Effects of altrenogest supplementation in late lactation on reproductive performance of primiparous sows

Genetic selection for hyperprolific sows resulted in higher proportion of low birthweight piglets and greater birthweight variation within the litter, increasing preweaning mortality. There is evidence that altrenogest supplementation improves post-weaning reproductive performance through higher ovulation rates, and increased embryo survival. This study aimed to evaluate the impacts of altrenogest supplementation during the last week of lactation in primiparous sows on subsequent reproductive performance. Ninety-six primiparous females were randomly assigned to two treatments: ALT-sows supplemented orally with 20 mg of altrenogest (n = 46) during the last six days of lactation up to 24 h before weaning; and CON- non-supplemented sows (n = 50). Ten sows from each experimental group were randomly selected to evaluate plasma progesterone concentrations on days 1 and 3 of treatment, at weaning and at 48, 72 and 96 h after estrus onset. Farrowings were monitored and piglets' individual birthweight, total number of piglets born, born alive, stillborn and mummified were recorded. Stillborn piglets were necropsied to assess organ weight. A subgroup of five females per treatment was euthanized on the day of estrus onset for morphological analysis of the reproductive tract. ALT females showed higher progesterone levels 72h after estrus onset (P < 0.05). Moreover, piglets' birthweight, total number of piglets born, liveborn, stillborn, and mummified were similar between experimental groups. Data collected from stillborn necropsies showed that birthweight was the main factor affecting organ weights (P < 0.05). Correlation analysis revealed that piglets weighing 600-800g presented higher brain:liver weight ratio, a determinant factor of intrauterine growth restriction, which was predominant in males (P < 0.05), and ALT females showed fewer piglets within that birthweight range (P < 0.05). Interestingly, ALT sows showed higher number, but smaller endometrial glands (P < 0.05). Taken together, short-term altrenogest supplementation in the last week of lactation increased progesterone levels after estrus onset, improving uterine vascularization and endometrial glands hyperplasia in the pre-implantation period, which benefit embryo development, leading to a decrease in the proportion of low birthweight piglets.

De novo reconstruction of a functional in vivo-like equine endometrium using collagen-based tissue engineering

To better understand molecular aspects of equine endometrial function, there is a need for advanced in vitro culture systems that more closely imitate the intricate 3-dimensional (3D) in vivo endometrial structure than current techniques. However, development of a 3D in vitro model of this complex tissue is challenging. This study aimed to develop an in vitro 3D endometrial tissue (3D-ET) with an epithelial cell phenotype optimized by treatment with a Rho-associated protein kinase (ROCK) inhibitor. Equine endometrial epithelial (eECs) and mesenchymal stromal (eMSCs) cells were isolated separately, and eECs cultured in various concentrations of Rock inhibitor (0, 5, 10 µmol) in epithelial medium (EC-medium) containing 10% knock-out serum replacement (KSR). The optimal concentration of Rock inhibitor for enhancing eEC proliferation and viability was 10 µM. However, 10 µM Rock inhibitor in the 10% KSR EC-medium was able to maintain mucin1 (Muc1) gene expression for only a short period. In contrast, fetal bovine serum (FBS) was able to maintain Muc1 gene expression for longer culture durations. An in vitro 3D-ET was successfully constructed using a collagen-based scaffold to support the eECs and eMSCs. The 3D-ET closely mimicked in vivo endometrium by displaying gland-like eEC-derived structures positive for the endometrial gland marker, Fork headbox A2 (FOXA2), and by mimicking the 3D morphology of the stromal compartment. In addition, the 3D-ET expressed the secretory protein MUC1 on its glandular epithelial surface and responded to LPS challenge by upregulating the expression of the interleukin-6 (IL6) and prostaglandin F synthase (PGFS) genes (P < 0.01), along with an increase in their secretory products, IL-6 (P < 0.01) and prostaglandin F2alpha (PGF2α) (P < 0.001) respectively. In the future, this culture system can be used to study both normal physiology and pathological processes of the equine endometrium.

CK1α deficiency impairs mouse uterine adenogenesis by inducing epithelial cell apoptosis through GSK3β pathway and inhibiting Foxa2 expression through p53 pathway†

Uterine glands and their secretions are crucial for conceptus survival and implantation in rodents and humans. In mice, the development of uterine gland known as adenogenesis occurs after birth, whereas the adenogenesis in humans initiates from fetal life and completed at puberty. Uterine adenogenesis involves dynamic epithelial cell proliferation, differentiation, and apoptosis. However, it is largely unexplored about the mechanisms governing adenogenesis. CK1α plays important roles in regulating cell division, differentiation, and death, but it is unknown whether CK1α affects adenogenesis. In the current study, uterus-specific CK1α knockout female mice (Csnk1a1d/d) were infertile resulted from lack of uterine glands. Subsequent analysis revealed that CK1α deletion induced massive apoptosis in uterine epithelium by activating GSK3β, which was confirmed by injections of GSK3β inhibitor SB216763 to Csnk1a1d/d females, and the co-treatment of SB216763 and CK1 inhibitor d4476 on cultured epithelial cells. Another important finding was that our results revealed CK1α deficiency activated p53, which then blocked the expression of Foxa2, an important factor for glandular epithelium development and function. This was confirmed by that Foxa2 expression level was elevated in p53 inhibitor pifithrin-α injected Csnk1a1d/d mouse uterus and in vitro dual-luciferase reporter assay between p53 and Foxa2. Collectively, these studies reveal that CK1α is a novel factor regulating uterine adenogenesis by inhibiting epithelial cell apoptosis through GSK3β pathway and regulating Foxa2 expression through p53 pathway. Uncovering the mechanisms of uterine adenogenesis is expected to improve pregnancy success in humans and other mammals.

Understanding bovine embryo elongation: a transcriptomic study of trophoblastic vesicles

Background: During the process of elongation, the embryo increases in size within the uterus, while the extra-embryonic tissues (EETs) develop and differentiate in preparation for implantation. As it grows, the ovoid embryo transforms into a tubular form first and then a filamentous form. This process is directed by numerous genes and pathways, the expression of which may be altered in the case of developmental irregularities such as when the conceptus is shorter than expected or when the embryo develops after splitting. In bovines, efforts to understand the molecular basis of elongation have employed trophoblastic vesicles (TVs)-short tubular EET pieces that lack an embryo-which also elongate in vivo. To date, however, we lack molecular analyses of TVs at the ovoid or filamentous stages that might shed light on the expression changes involved. Methods: Following in vivo development, we collected bovine conceptuses from the ovoid (D12) to filamentous stages (D18), sectioned them into small pieces with or without their embryonic disc (ED), and then, transferred them to a receptive bovine uterus to assess their elongation abilities. We also grew spherical blastocysts in vitro up to D8 and subjected them to the same treatment. Then, we assessed the differences in gene expression between different samples and fully elongating controls at different stages of elongation using a bovine array (10 K) and an extended qPCR array comprising 224 genes across 24 pathways. Results: In vivo, TVs elongated more or less depending on the stage at which they had been created and the time spent in utero. Their daily elongation rates differed from control EET, with the rates of TVs sometimes resembling those of earlier-stage EET. Overall, the molecular signatures of TVs followed a similar developmental trajectory as intact EET from D12-D18. However, within each stage, TVs and intact EET displayed distinct expression dynamics, some of which were shared with other short epithelial models. Conclusion: Differences between TVs and EET likely result from multiple factors, including a reduction in the length and signaling capabilities of TVs, delayed elongation from inadequate uterine signals, and modified crosstalk between the conceptus and the uterus. These findings confirm that close coordination between uterine, embryonic, and extra-embryonic tissues is required to orchestrate proper elongation and, based on the partial differentiation observed, raise questions about the presence/absence of certain developmental cues or even their asynchronies.

