Effects of insulin and insulin-like growth factors on proliferation of rat ovarian theca-interstitial cells.
Hyperplasia of the theca-interstitial (T-I) compartment, such as observed in polycystic ovary syndrome, is associated with ovarian dysfunction. Yet the mechanisms regulating proliferation of T-I cells are virtually unknown. This study was an investigation of the effects of insulin and insulin-like growth factors (IGF-I and IGF-II) on proliferation of rat T-I cells. Purified T-I cells were incubated in chemically defined media. Insulin (1-100 nM) and both IGFs (0.3-30 nM) dose-dependently stimulated DNA synthesis as determined by radiolabeled thymidine incorporation assay. IGF-I was most potent with EC50 = 1.4 +/- 0.4 nM, while IGF-II had EC50 = 4.3 +/- 0.18 nM and insulin had EC50 = 8.4 +/- 3.9 nM. The maximal effects of all three treatments were comparable. A combination of IGF-I at 10 nM (a concentration producing a near-maximal effect) with insulin or IGF-II resulted in DNA synthesis comparable to that achieved by IGF-I alone. IGF-I mutants with decreased affinity to IGF-binding proteins (IGFBPs)-long R3-IGF-I and des(1-3)IGF-I-produced greater effects on DNA synthesis than did IGF-I. The effects of insulin and IGFs on cell proliferation were confirmed by counting the steroidogenically active cells (stained positive for 3 beta-hydroxysteroid dehydrogenase [3 beta-HSD]) and steroidogenically inactive cells (3 beta-HSD negative). The number of steroidogenically active T-I cells was increased by insulin (by 3.7-fold, p < 0.001), IGF-I (by 3.2-fold, p < 0.001), and IGF-II (by 2.1-fold, p < 0.001). The number of steroidogenically inactive cells was not significantly altered. These findings indicate that 1) insulin- and IGF-dependent synthesis of DNA by T-I cells is stimulated via a common pathway, probably via type I IGF receptors; 2) endogenous IGFBPs may modify the effects of IGF-I; and 3) the increased DNA synthesis is reflected by an increase in the number of steroidogenically active cells. Insulin and the IGFs may play a role in the regulation of proliferation and differentiation of T-I cells under physiological and pathological conditions. In particular, the present observations may explain thecal and stromal hyperplasia accompanying hyperinsulinemic conditions such as polycystic ovary syndrome or hyperthecosis.
Duleba
A J
AJ
Yale University School of Medicine, Department of Obstetrics and Gynecology, New Haven, Connecticut 06520-8063, USA. antoni.duleba@qm.yale.edu
Spaczynski
R Z
RZ
Olive
D L
DL
Behrman
H R
HR
D015096:3-Hydroxysteroid Dehydrogenases / Q000378:metabolism; D000704:Analysis of Variance; D000818:Animals; D002455:Cell Division / Q000187:drug effects; D002478:Cells, Cultured; D004247:DNA / Q000096:biosynthesis; D005260:Female; D007328:Insulin / Q000494:pharmacology*; D018969:Insulin-Like Growth Factor Binding Proteins / Q000378:metabolism; D007334:Insulin-Like Growth Factor I / Q000494:pharmacology*; D007335:Insulin-Like Growth Factor II / Q000494:pharmacology*; D010053:Ovary / Q000166:cytology* / Q000187:drug effects / Q000378:metabolism; D051381:Rats; D017207:Rats, Sprague-Dawley; D012741:Sexual Maturation; D013799:Theca Cells / Q000166:cytology* / Q000187:drug effects / Q000378:metabolism; D013936:Thymidine / Q000378:metabolism; D014316:Tritium
D007328:Insulin; D018969:Insulin-Like Growth Factor Binding Proteins; D014316:Tritium; D007334:Insulin-Like Growth Factor I; D007335:Insulin-Like Growth Factor II; D004247:DNA; D015096:3-Hydroxysteroid Dehydrogenases; D013936:Thymidine