Abstract
Simple SummaryIn mammals, KISS-1 metastasis suppressor (KISS1) has emerged to stimulate the secretion of gonadotropin-releasing hormone (GnRH) to initiate the first estrus in the hypothalamus. However, KISS1 was recently demonstrated to be widely expressed in various ovarian compartments, including oocytes, granulosa cells (GCs) and theca cells. But the biological functionalities of KISS1 have not been explored in GCs. In this study, the overexpression plasmid of pcDNA3.1-KISS1 was built to explore the biological effects of KISS1 on the phosphoinositide 3-kinases (PI3K) signaling pathway, estrogen signaling pathway, cell apoptosis, cell cycle, and estradiol-17β (E2) secretion in porcine GCs. We found that overexpression of KISS1 could affect the PI3K signaling pathway, significantly decrease the apoptosis of GCs, and suppress GCs at G0/G1 phase of the cell cycle. Furthermore, overexpression of KISS1 could activate the estrogen synthesis signaling pathway and significantly increase the concentration of E2 in the supernatant and the mRNA expression levels of ESR1 and ESR2. These findings were highly accorded with the supposed role of KISS1 to promote the follicular development. This study would be of great interest for exploring the biological functionalities of KISS1 in regulating the maturation of follicles in mammals.Previous studies have strongly recommended that KISS-1 metastasis suppressor (KISS1) plays an essential gatekeeper of the initiation of reproductive maturation in mammals. However, KISS1 has been recently reported to highly express in ovarian granulosa cells (GCs). But the biological functionalities of KISS1 on cell apoptosis, cell cycle, and synthesis of estradiol-17β (E2) have not been explored in GCs. In this study, using porcine GCs as a cellular model, the overexpression plasmid of KISS1 was built to explore the biological effects of KISS1 on the PI3K signaling pathway, estrogen signaling pathway, cell apoptosis, cell cycle, and E2 secretion. We found that mRNA of KISS1 highly expressed in the ovary and significantly increased from immature to mature follicles in gilts. Overexpression of KISS1 could significantly increase the mRNA expression of PIK3CG, PIK3C1, and PDK1, and significantly decreased the mRNA levels of FOXO3, TSC2, and BAD of PI3K signaling pathway. Furthermore, results of the flow cytometry showed that overexpression of KISS1 significantly inhibited the apoptosis of GCs and decreased the percentage of GCs at G0/G1 phase of the cell cycle. Additionally, overexpression of KISS1 could increase the mRNA levels of Star, CYP17, 3B-HSD, 17B-HSD of estrogen synthesis signaling pathway, significantly increase the concentration of E2 in the supernatant of the cultured GCs, and up-regulate the mRNA expression levels of ESR1 and ESR2. These results suggested that KISS1 might suppress cell apoptosis through activating the PI3K signaling pathway and stimulate synthesis of E2 via boosting the estrogen synthesis signaling pathway. This study would be of great interests for exploring the biological functionalities of KISS1 in the folliculogenesis and sex steroid production of the ovaries in mammals.
Highlights
In many mammalian species, the initiation of first estrus indicating the sexual and reproductive maturation is activated as a result of an increase in the gonadotropin releasing hormone (GnRH)secretion [1,2]
The mRNA expression pattern of KISS-1 metastasis suppressor (KISS1) was first explored for tissues from gilts with the first standing reflex
To further investigate the biological role of KISS1 during the follicular maturation, the mRNA expression levels of KISS1 were examined in porcine porcinefrom follicles from immature mature
Summary
The initiation of first estrus indicating the sexual and reproductive maturation is activated as a result of an increase in the gonadotropin releasing hormone (GnRH)secretion [1,2]. Kisspeptins, the products of KISS1 gene, have recently emerged as an essential gatekeeper for the onset of first estrus via directing the stimulation of GnRH secretion at the hypothalamic level [3,4,5]. Compared with the theca cells and other ovarian cells, previous studies report that KISS1 mRNA expression is significantly higher in the GCs and suggest that GC is the major site for kisspeptin synthesis in ovaries of mammals [6,13]. These results suggest the proposal and essential role of KISS1 in ovaries of mammals
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