DOI 10.1095/biolreprod.104.036145 Expression of Basigin, an Inducer of Matrix Metalloproteinases, in the Rat Ovary1

The extensive tissue remodeling that occurs during follicular development, ovulatory rupture, and the formation and regres-sion of the corpus luteum (CL) requires local degradation of the extracellular environment by matrix metalloproteinases (MMPs). This report characterizes the expression pattern of basigin (Bsg), a putative regulator of MMP induction, in the rat ovary. An in-duced superovulation model (eCG/hCG) was used in immature rats to evaluate Bsg expression profiles in ovaries collected dur-ing the follicular phase, the preovulatory period, and the luteal lifespan. Levels of Bsg mRNA were unchanged through follicular growth (0–48 h post-eCG) and increased during postovulatory luteinization (24 and 48 h post-hCG; P, 0.01). Bsg expression persisted into pseudopregnancy (4–8 days post-hCG) and after functional luteal regression (12 days post-hCG). The profile of Bsg expression during regression of the CL was examined using a model of induced luteolysis. Both functional and structural regression was associated with a decline in Bsg expression lev-els. Bsg mRNA and protein localized to the theca of preovula-tory follicles (12 h post-hCG) and formative and functional CL (24 h–8 days post-hCG). Bsg expression profiles in the induced ovulation and CL regression models were similar to observations made in naturally cycling mature rats. In the cycling ovary, Bsg signaling localized to newly forming CL, the theca of preovu-latory follicles, and appeared to be lower in CL from previous estrous cycles. A putative regulatory mechanism of Bsg expres-sion was identified using an in vitro model; treatment of cul-tured granulosa cells with hCG significantly augmented Bsg mRNA expression levels. The processes of ovulation and luteo-genesis may be facilitated by Bsg expression and its induction or regulation of the MMPs. corpus luteum, follicular development, ovary, ovulation, theca cell