AROMATASE MESSENGER-RNA EXPRESSION IN INDIVIDUAL FOLLICLES FROM POLYCYSTIC OVARIES

Polycystic ovary syndrome (PCOS) is a-common reproductive disorder cha racterized by arrested follicular development prior to selection of a dominant follicle. Dominant follicles produce large amounts of oestrad iol but PCOS follicles do not. With several potential aromatase (P450( AROM)) inhibitors in follicular fluid, the question arises whether P45 0(AROM) is expressed in PCOS granulosa cells, but the activity is inhi bited, or whether P450(AROM) is not expressed in PCOS. The purpose of the present study was to determine whether P450(AROM) mRNA expression is altered in PCOS and to correlate P450(AROM) mRNA expression in indi vidual follicles with aromatase stimulatory bioactivity and oestradiol in the follicular microenvironments. P450(AROM) mRNA was measured in individual follicles from 16 PCOS and 48 regularly cycling control wom en by quantitative polymerase chain reaction (PCR) and correlated with follicular fluid oestradiol concentrations and aromatase stimulating bioactivity measured by the rat granulosa cells aromatase bioassay. Fo llicular fluid oestradiol was low in all control follicles <7 mm in di ameter. Some follicles greater than or equal to 7 mm contained elevate d oestradiol values (P < 0.01) and all had an androstenedione:oestradi ol ratio of <4. Only in granulosa cells from follicles greater than or equal to 7 mm with an androstenedione:oestradiol ratio of <4 were P45 0(AROM) mRNA levels increased (P< 0.05). These same follicles also con tained increased levels of aromatase stimulating bioactivity whereas f ollicles <7 mm or with androstenedione:oestradiol ratio of >4 containe d little or no bioactivity. All PCOS follicles contained low levels of oestradiol, P450(AROM) mRNA and aromatase stimulating bioactivity sim ilar to size-matched control follicles. These data indicate that P450( AROM) mRNA expression and oestradiol production begin in developing fo llicles when they reach similar to 7 mm in diameter. Oestradiol produc tion is low in PCOS follicles because there is insufficient aromatase stimulating bioactivity to increase P450(AROM) mRNA expression.