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Embryo survival and pre-implantation development depend on uterine luminal fluid, which is believed to play a role in early embryonic death and infertility in cows. Extracellular vesicles (EVs) in the uterine luminal fluid contain microRNAs (miRNAs), crucial mediators of intercellular communication. miRNAs regulate conceptus-maternal interactions and participate in embryonic development by suppressing gene expression. Therefore, we hypothesized that miRNAs in the intrauterine EVs of low-fertility cows would hinder embryonic survival and development. EVs were collected from the bovine uterine luminal fluid of both normal- and low-fertility cows 7 days post-estrus. Small RNA-sequencing analysis of miRNAs isolated from these EVs identified eight miRNAs that were highly expressed in normal-fertility cows (normal-fertility miRNAs) and eight with elevated expression in low-fertility cows (low-fertility miRNAs). These two sets of miRNAs were transfected into hatched blastocysts via lipofection. RNA-seq following lipofection with low-fertility miRNAs identified 424 differentially expressed genes (DEGs) relative to the control; in contrast, following lipofection with normal-fertility miRNAs, seven DEGs were identified. Pathway analysis of the DEGs identified following lipofection with low-fertility miRNAs revealed substantial enrichment of mitogen-activated protein kinase (MAPK) signaling. Expression of activator protein 1 (AP1) and interferon-tau (IFNT) mRNA was significantly lower in the low-fertility miRNA transfection group than in the control. IFNT is essential for maternal pregnancy recognition. Therefore, miRNAs in intrauterine EVs from low-fertility cows at 7 days post-estrus may inhibit embryo development and suppress IFNT expression by altering MAPK signaling.

DOI： 10.1096/fj.202401728R

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Dysfunction of central serotonergic neurons is known to cause depressive disorders in humans, who often show reproductive and/or glucose metabolism disorders. This study examined whether dorsal raphe (DR) serotonergic neurons sense high glucose availability to upregulate reproductive function via activating hypothalamic arcuate (ARC) kisspeptin neurons (= KNDy neurons), a dominant stimulator of gonadotropin-releasing hormone (GnRH)/gonadotropin pulses, using female rats and goats. RNA-seq and histological analysis revealed that stimulatory serotonin-2C receptor (5HT2CR) was mainly expressed in the KNDy neurons in female rats. The serotonergic reuptake inhibitor administration into the mediobasal hypothalamus (MBH), including the ARC, significantly blocked glucoprivic suppression of luteinizing hormone (LH) pulses and hyperglycemia induced by intravenous 2-deoxy-D-glucose (2DG) administration in female rats. A local infusion of glucose into the DR significantly increased in vivo serotonin release in the MBH and partly restored LH pulses and hyperglycemia in the 2DG-treated female rats. Furthermore, central administration of serotonin or a 5HT2CR agonist immediately evoked GnRH pulse generator activity, and central 5HT2CR antagonism blocked the serotonin-induced facilitation of GnRH pulse generator activity in ovariectomized goats. These results suggest that DR serotonergic neurons sense high glucose availability to reduce gluconeogenesis and upregulate reproductive function by activating GnRH/LH pulse generator activity in mammals.

DOI： 10.1038/s41598-024-58470-4

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Superovulation (SOV) treatment of cows results in unovulated follicles and inconsistent quality of the recovered embryos. It has been demonstrated that luteinizing hormone (LH) secretion is suppressed during SOV treatment of cows, which may cause insufficient follicle development and variation in the development of recovered embryos and unovulated follicles. Pulsatile gonadotropin-releasing hormone/LH secretion is controlled by the activity of kisspeptin, neurokinin B, and dynorphin (KNDy) neurons in the arcuate nucleus in many mammals. Since neurokinin B promotes the activity of KNDy neurons, we hypothesized that senktide, a neurokinin B receptor agonist, has potential as a therapeutic drug to improve the ovulation rate and quality of recovered embryos in SOV-treated cows via stimulation of LH secretion. Senktide was administered intravenously (30 or 300 nmol/min) for 2 h, beginning from 72 h after the start of SOV treatment. LH secretion was examined before and after administration, and embryos were collected 7 d after estrus. Senktide administration increased LH secretion in SOV-treated cows. The ratios of code 1, code 1 and 2, and blastocyst stage embryos to recovered embryos were increased by senktide (300 nmol/min) administration. Moreover, the mRNA levels of MTCO1, COX7C, and MTATP6 were upregulated in recovered embryos of senktide (300 nmol/min)-administered animals. These results indicate that the administration of senktide to SOV-treated cows enhances LH secretion and upregulates the expression of genes involved in mitochondrial metabolism in embryos, thereby improving embryo development and embryo quality.

