Endometrial expression of progesterone, estrogen, and oxytocin receptors and of 20α-hydroxysteroid dehydrogenase and cyclooxygenase II 2 and 5 days after ovulation in induced short and normal estrous cycles in dairy cows

Exposure to progesterone before an ovulation synchronization protocol increases the follicular diameter and fertility of multiparous suckled Bos taurus cows

The objective of this study was to evaluate the effect of administering injectable progesterone (P4i) before a timed artificial insemination (TAI) protocol on the follicular growth, ovulation, and pregnancy rate of Bos taurus suckled cows. The effect of P4i administration before the TAI on the pregnancy rate (P/AI) was evaluated in 576 suckled Bos taurus cows at 30-90 days postpartum. In addition, the effect of P4i administration before TAI on follicular dynamics was evaluated in subgroup of 401 suckled Bos taurus cows. On Day -10 (D-10), cows were divided into two experimental groups (Control and P4i). In this moment, P4i cows received i.m. 150 mg of injectable long-action progesterone. After that, both experimental groups received a synchronization protocol (Day 0; D0) that consisted of administration i.m. of 2 mg of estradiol benzoate and a progesterone intravaginal insert on D0. On Day 8 (D8), the progesterone insert was removed, and the cows received 500 μg of cloprostenol, 400 IU of eCG, and 1 mg of estradiol cypionate. TAI was performed 48 h after the removal of the progesterone insert. The ultrasound exams were performed in a subgroup of cows on Days 0, 8, 10 and 12 to evaluate the diameter of the largest follicle, rate of follicular growth and risks of single and double ovulation. The pregnancy diagnosis was performed 30 days after TAI in all cows to determine the pregnancy rate. The diameter of the largest follicle, on D10 (P = 0.84), rate of follicular growth (P = 0.14), ovulation rate (P = 0.40) and double ovulation rates (P = 0.23) did not differ between experimental groups. The pregnancy rate was greater in the P4i group [Control 46.2 % (133/288) vs. P4i 55.6 % (160/288); P = 0.03]. The diameter of the largest follicles (LF) on D0 (Control 11.6 ± 0.2 vs. P4i 13.3 ± 0.3) was greater (P = 0.01) in the P4i group. In conclusion, injectable progesterone before the ovulation synchronization protocol increased the diameter of the largest follicle on the D0 and the pregnancy rate in multiparous Bos taurus suckled beef cows.

A comparative transcriptome and proteomics study of post-partum ovarian cycle arrest in yaks (Bos grunniens)

Post-partum ovarian cycle arrest is the main factor affecting yak reproductive efficiency. There are few reports regarding the molecular regulatory mechanism of post-partum oestrus at transcriptome and proteome levels in yaks. Our previous studies focussed on the ovaries of yaks with post-partum ovarian cycle arrest and post-partum oestrus yaks. In this study, RNA sequencing transcriptomic study was combined with quantitative proteomic analyses to identify post-partum ovarian cycle-related genes and proteins. Consequently, 1,149 genes and 24 proteins were found to be up- or downregulated during post-partum oestrus. The analysis of differentially regulated genes identified three gene or protein pairs that were synchronously upregulated and no gene or protein pairs that were synchronously downregulated, suggesting that these upregulated genes may regulate the post-partum ovarian cycle. The functional classification of these differentially expressed genes and proteins indicated their connection with the oocyte meiosis, the oestrogen signalling pathway, the progesterone-mediated oocyte maturation and the gonadotrophin-releasing hormone (GnRH) signalling pathway. In this study, a total of six genes and two proteins involved in the oocyte meiosis, the oestrogen signalling pathway, the progesterone-mediated oocyte maturation and the GnRH signalling pathway were identified. The CSNK1A1, M91_09723, M91_11326, M91_21439, M91_19073, SHC2, Atf6b, M91_03062, HSPCA and calmodulin could regulate oestrus, respectively, in the post-partum so as to control the anoestrus status.

