Endometrial expression of the insulin-like growth factor system during uterine involution in the postpartum dairy cow

Development potential of selenium in the prevention and treatment of bovine endometritis

Endometritis is a common postpartum disease in cows. It delays uterine involution and impairs normal physiological function. This can result in long-term or even lifelong infertility and cause significant losses to the dairy farming industry. Traditional treatments like antibiotics possess certain shortcomings, such as antibiotic residues, the abuse of antibiotics, and increased antimicrobial resistance of pathogens. Alternative treatment strategies are needed to minimize the utilization of antibiotics in dairy production. As an essential trace element in animals, selenium (Se) plays a vital role in regulating immune function, the inflammatory response, and oxidative stress, affecting the speed and completeness of tissue repair. This paper reviewed previous studies to analyse the potential of Se in the prevention and treatment of bovine endometritis, aiming to provide a new direction to increase production capacity in the future.

Plane of nutrition and FSH-induced superovulation affect the expression of steroid hormone receptors and growth factors in caruncular tissue of non-pregnant sheep

Implantation is a critical step in the establishment of pregnancy and an important part of embryo-maternal contact. Uterine receptivity can be affected by changes in body condition and the maternal endocrine milieu, including those caused by the use of exogenous gonadotropins in controlled ovarian hyperstimulation to induce the development of multiple follicles. This study demonstrates the effects of FSH-mediated ovarian hyperstimulation on the caruncles of ewes under various feeding regimes. Sheep were classified into 3 categories: control fed (CF), overfed (OF), or underfed (UF). In each group, animals were superovulated with FSH or injected with a saline solution (non-treated control). Uterine caruncles were collected at the early (d 5) and mid-luteal phase (d 10) of the estrous cycle. The transcript levels of steroid hormone receptors (ESR1, ESR2, PGR) and growth factors (IGF1, IGF2, VEGFA) were investigated and their expression localized by immunohistochemical staining. As for the main findings, day of the estrous cycle affected expression of ESR1, IGF1 and IGF2, but not of ESR2, PGR and VEGFA; both feeding and superovulation had modulatory effects, with feeding (UF/OF) stimulating expression of all genes studied, and superovulation altering expression of some genes, eg IGF1, PGR and ESR1 and ESR2, in CF animals. Similarly, feeding (UF/OF) altered responsiveness to superovulation for PGR on d 5 and ESR1/ESR2 on d 5 and/or 10. Our data emphasize possible effects of dietary and/or hormonal stimuli on uterine physiology, which may affect pregnancy outcomes by disrupting uterine functionality.

Analysis of the transcriptome of bovine endometrial cells isolated by laser micro-dissection (2): impacts of post-partum negative energy balance on stromal, glandular and luminal epithelial cells

BACKGROUND

In post-partum dairy cows, the energy needs to satisfy high milk production induces a status of more or less pronounced Negative Energy Balance (NEB). NEB associated with fat mobilization impairs reproductive function. In a companion paper, we described constitutive gene expression in the three main endometrial cell types (stromal, glandular and luminal epithelial cells) isolated by laser capture micro-dissection (LCM) showing the specificities of their transcriptomic profiles. This study investigates the specific impact of NEB on gene expression in these cells around 80 days after parturition at day 15 of the oestrus cycle and describes their specific response to NEB.

RESULTS

Following the description of their constitutive expression, the transcriptome profiles obtained by RNA sequencing of the three cells types revealed that differences related to the severity of NEB altered mainly specific patterns of expression related to individual cell types. Number of differentially expressed genes between severe NEB (SNEB) and mild NEB (MNEB) cows was higher in ST than in LE and GE, respectively. SNEB was associated with differential expression of genes coding for proteins involved in metabolic processes and embryo-maternal interactions in ST. Under-expression of genes encoding proteins with functions related to cell structure was found in GE whereas genes encoding proteins participating in pro-inflammatory pathways were over-expressed. Genes associated to adaptive immunity were under-expressed in LE.

CONCLUSION

The severity of NEB after calving is associated with changes in gene expression around 80 days after parturition corresponding to the time of breeding. Specific alterations in GEs are associated with activation of pro-inflammatory mechanisms. Concomitantly, changes in the expression of genes encoding proteins involved in cell interactions and maternal recognition of pregnancy takes place in ST. The combination of these effects possibly altering the uterine environment and embryo maternal interactions may negatively influence the establishment of pregnancy.

