Expression of scavenger receptor class B1 in endometrium and endometriosis

Endometriosis is characterized by the presence of endometrial glands and stroma within the peritoneum and other extrauterine sites. The presence of aromatase, a key enzyme in the biosynthesis of estradiol, has been demonstrated in eutopic endometrial samples of women with moderate to severe endometriosis, but not in those of disease-free women. Animal studies have shown that high density lipoprotein provides precursor cholesterol pool for steroidogenesis. Scavenger receptor class B1, a 82-kDa cell surface protein, is involved in the binding of high density lipoprotein to target cells and promotes cholesteryl ester uptake. In this study we detected the presence of scavenger receptor class B1 in eutopic and ectopic endometrium. There was more scavenger receptor class B1 protein associated with endometriosis compared with matched endometrium. Two bands (82 and 45 kDa) were detected in the endometrium and endometriosis samples. Glycanase treatment indicated that the 45-kDa protein might be a nonglycosylated form of scavenger receptor class B1. Immunostaining of fixed tissues detected scavenger receptor class B1 in glandular epithelium of both tissues. Scavenger receptor class B1 and aromatase mRNA were increased in endometriosis tissues. Scavenger receptor class B1 expression in the endometrium and endometriosis supports a role for this receptor in the uptake of high density lipoprotein cholesterol, possibly supporting in situ estrogen production, which is detrimental in the progression of endometriosis.