Differing planes of nutrition alter serum and histotroph amino acid composition in nonpregnant, multiparous beef cows on day 3 of the estrous cycle

Endometrial-derived uterine histotroph is a critical component of nutrient supply to a growing conceptus throughout gestation; however, the effect of nutritional plane on histotroph nutrient composition remains unknown in multiparous cows. We hypothesized that differing planes of nutrition would alter histotroph and serum nutrient composition in beef cattle. Thus, we evaluated serum and histotroph amino acid and glucose composition, and serum non-esterified fatty acids (NEFA) and blood urea nitrogen (BUN) in cows individually fed to maintain body weight (BW; 0 kd/d, n = 9; CON) compared with those losing moderate BW (-0.7 kg/d, n = 9; NEG). After 49 d of differing nutritional planes, cows were subjected to the 7-d CoSynch + controlled internal drug release device estrus synchronization protocol and then slaughtered on day 62. Blood serum (days 0 and 62) and uterine histotroph [day 62; from uterine horns ipsilateral and contralateral to the corpus luteum (CL)] were collected and analyzed for concentrations of amino acids, glucose, and NEFA. Performance characteristics, body composition via ultrasound (days 0 and 62), and carcass characteristics were collected. Body condition score, change in BW, average daily gain, dry matter intake, and gain:feed were decreased (P ≤ 0.05) in NEG vs. CON cows. There were no differences in body composition or carcass characteristics, except an increase (P ≤ 0.05) in dressing percentage in NEG cows due to differences in gut fill, consistent with study design. Serum NEFA increased (P ≤ 0.05) in the NEG group, but there were no differences between NEG vs. CON in glucose or BUN. Serum histidine increased (P ≤ 0.05) and alanine, isoleucine, and tryptophan decreased (P ≤ 0.05) in NEG vs. CON cows. Compared with that of the uterine horn ipsilateral to the CL, histotroph from the uterine horn contralateral to the CL had increased (P ≤ 0.05) isoleucine, asparagine, and proline concentrations in NEG cows, and decreased (P ≤ 0.05) tryptophan as a proportion of essential and total amino acids. There were no differences in glucose concentrations of histotroph contralateral or ipsilateral to the CL. Cow nutritional plane does alter serum and histotroph amino acid composition, although the presence of an embryo may be necessary to fully elucidate these changes. Differences in serum and histotroph tryptophan should be given consideration in future studies due to its importance as an essential amino acid in protein synthesis and bioactive affects.

Single-cell insights into epithelial morphogenesis in the neonatal mouse uterus

The uterus is vital for successful reproduction in mammals, and two different types of epithelia (luminal and glandular) are essential for embryo implantation and pregnancy establishment. However, the essential cellular and molecular factors and pathways governing postnatal epithelium maturation, determination, and differentiation in developing uterus are yet to be elucidated. Here, the epithelium of the neonatal mouse uterus was isolated and subjected to single-cell transcriptome (scRNA-seq) analysis. Both the undifferentiated epithelium and determined luminal epithelium were heterogeneous and contained several different cell clusters based on single-cell transcription profiles. Substantial gene expression differences were evident as the epithelium matured and differentiated between postnatal days 1 to 15. Two new glandular epithelium-expressed genes (Gas6 and Cited4) were identified and validated by in situ hybridization. Trajectory analyses provided a framework for understanding epithelium maturation, lineage bifurcation, and differentiation. A candidate set of transcription factors and gene regulatory networks were identified that potentially direct epithelium lineage specification and morphogenesis. This atlas provides a foundation important to discover intrinsic cellular and molecular mechanisms directing uterine epithelium morphogenesis during a critical window of postnatal development.

An IFNT/FOXO1/PTGS2 axis regulates prostaglandin F2α synthesis in goat uterus during early pregnancy

In ruminants, IFN-tau (IFNT) regulates the production of prostaglandins (PG) in the endometrium, which is crucial for conceptus adhesion. However, the related molecular regulatory mechanisms remain unclear. Forkhead box O1 (FOXO1), a member of the FOXO subfamily of transcription factors, is known to be important for mouse implantation and decidualization. In this study, we determined the spatiotemporal expression profile of FOXO1 in goat endometrium during early pregnancy. FOXO1 was highly expressed in the glandular epithelium since the onset of conceptus adhesion (d 16 of pregnancy). Then, we validated that FOXO1 could bind to the promoter of prostaglandin-endoperoxide synthase 2 (PTGS2) and increase its transcription. And the expression profile of PTGS2 was similar to that of FOXO1 in the peri-implantation uterus. Moreover, IFNT could upregulate the levels of FOXO1 and PTGS2 in goat uterus and primary endometrial epithelium cells (EEC). In EEC, the intracellular content of PGF2α was positively correlated with the levels of IFNT and FOXO1. Altogether, we found an IFNT/FOXO1/PTGS2 axis that controls the synthesis of PGF2α but not prostaglandin E2 in goat uterine glands. These findings contribute to better understanding the function of FOXO1 in the reproductive physiology of goats and provide more insights into the implantation of small ruminants.

β-Hydroxybutyrate affects cell physiological parameters, inflammatory markers and hormone receptor expression in bovine endometrial gland cells in vitro

INTRODUCTION

After calving, dairy cows are commonly affected by negative energy balance (NEB), indicated by high β-Hydroxybutyrate (BHBA) blood levels. These are associated with subfertility frequently related to uterine inflammation. Since this could compromise functionality of endometrial glands that are essential for proper embryo implantation in sheep, we investigated effects of BHBA on bovine endometrial gland cells (BEGC) in vitro.

MATERIAL AND METHODS

BEGC were stimulated with different concentrations of BHBA over different periods. Cell metabolism and motility were examined by MTT-assay and Live-cell-imaging. The mRNA expression of the receptors for estrogen (ESR1, ESR2), progesterone (PR) and IFNτ (IFNAR1, IFNAR2), and the inflammatory cytokines TNFα and IL-6 was determined by RT-qPCR. Protein expression for PR and ESR1 was analyzed by semiquantitative Western Blot.

RESULTS

BEGC metabolism was significantly decreased after stimulation with 1.2, 1.8 and 2.4 mM BHBA over 24 and 36 h. Cell motility was significantly reduced by 1.8 and 2.4 mM BHBA already after 11 h. After 24 h stimulation, the ESR1 mRNA expression was significantly increased in BEGC stimulated with 0.6 mM BHBA. PR and TNFα mRNA expressions were increased in cells stimulated with 2.4 mM BHBA. Protein expression of ESR1 and PR was not altered.

DISCUSSION

Treatment with BHBA leads to restriction of BEGC metabolism and motility, and increased expression of TNFα, ESR1 and PR in vitro. This could explain how increased BHBA blood levels might compromise functionality of uterine glands in vivo and thus could contribute to compromised reproductive success of cows suffering from NEB.

An Integrative ATAC-Seq and RNA-Seq Analysis of the Endometrial Tissues of Meishan and Duroc Pigs

Meishan pigs are a well-known indigenous pig breed in China characterized by a high fertility. Notably, the number of endometrial grands is significantly higher in Meishan pigs than Duroc pigs. The characteristics of the endometrial tissue are related to litter size. Therefore, we used the assay for transposase-accessible chromatin with sequencing (ATAC-seq) and RNA-sequencing (RNA-seq) to analyze the mechanisms underlying the differences in fecundity between the breeds. We detected the key transcription factors, including Double homeobox (Dux), Ladybird-like homeobox gene 2 (LBX2), and LIM homeobox 8 (Lhx8), with potentially pivotal roles in the regulation of the genes related to endometrial development. We identified the differentially expressed genes between the breeds, including SOX17, ANXA4, DLX3, DMRT1, FLNB, IRF6, CBFA2T2, TFCP2L1, EFNA5, SLIT2, and CYFIP2, with roles in epithelial cell differentiation, fertility, and ovulation. Interestingly, ANXA4, CBFA2T2, and TFCP2L1, which were upregulated in the Meishan pigs in the RNA-seq analysis, were identified again by the integration of the ATAC-seq and RNA-seq data. Moreover, we identified genes in the cancer or immune pathways, FoxO signaling, Wnt signaling, and phospholipase D signaling pathways. These ATAC-seq and RNA-seq analyses revealed the accessible chromatin and potential mechanisms underlying the differences in the endometrial tissues between the two types of pigs.

