Regulation of transcripts encoding ADAMTS-1 (a disintegrin and metalloproteinase with thrombospondin-like motifs-1) and progesterone receptor by human chorionic gonadotropin in equine preovulatory follicles
One member of a new family of metalloproteinases, a disintegrin and metalloproteinase with thrombospondin-like motifs-1 (ADAMTS-1), has been found to be expressed and hormonally induced in granulosa cells of ovulating rodent follicles. Furthermore, the targeted disruption of the ADAMTS-1 gene resulted in ovarian defects associated with severely impaired fertility. While these data demonstrate the importance of ADAMTS-1 in rodent ovarian physiology, the potential role of ADAMTS-1 in the ovulatory process of monoovulatory species remains unknown. The objectives of this study were to clone the equine ADAMTS-1 primary transcript and to study its regulation during human chorionic gonadotropin (hCG)-induced ovulation. A 3573 bp follicular cDNA library clone was isolated and found to encode a nearly complete, highly conserved ADAMTS-1 homologue. Real-time RT-PCR analysis detected this transcript in diverse tIssues, including previously unreported sites of ADAMTS-1 expression such as the male reproductive tract, the follicular theca interna and the mature corpus luteum. The tIssue distribution of the progesterone receptor (PR), a known regulator of ADAMTS-1 expression in rodent preovulatory follicles, was found to overlap that of ADAMTS-1 in some tIssues. A study of the regulation of follicular ADAMTS-1 and PR mRNAs during the hCG-induced ovulatory process revealed distinct patterns of regulation in granulosa cells and in theca interna. In granulosa cells, ADAMTS-1 mRNA was found to be induced at 12 h post-hCG (P<0.05), followed by a return to basal levels by 30 h and a re-increase at 33-39 h (P<0.05). A concomitant increase in PR mRNA (P<0.05) was observed at 12 h post-hCG. In theca interna, abundant ADAMTS-1 mRNA was detected at all timepoints, and levels increased transiently at 33 h post-hCG (P<0.05), whereas no significant change was observed in PR mRNA. Together, these data demonstrate for the first time the hormonally regulated ovarian expression of ADAMTS-1 in a monoovulatory species, and identify a novel biphasic regulation of ADAMTS-1 in granulosa cells and a regulated expression in theca interna that were not previously observed in rodents.