PSXVI-12 Revolutionizing in vitro endometrial cell studies: A novel methodology to obtain bovine endometrial cells

Cultured primary endometrial cells are used extensively to study uterine function in cattle. However, most protocols harvest endometrial cells from slaughtered animals at estimated stages of the estrous cycle. The goal of this study was to establish and validate an in vivo, minimally invasive, and estrous cycle stage-specific method to obtain endometrial cells for culture. In Experiment 1, the uterine body of Bos indicus-influenced cows was sampled using a cytology brush (cytobrush) 4 days post estrus (D4; n = 13). Brushes were transported in medium (DMEM/F12, 3% Penicillin/Streptomycin and 2% of Fungizone) to the laboratory at ambient temperature. Cells were cultured in medium containing 10% FBS at 5% of CO2 (38°C). Confluent cells (~7 days of culture) were sub-cultured for two subsequent passages. Pools (n = 4) of cells from 2–3 animals, were frozen, thawed, and re-plated (passage 3). The relative transcript abundance of PPIA, ACTB, KRT18, VIM, OXTR, PGR, ESR1 and IFNAR1 were analyzed by qPCR and compared among fresh cells and cells from each passage. Abundance of KRT18 and VIM transcripts was similar across passages, while PGR, ESR1, OXTR and IFNAR1 transcripts decreased by 90, 96, 84, and 82 %; respectively in cultured compared to fresh cells (P < 0.05). In Experiment 2, passage 3 cells were cultured for 24 hours with 0 or 1ng/mL of recombinant bovine interferon-tau (rbIFNT; n = 3 replicates/treatment). The relative expression of a classical interferon stimulated gene, ISG15, was evaluated by qPCR. Expression of ISG15 was 6-fold greater (P < 0.05) in the rbIFNT treated cells compared to controls. In conclusion, the culture of endometrial cells collected by cytobrush is feasible, generates a monolayer enriched in epithelial cells and may be used as a model for physiological studies involving IFNT signaling. Further experiments to ascertain the physiological relevance of this model are underway.

Expression patterns of Arc mRNA after renewal of appetitive behavior in female rats.

Renewal of appetitive behavior depends on the gonadal hormonal state of the female rat. In this experiment the effect of female rat estrous cycle stage on renewal of appetitive behaviors is replicated and extended upon to understand how endogenous hormonal states around the estrous cycle drive renewal at the neuronal population level. Estrous cycle stage (i.e., proestrus (P, high hormone) or metestrus/diestrus (M/D, low hormone)) was considered during two important learning and behavioral expression windows: at extinction training and during LTM/renewal testing. First, rats in P during context-dependent extinction training but in some other stage of the estrous cycle during long-term memory and renewal testing (Different) were shown to exhibit more renewal of conditioned foodcup (but not conditioned orienting) behavior compared to rats in other estrous cycle groups. Next, cellular compartment analysis of temporal activity using fluorescence in situ hybridization (catFISH) was used to examine immediate early gene activity of Arc mRNA in neuronal populations after distinct context-stimulus exposures (i.e., extinction and acquisition test contexts). Arc mRNA expression patterns were examined in the prefrontal cortex (PFC), amygdala, hippocampus (HPC), and paraventricular nucleus of the thalamus. P-different rats showed differential neuronal population activity in the infralimbic cortex of the PFC, the lateral amygdaloid nucleus, and both CA1 and CA3 regions of the dorsal HPC. In each region P-different rats exhibited more co-expression and less specificity of Arc mRNA compared to other hormonal groups, indicating that renewal of appetitive foodcup behavior induces Arc mRNA in overlapping neuronal populations in female rats.

Estrous cycle plasticity in the central clock output to kisspeptin neurons: Implications for the preovulatory surge

Coordination of ovulation and behavior is critical to reproductive success in many species. During the female estrous cycle, the preovulatory gonadotropin surge occurs when ovarian follicles reach maturity and, in rodents, begins just before the daily onset of activity, ensuring ovulation coincides with sex behavior. Timing of the surge relies on projections from the suprachiasmatic nucleus (SCN), the locus of the central circadian clock, to hypothalamic circuits that regulate gonadotropin secretion. The cellular mechanisms through which the SCN controls these circuits and gates the preovulatory surge to the appropriate estrous cycle stage, however, are poorly understood. We investigated in mice the functional impact of SCN arginine-vasopressin (AVP) neuron projections to kisspeptin (Kiss1) neurons in the rostral periventricular area of the third ventricle (RP3V Kiss1), responsible for generating the preovulatory surge. Conditional anterograde tracing revealed that SCN AVP neurons innervate approximately half of the RP3V Kiss1 neurons. Optogenetic activation of SCN AVP projections in brain slices caused an AVP-mediated stimulation of RP3V Kiss1 action potential firing in proestrus, the cycle stage when the surge is generated. This effect was less prominent in diestrus, the preceding cycle stage, and absent in estrus, following ovulation. Remarkably, in estrus, activation of SCN AVP projections resulted in GABA-mediated inhibition of RP3V Kiss1 neuron firing, an effect rarely encountered in other cycle stages. Together, these data reveal functional plasticity in SCN AVP neuron output that drives opposing effects on RP3V Kiss1 neuron activity across the ovulatory cycle. This might contribute to gating activation of the preovulatory surge to the appropriate estrous cycle stage.