Regulation of synthesis of polyamines by progesterone, estradiol, and their receptors in uteri of cyclic ewes†

Progesterone (P4), estradiol (E2), and expression of their receptors (PGR and ESR1, respectively) by cells of the uterus regulate reproductive performance of mammals through effects on secretion and transport of nutrients into the uterine lumen. This study investigated the effect of changes in P4, E2, PGR, and ESR1 on expression of enzymes for the synthesis and secretion of polyamines. Suffolk ewes (n = 13) were synchronized to estrus (Day 0) and then, on either Day 1 (early metestrus), Day 9 (early diestrus), or Day 14 (late diestrus) of the estrous cycle, maternal blood samples were collected, and ewes were euthanized before obtaining uterine samples and uterine flushings. Endometrial expression of MAT2B and SMS mRNAs increased in late diestrus (P < 0.05). Expression of ODC1 and SMOX mRNAs decreased from early metestrus to early diestrus, and expression of ASL mRNA was lower in late diestrus than in early metestrus (P < 0.05). Immunoreactive PAOX, SAT1, and SMS proteins were localized to uterine luminal, superficial glandular, and glandular epithelia, stromal cells, myometrium, and blood vessels. Concentrations of spermidine and spermine in maternal plasma decreased from early metestrus to early diestrus and decreased further in late diestrus (P < 0.05). The abundances of spermidine and spermine in uterine flushings were less in late diestrus than early metestrus (P < 0.05). These results indicate that synthesis and secretion of polyamines are affected by P4 and E2, as well as the expression of PGR and ESR1 in the endometria of cyclic ewes.

Impact of postpartum metritis on the regeneration of endometrial glands in dairy cows

The postpartum uterus involutes to its pre-pregnant and fully functional state within approximately 60 d after calving. Uterine glands are essential for fertility but little is known about their regeneration postpartum. Likewise, the effect of uterine disease (metritis) on gland regeneration is unknown. We hypothesized that uterine glands would be regenerated early postpartum and that metritis would be associated with slower gland regeneration to affect their numbers later postpartum during the breeding period. Postpartum dairy cows were diagnosed as healthy (n = 17 and 9 for experiment [Exp.] 1 and 2) or metritis (n = 17 and 10 for Exp. 1 and 2, respectively) at 7 to 10 d postpartum. Cows were slaughtered at approximately 1 mo (Exp. 1) or approximately 80 or 165 d (Exp. 2) postpartum for the collection of the uterus. Uterine tissue was sectioned and the number of glandular cross-sections per unit area was counted and cross-sectional area measured. Cellular proliferation within the luminal epithelium (LE) and glandular epithelium (GE) was quantified by MKI67 (marker of cellular proliferation) immunohistochemistry. In early postpartum cows (Exp. 1), the greatest amount of MKI67 staining was found in the deep endometrium (cells closest to the myometrium). Cows with purulent material in the uterine lumen at d 30 slaughter (Exp. 1) had fewer endometrial glands per unit area in the deep and middle endometrium when compared with nonpurulent cows. The MKI67 staining was less in the deep endometrial GE and LE for purulent compared with nonpurulent cows. Estrus cyclicity was associated with a greater number of gland cross-sections in the deep and middle endometrium. Later postpartum (80 and 165 d; Exp. 2), there was greater glandular development compared with Exp. 1 and a tendency for a lesser number of gland cross-sections per unit area in diseased cows without an effect on MKI67 staining in the GE or LE. We conclude that uterine disease slows the development of uterine glands early postpartum (by 1 mo) through a mechanism that involves cellular proliferation within the GE. The impact of the early postpartum disease on glandular development later postpartum (Exp. 2) appeared to be less. Additional time, therefore, may allow recovery of the GE in later postpartum cows.

Review: Implantation and placentation in ruminants

Ruminants have a unique placenta in comparison to other mammalian species. Initially, they possess a non-invasive epitheliochorial type of placenta during conceptus elongation. As the conceptus trophectoderm begins to attach to the luminal epithelium (LE) of the endometrium, binucleate cells (BNCs) develop within the trophoblast of the chorion. The BNCs migrate and fuse with the uterine LE to form multinucleate syncytial plaques in sheep and hybrid trinucleate cells in cattle. This area of the ruminant placenta is semi-invasive synepitheliochorial. The BNCs form the foundation of the placental cotyledons and express unique placenta-specific genes including pregnancy-associated glycoproteins and chorionic somatomammotropin hormone 2 or placental lactogen. Attachment and interdigitation of cotyledons into endometrial caruncles form placentomes that are subsequently vascularized to provide essential nutrients for growth of the fetus. This chapter review will discuss historical and current aspects of conceptus implantation and placenta development in ruminant ungulates with a focus on cattle and sheep. Single-cell analysis promises to provide a much more detailed understanding of the different cell populations and insights into pathways mediating trophoblast and placenta. This fundamental is required to understand pregnancy loss and develop strategies to improve pregnancy outcomes in ruminants.

Review: Endometrial function in pregnancy establishment in cattle

The endometrium is fundamentally required for successful pregnancy in ruminants and species where the posthatching conceptus undergoes a protracted elongation and peri-implantation phase of pregnancy. Moreover, there are substantial waves of pregnancy loss during this pre- and peri-implantation period of pregnancy the precise source of which has not been clearly defined i.e., the maternal uterine contribution to this loss. Understanding the molecular interactions required for successful pregnancy in cattle will allow us to intervene to support pregnancy success during this vulnerable window. The endometrium contributes to most key developmental milestones of pregnancy establishment, including (1) contributing to the regulation of the oestrus cycle, (2) nourishing the preimplantation conceptus, (3) responding to the conceptus to create a more receptive microenvironment, (4) providing essential biophysical support, and (5) signalling and producing factors which affect the mother systemically. This review will summarise what we currently know about conceptus-maternal interactions as well as identify the gaps in our knowledge that could be filled with newer in vitro model approaches. These include the use of microfluidics, organ-on-a-chip devices, and bioinformatic approaches. This will help maximise food production efficiency (both meat and dairy) and decrease the environmental burden, while enhancing our understanding of the fundamental processes required for successful implantation in cattle.

Basolateral secretions of human endometrial epithelial organoids impact stromal cell decidualization

Uterine glands and, by inference, their secretions impact uterine receptivity, blastocyst implantation, stromal cell decidualization, and placental development. Changes in gland function across the menstrual cycle are primarily governed by the steroid hormones estrogen (E2) and progesterone (P4) but can also be influenced by extrinsic factors from the stroma. Using a human endometrial epithelial organoid system, transcriptome and proteome analyses identified distinct responses of the organoids to steroid hormones and prostaglandin E2 (PGE2). Notably, P4 and PGE2 modulated the basolateral secretion of organoid proteins, particularly cystatin C (CST3), serpin family A member 3 (SERPINA3), and stanniocalcin 1 (STC1). CST3, but not SERPINA3 or STC1, attenuated the in vitro stromal decidualization response to steroid hormones and PGE2. These findings provide evidence that uterine gland-derived factors impact stromal cell decidualization, which has implications for pregnancy establishment and fertility in women.

The impact of FSH stimulation and age on the ovarian and uterine traits and histomorphometry of prepubertal gilts

This study investigated the effect of age and follicle stimulating hormone (FSH) treatment on the estradiol (E2) plasma concentration, ovarian follicle development, endometrial histomorphometry, and ultrasonographic parameters of the ovaries and uterus in prepubertal gilts. Thirty-five prepubertal gilts were grouped according to age (140 or 160 d), and within each age, gilts were allotted to receive 100 mg of FSH (treated; G140 + FSH [n = 10] and G160 + FSH [n = 7]) or saline solution (control; G140 + control [n = 10] and G160 + control [n = 8]). The total dose of FSH was divided into 6 similar doses administered every 8 h (days 0-2). Before and after FSH treatment, blood sample was collected, and transabdominal scanning of the ovaries and uterus was performed. Twenty-four hours after the last FSH injection, the gilts were slaughtered and their ovaries and uterus were processed for histological and histomorphometric analysis. The histomorphometric parameters of the uterus differed (P < 0.05) between prepubertal gilts at 160 d and 140 d of age. Moreover, changes (P < 0.05) in uterine and ovarian ultrasound images occurred between 140 and 160 d of age. Age and FSH treatment did not affect (P > 0.05) E2 plasma concentrations. Follicle stimulating hormone treatment did not affect (P > 0.05) the early stage of folliculogenesis in the prepubertal gilts; however, the number of early atretic follicles decreased (P < 0.05) after the FSH treatment. Follicle stimulating hormone administration increased (P < 0.05) the number of medium follicles and decreased (P < 0.05) the number of small follicles in 140 and 160 d old gilts. In the endometrium, luminal/glandular epithelium height and glandular diameter increased (P < 0.05) after FSH treatment. Thus, injections of 100 mg of FSH stimulate the endometrium epithelium and induce follicular growth to a medium follicle size without affecting the preantral stages in prepubertal gilts; also, the uterine macroscopic morphometry does not change from 140 to 160 d of age.

