Disrupted function of tumor necrosis factor-alpha-stimulated gene 6 blocks cumulus cell-oocyte complex expansion.
During ovulation, the oocyte and surrounding somatic cumulus cells contained within a specialized, mucoid matrix are released from the ovary. One matrix component, TNF-alpha-stimulated gene 6 (TSG-6), is a hyaluronan binding protein induced in cumulus cells of preovulatory follicles by the LH surge and is decreased in cumulus cells of COX-2 and prostaglandin E2 (PGE2) receptor subtype EP2 null mice that exhibit impaired ovulation and cumulus expansion. To determine if TSG-6 was hormonally induced in cumulus cells in vitro and was functional during the formation of the expanded matrix, we established a cumulus cell-oocyte complex (COC) culture system. This system was used to analyze the effects of FSH, PGE2, EP2 receptor, and selected protein kinase inhibitors on TSG-6 production as well as specific antibodies to the TSG-6 link module on TSG-6 function. We document that TSG-6 message and protein are induced by cAMP/protein kinase A/MAPK signaling pathways and that blocking these cascades prevents expansion and the production of TSG-6. FSH but not PGE2 rescued expansion and production of TSG-6 in the EP2 null COCs, indicating that generation of a cAMP signal is essential. Furthermore, disruption of the functional interactions between TSG-6, inter-alpha trypsin inhibitor, and hyaluronan with specific antibodies severely altered matrix formation and cumulus expansion, as recorded by time-lapse imaging. Collectively, these results indicate that TSG-6 mRNA is induced in cumulus cells in culture by cAMP and that the secreted TSG-6 protein is a key structural component of the mouse COC matrix.
Ochsner
Scott A
SA
Department of Molecular and Cellular Biology, Baylor College of Medicine, Houston, Texas 77030, USA.
Day
Anthony J
AJ
Rugg
Marilyn S
MS
Breyer
Richard M
RM
Gomer
Richard H
RH
Richards
Joanne S
JS
D000818:Animals; D015815:Cell Adhesion Molecules / Q000096:biosynthesis / Q000235:genetics / Q000502:physiology*; D002478:Cells, Cultured; D015232:Dinoprostone / Q000494:pharmacology; D004791:Enzyme Inhibitors / Q000494:pharmacology; D005260:Female; D005640:Follicle Stimulating Hormone / Q000494:pharmacology; D051379:Mice; D008810:Mice, Inbred C57BL; D018345:Mice, Knockout; D009865:Oocytes / Q000502:physiology*; D006080:Ovarian Follicle / Q000166:cytology / Q000502:physiology*; D047428:Protein Kinase Inhibitors; D012333:RNA, Messenger / Q000378:metabolism; D018078:Receptors, Prostaglandin E / Q000502:physiology; D058307:Receptors, Prostaglandin E, EP2 Subtype; D015398:Signal Transduction / Q000502:physiology
D015815:Cell Adhesion Molecules; D004791:Enzyme Inhibitors; D047428:Protein Kinase Inhibitors; C545645:Ptger2 protein, mouse; D012333:RNA, Messenger; D018078:Receptors, Prostaglandin E; D058307:Receptors, Prostaglandin E, EP2 Subtype; C513057:Tnfaip6 protein, mouse; D005640:Follicle Stimulating Hormone; D015232:Dinoprostone