EXPRESSION OF CYCLOOXYGENASE 1 & 2 GENES IN PRIMATE OVULATORY FOLLICLES

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Little is known about the gonadotropin-stimulated molecular events in granulosa cells which lead to ovulation and luteinization of the follicle in primates. A novel subtractive hybridization strategy was used to identify gene products with enhanced expression in granulosa cells in response to the ovulatory LH surge. Granulosa cells were harvested from rhesus monkeys (n=3/group) receiving recombinant human gonadotropins (Ares Advanced Technology, Inc.) to stimulate the development of multiple large follicles, either before (nonluteinized) or 27 hours after (luteinized) administration of an ovulatory dose of gonadotropin. A reusable single-stranded cDNA library was prepared from nonluteinized and luteinized granulosa cells by reverse transcription of polyA+ RNA hybridized to oligo dT-linked magnetic beads. Oligonucleotide probes prepared by random priming of the luteinized granulosa cell cDNA library were allowed to hybridize with the nonluteinized granulosa cell cDNA library. Unhybridized oligonucleotides (representing genes with at least 8-fold enhanced expression by luteinized compared to nonluteinized granulosa cells) were used to screen a monkey luteal cDNA library. To date, cDNA sequences obtained from 37 positive plaques have been compared to available databases. Several cDNAs did not match any known sequences, suggesting that these represent novel gene products involved in ovulation and luteinization. Granulosa cell expression of thymosin b-10, ubiquitin, and various mitochondrial and ribosomal protein genes was also enhanced. cDNAs for cyclooxygenase (COX)-1 and COX-2 were obtained, and enhanced expression of both COX-1 and COX-2 in granulosa cells following the gonadotropin surge was verified by immunocytochemistry. Since the expression of COX genes by granulosa cells is enhanced following the ovulatory gonadotropin surge in rodents and domestic animals, these data confirm the successful selection of gonadotropin-stimulated genes and support a role for prostaglandins (PG) in periovulatory processes in primates. Future studies will examine the temporal relationship between the ovulatory gonadotropin surge, the initiation of COX-1 and COX-2 expression, and PG production by granulosa cells of primate follicles. The hypothesis that gonadotropin act directly at granulosa cells to stimulate COX expression and enhance the levels of biochemical markers related to luteinization and rupture of the follicle will be tested using a combination of in vitro and in vivo techniques. These studies are applicable to both the treatment of conditions contributing to infertility, such as luteinized unruptured follicle syndrome, as well as the development of new contraceptives which would block ovulation. The data described above forms the basis for a proposal for extramural funding.