Cholesterol uptake or trafficking, steroid biosynthesis, and gonadotropin responsiveness are defective in young poor responders.

ABSTRACT

OBJECTIVE: To investigate whether poor ovarian response in young patients undergoing in vitro fertilization simply involves lesser follicle growth due to diminished ovarian reserve or whether there are intrinsic perturbations in the ovary. DESIGN: A translational research study. SETTING: University Hospital Translational Research Center. PATIENT(S) A total of 40 patients undergoing in vitro fertilization (20 normal and 20 poor responders) with ovarian stimulation using a gonadotropin-releasing hormone antagonist and recombinant follicle-stimulating hormone were included in the study. INTERVENTION(S) None. MAIN OUTCOME MEASURE(S) Luteal granulosa cells obtained during oocyte retrieval procedures were used for the experiments. Cell culture, quantitative real-time polymerase chain reaction, immunoblotting, confocal time-lapse live-cell imaging, and hormone assays were used. RESULT(S) We tracked the steroidogenic pathway starting from the very initial step of cholesterol uptake to the final step of estradiol and progesterone production in luteal granulosa cells and identified some previously unknown intrinsic defects in the poor responders. Most notably, the expression of low-density lipoprotein receptors was significantly down-regulated and the uptake of cholesterol and its cytoplasmic accumulation and transportation to mitochondria were substantially delayed and reduced in the poor responders. Further, the expression of the steroidogenic enzymes steroidogenic acute regulatory protein, 3ß-hydroxysteroid dehydrogenase, and aromatase as well as gonadotropin receptors was defective, and the response of the cells to exogenous follicle-stimulating hormone and human chorionic gonadotropin was blunted, leading to compromised basal and gonadotropin-stimulated estradiol and progesterone production in the poor responders. CONCLUSION(S) This study demonstrates that poor ovarian response in young individuals should not simply be regarded as lesser follicle growth due to diminished ovarian reserve because the underlying pathogenetic mechanisms appear to be much more complex.