Complex mediation of uterine endometrial epithelial cell growth by insulin-like growth factor-II (IGF-II) and IGF-binding protein-2.
The coexpression of IGF (-I and -II) peptides, corresponding receptors, and IGF binding proteins (IGFBPs) in uterine endometrium suggests that a significant component of IGF action in this tissue is via autocrine or paracrine pathways, or both. The present study examined whether IGF-II and a major uterine-expressed IGF-II binding protein, IGFBP-2, modulate endometrial epithelial cell mitogenesis. Serum-deprived porcine endometrial glandular epithelial (GE) cells of early pregnancy were treated with various concentrations of IGFs, recombinant porcine (rp) IGFBP-2, or both, and examined for changes in cellular mitogenesis by incorporation of [(3)H]thymidine into DNA. Recombinant human (rh) IGF-II stimulated DNA synthesis in a dose-dependent manner. Human [Leu(27)]-IGF-II, an analog with selective affinity for the IGF-II (type II) receptor, increased thymidine uptake by twofold compared with untreated GE cells. When added in combination with an equimolar concentration of rhIGF-I, [Leu(27)]-IGF-II or rhIGF-II stimulated thymidine incorporation to a greater extent than did rhIGF-I alone. Ligand blot analysis of GE cell conditioned medium revealed the presence of four IGFBPs with molecular masses of 48, 31, 23, and 15 kDa. Physiological concentrations of rpIGFBP-2 (nM range) increased both basal and IGF-induced DNA synthesis in GE cells. At equimolar concentrations, Des(1-6)IGF-II (an IGF-II analog with much reduced affinity for IGFBPs) and rpIGFBP-2 had additive effects on GE cell mitogenesis, suggesting that the IGFBP-2 modulation of uterine cell growth may involve both IGF-dependent and IGF-independent pathways. Our results demonstrate the complex interplay of IGF system components in uterine endometrial epithelial growth regulation in vitro, identify IGF-II and IGFBP-2 as locally coexpressed uterine epithelial cell mitogens, and suggest the presence of a functional signaling pathway by which IGF-II stimulates epithelial cell proliferation via the type II receptor.
Badinga
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L
Interdisciplinary Concentration in Animal Molecular and Cell Biology, Department of Animal Science, University of Florida, Gainesville, Florida 32611, USA.
Song
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S
Simmen
R C
RC
Clarke
J B
JB
Clemmons
D R
DR
Simmen
F A
FA
D000818:Animals; D002455:Cell Division / Q000187:drug effects; D002478:Cells, Cultured; D017077:Culture Media, Conditioned / Q000737:chemistry; D004247:DNA / Q000096:biosynthesis / Q000235:genetics; D004305:Dose-Response Relationship, Drug; D004717:Endometrium / Q000166:cytology*; D004847:Epithelial Cells / Q000166:cytology* / Q000187:drug effects* / Q000378:metabolism; D005260:Female; D006801:Humans; D018971:Insulin-Like Growth Factor Binding Protein 2 / Q000737:chemistry / Q000235:genetics / Q000378:metabolism / Q000494:pharmacology*; D007334:Insulin-Like Growth Factor I / Q000494:pharmacology; D007335:Insulin-Like Growth Factor II / Q000031:analogs & derivatives / Q000494:pharmacology*; D008934:Mitogens / Q000494:pharmacology; D008970:Molecular Weight; D010455:Peptides / Q000494:pharmacology; D011247:Pregnancy; D012333:RNA, Messenger / Q000235:genetics / Q000378:metabolism; D011993:Recombinant Fusion Proteins / Q000737:chemistry / Q000235:genetics / Q000378:metabolism / Q000494:pharmacology; D013552:Swine
D017077:Culture Media, Conditioned; D018971:Insulin-Like Growth Factor Binding Protein 2; D008934:Mitogens; D010455:Peptides; D012333:RNA, Messenger; D011993:Recombinant Fusion Proteins; D007334:Insulin-Like Growth Factor I; D007335:Insulin-Like Growth Factor II; D004247:DNA