Insulin-like growth factor-I promotes cell proliferation in the absence of modulation of collagen phenotypes and utilizes IRS-1, not PLC-gamma 1, in corneal endothelial cells.
Corneal endothelial cells are differentiated cells and are thus incapable of physiologic regeneration. In a search for a growth factor that would promote optimal proliferation of corneal endothelial cells in the absence of other modulating activities, the effect of insulin-like growth factor-I (IGF-I) on rabbit corneal endothelial cells was studied. In addition, cellular effector molecules responsible for the signal pathway for IGF-I were studied. IGF-I at 50 ng/ml stimulated corneal endothelial cell proliferation after at least 8 h of treatment. IGF-I did not change cell shape of corneal endothelial cells: the cells treated with IGF-I at 50 ng/ml maintained polygonal morphology regardless of the duration of exposure. IGF-I did not alter collagen phenotypes either qualitatively or quantitatively: the treated cells continued to synthesize types IV and VIII collagen, as did the control cells. The steady-state levels of alpha 2(I) collagen RNA and alpha 2(IV) RNA were not altered by IGF-I treatment. Immunohistochemical analysis showed that IGF-I is present in corneal endothelium in vivo, while the underlying Descemet's membrane demonstrated no staining. Corneal endothelial cells also produce IGF binding protein-2 (IGFBP-2), which appears to bind IGF-I that has been introduced exogenously in the medium. Further investigation as to how the signals of IGF-I were transmitted for the biological activities demonstrated that the expression of insulin receptor substrate-1 (IRS-1) is up-regulated by IGF-I treatment, while PLC-gamma 1 expression is not altered by this growth factor.(ABSTRACT TRUNCATED AT 250 WORDS)
Choi
S H
SH
Department of Ophthalmology, University of Southern California School of Medicine, Los Angeles, USA.
Kay
E P
EP
Oh
D S
DS
Gu
X
X
Smith
R E
RE
D000818:Animals; D001483:Base Sequence; D002455:Cell Division / Q000187:drug effects; D048429:Cell Size; D002478:Cells, Cultured; D003094:Collagen / Q000096:biosynthesis*; D004247:DNA / Q000096:biosynthesis; D017931:DNA Primers / Q000737:chemistry; D004591:Electrophoresis, Polyacrylamide Gel; D004728:Endothelium, Corneal / Q000166:cytology* / Q000187:drug effects / Q000378:metabolism*; D005455:Fluorescent Antibody Technique; D015151:Immunoblotting; D055504:Insulin Receptor Substrate Proteins; D007334:Insulin-Like Growth Factor I / Q000494:pharmacology*; D007527:Isoenzymes / Q000378:metabolism; D008969:Molecular Sequence Data; D010641:Phenotype; D051966:Phospholipase C gamma; D010750:Phosphoproteins / Q000378:metabolism*; D011817:Rabbits; D010738:Type C Phospholipases / Q000378:metabolism; D015854:Up-Regulation
D017931:DNA Primers; D055504:Insulin Receptor Substrate Proteins; D007527:Isoenzymes; D010750:Phosphoproteins; D007334:Insulin-Like Growth Factor I; D003094:Collagen; D004247:DNA; D010738:Type C Phospholipases; D051966:Phospholipase C gamma