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Mol Cell Endocrinol. 2014 Feb 15;382(2):804-13. doi: 10.1016/j.mce.2013.10.031. Epub 2013 Nov 8.

Knockdown of TrkA in cumulus oocyte complexes (COCs) inhibits EGF-induced cumulus expansion by down-regulation of IL-6.

Author information

1
Hefei National Laboratory for Physical Sciences at Microscale and School of Life Sciences, University of Science and Technology of China, Hefei, Anhui 230026, China.
2
Hefei National Laboratory for Physical Sciences at Microscale and School of Life Sciences, University of Science and Technology of China, Hefei, Anhui 230026, China; The First Affiliated Hospital of Zhengzhou University, Zhengzhou, Henan 450052, China.
3
Hefei National Laboratory for Physical Sciences at Microscale and School of Life Sciences, University of Science and Technology of China, Hefei, Anhui 230026, China. Electronic address: feisun@ustc.edu.cn.

Abstract

Tyrosine kinase receptor A (TrkA), the high-affinity receptor of nerve growth factor (NGF), is known to play key roles in ovarian follicular development, such as assembly of early follicles and follicular ovulation. However, little is known about the roles of TrkA in cumulus oocyte complex (COC) expansion. In this study, we found that TrkA was abundant in large antral follicles and knockdown of TrkA in COCs attenuated epidermal growth factor (EGF)-induced COC expansion and further decreased the ovulation rate. The effect of TrkA on COC expansion was not mediated through downstream EGF effectors, phosphorylation of extracellular regulated protein kinases 1/2 (ERK1/2) or drosophila mothers against decapentaplegic protein (SMAD), or through up-regulation of COC expansion-related transcripts such as prostaglandin-endoperoxide synthase 2 (Ptgs2), hyaluronan synthase 2 (Has2), TNF-induced protein 6 (Tnfaip6) or pentraxin 3 (Ptx3). However, pharmacological blockade of TrkA transducing activity (K252α) in COCs decreased the mRNA expression and protein secretion of interleukin-6 (IL-6), identified from mRNA microarray of K252α-treated COCs. Meanwhile, knockdown of IL-6 attenuated EGF-induced COC expansion. In addition, IL-6 rescued the inhibitory effect of K252α on EGF-induced cumulus expansion. Therefore, IL-6 may act as a new potential cumulus expansion-related transcript, which may be involved in the integration of TrkA and EGF signaling in affecting COC expansion. Here, we provide mechanistic insights into the roles of TrkA in EGF-induced cumulus expansion. Understanding potential cross-points between TrkA and EGF affecting cumulus expansion will help in the discovery of new therapeutic targets in ovulation-related diseases.

KEYWORDS:

BMSC; CCs; CEEFs; COC expansion; COCs; Cumulus oocyte complexes (COCs); EGF; ELISA; GCs; Has2; IL-6; Interleukin-6 (IL-6); NGF; Neurotrophic tyrosine kinase receptor type 1 (TrkA); Ptgs2; Ptx3; TNF-induced protein 6; Tnfaip6; TrkA; bone marrow stromal cells; cumulus cells; cumulus oocyte complexes; eCG; enzyme-linked immunosorbent assay; epidermal growth factor; equine chorionic gonadotropin; granulosa cells; hyaluronan synthase 2; interleukin-6; nerve growth factor; oocyte-secreted cumulus expansion-enabling factors; pentraxin 3; prostaglandin-endoperoxide synthase 2; tyrosine receptor kinase A

PMID:
24215827
DOI:
10.1016/j.mce.2013.10.031
[Indexed for MEDLINE]

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