All ETDs from UAB

Advisory Committee Chair

Clyde Guidry

Advisory Committee Members

Christine Curcio

Kent Keyser

Timothy Kraft

Shu-Zhen Wang

Document Type


Date of Award


Degree Name by School

Doctor of Philosophy (PhD) School of Optometry


The goal of this study was to determine the influence, if any, of the insulin-like growth factors (IGFs) on retinal pigment epithelial (RPE) cell tractional force generation and the contributions of vitreous insulin-like growth factor binding proteins (IGFBPs) towards control of IGF activity. Another objective was to evaluate RPE cells as a potential source of all six high-affinity IGFBPs and to determine if IGFBP biosynthesis is modulated in concert with phenotype changes and growth factor stimuli known to be present in disease. RPE generate tractional forces in response to IGF-I and -II with IGF-I being the more potent stimulus. Differential RPE responses to non-IGFBP binding analogue, R3IGF-I reflected minor amounts of endogenous IGFBP production. IGFBPs -2, -3 and -5 were effective inhibitors of both ligands while IGFBP-6 reduced cell responses to IGF-II only. IGFBP direct effects on the cells were binding protein-specific in that only IGFBP- 1 had detectable stimulatory effects and IGFBPs -3, -4, -5 and -6 inhibited RPE responses. Changes in RPE phenotype occur very early in culture and can be defined by differential expression of cytoskeletal proteins. Normal RPE are immunoreactive for cytokeratin 18 and negative for cytokeratin 19, vimentin and α smooth muscle actin (αSMA). At seven days (7d) in culture, RPE cells express cytokeratins 18, 19 and vimentin. After 35 days (35d) in continuously proliferating cultures, RPE cells express cytokeratin 19, vimentin and αSMA. RT-PCR studies revealed that normal RPE express IGFBP-2 -3, -4, -5 and -6, but not IGFBP-1. Following introduction in to culture, ‘early reactive’ (7d) and ‘myofibroblastic’ (35d) RPE possess detectable message for IGFBP-3, -5 and -6. However, Northern, Western ligand and Western blots suggest that functional IGFBP production by these RPE is limited to IGFBP-5 and this secretory profile is not under the influence of IGF system ligands. These data provide compelling evidence that RPE cells produce as well as respond to IGF system components, signals that drive the fibrocontractive process in proliferative vitreoretinopathy.

Included in

Optometry Commons



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