Failures in hypothalamic kisspeptin/Kiss1r signaling are associated with infertility, and in vitro studies have shown that kisspeptin can modulate angiogenesis and immune activity. Because there is no in vivo research on the functional relationship between these factors in the reproductive system, especially in domestic cats, we evaluated the expression profile of kisspeptin/Kiss1r and angiogenic and immunological mediators in the genital tract of cyclic cats and of those with pyometra. The uterus of cats in diestrus exhibited greater gene and protein expression of Kiss1, as well as Vegf, Pigf, Mif, and Il6. In contrast, Kiss1r presented greater expression in proestrus/estrus, similarly to that observed for the immunostaining of INFγ, MIF, TNFα, and IL10. These factors were positively correlated with Kiss1 and/or Kiss1r, and a positive correlation between Kiss1 and Kiss1r was also observed in the uterus of cats during the estrous cycle. Cats with pyometra showed greater immunostaining of Kiss1 and Kiss1r on the endometrial surface and reduced immunostaining of Kiss1 in deep glands, whereas there was a significant reduction in Vegf, Pigf, Mif, and Il6 mRNA, and an increase in Tnf mRNA. The findings reveal that there is a gene correlation between kisspeptin/Kiss1r and angiogenic and immune mediators in the uterus of the domestic cat, which are modulated by the estrous cycle, and that pyometra affects the expression of these mediators. This study suggests, for the first time, a functional relationship between the Kiss/Kiss1r system and angiogenic and immune mediators in the female genital tract.

Gestational diseases such as preeclampsia and gestational diabetes cause inflammasome activation and pyroptosis in the placenta and changes in placental kisspeptin levels. Although maternal hypothyroidism also reduces the kisspeptin/Kiss1R system at the maternal-fetal interface, there is still no information on whether this dysfunction causes inflammasome activation and pyroptosis in the placenta or influences the modulatory role of kisspeptin in these processes. This study aimed to evaluate whether hypothyroidism activates the inflammasome-NLRP3 pathway and pyroptosis at the maternal-fetal interface of rats and whether kisspeptin can modulate these processes. Hypothyroidism was induced in Wistar rats by the administration of propylthiouracil. Kisspeptin-10 (Kp10) treatment began on the 8th day of gestation (DG). Gene and/or protein expressions of NLRP3, Caspase 1, IL-1β, IL-18, and Gasdermin D (Gsmd) were evaluated in the deciduae and placentae at the 18th DG. Hypothyroidism increased the decidual and placental stainings of NLRP3, IL-1β, and Gasdermin D, and increased the gene expressions of Nlrp3, Ilβ, and Il18 in the placenta and of Gsmd in the decidua. Treatment with Kp10 suppressed the increase in NLRP3/Nlrp3, IL-1β, Il18, and Gasdermin D/Gsmd caused by hypothyroidism at the maternal-fetal interface. However, Kp10 increased the placental gene expressions of Casp1 and Il1β. The findings demonstrated that maternal hypothyroidism activated the inflammasome-NLRP3 pathway and pyroptosis at the maternal-fetal interface of rats and that treatment with Kp10 was able to block these processes, thus suggesting that kisspeptin analogues may be promising in the treatment of gestational diseases that involve inflammasome activation and pyroptosis.

The Kisspeptin/Kiss1r system is a key regulator of reproduction by stimulating gonadotrophin-releasing hormone (GnRH) and luteinizing hormone (LH) release, and in vitro studies have shown that Kisspeptin can modulate angiogenesis and immune function, factors that are also essential for reproduction However, there are no studies on the expression of Kisspeptin/Kiss1r at the maternal-fetal interface in domestic cats and its relationship with angiogenic and immunological mediators. Thus, our objective was to evaluate the spatiotemporal expression profile of Kisspeptin/Kiss1r and angiogenic and immunological mediators in the uterus and placenta of domestic cats during pregnancy. Uterus and placenta samples were collected from cats in mid pregnancy (N = 6) and late pregnancy (N = 6), in addition to uterus from non-pregnant cats in diestrus (N = 7), to evaluate protein and gene expression of Kiss1, Kiss1r, VEGF, Flk-1, PLGF, INFγ, MIF, TNFα, IL6, and IL10 by immunohistochemistry and qPCR. Pregnancy increased the uterine expression of Kiss1 and Kiss1r, especially at the late pregnancy, in addition to upregulating INFy, MIF, Vegf, Il10, and Tnf and downregulating Plgf. Higher placental expression of Kiss1r and Plgf mRNA occurred at the late pregnancy, while the expression of Kiss1, VEGF, Flk-1, INFy, TNFα, Il6, and IL10 was higher in the mid of pregnancy. A positive correlation between Kiss1 and Tnf was observed in the placenta, while Kiss1r had a negative correlation with Infγ, Il6, and Il10. The findings reveal that Kisspeptin/Kiss1r and angiogenic and immunological mediators at the maternal-fetal interface of pregnant cat have a gene correlation and are modulated by the gestational age. These data suggest possible functional links of Kisspeptin in placental angiogenesis and immunology.

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