Abstract
Miscarriage is defined as the spontaneous loss of pregnancy occurring from implantation to mid gestation, and in humans is the most common pregnancy complication. A higher maternal age is associated with increased likelihood of miscarriage. Therefore, it is important to investigate the mechanism by which miscarriage occurs to ensure healthy term pregnancies.
The circulating levels of kisspeptin (a neuropeptide, but also a placental hormone) in women experiencing miscarriage are lower compared to women with full term pregnancies. Kisspeptin also inhibits excessive trophoblast invasion during implantation and stimulates progesterone secretion (another hormone for maintaining a healthy pregnancy). Thus, reduced levels of these hormones may result in failed implantation, and consequently cause miscarriage.
This project aimed to confirm a direct relationship between kisspeptin and progesterone levels in relation to miscarriage, and then establish whether inhibiting the secretion of kisspeptin would change the pregnancy outcome in young mice.
The first experiment showed that aged mice (8 months, equivalent to a ~35 years old woman) in comparison to young mice (2-3 months), have a significantly lower number of healthy embryos (mean ± SEM: 2.83 ± 0.872 vs 6.82 ± 0.772; p<0.01). There was also a significant positive correlation between the levels of kisspeptin and progesterone during healthy pregnancy (r=0.63; p<0.01).
The second experiment entailed a young transgenic mouse model (2-4 months old) which used cre-lox technology to express an inhibitory designer receptor exclusively activated by a designer drug (DREADD) only in kisspeptin cells. The inhibition of kisspeptin secretion was carried out using clozapine n-oxide (CNO) in drinking water. Experimental and control mice received CNO from either embryonic day 5.5 (CNO5.5) or from embryonic day 7.5 (CNO7.5), both until the end of the experiment. There was no significant difference in the number of embryos between experimental and control mice. When analysing hormonal data, there was also no significant difference found between kisspeptin levels in the experimental and control groups.
It seems I was not able to reduce the circulating levels of kisspeptin in young mice, likely due to the absence of the inhibitory DREADD (hm4Di) within the placenta. Future directions for this project would include investigating the kisspeptin profile of a mouse throughout a normal pregnancy to see whether it reflects the same kisspeptin levels seen in humans. Furthering on from this, repeating the experiments using another mouse line that has been validated to express cre in the placenta (and therefore drive DREADD expression in this organ) would be worth investigating. Finally, the ability to stimulate kisspeptin secretion with a stimulatory DREADD (hM3Dq) would help to determine whether it has effects at reducing the rate of miscarriage and could be used as a potential supplement during pregnancy for those at risk.