Prss29 Cre recombinase mice are useful to study adult uterine gland function

All mammalian uteri contain glands in their endometrium that develop only or primarily after birth. In mice, those endometrial glands govern post implantation pregnancy establishment via regulation of blastocyst implantation, stromal cell decidualization, and placental development. Here, we describe a new uterine glandular epithelium (GE) specific Cre recombinase mouse line that is useful for the study of uterine gland function during pregnancy. Utilizing CRISPR-Cas9 genome editing, Cre recombinase was inserted into the endogenous serine protease 29 precursor (Prss29) gene. Both Prss29 mRNA and Cre recombinase activity was specific to the GE of the mouse uterus following implantation, but was absent from other areas of the female reproductive tract. Next, Prss29-Cre mice were crossed with floxed forkhead box A2 (Foxa2) mice to conditionally delete Foxa2 specifically in the endometrial glands. Foxa2 was absent in the glands of the post-implantation uterus, and Foxa2 deleted mice exhibited complete infertility after their first pregnancy. These results establish that Prss29-Cre mice are a valuable resource to elucidate and explore the functions of glands in the adult uterus.

Bovine and human endometrium-derived hydrogels support organoid culture from healthy and cancerous tissues

Organoid technology has provided unique insights into human organ development, function, and diseases. Patient-derived organoids are increasingly used for drug screening, modeling rare disorders, designing regenerative therapies, and understanding disease pathogenesis. However, the use of Matrigel to grow organoids represents a major challenge in the clinical translation of organoid technology. Matrigel is a poorly defined mixture of extracellular matrix proteins and growth factors extracted from the Engelbreth–Holm–Swarm mouse tumor. The extracellular matrix is a major driver of multiple cellular processes and differs significantly between tissues as well as in healthy and disease states of the same tissue. Therefore, we envisioned that the extracellular matrix derived from a native healthy tissue would be able to support organoid growth akin to organogenesis in vivo. Here, we have developed hydrogels from decellularized human and bovine endometrium. These hydrogels supported the growth of mouse and human endometrial organoids, which was comparable to Matrigel. Organoids grown in endometrial hydrogels were proteomically more similar to the native tissue than those cultured in Matrigel. Proteomic and Raman microspectroscopy analyses showed that the method of decellularization affects the biochemical composition of hydrogels and, subsequently, their ability to support organoid growth. The amount of laminin in hydrogels correlated with the number and shape of organoids. We also demonstrated the utility of endometrial hydrogels in developing solid scaffolds for supporting high-throughput, cell culture–based applications. In summary, endometrial hydrogels overcome a major limitation of organoid technology and greatly expand the applicability of organoids to understand endometrial biology and associated pathologies.

Development and characterization of human fetal female reproductive tract organoids to understand Müllerian duct anomalies

Müllerian ducts are paired tubular structures that give rise to most of the female reproductive organs. Any abnormalities in the development and differentiation of these ducts lead to anatomical defects in the female reproductive tract organs categorized as Müllerian duct anomalies. Due to the limited access to fetal tissues, little is understood of human reproductive tract development and the associated anomalies. Although organoids represent a powerful model to decipher human development and disease, such organoids from fetal reproductive organs are not available. Here, we developed organoids from human fetal fallopian tubes and uteri and compared them with their adult counterparts. Our results demonstrate that human fetal reproductive tract epithelia do not express some of the typical markers of adult reproductive tract epithelia. Furthermore, fetal organoids are grossly, histologically, and proteomically different from adult organoids. While external supplementation of WNT ligands or activators in culture medium is an absolute requirement for the adult reproductive tract organoids, fetal organoids are able to grow in WNT-deficient conditions. We also developed decellularized tissue scaffolds from adult human fallopian tubes and uteri. Transplantation of fetal organoids onto these scaffolds led to the regeneration of the adult fallopian tube and uterine epithelia. Importantly, suppression of Wnt signaling, which is altered in patients with Müllerian duct anomalies, inhibits the regenerative ability of human fetal organoids and causes severe anatomical defects in the mouse reproductive tract. Thus, our fetal organoids represent an important platform to study the underlying basis of human female reproductive tract development and diseases.

Maternal iron supplementation during pregnancy affects placental function and iron status in offspring

BACKGROUND

Iron deficiency and overload during pregnancy damage to maternal and fetal health. Placenta as an organ for the transport of nutrients between mother and fetus protects fetus from the harmful effects of iron deficiency and iron overload through regulation of placental iron homeostasis.

METHODS

To determine the effect of dietary iron supplementation during pregnancy on reproduction and the mechanism of placental iron regulation, we designed dietary high iron (HI: 344 mg/kg), medium iron (MI: 40 mg/kg), low iron (LI: 2 mg/kg) groups of pregnant female mice fed ferrous citrate 2 weeks before mating to 18.5 days of gestation.

RESULTS

We find dietary iron supplementation during pregnancy effect maternal liver iron, placental iron, hemoglobin and fetal iron. Dietary iron significantly improves reproductive performance as litter weight and fetal weight. Correlation analysis suggest placental iron increased with liver iron, higher and lower liver iron is not conducive to the accumulation of fetal iron, placental iron deficiency and excess reduce litter weight. Placental transcriptome analysis revealed DEGs with the same trend in HI and LI groups compared with MI group, dietary iron may change biology process of ion transport and gland development in placenta. Granzyme may affect the placental trophoblast structure prior to delivery with iron overload uniquely.

CONCLUSION

This research highlights the importance of moderate iron supplements in pregnancy due to damage of reproduction by affecting placental function under different dose of maternal iron supplementation.

The Influence of the Prolactins on the Development of the Uterus in Neonatal Mice

The endometrial gland is one of the most important components of the mammalian uterus. However, few studies have been conducted on the regulatory mechanisms of adenogenesis during the development of endometrium. In the present study, we detected the genes expression of 35 different prolactin family members (PRLs) together with the prolactin receptor (PRL-R) in the endometrium of neonatal mice along with the adenogenesis process, to address which prolactin-like genes play a key role during gland development in mice. We found that: (1) The expression of Prl1a1, Prl3d1, Prl5a1, Prl7a1, Prl7a2, Prl7d1, Prl8a6, Prl8a8, and Prl8a9 genes were significantly increased along with the development of uterine glands. Prl7c1 and Prl8a1 were observably up-regulated on Postnatal day 5 (PND5) when the uterine glandular bud invagination begins. Prl3a1, Prl3b1, and Prl7b1 suddenly increased significantly on PND9. But, Prl3c1 and Prl8a2 were markedly down-regulated on PND5 and the expression of Prl6a1 and Prlr were stable extremely. (2) After continuous injection of Progesterone (P4), a well-known method to suppress the endometrial adenogenesis, the expression of Prl1a1, Prl3d1, Prl5a1, Prl7a1, Prl7a2, Prl7d1, Prl8a6, Prl8a8, Prl8a9, and Prlr were suppressed on PND7. And on PND9, Prl1a1, Prl3d1, Prl8a6, Prl8a8, and Prl8a9 were significantly inhibited. (3) Further analysis of the epithelial and stroma showed that these PRLs were mainly expressed in the endometrial stroma of neonatal mice. Our results indicate that multiple PRLs are involved in uterine development and endometrial adenogenesis. Continued progesterone therapy may alter the expression pattern of these PRLs in endometrial stromal cells, thereby altering the interaction and communication between stroma and epithelium, and ultimately leading to complete suppression of endometrial adenogenesis.

Progesterone differentially affects the transcriptomic profiles of cow endometrial cell types

Background

The endometrium is a heterogeneous tissue composed of luminal epithelial (LE), glandular epithelial (GE), and stromal cells (ST), experiencing progesterone regulated dynamic changes during the estrous cycle. In the cow, this regulation at the transcriptomic level was only evaluated in the whole tissue. This study describes specific gene expression in the three types of cells isolated from endometrial biopsies following laser capture microdissection and the transcriptome changes induced by progesterone in GE and ST cells.

