Abstract
Context
Human granulosa cells (hGCs) produce and respond to insulin-like growth factor 2 (IGF2) but whether the oocyte participates in IGF2 regulation in humans is unknown.
Objective
To determine the role of oocyte-secreted factors (OSFs) such as growth differentiation factor 9 (GDF9) and bone morphogenetic protein 15 (BMP15) in IGF2 production by hGCs.
Design
Primary human cumulus GCs in culture.
Setting
University infertility center.
Patients or Other Participants
GCs of women undergoing in vitro fertilization.
Intervention(s)
Cells treated with GDF9 and BMP15 in the presence of vehicle, follicle-stimulating hormone (FSH), dibutyryl cyclic-AMP (dbcAMP), or mothers against decapentaplegic homolog (SMAD) inhibitors.
Main Outcome Measure(s)
Quantification of mRNA, protein, promoter activity, and DNA methylation.
Results
FSH stimulation of IGF2 (protein and mRNA) was significantly potentiated by the GDF9 and BMP15 (G+B) combination (P < 0.0001) in a concentration-dependent manner showing a maximal effect at 5 ng/mL each. However, GDF9 or BMP15 alone or in combination (G+B) have no effect on IGF2 in the absence of FSH. FSH stimulated IGF2 promoter 3 activity, but G+B had no effect on promoter activity. G+B potentiated IGF2 stimulation by cAMP. SMAD3 inhibitors inhibited G+B enhancement of IGF2 stimulation by FSH (P < 0.05) but had no effect on FSH induction. Moreover, inhibition of insulin-like growth factor receptor partially blocked G+B potentiation of FSH actions (P < 0.009).
Conclusions
For the first time, we show that the oocyte actively participates in the regulation of IGF2 expression in hGCs, an effect that is mediated by the specific combination of G+B via SMAD2/3, which in turn target mechanisms downstream of the FSH receptor.
Oxytocin affects the release of steroids, insulin-like growth factor-I, prostaglandin F2 and cyclic nucleotides by human granulosa cells in vitro
