Simulation of human luteal endocrine function with granulosa lutein cell culture

Human granulosa cells collected from in vitro fertilization have previously been cultured to provide a system to simulate the granulosa lutein cells of the corpus luteum. In most of these systems, the cultures have been relatively short term, and attempts to simulate the normal pattern of hormone production observed during the luteal phase of the cycle have not been reported. Additionally, the hormone relaxin has generally been absent from the endocrine analysis of these systems. In this report, methods were used that supported secretion of ovarian steroids and relaxin that mimics the profiles of these hormones in vivo. This system was used to observe the endocrine responses of the granulosa lutein cells to three different protocols of CG administration designed to mimic the normal luteal phase, early pregnancy, and early pregnancy followed by pregnancy loss. The normal luteal phase was simulated by a constant baseline (0.02 IU/mL) CG model to simulate a nonconceptive cycle (baseline). The second model was baseline CG until day 8 of culture, followed by daily doubling from days 9-17 to simulate an early pregnancy (rescue-plateau). CG concentrations were then held constant from days 17-20 (5.12 IU/mL). A third model (rescue-drop) was used that was identical to the early pregnancy model except that on day 17 CG was returned to baseline concentrations (0.02 IU/mL) to simulate an early pregnancy loss. Baseline CG stimulation resulted in profiles of estrogen, progesterone, and relaxin secretion in culture that were closely related to secretory profiles previously reported in serum during the nonconceptive luteal phase. The timing of appearance of relaxin secretion and later declines in steroid and relaxin secretion paralleled that observed in serum. In the CG rescue protocols, ovarian steroids rose in response to daily doubling of CG and fell when CG either plateaued or fell. Relaxin did not show an increase in response to increasing CG, but its secretion did not drop when CG concentrations plateaued or dropped. This cell culture system model mimics the profile of ovarian steroids and relaxin seen in serum during the nonconceptive luteal phase, although the relative magnitude of the hormones was not the same as seen in vivo. It was also used to investigate responses to luteal rescue protocols designed to simulate early pregnancy and pregnancy loss. This culture system may be useful to study differences in endocrine response in granulosa cells collected from different patients and to provide information of clinical relevance. This culture system provides a model to study luteal function and its response to different protocols of luteal rescue and thus may provide insight into early pregnancy and pregnancy loss.