Antisense epidermal growth factor oligodeoxynucleotides inhibit follicle-stimulating hormone-induced in vitro DNA and progesterone synthesis in Hamster preantral follicles

Whether FSH-induced follicular DNA synthesis in the hamster involves epidermal growth factor (EGF) message induction and translation was evaluated using antisense EGF oligodeoxynucleotides. The 15 base pair antisense oligomers synthesized according to mouse EGF cDNA sequence downstream from the 5′-ATG start site hybridized with a 4.4-kilobase message of mouse submaxillary glands and with 4.0 kilobases of mRNA of hamster submaxillary glands, kidney, and ovaries. Preantral follicles at stages 1-7 were enzymatically and mechanically isolated from adult, cyclic hamsters on day 4:0900 h (day 1 = estrus), and follicles at stages 1-5 were isolated from hamsters hypophysectomized for 10 days. Follicles were preexposed to either antisense or sense EGF thio-oligomers for 1, 12, or 24 h and then cultured for an additional 24 h in the absence or presence of ovine-FSH (100 ng/ml) or recombinant murine EGF (50 ng/ml), and 1 μCi/ml [³H]thymidine. Follicular [³H]thymidine incorporation and EGF and steroid (progesterone, androstenedione, and 17β-estradiol) production were monitored to assess the molecular mechanism of FSH regulation of follicular development. Antisense oligomers significantly inhibited FSH-induced follicular DNA synthesis and progesterone but not androgen or estrogen production with a latency of 24 h. The oligomer inhibition of FSH action was effectively reversed by exogenous EGF. Antisense oligomers significantly inhibited follicular EGF synthesis in vitro. These results suggest that EGF message is expressed in the hamster ovary, and one of the molecular mechanisms of FSH regulation of hamster preantral folliculogenesis involves EGF mRNA induction and translation. A disruption of the cascade by antisense oligomers results in an inhibition of EGF synthesis and a subsequent block in DNA replication. Second, these results also suggest that FSH controls cell proliferation and steroidogenesis by two different signal pathways and a part of the FSH-induced progesterone production is mediated by EGF.