Estrous cycle disruption during experimental autoimmune encephalomyelitis is followed by the changes in hypothalamic kisspeptin expression

Abstract

Introduction. Multiple sclerosis (MS) is a chronic neuroinflammatory disease that is at least twice as common in women as it is in men. Since the effects of neuroinflammation on reproductive functions haven't been thoroughly investigated in MS or its animal models, we wanted to explore the changes in the hypothalamo-pituitary-gonadal axis, in a rat model of MS, experimental autoimmune encephalomyelitis (EAE), focusing on kisspeptin as a key regulator of the mammalian reproductive axis. Methods. Dark-Agouti rats were used and EAE actively induced by an intradermal injection of 150 µl mixture of the spinal cord homogenate and complete Freund’s adjuvant (CFA). Naïve animals served as controls. The rats were examined daily for disease symptoms, weight changes, and estrous cycle phase. The animals were sacrificed 9, 14 and 28 days after induction, corresponding to the phases of the disease – onset, peak, and recovery, respectively. The hypothalamic tissue was isolated and the obtained cDNA used for qRT-PCR. For kisspeptin immunohistochemistry, the whole brains were fixed, cryo-preserved and cut on a cryotome. Results. With the onset of the disease, females stop cycling and get arrested in diestrus phase, which is accompanied with a significant drop in serum luteinizing hormone levels.HypothalamicKiss1mRNA expression was significantly lower at the peak of the disease, compared to the control group. Immunohistochemical analysis indicates a decrease of kisspeptin immunoreactivity in the arcuate nucleus and median eminence. Conclusion. Our results implicate that EAE affects the expression of kisspeptin and thus the regulation of hypothalamo-pituitarygonadal axis, but further analyses are needed to explain the details of this process.