GnRH pulse generator activity in mouse models of polycystic ovary syndrome

One in ten women in their reproductive age suffer from polycystic ovary syndrome (PCOS) that, alongside subfertility and hyperandrogenism, typically presents with increased luteinizing hormone (LH) pulsatility. As such, it is suspected that the arcuate kisspeptin (ARN^KISS) neurons that represent the GnRH pulse generator are dysfunctional in PCOS. We used herein vivoGCaMP fiber photometry and other approaches to examine the behavior of the GnRH pulse generator in two mouse models of PCOS. We began with the peripubertal androgen (PPA) mouse model of PCOS but found that it had a reduction in the frequency of ARN^KISSneuron synchronization events (SEs) that drive LH pulses. Examining the prenatal androgen (PNA) model of PCOS, we observed highly variable patterns of pulse generator activity with no significant differences detected in ARN^KISSneuron SEs, pulsatile LH secretion, or serum testosterone, estradiol, and progesterone concentrations. However, an unsupervised machine learning approach identified that the ARN^KISSneurons of acyclic PNA mice continued to exhibit cyclical patterns of activity similar to that of normal mice. The frequency of ARN^KISSneuron SEs was significantly increased in algorithm-identified “diestrous stage” PNA mice compared to controls. In addition, ARN^KISSneurons exhibited reduced feedback suppression to progesterone in PNA mice and their pituitary gonadotrophs were also less sensitive to GnRH. These observations demonstrate the importance of understanding GnRH pulse generator activity in mouse models of PCOS. The existence of cyclical GnRH pulse generator activity in the acyclic PNA mouse indicates the presence of a complex phenotype with deficits at multiple levels of the hypothalamo-pituitary-gonadal axis.