Results

Endometrial LE, GE, and ST cells show specific transcriptomic profiles. Most of the differentially expressed genes (DEGs) in response to progesterone are cell type-specific (96%). Genes involved in cell cycle and nuclear division are under-expressed in the presence of progesterone in GE, highlighting the anti-proliferative action of progesterone in epithelial cells. Elevated progesterone concentrations are also associated with the under-expression of estrogen receptor 1 (ESR1) in GE and oxytocin receptor (OXTR) in GE and ST cells. In ST cells, transcription factors such as SOX17 and FOXA2, known to regulate uterine epithelial-stromal cross-talk conveying to endometrial receptivity, are over-expressed under progesterone influence.

Conclusions

The results from this study show that progesterone regulates endometrial function in a cell type-specific way, which is independent of the expression of its main receptor PGR. These novel insights into uterine physiology present the cell compartment as the physiological unit rather than the whole tissue.

Supplementary Information

The online version contains supplementary material available at 10.1186/s12864-022-08323-z.

Exocrine gland structure-function relationships

Fluid secretion by exocrine glandular organs is essential to the survival of mammals. Each glandular unit within the body is uniquely organized to carry out its own specific functions, with failure to establish these specialized structures resulting in impaired organ function. Here, we review glandular organs in terms of shared and divergent architecture. We first describe the structural organization of the diverse glandular secretory units (the end-pieces) and their fluid transporting systems (the ducts) within the mammalian system, focusing on how tissue architecture corresponds to functional output. We then highlight how defects in development of end-piece and ductal architecture impacts secretory function. Finally, we discuss how knowledge of exocrine gland structure-function relationships can be applied to the development of new diagnostics, regenerative approaches and tissue regeneration.

Evaluation of bovine uterine gland functions in 2D and 3D culture system

In ruminants, uterine glands play key roles in the establishment of pregnancy by secreting various factors into the uterine lumen. Although a three-dimensional (3D) culture system has been used for investigating cellular functions in vitro, the detailed functions of uterine gland have not been fully elucidated. In this study, we examined the benefits of 3D culture system to examine the innate functions of bovine uterine glands. Isolated bovine uterine glands were cultured on Matrigel (2D) or in Matrigel (3D), respectively, and the mRNA levels of secreted proteins (SERPINA14, MEP1B, APOA1, ARSA, CTGF, and SPP1) were measured in isolated and cultured uterine glands. The protein expression of estrogen receptor β (ERβ) and progesterone receptor (PR) and the establishment of apico-basal polarity were examined. In isolated uterine glands, the mRNA levels of secreted proteins changed during the estrous cycle. Although uterine glands cultured in both 2D and 3D expressed ERβ and PR, progesterone did not affect SERPINA14 mRNA expression. The expression of APOA1 mRNA in 2D cultured uterine glands did not respond to estrogen and progesterone. Additionally, the mRNA levels of secreted proteins in the 3D culture system were significantly higher than those in the 2D culture system, which might be attributed to the different cellular morphology between them. The locations of ZO-1 and β-catenin in 2D cultured uterine glands were disordered compared with 3D cultured uterine glands. These results showed that the hormonal responsiveness of secreted factor expression and cellular morphology were different between 2D and 3D cultured bovine uterine glands.

Uterine glands impact embryo survival and stromal cell decidualization in mice

Uterine glands are essential for the establishment of pregnancy and have critical roles in endometrial receptivity to blastocyst implantation, stromal cell decidualization, and placentation. Uterine gland dysfunction is considered a major contributing factor to pregnancy loss, however our understanding of how glands impact embryo survival and stromal cell decidualization is incomplete. Forkhead box A2 (FOXA2) is expressed only in the glandular epithelium and regulates its development and function. Mice with a conditional deletion of FOXA2 in the uterus are infertile due to defective embryo implantation arising from a lack of leukemia inhibitory factor (LIF), a critical factor of uterine gland origin. Here, a glandless FOXA2-deficient mouse model, coupled with LIF repletion to rescue the implantation defect, was used to investigate the roles of uterine glands in embryo survival and decidualization. Studies found that embryo survival and decidualization were compromised in glandless FOXA2-deficient mice on gestational day 6.5, resulting in abrupt pregnancy loss by day 7.5. These findings strongly support the hypothesis that uterine glands secrete factors other than LIF that impact embryo survival and stromal cell decidualization for pregnancy success.

Uterine infection alters the transcriptome of the bovine reproductive tract three months later

Infection of the postpartum uterus with pathogenic bacteria is associated with infertility months later in dairy cattle. However, it is unclear whether these bacterial infections lead to long-term changes in the reproductive tract that might help explain this infertility. Here we tested the hypothesis that infusion of pathogenic bacteria into the uterus leads to changes in the transcriptome of the reproductive tract 3 months later. We used virgin Holstein heifers to avoid potential confounding effects of periparturient problems, lactation, and negative energy balance. Animals were infused intrauterine with endometrial pathogenic bacteria Escherichia coli and Trueperella pyogenes (n = 4) and compared with control animals (n = 6). Three months after infusion, caruncular and intercaruncular endometrium, isthmus and ampulla of the oviduct, and granulosa cells from ovarian follicles >8 mm diameter were profiled by RNA sequencing. Bacterial infusion altered the transcriptome of all the tissues when compared with control. Most differentially expressed genes were tissue specific, with 109 differentially expressed genes unique to caruncular endometrium, 57 in intercaruncular endometrium, 65 in isthmus, 298 in ampulla, and 83 in granulosa cells. Surprisingly, despite infusing bacteria into the uterus, granulosa cells had more predicted upstream regulators of differentially expressed genes than all the other tissues combined. In conclusion, there were changes in the transcriptome of the endometrium, oviduct and even granulosa cells, 3 months after intrauterine infusion of pathogenic bacteria. These findings imply that long-term changes throughout the reproductive tract could contribute to infertility after bacterial infections of the uterus.

Capture and metabolomic analysis of the human endometrial epithelial organoid secretome

Suboptimal uterine fluid (UF) composition can lead to pregnancy loss and likely contributes to offspring susceptibility to chronic adult-onset disorders. However, our understanding of the biochemical composition and mechanisms underpinning UF formation and regulation remain elusive, particularly in humans. To address this challenge, we developed a high-throughput method for intraorganoid fluid (IOF) isolation from human endometrial epithelial organoids. The IOF is biochemically distinct to the extraorganoid fluid (EOF) and cell culture medium as evidenced by the exclusive presence of 17 metabolites in IOF. Similarly, 69 metabolites were unique to EOF, showing asymmetrical apical and basolateral secretion by the in vitro endometrial epithelium, in a manner resembling that observed in vivo. Contrasting the quantitative metabolomic profiles of IOF and EOF revealed donor-specific biochemical signatures of organoids. Subsequent RNA sequencing of these organoids from which IOF and EOF were derived established the capacity to readily perform organoid multiomics in tandem, and suggests that transcriptomic regulation underpins the observed secretory asymmetry. In summary, these data provided by modeling uterine luminal and basolateral fluid formation in vitro offer scope to better understand UF composition and regulation with potential impacts on female fertility and offspring well-being.

Gene expression of bovine endometrial epithelial cells cultured in matrigel

Glandular epithelial cells (GE) in the endometrium are thought to support the elongation and survival of ruminant embryos by secreting histotrophs. In the present study, the gene expression of bovine endometrial epithelial cells cultured in matrigel was analyzed and examined whether it could be an in vitro model of GE. Bovine endometrial epithelial cells (BEE) and stromal cells (BES) were isolated from the slaughterhouse uteri and cultured in DMEM/F12 + 10% FBS. BEE showed the gland-like structure morphological changes when cultured in 15% matrigel but could not be identified in higher concentrations of the matrigel (30% or 60%). The expression of typical genes expressed in GE, SERPINA14 and GRP, was substantially high in matrigel-cultured BEE than in monolayer (P  <  0.05). P4 and INFα have no significant effect on the SERPINA14 expression of BEE cultured in matrigel without co-culture with BES. On the other hand, when BEE were co-cultured with BES in matrigel culture, the expression of FGF13 was increased by the P4 treatment (P  <  0.05). Furthermore, SERPINA14 and TXN expressions were increased by P4 + IFNα treatment (P  <  0.05). These results demonstrate the appropriate conditions for BEE to form glandular structures in matrigel and the effect of co-culture with BES. The present study highlighted the possible use of matrigel for the culture of BEE to investigate the expression of cell-specific glandular epithelial genes as well as P4 and type-I IFN as factors controlling endometrial function during the implantation period.