Rumen-Protected Glucose Stimulates the Insulin-Like Growth Factor System and mTOR/AKT Pathway in the Endometrium of Early Postpartum Dairy Cows

This study aimed to elucidate the effects of a dietary rumen-protected glucose (RPG) addition on uterine involution through the analysis of an insulin-like growth factor (IGF) system and associated pathways in the post-natal endometrium. Twelve Holstein cows were assigned equally to two groups: a control group (CT) and an RPG group (200 g of RPG per cow per day). The plasma content of insulin-like growth factor 1 (IGF1) was determined by using the ELISA method. Expressions of IGF members, the matrix metalloproteinase, protein kinase B (AKT)/mechanistic target of rapamycin complex1 (mTOR) signaling pathway, and cell proliferation factors (proliferating cell nuclear antigen (PCNA) and Ki67) were detected using real-time polymerase chain reaction, Western blot, immunohistochemistry, and immunofluorescence, respectively. The results showed that the positive cells of PCNA and Ki67 were increased in the endometrium of RPG versus CT cows. The RPG addition significantly increased the plasma IGF1 level 14 d after delivery. The mRNA expressions of the IGF family members (IGF1, IGF2, type 1 IGF receptor (IGF1R) and IGF-binding proteins (IGFBP1, IGFBP2, IGFBP4 and IGFBP5)) were upregulated, and mRNA expressions of matrix metalloproteinase MMP3 and MMP9 were downregulated in cows from the RPG group compared with the CT group. Meanwhile, the protein expressions of IGF1, IGF2, IGF1R, IGFBP1 and IGFBP4 were upregulated in cows from the RPG group compared with the CT group. Immunohistochemical analysis identified a positive response for IGF1R and IGF2R in the endometrium of RPG versus CT cows. Furthermore, the RPG supplementation increased the protein expressions of phosphorylated (p)-AKT to total AKT and p-mTOR to total mTOR ratio in the endometrium. The current results indicated that the RPG supplementation promoted the proliferation of endometrial cells by stimulating the IGFs and mTOR/AKT pathway in the early post-natal endometrium of dairy cows.

Effect of metritis on endometrium tissue transcriptome during puerperium in Holstein lactating cows

The objective of this prospective cohort study was to evaluate the effect of parity and uterine health status postpartum on the gene expression profile of the endometrium early post-partum. Twenty-four Holstein cows were randomly selected (16 multiparous (MP) and 8 primiparous (PP)) and endometrium biopsies were collected on days 1, 3, and 6 after calving and clinically monitored for metritis. Rectal temperature was measured twice and fever was defined as a temperature ≥39.5 °C. A case of metritis was diagnosed with the presence of red-brown watery, foul-smelling uterine discharge or a purulent discharge with more than 50% pus and fever between days 1 and 6 postpartum. Cows were then retrospectively selected (cows diagnosed with metritis were paired with healthy ones) to analyze the expression of 66 genes measured on the NanoString nCounter Analysis System. The genes selected were related with adhesion, immune system, steroid and prostaglandin biosynthesis regulation, insulin metabolism and transcription factors, and nutrient transporters. The results indicated a different pattern on genes related to immune function by parity. PTX3, involved in antigen presentation, was increased in healthy MP compared with healthy PP whereas inflammatory cytokine TNFα and complement-related protein SERPING1 was upregulated in MP compared with PP (P < 0.05). As expected, presence of a metritis condition affected the expression of genes related to immune function. There was an increased expression of the antiviral factor MX2 and MYH10 gene, which is involved in macrophages recruitment, in metritic compared with healthy cows (P < 0.05). Differences in uterine involution from cows diagnosed with metritis were reflected by the downregulation of IGF1 (P < 0.10), involved in endometrium remodeling, and a possible compensatory upregulation of its receptor IGFR1 (P < 0.05). A greater expression of prostaglandins and oxytocin receptors (PGR and OXTR), involved in the involution process, were observed in metritic PP compared with healthy PP (P < 0.05). Overall, it seems that metritis significantly modulate processes closely tied with the physical involution of the uterus early post-partum (IGF1, IGFR1, PGR, OXTR), whereas both metritis and multiparous cows tended to upregulate genes related to immune response (PTX3, TNFα, SERPING1, MX2, MYH10).