Effect of Intrauterine Infusion of Equine Fresh Platelets-Rich Plasma (PRP) or Lyophilized PRP (L-GFequina) on Ovarian Activity and Pregnancy Rate in Repeat Breeder Purebred Arabian Mares

Simple Summary

Persistent endometritis is one of the major causes of infertility in mares and results in endometrium degeneration, namely, endometrosis. Platelets-rich plasma (PRP) is an emerging therapeutic application in tissue regeneration because of its high concentration of growth factors with a high mitogenic and anti-inflammatory potential, but reduced preservation time. L-GF^equina is a freeze-dried, stabilized, platelet-rich plasma product (PP) that can be stored at 2 to 8 °C for several months. It can be easily used after reconstitution with sterile saline or water, eliminating the need for repeated blood product collection and special equipment. The intrauterine infusion of equine platelet-rich plasma or L-GF^equina can be used indistinctly in repeat breeder mares, shortening the estrous cycle, with no significant effect on the follicular diameter, as well as increasing pregnancy rate in Arabian purebred mares.

Abstract

This study was designed to examine the effect of the intrauterine infusion of platelet-rich plasma (PRP) or equine lyophilized growth factor (L-GF^equina) on the follicular growth, endometrial thickness, estrus cycle length, and pregnancy rate in purebred Arabian mares. A total of 73 purebred Arabian mares who experienced repeat breeding for three successive cycles were randomly divided into the following three groups: control group, without treatment; second Group (PRP group), in which mares were intrauterine infused with 20 mL of fresh PRP on the second day after the end of physic estrus phase; and the third group (L-GF^equina Group), consisting of mares that were intrauterine infused with 20 mL of reconstituted lyophilized horse platelets growth factors (L-GF^equina) on the second day after the estrus phase. The results showed no significant difference between control and treated groups in the diameter of the preovulatory follicles during the post treatment cycle. The endometrium thickness increased significantly in the L-GF^equina and PRP groups ahead of the non-treated group. Intrauterine L-GF^equina or PRP administration shortened the estrus cycle length. A higher pregnancy rate was recorded in the L-GF^equina and PRP treated mares. In conclusion, the intrauterine infusion of L-GF^equina or PRP increased the endometrial thickness and pregnancy rate and could be used to improve fertility in Arabian purebred mares who experienced from repeat breeding.

Local sex steroid hormone milieu in the bovine oviduct ipsilateral and contralateral to preovulatory follicle or corpus luteum during the periovulatory phase

Estradiol-17β (E2) and progesterone (P4) regulate oviductal functions, providing a suitable environment for the transport and maturation of gametes, fertilization, and embryonic development. In addition to the E2 and P4 nuclear receptors, estrogen receptor (ESR) α and β, nuclear progesterone receptor (PGR), nongenomic mechanisms through G protein-coupled estrogen receptor (GPER1), and progesterone receptor membrane component (PGRMC) 1 and 2 mediate E2 and P4 actions. This study aimed to characterize the local endocrine environment of the oviduct by examining the oviductal E2 and P4 concentrations and their receptors' mRNA expression during the periovulatory phase. The bovine oviducts were collected in a slaughterhouse and the days postovulation were estimated according to state of the ovaries and the uterus. Samples of the ampulla and isthmus ipsilateral and contralateral to the preovulatory follicle or corpus luteum were collected on Days 19 to 21, Days 0 to 1, Days 2 to 4, and Days 5 to 7 of the estrous cycle. The effects of the estrous cycle phase and oviductal region (ampulla and isthmus) and side (ipsilateral and contralateral) were analyzed by 3-way ANOVA. Moreover, to clarify the regulatory mechanisms of the mRNA expression of hormone receptors, the effects of E2 and P4 on mRNA expression in the oviduct were examined by multiple linear regression. The oviductal endocrine milieu on Days 19 to 21 was characterized by an E2-dominant environment with high E2 and low P4, high ESR1 and PGR mRNA expression, and low ESR2, GPER1, and PGRMC2 mRNA expression, whereas the corresponding on Days 0 to 1 was characterized by the endocrine milieu without hormone dominance. The environment on Days 2 to 4 and Day 5 to 7 was characterized by opposite tendency of oviductal hormone concentrations and their receptors' mRNA expression to Days 19 to 21. Additionally, the ipsilateral oviduct had the more P4-dominant endocrine milieu, with lower E2 and higher P4 concentrations, and different expression of ESR1/2, GPER1, PGR, and PGRMC2 mRNA when compared with the contralateral oviduct on Days 2 to 4 and Days 5 to 7, except for PGRMC1. Although oviductal E2 and P4 influenced the mRNA expression of ESR1/2, GPER1, PGR, and PGRMC1/2, their effects were different between regions and sides. In summary, the oviductal endocrine milieu varies according to the estrous cycle phase and the oviductal region and side, which may be involved in the estrous cycle phase-specific and oviductal region-specific and side-specific functions.