The Elusive Endometrial Epithelial Stem/Progenitor Cells

The human endometrium undergoes approximately 450 cycles of proliferation, differentiation, shedding and regeneration over a woman's reproductive lifetime. The regenerative capacity of the endometrium is attributed to stem/progenitor cells residing in the basalis layer of the tissue. Mesenchymal stem cells have been extensively studied in the endometrium, whereas endometrial epithelial stem/progenitor cells have remained more elusive. This review details the discovery of human and mouse endometrial epithelial stem/progenitor cells. It highlights recent significant developments identifying putative markers of these epithelial stem/progenitor cells that reveal their in vivo identity, location in both human and mouse endometrium, raising common but also different viewpoints. The review also outlines the techniques used to identify epithelial stem/progenitor cells, specifically in vitro functional assays and in vivo lineage tracing. We will also discuss their known interactions and hierarchy and known roles in endometrial dynamics across the menstrual or estrous cycle including re-epithelialization at menses and regeneration of the tissue during the proliferative phase. We also detail their potential role in endometrial proliferative disorders such as endometriosis.

Insights into the lipidome and primary metabolome of the uterus from day 14 cyclic and pregnant sheep†

In ruminants, conceptus elongation requires the endometrium and its secretions. The amino acid, carbohydrate, and protein composition of the uterine lumen during early pregnancy has been defined in sheep; however, a comprehensive understanding of metabolomic changes in the uterine lumen is lacking, particularly with respect to lipids. Here, the lipidome and primary metabolome of the uterine lumen, endometrium, and/or conceptus was determined on day 14 of the estrous cycle and pregnancy. Lipid droplets and select triglycerides were depleted in the endometrium of pregnant ewes. In contrast, select ceramides, diglycerides, and non-esterified fatty acids as well as several phospholipid classes (phosphatidylcholine, phosphatidylinositol, phosphatidylglycerols, and diacylglycerols) were elevated in the uterine lumen of pregnant ewes. Lipidomic analysis of the conceptus revealed that triglycerides are particularly abundant within the conceptus. Primary metabolite analyses found elevated amino acids, carbohydrates, and energy substrates, among others, in the uterine lumen of pregnant ewes. Collectively, this study supports the hypothesis that lipids are important components of the uterine lumen that govern conceptus elongation and growth during early pregnancy.

Progress and challenges in developing organoids in farm animal species for the study of reproduction and their applications to reproductive biotechnologies

Within the past decades, major progress has been accomplished in isolating germ/stem/pluripotent cells, in refining culture medium and conditions and in establishing 3-dimensional culture systems, towards developing organoids for organs involved in reproduction in mice and to some extent in humans. Haploid male germ cells were generated in vitro from primordial germ cells. So were oocytes, with additional support from ovarian cells and subsequent follicle culture. Going on with the female reproductive tract, spherical oviduct organoids were obtained from adult stem/progenitor cells. Multicellular endometrial structures mimicking functional uterine glands were derived from endometrial cells. Trophoblastic stem cells were induced to form 3-dimensional syncytial-like structures and exhibited invasive properties, a crucial point for placentation. Finally, considering the embryo itself, pluripotent embryonic cells together with additional extra-embryonic cells, could self-organize into a blastoid, and eventually into a post-implantation-like embryo. Most of these accomplishments have yet to be reached in farm animals, but much effort is devoted towards this goal. Here, we review the progress and discuss the specific challenges of developing organoids for the study of reproductive biology in these species. We consider the use of such organoids in basic research to delineate the physiological mechanisms involved at each step of the reproductive process, or to understand how they are altered by environmental factors relevant to animal breeding. We evaluate their potential in reproduction of animals with a high genetic value, from a breeding point of view or in the context of preserving local breeds with limited headcounts.

Prenatal development in Lagostomus maximus (Rodentia, Chinchillidae): A unique case among eutherian mammals of physiological embryonic death

Embryonic death followed by resorption is a conserved process in mammals. Among the polyovular species, Lagostomus maximus (plains viscacha) constitutes a model of early and physiological embryonic death, since out of a total of 10-12 implants, 8-10 are resorbed during early/intermediate gestation, surviving are only the most caudal implantations of each uterine horn. This regular reproductive event is unique to this species, but many characteristics of the implantations during the early gestation of L. maximus, when embryonic death processes begin are unknown. The aim of the present work was to analyze the implantation sites of this species using morphological, morphometric, histochemical, lectinhistochemical, and immunohistochemical techniques to infer the possible causes of this event. Macroscopically, the length and width of the implantation sites significantly increased in a craniocaudal direction. Histochemically, the implantation sites did not differ in the expression of glycoconjugates and glycosidic residues. Furthermore, no variations were observed in cell renewal, hormone receptor expression, and decidualization. Both the glandular and vascular areas of the implantation sites significantly increased in the craniocaudal axis. Some necrotic cells and an inflammatory response with a predominance of lymphocytes and fibrin were observed in the cranial and middle but not in the caudal implantation sites. We conclude that signs of embryonic death and resorption are already observed in the early gestation of L. maximus. Our results reaffirm the hypothesis that postulates the key potential role of uterine glands and blood vessels in the gestation of the species, with emphasis on embryonic death. This pattern of embryonic death in L. maximus makes this species an unconventional mammalian model, which adds to the peculiarities of polyovulation (200-800 oocytes/estrus) and hemochorial placentation.

The effects of maternal nutrition during the first 50 d of gestation on the location and abundance of hexose and cationic amino acid transporters in beef heifer uteroplacental tissues

We hypothesized that maternal nutrition during the first 50 d of gestation would influence the abundance of hexose transporters, SLC2A1, SLC2A3, and SLC2A5, and cationic amino acid transporters, SLC7A1 and SLC7A2, in heifer uteroplacental tissues. Angus-cross heifers (n = 43) were estrus synchronized, bred via artificial insemination, and assigned at breeding to 1 of 2 dietary intake groups (CON = 100% of requirements to achieve 0.45 kg/d of BW gain or RES = 60% of CON intake) and ovariohysterectomized on day 16, 34, or 50 of gestation (n = 6 to 9/d) in a completely randomized design with a 2 × 3 factorial arrangement of treatments. Uterine cross-sections were collected from the horn ipsilateral to the corpus luteum, fixed in 10% neutral buffered formalin, sectioned at 5 µm, and stained via immunofluorescence for transporters. For each image, areas of fetal membrane (FM; chorioallantois), luminal epithelium (ENDO), superficial glands (SG), deep glands (DG), and myometrium (MYO) were analyzed separately for relative intensity of fluorescence as an indicator of transporter abundance. Analysis of FM was only conducted for days 34 and 50. No transporters in target areas were influenced by a day × treatment interaction (P ≥ 0.06). In ENDO, all transporters were differentially abundant from days 16 to 50 of gestation (P ≤ 0.04), and SLC7A2 was greater (P = 0.05) for RES vs. CON. In SG, SLC7A1 and SLC7A2 were greater (P ≤ 0.04) at day 34 vs. day 16. In DG, SLC2A3 and SLC7A1 were greater (P ≤ 0.05) for CON vs. RES heifers; furthermore, SLC7A1 was greater (P < 0.01) at day 50 vs. days 16 and 34 of gestation. In MYO, SLC7A1 was greater (P < 0.01) for CON vs. RES and was greater (P = 0.02) at days 34 and 50 vs. day 16. There were no differences in FM (P ≥ 0.06). Analysis of all uterine tissues at day 16 determined that SLC2A1, SLC2A3, and SLC7A2 were all differentially abundant across uterine tissue type (P < 0.01), and SLC7A1 was greater (P = 0.02) for CON vs. RES. Analysis of all uteroplacental tissues at days 34 and 50 demonstrated that all transporters differed (P < 0.01) across uteroplacental tissues, and SLC7A1 was greater (P < 0.01) for CON vs. RES. These data are interpreted to imply that transporters are differentially affected by day of gestation, and that hexose and cationic amino acid transporters are differentially abundant across utero-placental tissue types, and that SLC7A1 is responsive to maternal nutritional treatment.

