PARENT SESSION
OVARY - B

Tuesday, August 3, 2004
10:30 AM–12:30 PM
Buchanan Courtyard

(484) OOCYTES OF PRIMORDIAL FOLLICLES IN THE BABOON FETAL OVARY EXPRESS ESTROGEN RECEPTOR mRNA.

Bocca, Silvina^{1, 2}, Billiar, Reinhart¹, Davies, William¹, Albrecht, Eugene³, Pepe, Gerald¹, ¹ Eastern Virginia Medical School, Norfolk, VA² Eastern Virginia Medical School, Norfolk, VA³ University of Maryland School of Medicine, Baltimore, MD

ABSTRACT- We previously showed that in fetal ovaries of baboons deprived of estrogen, primordial follicles were 50% less numerous and contained oocytes with a reduced number of microvilli. Because oocytes rely on surrounding granulosa cells for substrate exchange, we proposed that estrogen regulates development of follicles with oocytes comprised of microvilli for long term survival. Although estrogen receptor (ER) and ER are detected by immunocytochemistry in pregranulosa (ER, ER) and granulosa (ER) cells of the primate fetal ovary, whether oocytes express ER is unknown. Therefore, we used Laser Capture Microdissection (LCM) and real time RT-PCR to determine whether ER/ mRNAs were expressed in oocytes of fetal ovaries obtained on day 165 of gestation (term = day 184) from baboons in which estrogen was suppressed (>95%) by administration of an aromatase inhibitor on days 100-165 (n=4) and from estrogen-replete animals untreated (n=3) or treated with aromatase inhibitor and estrogen (n=1). Oocyte nuclei and immediate surrounding cytoplasm from primordial follicles of paraffin embedded and frozen ovaries (mRNA results comparable) were captured onto an LCM cap (80-200 oocytes/2-3 sections/per animal), total RNA extracted and ER, ER, GATA-4 (granulosa cell specific marker) mRNAs and 18S rRNA determined and PCR products verified by sequencing. ER mRNA was expressed by oocytes of fetal ovaries from estrogen-replete animals, oocytes and endometrium of adult baboon ovary and uterus, respectively, and in fetal oocytes of 2 of 4 estrogen-suppressed animals. ER mRNA however, was not detected in adult oocytes or in fetal oocytes of estrogen-replete baboons but was expressed in fetal oocytes of 2 of 4 estrogen-suppressed animals as well as in adult baboon endometrium. Although 18S rRNA was expressed in all cells examined, GATA-4 mRNA was not detected in any fetal or adult oocytes but was detected in LCM captured granulosa cells confirming purity of isolated oocytes. Collectively, these results are the first to show that the oocyte of primordial follicles in the primate fetal ovary expresses ER mRNA and therefore provides a potential mechanism by which estrogen regulates oocyte microvillus development. Supported by NIH U54 HD 36207 as part of the Specialized Cooperative Centers Program in Reproduction Research.

KEY WORDS: fetal ovary, estrogen, estrogen receptor, folliculogenesis