Effects of hCG administration on corpus luteum development and plasma sex steroid hormone concentration in beef heifers differ according to the locational relationships of the original corpus luteum and the first-wave dominant follicle

The aims of this study were to compare the effects of an intramuscular human chorionic gonadotropin (hCG) administration on corpus luteum (CL) development, plasma progesterone (P4) and estradiol (E2) concentration in ipsilateral (first-wave dominant follicle [W1DF] in the same ovary as the CL) and contralateral (W1DF and CL in opposite ovaries) cattle. Cross-bred beef heifers (Holstein × Japanese black, n=83) with synchronized ovulation were randomly assigned to either treatment with 1,500 IU hCG or no treatment on day 5 post-ovulation and were subdivided into ipsilateral (hCG treatment, n=21; no treatment, n=23) or contralateral (hCG treatment, n=17; no treatment, n=17) groups. Five heifers were excluded from the study, as they presented with double ovulation in response to hCG treatment. The effects of hCG treatment, location (ipsilateral and contralateral), and the number of days post-ovulation (days 5, 7, and 14) were analyzed using three-way ANOVA. hCG treatment significantly increased CL diameter on day 7 and plasma P4 concentration on days 7 and 14 in the contralateral group, but not the ipsilateral group. In contrast, hCG treatment decreased plasma E2 concentration on days 7 and 14 in both groups. In summary, our results indicate that the hCG treatment more significantly promoted CL development and increased plasma P4 concentration in the contralateral than in the ipsilateral group.

Possible roles of local oviductal estradiol-17β in luteal formation phase on the function of bovine oviductal epithelium

Oviducts play an important role in the reproductive process, such as in gamete transport, fertilization, and early embryonic development. However, the regulation of oviductal function during luteal formation phase (3−5 days post-ovulation), which is a crucial phase for early embryonic development, remains poorly understood. This study investigated the roles of oviductal estradiol-17β (E2) and progesterone (P4) concentrations on bovine oviductal functions in the luteal formation phase using RT-qPCR for some genes of oviductal epithelial cells. Bovine oviducts ipsilateral to the corpus luteum (CL) in the luteal formation phase were collected from a slaughterhouse. The concentration of oviductal E2 was positively correlated with the mRNA expressions of nuclear P4 receptor (PGR) and protein disulfide isomerase family A member 4 (PDIA4), which is related to protein secretion, in the ampulla and with estrogen receptor α (ESR1) mRNA expression in the isthmus. In contrast, the concentration of oviductal P4 was not correlated with oviductal mRNA expressions in either regions. Furthermore, for the candidate factor related to the oviductal E2 concentration, the CL parameters (CL size and tissue P4 concentration), first-wave dominant follicle (W1DF) parameters (follicle size and intrafollicular E2 concentration), and W1DF location (ipsilateral or contralateral to CL) did not influence the oviductal E2 concentration. In conclusion, our results suggest that the local oviductal E2 is a potential oviductal function regulator during the luteal formation phase.

The newly established bovine endometrial gland cell line (BEGC) forms gland acini in vitro and is only IFNτ-responsive (MAPK42/44 activation) after E2 and P4-pre-incubation

INTRODUCTION

Uterine glands (UG) are crucial for the establishment of ruminant pregnancy and influenced (orchestrated manner) by estrogen (E₂), progesterone (P₄) and interferon tau (IFNτ). In the study we established a bovine endometrial glandular cell line (BGEC) and tested its functional reactivity (signaling) to IFNτ.