In vitro models of the human endometrium: evolution and application for women's health

The endometrium is the inner lining of the uterus that undergoes complex regeneration and differentiation during the human menstrual cycle. The process of endometrial shedding, regeneration, and differentiation is driven by ovarian steroid hormones and prepares the endometrium and intrauterine environment for embryo implantation and pregnancy establishment. Endometrial glands and their secretions are essential for pregnancy establishment, and cross talk between the glandular epithelium and stromal cells appears vital for decidualization and placental development. Despite being crucial, the biology of the human endometrium during pregnancy establishment and most of pregnancy is incomplete, given the ethical and practical limitations of obtaining and studying endometrium from pregnant women. As such, in vitro models of the human endometrium are required to fill significant gaps in understanding endometrial biology. This review is focused on the evolution and development of in vitro three-dimensional models of the human endometrium and provides insight into the challenges and promises of those models to improve women's reproductive health.

Neonatal exposure to a glyphosate-based herbicide alters the uterine differentiation of prepubertal ewe lambs

The exposure to endocrine-disrupting compounds (EDCs), such as glyphosate-based herbicides (GBHs), during early life might alter female fertility. The aim of the present study was to evaluate the effects of neonatal exposure to a GBH on sheep uterine development. To achieve this, Friesian ewe lambs were exposed to GBH (2 mg/kg of body weight/day; n = 12) or vehicle (controls; n = 10) through s.c. injections, from postnatal day (PND) 1 to PND14; on PND45, the uteri were obtained to evaluate histomorphological and molecular parameters. Morphological parameters were determined by picrosirius-hematoxylin staining. Protein expression of Ki67 (as a cell proliferation marker), p27, and molecules involved in uterine organogenetic differentiation was measured by immunohistochemistry. We also determined the mRNA expression of the IGF molecular pathway by RT-PCR. Although histomorphology was not modified, the uteri of GBH-exposed ewe lambs showed lower cell proliferation, together with higher p27 protein expression. In addition, the uteri of GBH-exposed ewe lambs showed increased gene expression of insulin-like growth factor binding protein 3 (IGFBP-3), decreased expression of ERα in the luminal (LE) and glandular (GE) epithelia and in the subepithelial stroma (SS), and lower PR expression in the LE but higher in the GE and SS. In addition, GBH treatment decreased the uterine expression of Wnt5a in the GE, of Wnt7a in the SS, of β-catenin in the LE and GE, of Hoxa10 in the SS, and of Foxa2 in the GE as compared with controls. In conclusion, neonatal exposure to GBH decreased cell proliferation and altered the expression of molecules that control proliferation and development in the uterus. All these changes might have adverse consequences on uterine differentiation and functionality, affecting the female reproductive health of sheep. GBH may be responsible for uterine subfertility, acting as an EDC.

Long non-coding RNA366.2 controls endometrial epithelial cell proliferation and migration by upregulating WNT6 as a ceRNA of miR-1576 in sheep uterus

Long non-coding RNAs (lncRNAs) play an important regulatory role in mammalian fecundity. Currently, most studies are primarily concentrated on ovarian lncRNAs, ignoring the influence of uterine lncRNAs on the fecundity of female sheep. In this study, we found a higher density of uterine glands and endometrial microvessel density (MVD) in high prolificacy group of Hu sheep compared to low prolificacy groups (p < 0.05) as well as an increased level of serum placental growth factor (PLGF). Hundreds of differentially expressed (DE) lncRNAs were identified in Hu sheep with different fecundity by RNA sequencing (RNA-seq), and their targets were enriched in some signaling pathways involved in endometrial functions, such as the estrogen signaling pathway, nuclear factor kappa B (NF-κB) signaling pathway, oxytocin signaling pathway, and Wnt signaling pathway. Furthermore, the underlying mechanisms of competitive endogenous RNA (ceRNA) of lncRNA366.2-miR-1576- WNT6 were determined by bioinformatics analysis. Functionally, our results indicated that lncRNA366.2 promoted endometrial epithelial cell (EEC) proliferation, migration, and growth factor expression by sponging miR-1576 to upregulate WNT6 expression and activate the Wnt/β-catenin pathway. Taken together, our research indicated the regulatory mechanism of the lncRNA366.2-miR-1576-WNT6 in EEC proliferation and migration. Furthermore, this study provides a new theoretical reference for the identification of candidate genes related to fecundity.

Mating to Intact, but Not Vasectomized, Males Elicits Changes in the Endometrial Transcriptome: Insights From the Bovine Model

An appropriate female reproductive environment is essential for pregnancy success. In several species, including mice, pigs and horses, seminal plasma (SP) components have been shown to modulate this environment, leading to increased embryo viability and implantation. Due to the characteristics of mating in the aforementioned species, SP comes into direct contact with the uterus. However, it is questionable whether any SP reaches the uterus in species that ejaculate inside the vagina, such as humans and cattle. Hence, we hypothesized that sperm, perhaps acting as a vehicle for SP factors, play a more important role in the modulation of the maternal uterine environment in these species. In addition, changes elicited by SP and/or sperm may originate in the vagina and propagate to more distal regions of the female reproductive tract. To test these hypotheses, a bovine model in which heifers were mated to intact or vasectomized bulls or were left unmated was used. RNA-sequencing of endometrial samples collected 24 h after mating with a vasectomized bull did not reveal any differentially expressed genes (DEGs) in comparison with control samples. However, the endometrium of heifers mated with intact bulls exhibited 24 DEGs when compared to heifers mated with vasectomized bulls, and 22 DEGs when compared to unmated control heifers. The expression of a set of cytokines (IL6, IL1A, IL8, and TNFA) and candidate genes identified in the endometrial RNA-sequencing (PLA2G10, CX3CL1, C4BPA, PRSS2, BLA-DQB, and CEBPD) were assessed by RT-qPCR in the vagina and oviductal ampulla. No differences in expression of these genes were observed between treatments in any region. However, mating to both intact and vasectomized bulls induced an increase in IL1A and TNFA expression in the vagina compared to the oviduct. These data indicate that sperm, but not secretions from the accessory glands alone, induce modest changes in endometrial gene expression after natural mating in cattle. However, it is not clear whether this effect is triggered by inherent sperm proteins or SP proteins bound to sperm surface at the time of ejaculation.

Effects of oestrous synchronization with altrenogest in gilts on endometrial and embryonic characteristics

The use of altrenogest (ALT) supplementation for oestrous synchronization improves subsequent reproductive performance of gilts and sows. However, the causes of this improvement in reproductive performance after ALT treatment are not fully/clearly understood. The objective of this study was to evaluate the effects of ALT supplementation for oestrous synchronization in gilts on the endometrial glands and embryonic development characteristics at 28 days of pregnancy. Pregnant gilts were divided into two experimental treatments: Control (did not receive ALT; n = 9 gilts) and ALT (ALT feeding at 20 mg/day for 18 days; n = 9 gilts). At 28 days of pregnancy, six gilts from each treatment were slaughtered, and reproductive tracts were immediately evaluated. There was no statistical difference (P > 0.05) between treatments regarding ovulation rate, number of embryos, number of vital embryos and number of non-vital embryos. Embryo weight, length and embryonic vesicle weight were lower in ALT treatment compared with Control (P < 0.01), and it was lower in the cervical uterine region compared with apex uterine region, respectively (P < 0.05). Higher values of gland duct area, gland duct perimeter, percentage of the glandular area and total endometrial area were observed in ALT treatment compared with Control (P < 0.05). The use of ALT during 18 days for oestrous synchronization in gilts increased the gland duct area, perimeter and total endometrial area but did not increase the embryo number and embryo size at day 28 of pregnancy.

