Expression and regulation of stromal cell-derived factor-1 (SDF1) and chemokine CXC motif receptor 4 (CXCR4) in equine and bovine preovulatory follicles.

Abstract The interaction between stromal cell-derived factor-1 (SDF1) and chemokine CXC motif receptor 4 (CXCR4) has been implicated in leukocyte attraction, tissue remodeling and angiogenesis. The objective of the present study was to characterize the expression and regulation of SDF1 and CXCR4 in equine follicles during the ovulatory process. Equine preovulatory follicles were isolated during estrus 0–39 h after hCG treatment. Follicle wall preparations (theca interna with attached granulosa cells) and isolated preparations of granulosa cells and theca interna were obtained, and total RNA extracts were analyzed by RT-PCR/Southern blot. Results showed that levels of CXCR4 transcripts were induced by hCG in follicles at 36 h post-hCG ( P SDF1 transcripts were very low in granulosa cells but high in theca interna cells throughout most of the ovulatory period. Studies in vivo performed with bovine preovulatory follicles collected 0–24 h post-hCG revealed a marked and significant up-regulation of CXCR4 transcripts after hCG ( P CXCR4 mRNA up-regulation was observed in cultures of bovine granulosa cells treated with forskolin ( P CXCR4 mRNA was suppressed by co-treatment with inhibitors of PKA, ERK1/2 and EGFR, and by the progesterone receptor antagonist RU486 ( P CXCR4 transcript levels, whereas co-treatment with forskolin and a CXCR4 antagonist repressed the expression of several ovulation-related genes. Collectively, this study describes for the first time the gonadotropin-dependent up-regulation of CXCR4 transcript in ovarian follicles of large monoovulatory species, provides some insights into the regulation of CXCR4 gene expression in granulosa cells, and identifies a potential link between follicular SDF1/CXCR4 activation and the regulation of ovulation-related genes.