Mol. Hum. Reprod. Advance Access originally published online on April 15, 2005
Molecular Human Reproduction 2005 11(5):319-324; doi:10.1093/molehr/gah168
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Insulin and insulin-like growth factors inhibit and luteinizing hormone augments ovarian theca-interstitial cell apoptosis
1Department of Gynecology and Obstetrics, Division of Infertility and Reproductive Endocrinology, Poznan University of Medical Sciences, 60-535 Poznan, Poland, 2Department of Obstetrics and Gynecology, Vincent Center for Reproductive Biology, Massachusetts General Hospital/Harvard Medical School, Boston, Massachusetts 02114, USA and 3Department of Obstetrics and Gynecology, Yale University School of Medicine, New Haven, CT 06510, USA
4 To whom correspondence should be addressed at: Department of Obstetrics and Gynecology, Yale University School of Medicine, 333 Cedar Street, New Haven, CT 06520, USA. Email: antoni.duleba{at}yale.edu
Theca-interstitial (T-I) cells play a fundamental role in the control of ovarian function. Steroidogenic activity and growth of the T-I cells are regulated by many paracrine and endocrine factors. However, little is known about the mechanisms controlling T-I death. In an in vitro model of apoptosis, purified rat T-I cells were cultured for 24 h with serum and subsequently for up to an additional 24 h with serum or in serum-free medium with or without insulin, insulin-like growth factors (IGF-I and IGF-II) and LH or 8-bromo-cyclic AMP (8Br-cAMP). Apoptosis was identified by histological assessment of nuclear morphology and by detection of internucleosomal cleavage and quantified by determination of [
32P]-dideoxy-ATP 3'-end labeling of low molecular weight DNA. Serum withdrawal resulted in nuclear condensation and fragmentation into apoptotic bodies of T-I cells and led to pronounced DNA cleavage. Insulin (10 nM) protected T-I cells from apoptosis, reducing DNA fragmentation by 39 ± 8% compared to serum-free controls. IGF-I (10 nM) and IGF-II (10 nM) had comparable antiapoptotic effects, decreasing DNA fragmentation by 55 ± 9% and 37 ± 14%, respectively. In contrast, LH (100 ng/ml) and 8Br-cAMP (1 mM) augmented the pro-apoptotic effect of serum withdrawal, increasing DNA fragmentation by 85 ± 55% and 72 ± 42%, respectively. The antiapoptotic effects of insulin and IGFs and the pro-apoptotic effect of LH, acting via the cAMP system, may be important in the maintenance of T-I homeostasis. Moreover, excessive levels of insulin and free IGFs may lead to T-I cell hyperplasia characteristic of conditions such as polycystic ovary syndrome.
Key words: apoptosis/insulin/insulin-like growth factors/LH/ovary/theca-interstitial cells
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