Chemical Constituents and Antidepressant-Like Effects in Ovariectomized Mice of the Ethanol Extract of Alternanthera philoxeroides

The previously unreported flavone glycoside, demethyltorosaflavone B (2) and the E-propenoic acid substituted flavone, torosaflavone E (3a), were isolated together with nine previously reported metabolites, including indole-3-carbaldehyde, oleanonic acid, vanillic acid, p-hydroxybenzoic acid, altheranthin (1a), alternanthin B (1b), demethyltorosaflavone D (3b), luteolin 8-C-E-propenoic acid (4) and chrysoeriol 7-O-rhamnoside (5), from the ethanol extract of the aerial part of Althernanthera philoxeroides. The crude ethanol extract was evaluated for its in vitro estrogenic activity in MCF-7 breast cancer cell line. The crude ethanol extract was also investigated in vivo for its antidepressant-like effects on ovariectomized mice using tail suspension and forced swimming tests, while its effect on the locomotor activity was evaluated by a Y-maze test. The effect of the crude extract on the serum corticosterone level, size and volume of uterus of the ovariectomized mice were also investigated. The expression of the mouse cyclic adenosine monophosphate (cAMP) response element-binding protein (CREB), brain-derived neurotrophic factor (BDNF) and β-actin mRNAs in hippocampus and frontal cortex was also evaluated, using semiquantitative reverse transcription-polymerase chain reaction. The crude extract and the isolated compounds 1a, 1b, 3a, 3b and 5, were evaluated for their inhibitory effects on monoamine oxidases (MAOs)-A and -B.

Symposium review: Mechanisms linking metabolic stress with innate immunity in the endometrium

Bacterial infections of the uterus after parturition are ubiquitous in dairy cattle and often cause uterine disease, such as metritis or endometritis. However, the metabolic stress associated with milk production increases the risk of developing disease. Resolution of bacterial infections requires rapid and robust innate immune responses, which depend on host cell receptors recognizing pathogen-associated molecular patterns, such as lipopolysaccharide (LPS) from gram-negative bacteria. Here, we argue that metabolic stress impairs the inflammatory response to pathogens. Glucose and glutamine are the major energy sources for cells, but their abundance is reduced in postpartum dairy cows. Furthermore, inflammatory responses exacerbate metabolic stress, with animals and tissues consuming more glucose when challenged with LPS. However, depriving endometrial tissue of glucose or glutamine impairs the secretion of IL-1β, IL-6, and IL-8 in response to pathogen-associated molecular patterns. Glycolysis and the intracellular sensor of energy, AMP-activated protein kinase, are important for the response to LPS because perturbing glycolysis or AMP-activated protein kinase activity reduces the secretion of IL-1β, IL-6, and IL-8 in the endometrium. The mevalonate pathway for cellular cholesterol synthesis may also be linked to immunity, as inhibition of the terminal enzyme in the pathway, squalene synthase, reduces inflammatory responses to pathogenic bacteria and LPS. In contrast, only modest effects on inflammation are found when modulating the sensor of cellular nutrient satiety, mammalian target of rapamycin, or the endocrine regulator of metabolism, insulin-like growth factor-1. We suggest that stressing cellular metabolism increases the risk of uterine disease by impairing endometrial defenses.

Involvement of plasma adipokines in metabolic and reproductive parameters in Holstein dairy cows fed with diets with differing energy levels

This study aimed to investigate the association between plasma adipokine concentrations and metabolic and reproductive parameters in Holstein dairy cows fed diets with different energy levels during the peripartum period. The experiment started 1 mo before first calving and was maintained for 2 lactations. Dry matter intake and energy balance in animals fed a low-energy (LE) diet were significantly lower than that of animals fed a high-energy (HE) diet in the first lactation. Body weight, milk production, back fat thickness, and plasma concentrations of fatty acids, glucose, and insulin were not affected by diet, whereas plasma leptin and adiponectin concentrations were lower and plasma resistin concentrations higher in animals fed the LE diet. Unlike concentrations of adiponectin, plasma resistin concentrations were positively correlated with back fat thickness and plasma fatty acids concentrations and negatively correlated with dry matter intake and plasma leptin concentrations. No effect of diet was found on reproductive variables; that is, pregnancy rates at 35 or 90 d after artificial insemination (AI); numbers of small (3-5 mm), medium (>5 and ≤7 mm), and large (>7 mm) follicles; calving-to-AI and calving-to-calving intervals; and magnitude and duration of the LH surge. However, the commencement of luteal activity after first calving occurred sooner and the frequency of LH pulses was higher in the HE group than in the LE group. A significant positive correlation was found between the number of follicles (of any size) and the area under the curve of plasma resistin concentrations. The number of small follicles was also positively correlated with the nadir of plasma resistin concentrations. Taken together, these results suggest that dietary energy content in the range applied here can alter the resumption of ovarian activity and LH pulsatility without affecting fat mobilization. Plasma adipokine profiles (leptin, resistin, and adiponectin) were significantly altered by diet and negative energy balance but relationships with reproductive variables were limited to follicular growth characteristics and plasma resistin concentrations.

