title: Insulin-like 3-induced rat preantral follicular growth is mediated by growth differentiation factor 9.
abstract: The communication of somatic cells and oocytes by intrafollicular paracrine factors is essential for follicular growth in the ovary. Insulin-like 3 (INSL3) is a theca cell-secreted paracrine factor. Androgens and growth differentiation factor 9 (GDF9), an oocyte-derived growth factor, are essential for follicular development. Using a rat preantral follicle culture model, we examined in the present study the influence of INSL3 on preantral follicular growth and the molecular mechanisms involved. We have observed that the receptor for INSL3, relaxin/insulin-like family peptide receptor 2 (RXFP2), was exclusively expressed in oocytes. Recombinant INSL3 stimulated Gdf9 expression, preantral follicular growth, and testosterone synthesis in vitro. Inhibition of the cAMP/protein kinase A signaling pathway (with cAMP antagonist, 8-bromoadenosine 3',5'-cyclic monophosphorothioate, Rp-isomer) attenuated INSL3-induced Gdf9 expression and preantral follicular growth. Moreover, knocking down Gdf9 expression (with small interfering RNA) or inhibiting GDF9 signaling (with SB431542, an activin receptor-like kinase receptor 5 inhibitor, or specific inhibitor of mothers against decapentaplegic homolog 3) or androgen action (with flutamide, an androgen receptor antagonist) suppressed INSL3-induced preantral follicular growth. In addition, LH and DHT regulated the expression of Insl3 mRNA in preantral follicles. These observations suggest that INSL3 is a key theca cell-derived growth factor for preantral follicle and that its action is mediated by GDF9.
authors.affiliation: State Key Laboratory in Reproductive Medicine (K.X., J.L.), Centre for Clinical Reproductive Medicine, Nanjing Medical University, Nanjing 210029, China; Departments of Obstetrics and Gynecology and Cellular and Molecular Medicine (K.X., J.Y.K., B.K.T.) and Interdisciplinary School of Health Sciences (B.K.T.), University of Ottawa, and Chronic Disease Program (K.X., J.Y.K., B.K.T.), Ottawa Hospital Research Institute, Ottawa K1H 8L6, Canada; and World Class University Biomodulation Major (J.Y.K., B.K.T.), Department of Agricultural Biotechnology, College of Agriculture and Life Sciences, Seoul National University, Seoul 151-742, Republic of Korea.
authors.forename: Kai
authors.initials: K
authors.lastname: Xue
authors.forename: Ji Young
authors.initials: JY
authors.lastname: Kim
authors.forename: Jia-yin
authors.initials: JY
authors.lastname: Liu
authors.forename: Benjamin K
authors.initials: BK
authors.lastname: Tsang
mesh_terms: D000818:Animals; D000242:Cyclic AMP / Q000378:metabolism; D005260:Female; D006107:Granulosa Cells / Q000166:cytology; D055429:Growth Differentiation Factor 9 / Q000378:metabolism*; D007150:Immunohistochemistry; D007328:Insulin / Q000378:metabolism*; D051379:Mice; D009865:Oocytes / Q000166:cytology; D006080:Ovarian Follicle / Q000254:growth & development*; D011506:Proteins / Q000378:metabolism*; D034741:RNA, Small Interfering / Q000378:metabolism; D051381:Rats; D017207:Rats, Sprague-Dawley; D043562:Receptors, G-Protein-Coupled / Q000378:metabolism; D015398:Signal Transduction; D013739:Testosterone / Q000378:metabolism; D013799:Theca Cells / Q000378:metabolism
chemical_list: C525899:Gdf9 protein, rat; D055429:Growth Differentiation Factor 9; D007328:Insulin; C084797:Leydig insulin-like protein; D011506:Proteins; D034741:RNA, Small Interfering; D043562:Receptors, G-Protein-Coupled; C511608:Rxfp2 protein, rat; D013739:Testosterone; D000242:Cyclic AMP