Human oocyte maturation is dependent on LH-stimulated accumulation of the epidermal growth factor-like growth factor, amphiregulin

Hum Reprod. 2010 Oct;25(10):2569-78. doi: 10.1093/humrep/deq212. Epub 2010 Aug 18.

Abstract

Background: The LH surge promotes ovulation via activation of multiple signaling networks in the ovarian follicle. Studies in animal models have shown the importance of LH-induced activation of the epidermal growth factor (EGF)signaling network in critical peri-ovulatory events. We investigated the biological significance of regulatory mechanisms mediated by EGF-like growth factors during LH stimulation in humans.

Methods: We characterized the EGF signaling network in mature human ovarian follicles using in vivo and in vitro approaches. Amphiregulin (AREG) levels were measured in 119 follicular fluid (FF) samples from IVF/ICSI patients. Biological activity of human FF was assessed using in vitro oocyte maturation, cumulus expansion and cell mitogenic assays.

Results: AREG is the most abundant EGF-like growth factor accumulating in the FF of mature follicles of hCG-stimulated patients. No AREG was detected before the LH surge or before hCG stimulation of granulosa cells in vitro, demonstrating that the accumulation of AREG requires gonadotrophin stimulation. Epiregulin and betacellulin mRNA were detected in both human mural and cumulus granulosa cells, although at significantly lower levels than AREG. FF from stimulated follicles causes cumulus expansion and oocyte maturation in a reconstitution assay. Immunodepletion of AREG abolishes the ability of FF to stimulate expansion (P < 0.0001) and oocyte maturation (P < 0.05), confirming the biological activity of AREG. Conversely, mitogenic activity of FF remained after depletion of AREG, indicating that other mitogens accumulate in FF. FF from follicles yielding an immature germinal vesicle oocyte or from an oocyte that develops into an aberrant embryo contains lower AREG levels than that from follicles yielding a healthy oocyte (P = 0.008).

Conclusions: EGF-like growth factors play a role in critical peri-ovulatory events in humans, and AREG accumulation is a useful marker of gonadotrophin stimulation and oocyte competence.

Publication types

  • Research Support, N.I.H., Extramural

MeSH terms

  • Adult
  • Amphiregulin
  • Betacellulin
  • Biomarkers / analysis
  • Biomarkers / metabolism
  • Chorionic Gonadotropin / metabolism
  • EGF Family of Proteins
  • Epidermal Growth Factor / analysis
  • Epidermal Growth Factor / metabolism
  • Epiregulin
  • Female
  • Follicular Fluid / chemistry
  • Follicular Fluid / metabolism
  • Glycoproteins / analysis
  • Glycoproteins / metabolism*
  • Granulosa Cells / chemistry
  • Granulosa Cells / metabolism
  • Humans
  • Intercellular Signaling Peptides and Proteins / analysis
  • Intercellular Signaling Peptides and Proteins / metabolism*
  • Luteinizing Hormone / pharmacology*
  • Middle Aged
  • Mitosis / drug effects
  • Oocytes / chemistry
  • Oocytes / growth & development*
  • Oocytes / metabolism*
  • Oogenesis / drug effects*

Substances

  • AREG protein, human
  • Amphiregulin
  • BTC protein, human
  • Betacellulin
  • Biomarkers
  • Chorionic Gonadotropin
  • EGF Family of Proteins
  • EREG protein, human
  • Epiregulin
  • Glycoproteins
  • Intercellular Signaling Peptides and Proteins
  • Epidermal Growth Factor
  • Luteinizing Hormone