Endometrial gene expression in primiparous dairy cows at the end of the voluntary waiting period is affected by nutrition: Total mixed ration vs increasing levels of herbage allowance

The study postulated that differential nutritional management during the early lactation period would be reflected in endometrial expression of genes related to embryo growth at the end of the voluntary waiting period. Thus, the effect of the combined use of total mixed ration (TMR) and grazing under different herbage allowances during the first 75 days post-partum (DPP) on endometrial gene expression was evaluated in primiparous dairy cows. Cows were blocked by body weight, age and body condition score and randomly assigned to three grazing treatments: high (HA, 30 kg DM per cow per day), medium (MA, 15 kg DM per cow per day) and low (LA, 7.5 kg DM per cow per day) herbage allowance (mixed pasture, 2,600 kg DM per ha) plus 8 kg DM of supplement or TMR (55% forage, 45% concentrate) fed ad libitum (TMR) from calving to 75 DPP. At 57 DPP, cows were synchronized for oestrus (day 0, 68 DPP) and at day 7, endometrial biopsies were obtained. The nutritional treatment did not affect insulin, IGF-1 and leptin concentrations on days 0, 4 or 7. Expression of IGF1, IGFBP3, IGFBP4, ADIPOR1 and ADIPOR2 mRNA was significantly affected by the nutritional treatment. Endometrial IGF1 and IGFBP4 mRNA were twofold greater in TMR and HA than MA and LA cows. Expression of IGFBP3 and ADIPOR1 mRNAs was greater in TMR and HA than MA cows, but did not differ from LA cows. All groups had greater expression of ADIPOR2 mRNA than MA cows. This study provided solid evidence of the importance of nutritional management during early lactation on uterine environment at the end of the voluntary waiting period. The greater expression of genes related to embryo growth and uterine function (IGF system, progesterone and adiponectin receptors) in cows fed diets maximizing energy intake suggests a favourable environment for embryonic growth, which may explain the improved reproductive performance of cows in good energy balance.

Matrix Metalloproteinase Expression in the Rat Myometrium During Pregnancy, Term Labor, and Postpartum

Pregnancy, spontaneous term labor (TL), and postpartum (PP) involution are associated with changes in the cellular and extracellular matrix composition of the uterus. Both the uterine smooth muscle (myometrium) and the infiltrating peripheral blood leukocytes involved in the activation of labor secrete extracellular matrix-degrading enzymes (matrix metalloproteinases, MMPs) that can modulate cellular behavior and barrier function. MMP expression is induced by mechanical stretch in several tissues. We hypothesized that the expression and activity of myometrial MMPs and their tissue inhibitors (TIMPs) are modulated in preparation for TL and PP involution and are regulated by mechanical stretch of uterine walls imposed by the growing fetus. Myometrial tissues were collected from bilaterally and unilaterally pregnant rats across gestation, TL, and PP. Total RNA and proteins were subjected to real-time PCR and immunoblotting, respectively, and tissue localization and activity was examined by immunohistochemistry and in situ zymography. We found that Mmp7, Mmp11, and Mmp12 mRNA levels were upregulated during TL and PP, while Mmp2, Mmp3, Mmp8, Mmp9, Mmp10, and Mmp13 mRNAs were only upregulated during PP. Timp1–Timp4 were stably expressed throughout gestation with some fluctuations PP. Active MMP2 was induced in the empty uterine horn during gestation and in the gravid PP uterus, suggesting negative regulation by biological mechanical stretch. We conclude that specific subsets of uterine MMPs are differentially regulated in the rat myometrium in preparation for two major events: TL and PP uterine involution.