METHODS

BGEC was characterized by light microscopy (LM), epithelial markers (ezrin, CK18) [immunofluorescence (IF)/immunohistochemistry (IHC)] and ultrastructure (TEM/SEM) (apical microvilli). In vitro formation of gland acini and transepithelial-electric-resistance (TEER) measurements (EVOM) were done. The expression of mRNA-transcripts (RT-PCR) of steroid receptors (PR, PGRMC1/2, ESR1/2) and the IFNτ-system (IFNAR1/2, IRF1, 2, 9) was checked. BEGC was stimulated with IFNτ (10 ng/ml;1000 ng/ml) (15 min) after steroid pre-treatment [10 pg/ml E₂ (two days)/20 ng/ml P₄ (two days)]. Activation of MAPK42/44;STAT1 was evaluated (densitometrical Western Blot).

RESULTS

BGEC cells expressed epithelial markers and possessed apical microvilli. High TEER-values could be measured (2320-2620 ohm/cm²). The assembled BEGC acini (25 days) were similar to UG in vivo (markers/ultrastructure). All transcripts (steroid receptors/IFNτ-system) could be detected in BEGC (mRNA). MAPK42/44 were significantly activated after E₂/P₄ pre-treatment and IFNτ stimulation (10 ng/ml) (p < 0.05), whilst 1000 ng/ml IFNτ did not activate MAPK42/44. Neither a STAT1 (by IFNτ) nor an activation (MAPK42/44;STAT1) by IFNτ-only was observed.

DISCUSSION

BGEC retains its epithelial phenotype in culture and forms gland acini in vitro thereby confirming its glandular character. Cells were only reactive to (low) IFNτ concentrations when pre-treated with steroids thereby closely resembling implantation physiology in vivo. BEGC can be used as a bovine implantation model to study embryo-maternal communication during early pregnancy in cattle.

The somatotropic axis during the physiological estrus cycle in dairy heifers--Effect on hepatic expression of GHR and SOCS2

Pituitary growth hormone (GH) release and hepatic insulin-like growth factor-I (IGF-I) production increase after an injection of 17β-estradiol (E2) in ovariectomized dairy cattle. However, whether endogenous sexual steroid hormones also influence the hepatic GH receptor (GHR) signaling pathway during a physiological estrus cycle remains unclear. The aim of this study was to analyze the hepatic GHR signaling pathway during the luteal phase and after a period of increased E2 concentrations (after ovulation) as well as in 7 heifers before ovulation. Ovarian ultrasounds were performed daily during repeated physiological cycles (n = 56) of 30 Holstein Friesian heifers to determine ovulation [before ovulation (n = 7, bOv) and after ovulation 24-60 h after the appearance of estrus signs (n = 49, aOv)] and luteal phase (CLP; d 12 ± 1 after ovulation). Blood samples and liver biopsies were obtained, and blood concentrations of E2, P4, insulin-like growth factor (IGF)-I, IGF-II, and GH were measured. In the liver biopsies, we determined mRNA expression of the estrogen receptor α (ERα), GHR, Janus kinase 2 (JAK2), signal transducer and activator of transcription 5B (STAT5B), suppressor of cytokine signaling (SOCS)2 and 3, IGF-I, and IGF-II by quantitative reverse transcription-PCR. The concentration of E2 was higher bOv than aOv and CLP, as expected. The concentrations of IGF-I and GH were higher bOv and aOv compared with CLP. In contrast, concentrations of IGF-II were lower aOv compared with bOv and CLP. The mRNA expression of GHR was higher in liver biopsies obtained bOv compared with aOv and CLP. Notably, the expression of SOCS2 was higher bOv than aOv and in the CLP. Increased hepatic expression of SOCS2 during estrus was detectable when IGF-I concentrations were high; this result might indicate that SOCS2 expression attenuates the GHR signal transduction pathway during the phase of increased pituitary GH release. In conclusion, hepatic GHR and SOCS2 mRNA expression appeared to be promptly and sensitively regulated by increased E2 levels before ovulation of dairy heifers.