiation factors. Previous studies have shown that insulin and fetal bovine serum share with lentropin the ability to stimulate lens fiber formation from cultured epithelial cells. In the present study, a number of hormones and growth factors were assayed for lentropin activity. Of those tested, the only substances that had this activity were the insulin-like growth factors (IGFs) somatomedin C (Sm-C/IGF-I) and multiplication-stimulating activity (MSA/IGF-II). Sm-C/IGF-I was approximately 30 times more potent than insulin or MSA/IGF-II in promoting fiber cell formation. A monoclonal antibody to human Sm-C/IGF-I inhibited purified Sm-C/IGF-I, fetal bovine serum, and chicken vitreous humor from stimulating fiber cell differentiation in vitro. This antibody has been shown not to crossreact with insulin and did not block insulin-stimulated lens fiber formation. These findings indicate that lentropin is related to the IGFs and that these factors may play important roles in controlling cell differentiation, in addition to their better-known ability to stimulate cell division.

C. Arruti

Papers

Morphological changes and growth stimulation of bovine epithelial lens cells by a retinal extract in vitro.