Glucose Availability and AMP-Activated Protein Kinase Link Energy Metabolism and Innate Immunity in the Bovine Endometrium

Defences against the bacteria that usually infect the endometrium of postpartum cattle are impaired when there is metabolic energy stress, leading to endometritis and infertility. The endometrial response to bacteria depends on innate immunity, with recognition of pathogen-associated molecular patterns stimulating inflammation, characterised by secretion of interleukin (IL)-1β, IL-6 and IL-8. How metabolic stress impacts tissue responses to pathogens is unclear, but integration of energy metabolism and innate immunity means that stressing one system might affect the other. Here we tested the hypothesis that homeostatic pathways integrate energy metabolism and innate immunity in bovine endometrial tissue. Glucose deprivation reduced the secretion of IL-1β, IL-6 and IL-8 from ex vivo organ cultures of bovine endometrium challenged with the pathogen-associated molecular patterns lipopolysaccharide and bacterial lipopeptide. Endometrial inflammatory responses to lipopolysaccharide were also reduced by small molecules that activate or inhibit the intracellular sensor of energy, AMP-activated protein kinase (AMPK). However, inhibition of mammalian target of rapamycin, which is a more global metabolic sensor than AMPK, had little effect on inflammation. Similarly, endometrial inflammatory responses to lipopolysaccharide were not affected by insulin-like growth factor-1, which is an endocrine regulator of metabolism. Interestingly, the inflammatory responses to lipopolysaccharide increased endometrial glucose consumption and induced the Warburg effect, which could exacerbate deficits in glucose availability in the tissue. In conclusion, metabolic energy stress perturbed inflammatory responses to pathogen-associated molecular patterns in bovine endometrial tissue, and the most fundamental regulators of cellular energy, glucose availability and AMPK, had the greatest impact on innate immunity.

Global transcriptomic profiling of bovine endometrial immune response in vitro. I. Effect of lipopolysaccharide on innate immunity

The dysregulation of endometrial immune response to bacterial lipopolysaccharide (LPS) has been implicated in uterine disease and infertility in the postpartum dairy cow, although the mechanisms are not clear. Here, we investigated whole-transcriptomic gene expression in primary cultures of mixed bovine epithelial and stromal endometrial cells. Cultures were exposed to LPS for 6 h, and cellular response was measured by bovine microarray. Approximately 30% of the 1006 genes altered by LPS were classified as being involved in immune response. Cytokines and chemokines (IL1A, CX3CL1, CXCL2, and CCL5), interferon (IFN)-stimulated genes (RSAD2, MX2, OAS1, ISG15, and BST2), and the acute phase molecule SAA3 were the most up-regulated genes. Ingenuity Pathway Analysis identified up-regulation of many inflammatory cytokines and chemokines, which function to attract immune cells to the endometrium, together with vascular adhesion molecules and matrix metalloproteinases, which can facilitate immune cell migration from the tissue toward the uterine lumen. Increased expression of many IFN-signaling genes, immunoproteasomes, guanylate-binding proteins, and genes involved in the intracellular recognition of pathogens suggests important roles for these molecules in the innate defense against bacterial infections. Our findings confirmed the important role of endometrial cells in uterine innate immunity, whereas the global approach used identified several novel immune response pathways triggered by LPS in the endometrium. Additionally, many genes involved in endometrial response to the conceptus in early pregnancy were also altered by LPS, suggesting one mechanism whereby an ongoing response to infection may interfere with the establishment of pregnancy.

Relationships between Circulating Urea Concentrations and Endometrial Function in Postpartum Dairy Cows

Simple Summary

Dairy cows fed high levels of protein to increase milk yield tend to have reduced fertility but the reasons behind this are unclear. Differing dietary protein levels are reflected in altered urea concentrations in both blood and other tissues including the uterus. We showed that the circulating urea concentration was highly correlated to changed expression levels of many genes in the endometrium shortly after calving. These were predominantly associated with tissue repair, innate immunity and lipid metabolism. A subsequent study found no effect of altered urea concentration on endometrial gene expression in vitro implying that the dietary influence is indirect.

Abstract

Both high and low circulating urea concentrations, a product of protein metabolism, are associated with decreased fertility in dairy cows through poorly defined mechanisms. The rate of involution and the endometrial ability to mount an adequate innate immune response after calving are both critical for subsequent fertility. Study 1 used microarray analysis to identify genes whose endometrial expression 2 weeks postpartum correlated significantly with the mean plasma urea per cow, ranging from 3.2 to 6.6 mmol/L. The biological functions of 781 mapped genes were analysed using Ingenuity Pathway Analysis. These were predominantly associated with tissue turnover (e.g., BRINP1, FOXG1), immune function (e.g., IL17RB, CRISPLD2), inflammation (e.g., C3, SERPINF1, SERPINF2) and lipid metabolism (e.g., SCAP, ACBD5, SLC10A). Study 2 investigated the relationship between urea concentration and expression of 6 candidate genes (S100A8, HSP5A, IGF1R, IL17RB, BRINP1, CRISPLD2) in bovine endometrial cell culture. These were treated with 0, 2.5, 5.0 or 7.5 mmol/L urea, equivalent to low, medium and high circulating values with or without challenge by bacterial lipopolysaccharide (LPS). LPS increased S100A8 expression as expected but urea treatment had no effect on expression of any tested gene. Examination of the genes/pathways involved suggests that plasma urea levels may reflect variations in lipid metabolism. Our results suggest that it is the effects of lipid metabolism rather than the urea concentration which probably alter the rate of involution and innate immune response, in turn influencing subsequent fertility.