Effects of spaceflight aboard the International Space Station on mouse estrous cycle and ovarian gene expression

Ovarian steroids dramatically impact normal homeostatic and metabolic processes of most tissues within the body, including muscle, bone, neural, immune, cardiovascular, and reproductive systems. Determining the effects of spaceflight on the ovary and estrous cycle is, therefore, critical to our understanding of all spaceflight experiments using female mice. Adult female mice (n = 10) were exposed to and sacrificed on-orbit after 37 days of spaceflight in microgravity. Contemporary control (preflight baseline, vivarium, and habitat; n = 10/group) groups were maintained at the Kennedy Space Center, prior to sacrifice and similar tissue collection at the NASA Ames Research Center. Ovarian tissues were collected and processed for RNA and steroid analyses at initial carcass thaw. Vaginal wall tissue collected from twice frozen/thawed carcasses was fixed for estrous cycle stage determinations. The proportion of animals in each phase of the estrous cycle (i.e., proestrus, estrus, metestrus, and diestrus) did not appreciably differ between baseline, vivarium, and flight mice, while habitat control mice exhibited greater numbers in diestrus. Ovarian tissue steroid concentrations indicated no differences in estradiol across groups, while progesterone levels were lower (p < 0.05) in habitat and flight compared to baseline females. Genes involved in ovarian steroidogenic function were not differentially expressed across groups. As ovarian estrogen can dramatically impact multiple non-reproductive tissues, these data support vaginal wall estrous cycle classification of all female mice flown in space. Additionally, since females exposed to long-term spaceflight were observed at different estrous cycle stages, this indicates females are likely undergoing ovarian cyclicity and may yet be fertile.

Estrous cycle impacts microRNA content in extracellular vesicles that modulate bovine cumulus cell transcripts during in vitro maturation†

Extracellular vesicles (EVs) are nanoparticles secreted by ovarian follicle cells. Extracellular vesicles are an important form of intercellular communication, since they carry bioactive contents, such as microRNAs (miRNAs), mRNAs, and proteins. MicroRNAs are small noncoding RNA capable of modulating mRNA translation. Thus, EVs can play a role in follicle and oocyte development. However, it is not clear if EV contents vary with the estrous cycle stage. The aim of this study was to investigate the bovine miRNA content in EVs obtained from follicles at different estrous cycle stages, which are associated with different progesterone (P4) levels in the follicular fluid (FF). We collected FF from 3 to 6 mm follicles and evaluated the miRNA profile of the EVs and their effects on cumulus-oocyte complexes during in vitro maturation. We observed that EVs from low P4 group have a higher abundance of miRNAs predicted to modulate pathways, such as MAPK, RNA transport, Hippo, Cell cycle, FoxO, oocyte meiosis, and TGF-beta. Additionally, EVs were taken up by cumulus cells and, thus, affected the RNA global profile 9 h after EV supplementation. Cumulus cells supplemented with EVs from low P4 presented upregulated genes that could modulate biological processes, such as oocyte development, immune responses, and Notch signaling compared with genes of cumulus cells in the EV free media or with EVs from high P4 follicles. In conclusion, our results demonstrate that EV miRNA contents are distinct in follicles exposed to different estrous cycle stage. Supplementation with EVs impacts gene expression and biological processes in cumulus cells.

Physical Linkage of Estrogen Receptor α and Aromatase in Rat: Oligocrine and Endocrine Actions of CNS-Produced Estrogens

Rapid-signaling membrane estrogen receptors (mERs) and aromatase (Aro) are present throughout the central nervous system (CNS), enabling acute regulation of CNS estrogenic signaling. We previously reported that spinal membrane Aro (mAro) and mERα oligomerize (1). As their organizational relationship would likely influence functions of locally produced estrogens, we quantified the mAro and mERα that are physically associated and nonassociated in two functionally different regions of rat CNS: the spinal cord, which has predominantly neural functionalities, and the hypothalamus, which has both neural and endocrine capabilities. Quantitative immunoprecipitation (IP), coimmunoprecipitation, and Western blot analysis were used to quantify the associated and nonassociated subpopulations of mAro and mERα. Regardless of estrous-cycle stage, virtually all mAro was oligomerized with mERα in the spinal cord, whereas only ∼15% was oligomerized in the hypothalamus. The predominance of nonassociated mAro in the hypothalamus, in combination with findings that many hypothalamic Aro-immunoreactive neurons could be retrogradely labeled with peripherally injected Fluoro-Gold, suggests that a portion of hypothalamic estrogens is secreted, potentially regulating pituitary function. Moreover, circulating estrogens increased hypothalamic Aro activity (quantified by the tritiated water-release assay) in the absence of increased Aro protein, revealing nongenomic regulation of Aro activity in the mammalian CNS. The demonstrated presence of associated and nonassociated mAro and mERα subpopulations in the CNS suggests that their selective targeting could restore impaired estrogen-dependent CNS functionalities while minimizing unwanted effects. The full physiological ramifications of brain-secreted estrogens remain to be explored.

The cytological examination of vaginal smears in dogs

The cytological examination of vaginal smears is a simple, quick and inexpensive method for determination of the estrous cycle stage in dogs. Also, the procedure of vaginal smear collection is painless for the animal. Smears are examined under light microscope, after they have been stained by a proper staining method. The results are based on the observation of cytological alterations of the epithelium cells under the influence of ovarian hormones.