Endometrial leukemia inhibiting factor (LIF) and integrin αvβ3 (ITG αvβ3) expression after kisspeptin trigger of ovulation in mice

Objective: Kisspeptin (KISS-1) is a hypothalamic neuropeptide that regulates hypothalamic pituitary ovarian axis function. Pre-ovulatory rise in serum KISS-1 leads to luteinizing hormone (LH) surge that triggers final oocytes maturation and ovulation. Exogenous trigger of ovulation is used in ovarian hyper-stimulation for some infertility cases. KISS-1 and its receptor (KISS-1R) are also expressed in the endometrium. Previous studies in mice showed increased endometrial KISS-1/KISS-1R expression around time of implantation with suggested implication in successful implantation (1,2). In this study, we evaluated the expression of two important endometrial implantation markers, LIF and ITG αVβ3 after using KISS-1 as a trigger for ovulation compared to human chorionic gonadotrophin (hCG) or placebo in super-ovulated mice.

Design: Experimental animal study.

Materials and Methods: A total of 15 female (C57BL/6J) mice were super-ovulated via intraperitoneal injection of 5 IU pregnant mare serum gonadotrophin (Day 1). 48 hours later, mice were injected with either 1× phosphate buffer saline (Group A), 5 IU hCG (Group B), or 3 nmol KISS-1 (Group C) (5 mice/group). On (Day 7), mice were euthanized and uteri were excised. Paraformaldehyde-fixed paraffin-embedded sections of mouse uteri were cut and stained by Immunohistchemistry using 2 specific antibodies against LIF and ITG αVβ3. Slides were then scored for abundance and intensity of staining in both glandular epithelium (GE) and stromal cells (SCs) of endometrium using histoscore (H-score) method. Data were analyzed using Kruskal-Wallis test followed by Mann-Whitney U test for pairwise comparisons.

Results: All ranks of the mean H-scores of group C were higher compared to both group B and group A in a descending manner (Table 1).

Table 1: Results of Kruskal-Wallis test comparing ranks of mean H-scores of different groups.

LIF expression was significantly higher in both GE and SCs of group C compared to group A, but only higher in SCs when compared to group B (p=0.009). On the other hand, ITG αVβ3 expression was significantly higher in SCs of group C compared to group A only, with no difference in GE among the 3 groups. Additionally, we noticed increased vascularity and size of uteri excised from mice in group C compared to groups A and B.

Conclusions: Our study shows a tendency of higher expression of some implantation markers in mice endometrium after kisspeptin trigger of ovulation compared to hCG or placebo. Further studies are needed to correlate these results with pregnancy outcomes.

Support: None

References:

1. Zhang P, Tang M, Zhong T, Lin Y, Zong T, Zhong C, et al. Expression and function of kisspeptin during mouse decidualization. PloS one. 2014;9(5):e97647.
2. Calder M, Chan YM, Raj R, Pampillo M, Elbert A, Noonan M, et al. Implantation failure in female Kiss1-/- mice is independent of their hypogonadic state and can be partially rescued by leukemia inhibitory factor. Endocrinology. 2014;155(8):3065-78.