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1 May 2004 Estrogen Is Not Directly Required for Oocyte Developmental Competence
Kim Huynh, Gayle Jones, George Thouas, Kara L. Britt, Evan R. Simpson, Margaret E. E. Jones
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Oocyte maturation and ovulation require a coordinated interaction between gonadotrophs, steroid hormones, and growth factors. The extent to which estrogen is required in this process, however, remains unclear. To better understand the role of estrogen in maintaining developmental competence of mammalian oocytes, we studied the Aromatase knockout (ArKO) mouse, which has been genetically engineered to be incapable of synthesizing endogenous estrogen. Previous studies have established that ArKO female mice are anovulatory with ovaries that progressively degenerate, developing hemorrhagic cystic follicles. In young ArKO females, however, apparently healthy follicles and oocytes have been observed. We investigated if these oocytes could be induced to ovulate, then mature, fertilize, and develop in vitro. Following a standard superovulation protocol, ArKO oocytes did not ovulate. When recovered manually from the ovary, however, ArKO oocytes successfully progressed through in vitro maturation, fertilization, and development to the blastocyst stage at the same rate as wild-type and heterozygote littermates. Therefore, it appears that estrogen is not required for the production and growth of oocytes capable of maturation and complete preimplantation development but is required for continued follicle growth and feedback regulation of ovulation.

Kim Huynh, Gayle Jones, George Thouas, Kara L. Britt, Evan R. Simpson, and Margaret E. E. Jones "Estrogen Is Not Directly Required for Oocyte Developmental Competence," Biology of Reproduction 70(5), 1263-1269, (1 May 2004).
Received: 11 August 2003; Accepted: 1 December 2003; Published: 1 May 2004
cumulus cells
gamete biology
in vitro fertilization
oocyte development
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