Effects of endogenous growth differentiation factor 9 on activin A-induced inhibin B production in human granulosa-lutein cells.
BACKGROUND
We recently reported on the effects of exogenous growth differentiation factor 9 (GDF9) in enhancing activin A-induced inhibin beta(B)-subunit mRNA and inhibin B levels in human granulosa-lutein (hGL) cells by modulating key components of the activin signaling pathway. We undertook the following study to characterize the role of endogenous GDF9 in this regard.


METHODS
We compared inhibin subunit (alpha, beta(A), and beta(B)) mRNA and inhibin B levels and activation of activin receptors (ACVRs) and Smad signaling pathway in hGL cells obtained from women undergoing in vitro fertilization and cultured with and without activin A treatment after GDF9-targeting small interfering RNA transfection. GDF9, inhibin subunits, ACVR2B/1B and Smad2/3/4/7 mRNA and/or protein levels, Smad phosphorylation, and inhibin B were assessed with RT-PCR, immunoblotting, and ELISA. Data were analyzed by ANOVA followed by Tukey's test.


RESULTS
GDF9 was detected as mRNA and protein in hGL cells and protein in follicular fluid from all 11 patients tested. Reduced endogenous GDF9 expression after targeting small interfering RNA transfection was associated with decreased ACVR2B/1B and Smad2/3/4 but increased inhibitory Smad7 mRNA and protein levels and, consequently, reduced activin A-induced beta(B)-subunit mRNA and inhibin B levels.


CONCLUSIONS
We report here for the first time autocrine roles for endogenous GDF9 in hGL cells in enhancing activin A-induced beta(B)-subunit mRNA and inhibin B levels via key components of the activin signaling pathway. However, the relative contributions of GDF9 in granulosa cells vs. oocyte as autocrine/paracrine regulators of beta(B)-subunit and inhibin B production in normal and abnormal human ovarian functions remain to be determined.
Department of Obstetrics and Gynaecology, Child and Family Research Institute, University of British Columbia, 4490 Oak Street, Vancouver, British Columbia, Canada V6H 3V5.
Feng-Tao
FT
Shi
Anthony P
AP
Cheung
He-Feng
HF
Huang
Peter C K
PC
Leung
D029404:Activin Receptors / Q000187:drug effects; D028341:Activins / Q000494:pharmacology*; D000328:Adult; D015153:Blotting, Western; D002478:Cells, Cultured; D005260:Female; D006107:Granulosa Cells / Q000187:drug effects / Q000378:metabolism*; D055429:Growth Differentiation Factor 9 / Q000235:genetics* / Q000502:physiology*; D006801:Humans; D007265:Inhibins / Q000096:biosynthesis*; D008184:Luteal Cells / Q000187:drug effects / Q000378:metabolism*; D008597:Menstrual Cycle / Q000502:physiology; D012333:RNA, Messenger / Q000096:biosynthesis / Q000235:genetics; D034741:RNA, Small Interfering; D020133:Reverse Transcriptase Polymerase Chain Reaction; D015398:Signal Transduction / Q000235:genetics / Q000502:physiology; D051785:Smad Proteins / Q000378:metabolism; D014162:Transfection
C525897:GDF9 protein, human; D055429:Growth Differentiation Factor 9; D012333:RNA, Messenger; D034741:RNA, Small Interfering; D051785:Smad Proteins; C422405:activin A; C422364:inhibin B; D028341:Activins; D007265:Inhibins; D029404:Activin Receptors