DOI： 10.1093/biolre/ioad039

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To investigate possible causes of reproductive failure, we conducted global endometrial gene expression analyses in fertile and subfertile cows. Ingenuity pathway analysis showed that RICTOR and SIRT3 are significant upstream regulators for highly expressed genes in fertile cows, and are predicted to be activated upstream regulators of normal mitochondrial respiration. Canonical pathway analysis revealed that these highly expressed genes are involved in the activation of mitochondrial oxidative phosphorylation. Therefore, in subfertile cows, the inactivation of RICTOR and SIRT3 may correlate with decreased capacity of mitochondrial respiration. Furthermore, the expression levels of most mitochondrial DNA genes and nuclear genes encoding mitochondrial proteins were higher in subfertile cows. The mitochondrial DNA copy number was significantly higher in the endometrium of subfertile cows, whereas the ATP content did not differ between fertile and subfertile cows. Quantitative reverse transcription-PCR analysis demonstrated that the expression of PGC1a, TFAM, MFN1, FIS1, and BCL2L13 were significantly lower in subfertile cows. In addition, transmission electron microscopy images showed mitochondrial swelling in the endometrial cells of the subfertile cow. These results suggest that poor-quality mitochondria accumulate in the endometrium owing to a reduced capacity for mitochondrial biogenesis, fusion, fission, and degradation in subfertile cows, and may contribute to infertility.

DOI： 10.1002/mrd.23670

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Language：English   Publisher：Frontiers in Neuroendocrinology  

Reproductive behaviors are sexually differentiated: for example, male rodents show mounting behavior, while females in estrus show lordosis behavior as sex-specific sexual behaviors. Kisspeptin neurons govern reproductive function via direct stimulation of gonadotropin-releasing hormone (GnRH) and subsequent gonadotropin release for gonadal steroidogenesis in mammals. First, we discuss the role of hypothalamic kisspeptin neurons as an indispensable regulator of sexual behavior by stimulating the synthesis of gonadal steroids, which exert “activational effects” on the behavior in adulthood. Second, we discuss the central role of kisspeptin neurons that are directly involved in neural circuits controlling sexual behavior in adulthood. We then focused on the role of perinatal hypothalamic kisspeptin neurons in the induction of perinatal testosterone secretion for its “organizational effects” on masculinization/defeminization of the male brain in rodents during a critical period. We subsequently concluded that kisspeptin neurons are key players in bridging the endocrine system and sexual behavior in mammals.

DOI： 10.1016/j.yfrne.2021.100952

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Language：English   Publisher：Frontiers in Neuroendocrinology  

Accumulating findings during the past decades have demonstrated that the hypothalamic arcuate kisspeptin neurons are supposed to be responsible for pulsatile release of gonadotropin-releasing hormone (GnRH) to regulate gametogenesis and steroidogenesis in mammals. The arcuate kisspeptin neurons express neurokinin B (NKB) and dynorphin A (Dyn), thus, the neurons are also referred to as KNDy neurons. In the present article, we mainly focus on the cellular and molecular mechanisms underlying GnRH pulse generation, that is focused on the action of NKB and Dyn and an interaction between KNDy neurons and astrocytes to control GnRH pulse generation. Then, we also discuss the factors that modulate the activity of KNDy neurons and consequent pulsatile GnRH/LH release in mammals.

DOI： 10.1016/j.yfrne.2021.100968

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：The Japan Endocrine Society  

<p>Prenatal and postnatal biphasic increases in plasma testosterone levels derived from perinatal testes are considered critical for defeminizing/masculinizing the brain mechanism that regulates sexual behavior in male rats. Hypothalamic kisspeptin neurons are indispensable for stimulating GnRH and downstream gonadotropin, as well as the consequent testicular testosterone production/release in adult male rats. However, it is unclear whether kisspeptin is responsible for the increase in plasma testosterone levels in perinatal male rats. The present study aimed to investigate the role of <i>Kiss1</i>/kisspeptin in generating perinatal plasma LH and the consequent testosterone increase in male rats by comparing the plasma testosterone and LH profiles of wild-type (<i>Kiss1</i>^+/+) and <i>Kiss1</i> knockout (<i>Kiss1</i>^–/–) male rats. A biphasic pattern of plasma testosterone levels, with peaks in the prenatal and postnatal periods, was found in both <i>Kiss1</i>^+/+ and <i>Kiss1</i>^–/– male rats. Postnatal plasma testosterone and LH levels were significantly lower in <i>Kiss1</i>^–/– male rats than in <i>Kiss1</i>^+/+ male rats, whereas the levels in the prenatal embryonic period were comparable between the genotypes. Exogenous kisspeptin challenge significantly increased plasma testosterone and LH levels and the number of c-Fos-immunoreactive GnRH neurons in neonatal <i>Kiss1</i>^–/– and <i>Kiss1</i>^+/+ male rats. <i>Kiss1</i> and <i>Gpr54</i> (kisspeptin receptor gene) were found in the testes of neonatal rats, but kisspeptin treatment failed to stimulate testosterone release in the cultured testes of both genotypes. These findings suggest that postnatal, but not prenatal, testosterone increase in male rats is mainly induced by central kisspeptin-dependent stimulation of GnRH and consequent LH release.</p>

DOI： 10.1507/endocrj.ej21-0620

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