Cell-specific localization of oestrogen receptor beta (ESR2) mRNA within various bovine ovarian cell types using in situ hybridization

The localization of oestrogen receptor beta (ESR2) mRNA, in this article denominated as (ERbeta) mRNA, was examined using in situ hybridization in the ovaries of randomly selected cows, irrespective of the cycle stage of the animals. A 602-bp fragment of ERbeta mRNA was cloned, sequenced and digoxigenin (DIG)-labelled. Semi-quantitative evaluation showed that the scores for ERbeta mRNA were moderate to high in the follicle cells of both primordial and primary follicles, but lower in granulosa cells of secondary follicles. In vital tertiary follicles, the total ERbeta mRNA expression was low but varied between the different animals. In both obliterative and cystic atretic follicles, high to moderate ERbeta mRNA scores were noticed in the granulosa cells. The stroma cells surrounding primordial and primary follicles and the theca cells of secondary follicles showed moderate ERbeta mRNA levels, whereas the ERbeta mRNA score in theca interna and theca externa cells of vital tertiary follicles was distinctly higher. In the theca cells of atretic follicles the score was even higher. Cells of corpora hemorrhagica and corpora lutea had moderate ERbeta mRNA scores, while higher scores were seen in cells of corpora albicantia. Cells of the surface epithelium had a moderate score for ERbeta mRNA, whereas cells of the tunica albuginea and deep stroma showed high ERbeta mRNA scores. The present findings have clearly established a cell-specific localization of ERbeta mRNA in several cell types in the bovine ovary.