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Effects and mechanisms of growth differentiation factor 9 on activin A-regulated inhibin B and progesterone production in human granulosa cells Shi, Fengtao
Abstract
Activin A (homodimer of inhibin βA-subunit) is known to increase inhibin βB-subunit and inhibin B (heterodimer of inhibin α- and βB-subunit) levels and decrease progesterone accumulation in human granulosa cells. Growth differentiation factor 9 (GDF9) is a potent paracrine regulator of ovarian function, but its overall effects, particularly relating to activin A actions, are unknown. We examined the potential crosstalk between activin A and GDF9 in primary cultures of human granulosa-lutein (hGL) cells. Pretreatment of hGL cells with GDF9 for 24 h resulted in an increased expression of activin receptors and Smad2/3, and decreased inhibitory Smad7 activity. These effects were attenuated by BMP type II receptor ectodomain (BMPR2 ECD), a GDF9 antagonist. These GDF9-induced changes, in turn, increased the cellular response to activin A stimulation and resulted in significantly greater production of βB-subunit mRNA and inhibin B compared to activin A treatment alone. Interestingly, endogenous GDF9 mRNA and protein were detected in hGL cells. Reduction of endogenous GDF9 by GDF9 siRNA resulted in decreased levels of activin receptors and Smad2/3/4, but increased expression of Smad7. Consequently, GDF9 siRNA treatment significantly attenuated the stimulation of activin A on βB-subunit mRNA and inhibin B levels. Additionally, GDF9 suppressed the expression of follistatin (FST) and follistatin-like 3 (FSTL3), which are extracellular inhibitors of activin A. These effects were attenuated by BMPR2 ECD and GDF9 siRNA. Treatment with FST or FSTL3 siRNA augmented activin A-induced βB-subunit mRNA levels. Conversely, GDF9 enhancement of activin A-induced βB-subunit mRNA was attenuated by FST. Activin A decreased expression of StAR but not P450scc and 3βHSD, this effect lead to reduced basal and FSH-induced progesterone accumulation. GDF9 reversed these effects of activin A on StAR and progesterone; these GDF9 effects were attenuated by inhibin α-subunit siRNA. Together, these findings support a novel hypothesis that GDF9 exerts both paracrine and autocrine control of key components in the activin receptor-signaling pathway and the extracellular inhibition of activin A in hGL cells. As a result, GDF9 may serve to enhance activin A-induced accumulation of inhibin B, which in turn acts to reverse activin A suppression of progesterone accumulation during granulosa cell luteinization.
Item Metadata
Title |
Effects and mechanisms of growth differentiation factor 9 on activin A-regulated inhibin B and progesterone production in human granulosa cells
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Creator | |
Publisher |
University of British Columbia
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Date Issued |
2010
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Description |
Activin A (homodimer of inhibin βA-subunit) is known to increase inhibin βB-subunit and inhibin B (heterodimer of inhibin α- and βB-subunit) levels and decrease progesterone accumulation in human granulosa cells. Growth differentiation factor 9 (GDF9) is a potent paracrine regulator of ovarian function, but its overall effects, particularly relating to activin A actions, are unknown.
We examined the potential crosstalk between activin A and GDF9 in primary cultures of human granulosa-lutein (hGL) cells. Pretreatment of hGL cells with GDF9 for 24 h resulted in an increased expression of activin receptors and Smad2/3, and decreased inhibitory Smad7 activity. These effects were attenuated by BMP type II receptor ectodomain (BMPR2 ECD), a GDF9 antagonist. These GDF9-induced changes, in turn, increased the cellular response to activin A stimulation and resulted in significantly greater production of βB-subunit mRNA and inhibin B compared to activin A treatment alone.
Interestingly, endogenous GDF9 mRNA and protein were detected in hGL cells. Reduction of endogenous GDF9 by GDF9 siRNA resulted in decreased levels of activin receptors and Smad2/3/4, but increased expression of Smad7. Consequently, GDF9 siRNA treatment significantly attenuated the stimulation of activin A on βB-subunit mRNA and inhibin B levels.
Additionally, GDF9 suppressed the expression of follistatin (FST) and follistatin-like 3 (FSTL3), which are extracellular inhibitors of activin A. These effects were attenuated by BMPR2 ECD and GDF9 siRNA. Treatment with FST or FSTL3 siRNA augmented activin A-induced βB-subunit mRNA levels. Conversely, GDF9 enhancement of activin A-induced βB-subunit mRNA was attenuated by FST.
Activin A decreased expression of StAR but not P450scc and 3βHSD, this effect lead to reduced basal and FSH-induced progesterone accumulation. GDF9 reversed these effects of activin A on StAR and progesterone; these GDF9 effects were attenuated by inhibin α-subunit siRNA.
Together, these findings support a novel hypothesis that GDF9 exerts both paracrine and autocrine control of key components in the activin receptor-signaling pathway and the extracellular inhibition of activin A in hGL cells. As a result, GDF9 may serve to enhance activin A-induced accumulation of inhibin B, which in turn acts to reverse activin A suppression of progesterone accumulation during granulosa cell luteinization.
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Genre | |
Type | |
Language |
eng
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Date Available |
2010-10-06
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Provider |
Vancouver : University of British Columbia Library
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Rights |
Attribution-NonCommercial-NoDerivatives 4.0 International
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DOI |
10.14288/1.0071346
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URI | |
Degree | |
Program | |
Affiliation | |
Degree Grantor |
University of British Columbia
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Graduation Date |
2010-11
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Campus | |
Scholarly Level |
Graduate
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Rights URI | |
Aggregated Source Repository |
DSpace
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Rights
Attribution-NonCommercial-NoDerivatives 4.0 International