Analysis of the uterine lumen in fertility-classified heifers: II. Proteins and metabolites†

Survival and growth of the bovine conceptus is dependent on endometrial secretions or histotroph. Previously, serial blastocyst transfer was used to classify heifers as high fertile (HF), subfertile (SF), or infertile (IF). Here, we investigated specific histotroph components (proteins and metabolites) in the uterine lumen of day 17 fertility-classified heifers. Interferon tau (IFNT) was more abundant in uterine lumenal fluid (ULF) of pregnant HF than SF animals as the conceptus was longer in HF heifers. However, no differences in endometrial expression of selected classical and nonclassical interferon-stimulated genes (ISGs) were observed, suggesting that IFNT signaling in the endometrium of pregnant HF and SF heifers was similar. Pregnancy significantly increased the abundance of several proteins in ULF. Based on functional annotation, the abundance of a number of proteins involved in energy metabolism, oxidative stress, amino acid metabolism, and cell proliferation and differentiation were greater in the ULF of pregnant HF than SF heifers. Metabolomics analysis found that pregnancy only changed the metabolome composition of ULF from HF heifers. The majority of the metabolites that increased in the ULF of pregnant HF as compared to SF heifers were associated with energy and amino acid metabolism. The observed differences in ULF proteome and metabolome are hypothesized to influence uterine receptivity with consequences on conceptus development and survival in fertility-classified heifers.

Genital abnormalities associated to lack of uterine adenogenesis or endometrial gland dysgenesis of female dromedary camels (Camelus dromedarius)

Background:

The developmental disruption of the müllerian duct and the endometrial dynamic can generate genital lesions that could contribute to infertility.

Aim:

This paper discusses two cases of genital conditions associated to endometrial gland pathologies in nulliparous female camels.

Methods:

Macroscopic examinations and histopathological description were performed on congenital and acquired genital abnormalities with endometrial gland anomalies.

Results:

The first case is endometrial gland agenesis associated to unilateral uterine aplasia, and the second case is endometrial gland dysgenesis associated to metritis. The prevalence of each case is estimated to be 0.6%. The most specific microscopic features associated to the endometrial gland agenesis were the presence of endometrial stromal proliferation and homogenous hyalinization of the myometrium. The acute metritis was associated to endometrial-activated stroma with focal infiltration with inflammatory cells on the endometrium and myometrium and the spontaneous endometrial gland dysgenesis.

Conclusion:

This study reveals the importance of congenital abnormalities during the routine reproductive examination of peripubertal animals, as well as the association of histopathological complementary examination for the research functional and inflammatory anomalies of the uterus. Genetic screening of breeders would be very important in the search for genetic risk factors associated with these congenital pathologies, which can be disseminated by reproductive biotechnologies.

Development of the human placenta

The placenta is essential for normal in utero development in mammals. In humans, defective placental formation underpins common pregnancy disorders such as pre-eclampsia and fetal growth restriction. The great variation in placental types across mammals means that animal models have been of limited use in understanding human placental development. However, new tools for studying human placental development, including 3D organoids, stem cell culture systems and single cell RNA sequencing, have brought new insights into this field. Here, we review the morphological, molecular and functional aspects of human placental formation, with a focus on the defining cell of the placenta - the trophoblast.

Self-renewing endometrial epithelial organoids of the human uterus

The human endometrium is essential in providing the site for implantation and maintaining the growth and survival of the conceptus. An unreceptive endometrium and disrupted maternal-conceptus interactions can cause infertility due to pregnancy loss or later pregnancy complications. Despite this, the role of uterine glands in first trimester human pregnancy is little understood. An established organoid protocol was used to generate and comprehensively analyze 3-dimensional endometrial epithelial organoid (EEO) cultures from human endometrial biopsies. The derived EEO expand long-term, are genetically stable, and can be cryopreserved. Using endometrium from 2 different donors, EEO were derived and then treated with estrogen (E2) for 2 d or E2 and medroxyprogesterone acetate (MPA) for 6 d. EEO cells were positive for the gland marker, FOXA2, and exhibited appropriate hormonal regulation of steroid hormone receptor expression. Real-time qPCR and bulk RNA-sequencing analysis revealed effects of hormone treatment on gene expression that recapitulated changes in proliferative and secretory phase endometrium. Single-cell RNA sequencing analysis revealed that several different epithelial cell types are present in the EEO whose proportion and gene expression changed with hormone treatment. The EEO model serves as an important platform for studying the physiology and pathology of the human endometrium.

Uterine Glands: Developmental Biology and Functional Roles in Pregnancy

All mammalian uteri contain glands in the endometrium that develop only or primarily after birth. Gland development or adenogenesis in the postnatal uterus is intrinsically regulated by proliferation, cell-cell interactions, growth factors and their inhibitors, as well as transcription factors, including forkhead box A2 (FOXA2) and estrogen receptor α (ESR1). Extrinsic factors regulating adenogenesis originate from other organs, including the ovary, pituitary, and mammary gland. The infertility and recurrent pregnancy loss observed in uterine gland knockout sheep and mouse models support a primary role for secretions and products of the glands in pregnancy success. Recent studies in mice revealed that uterine glandular epithelia govern postimplantation pregnancy establishment through effects on stromal cell decidualization and placental development. In humans, uterine glands and, by inference, their secretions and products are hypothesized to be critical for blastocyst survival and implantation as well as embryo and placental development during the first trimester before the onset of fetal-maternal circulation. A variety of hormones and other factors from the ovary, placenta, and stromal cells impact secretory function of the uterine glands during pregnancy. This review summarizes new information related to the developmental biology of uterine glands and discusses novel perspectives on their functional roles in pregnancy establishment and success.

Review: Maternal programming of development in the pig and the lactocrine hypothesis

Maternal effects on development are profound. Together, genetic and epigenetic maternal effects define the developmental trajectory of progeny and, ultimately, offspring phenotype. Maternally provisioned environmental conditions and signals affect conceptus, fetoplacental and postnatal development from the time of conception until weaning. In the pig, reproductive tract development is completed postnatally. Porcine uterine growth and uterine endometrial development occur in an ovary-independent manner between birth (postnatal day = PND 0) and PND 60. Milk-borne bioactive factors (MbFs), exemplified by relaxin, communicated from lactating dam to nursing offspring via a lactocrine mechanism, represent an important source of extraovarian uterotrophic support in the neonatal pig. Lactocrine deficiency from birth affects both the neonatal porcine uterine developmental program and trajectory of uterine development, with lasting consequences for endometrial function and uterine capacity in adult female pigs. The potential lactocrine signaling window extends from birth until the time of weaning. However, it is likely that the maternal lactocrine programming window - that period when MbFs communicated to nursing offspring have the greatest potential to affect critical organizational events in the neonate - encompasses a comparatively short period of time within 48 h of birth. Lactocrine deficiency from birth was associated with altered patterns of endometrial gene expression in neonatally lactocrine-deficient adult gilts during a critical period for conceptus-endometrial interaction on pregnancy day 13, and with reduced litter size, estimated at 1.4 pigs per litter, with no effect of parity. Data were interpreted to indicate that reproductive performance of female pigs that do not receive sufficient colostrum from birth is permanently impaired. Observations to date suggest that lactocrine-dependent maternal effects program postnatal development of the porcine uterus, endometrial functionality and uterine capacity. In this context, reproductive management strategies and husbandry guidelines should be refined to ensure that such practices promote environmental conditions that will optimize uterine capacity and fecundity. This will entail careful consideration of factors affecting lactation, the quality and abundance of colostrum/milk, and practices that will afford neonatal pigs with the opportunity to nurse and consume adequate amounts of colostrum.

Relaxin and the 'Milky Way': The lactocrine hypothesis and maternal programming of development

Maternal effects on early postnatal development in mammals are mediated, in part, by milk-borne bioactive factors transmitted from mother to nursing offspring. The term 'lactocrine' was coined to describe this mode of signaling. Relaxin (RLX), one of a family of neohormones found in mammals, is detectable in milk from multiple species. In the pig, evidence of bioactive proRLX in colostrum/milk, immunoreactive RLX in the circulation of nursed neonates, and RLX receptor expression in RLX-sensitive neonatal female reproductive tract tissues, established RLX as a prototypical lactocrine-active factor. Observations provided the foundation for the lactocrine hypothesis for maternal programming of postnatal development. Studies designed to test the lactocrine hypothesis provided insights into both short-term effects of milk-borne bioactive factors in the neonate, and long-term consequences of maternal lactocrine programming of endometrial function and fecundity in adults. Thus, RLX led to the 'Milky Way'.