Bone morphogenetic protein-6 enhances gonadotrophin-dependent progesterone and inhibin secretion and expression of mRNA transcripts encoding gonadotrophin receptors and inhibin/activin subunits in chicken granulosa cells.
The aims were to examine ovarian expression of bone morphogenetic protein (BMP) ligands/receptor mRNAs in the chicken and to test the hypothesis that theca-derived BMP(s) modulates granulosa cell function in a paracrine manner. RT-PCR revealed expression of multiple BMPs in granulosa and theca cells from pre hierarchical and preovulatory follicles with greater expression in theca cells; both cell types expressed BMP receptors-IA, -IB and -II consistent with tissue responsiveness. Preovulatory granulosa cells (F1, F2 and F3/4) were cultured with BMP-6 (expressed by theca but not granulosa) in the presence/absence of LH, FSH or 8-Br-cAMP. BMP-6 increased 'basal' and gonadotrophin-induced inhibin-A and progesterone secretion by each cell type but did not enhance the effect of 8-Br-cAMP. This indicates that the observed synergism between BMP-6 and gonadotrophin might involve BMP-induced up-regulation of gonadotrophin receptors. In support of this, BMP-6 alone increased LH-receptor (LHR) mRNA in F1 cells and FSH-receptor (FSHR) mRNA in F1, F2 and F3/4 cells. BMP-6 also enhanced LH/FSH-induced LHR transcript amount in each cell type but did not raise FSHR transcript amounts above those induced by BMP-6 alone. To further explore BMP-6 action on inhibin-A secretion, we quantified inhibin/activin subunits (alpha, beta(A), beta(B)) mRNAs. Consistent with its effect on inhibin-A secretion, BMP-6 enhanced 'basal' expression of alpha- and beta(A)-subunit mRNA in F1, F2 and F3/4 cells, and beta(B)-subunit mRNA in F3/4 cells. BMP-6 markedly enhanced FSH/LH-induced expression of alpha-subunit in all follicles and FSH-induced beta(A)-subunit in F2 and F3/4 follicles but not in F1 follicles. Neither BMP-6 alone, nor FSH/LH alone, affected 'basal' beta(B) mRNA abundance. However, co-treatment with gonadotrophin and BMP-6 greatly increased beta(B)-subunit expression, the response being lowest in F1 follicles and greatest in F3/4 follicles. Collectively, these results support the hypothesis that intraovarian BMPs of thecal origin have a paracrine role in modulating granulosa cell function in the chicken in a preovulatory stage-dependent manner.
School of Biological Sciences, University of Reading, AMS Building, Whiteknights, Reading, RG6 6AJ, UK.
Sara L
SL
Al-Musawi
Richard T
RT
Gladwell
Philip G
PG
Knight
D028341:Activins / Q000235:genetics; D000818:Animals; D055418:Bone Morphogenetic Protein 6; D019485:Bone Morphogenetic Proteins / Q000032:analysis / Q000378:metabolism / Q000502:physiology*; D002470:Cell Survival; D002478:Cells, Cultured; D002645:Chickens / Q000378:metabolism*; D005260:Female; D006065:Gonadotropins, Pituitary / Q000494:pharmacology; D006107:Granulosa Cells / Q000378:metabolism*; D007118:Immunoassay; D007265:Inhibins / Q000235:genetics / Q000378:metabolism; D019899:Paracrine Communication; D011374:Progesterone / Q000378:metabolism; D012333:RNA, Messenger / Q000032:analysis; D011967:Receptors, Gonadotropin / Q000235:genetics; D020133:Reverse Transcriptase Polymerase Chain Reaction; D013799:Theca Cells / Q000378:metabolism
D055418:Bone Morphogenetic Protein 6; D019485:Bone Morphogenetic Proteins; D006065:Gonadotropins, Pituitary; D012333:RNA, Messenger; D011967:Receptors, Gonadotropin; C422362:inhibin A; C422364:inhibin B; D028341:Activins; D011374:Progesterone; D007265:Inhibins