Kiss1 and Kiss1r mRNA expression in the rat placenta: changes with gestational age and regulation by glucocorticoids

Kisspeptin, the neuropeptide product of the KISS1 gene, is synthesized by neurons within the hypothalamus and is critical for fertility. Human placenta also expresses KISS1 and kisspeptin receptor (KISS1R) mRNA within the trophoblast compartment, where it is thought to act as a physiological invasion inhibitor.

We determined the expression of Kiss1 mRNA in rat placenta and examined the effect of gestational age and feto-placental growth restriction, achieved through excess maternal glucocorticoid exposure.

Dexamethasone induced fetal growth restriction at both day 16 and day 22 of gestation, but placental growth restriction only at day 22. Real-time quantitative RT-PCR revealed an increase in Kiss1 and Kiss1r mRNA from day 16-22 in the labyrinth and junctional zones of the rat placenta. Immunolocalization confirmed kisspeptin expression in the placenta and was prominent in trophoblast tissue. Dexamethasone exposure elevated the expression of Kiss1 mRNA in the labyrinth and junctional zones of day 16 placentas. In contrast, Kiss1 mRNA in the labyrinth zone was reduced following dexamethasone-treatment at day 22. Kiss1r expression was increased in both placental zones at day 16 and 22 in response to dexamethasone-treatment.

We confirm the presence of Kiss1 and Kiss1r mRNA in the rat placenta with expression increasing over the final third of pregnancy, suggestive of a role in restricting placental growth. Furthermore, the effects of dexamethasone on placental Kiss1/Kiss1r suggest glucocorticoid-induced placental growth retardation could be mediated, in part, via early stimulation of Kiss1 and the subsequent inhibition of trophoblast proliferation and invasion.