The effect of polymorphism in gene of insulin-like growth factor-I on the serum periparturient concentration in Holstein dairy cows

OBJECTIVE

To investigate the relationship between polymorphism within the 5'-untranslated region (5'-UTR) of IGF-I gene and its periparturient concentration in Iranian Holstein dairy cows.

METHODS

Blood samples (5 mL, n = 37) were collected by caudal venipuncture from each animal into sample tubes containing the EDTA and DNA was extracted from blood. In order to measure IGF-I concentration the collection of blood samples (n = 111) was also done at 14 d before calving (prepartum), 25 and 45 d postpartum.

RESULTS

We found evidence for a significant effect of C to T mutation in position 512 of IGF-I gene on its serum concentration in dairy cows in Iran. Cows with CC genotype had significantly higher concentration (Mean±SD) of IGF-I at 14 d prepartum (91.8±18.1) µg/L compared to those with TT genotype (73.3±14.4) µg/L (P=0.04). A significant trend (quadratic) was found for IGF-I concentration, as higher in CC cows compared to ones with TT genotype, during the 14 d before calving to 45 d postpartum (P=0.01).

CONCLUSIONS

We concluded that C/T transition in the promoter region of IGF-I gene can influence the serum concentration of IGF-I in periparturient dairy cows.

Effects of parturition and feed restriction on concentrations and distribution of the insulin-like growth factor-binding proteins in plasma and cerebrospinal fluid of dairy cows

Hormones and metabolites act as satiety signals in the brain and play an important role in the control of feed intake (FI). These signals can reach the hypothalamus and brainstem, 2 major centers of FI regulation, via the blood stream or the cerebrospinal fluid (CSF). During the early lactation period of high-yielding dairy cows, the increase of FI is often insufficient. Recently, it has been demonstrated that insulin-like growth factors (IGF) may control FI. Thus, we asked in the present study if IGF-binding proteins (IGFBP) are regulated during the periparturient period and in response to feed restriction and therefore might affect FI as well. In addition, we specifically addressed conditional distribution of IGFBP in plasma and CSF. In one experiment, 10 multiparous German Holstein dairy cows were fed ad libitum and samples of CSF and plasma were obtained before morning feeding on d -20, -10, +1, +10, +20, and +40 relative to calving. In a second experiment, 7 cows in second mid-lactation were sampled for CSF and plasma after ad libitum feeding and again after feeding 50% of the previous ad libitum intake for 4 d. Intact IGFBP-2, IGFBP-3, and IGFBP-4 were detected in plasma by quantitative Western ligand blot analysis. In CSF, we were able to predominantly identify intact IGFBP-2 and a specific IGFBP-2 fragment containing detectable binding affinities for biotinylated IGF-II. Whereas plasma concentrations of IGFBP-2 and IGFBP-4 increased during the periparturient period, IGFBP-3 was unaffected over time. In CSF, concentrations of IGFBP-2, both intact and fragmented, were not affected during the periparturient period. Plasma IGF-I continuously decreased until calving but remained at a lower concentration in early lactation than in late pregnancy. Food restriction did not affect concentrations of IGF components present in plasma or CSF. We could show that the IGFBP profiles in plasma and CSF are clearly distinct and that changes in IGFBP in plasma do not simply correspond in the brain. We thus assume independent control of IGFBP distribution between plasma and CSF. Due to the known anorexic effect of IGF-I, elevated plasma concentrations of IGFBP-2 and IGFBP-4 during the postpartum period in conjunction with reduced plasma IGF-I concentrations may be interpreted as an endocrine response against negative energy balance in early lactation in dairy cows.

Associations between lipid metabolism and fertility in the dairy cow

Dairy cows mobilise body tissues to support milk production and, because glucose supplies are limited, lipids are used preferentially for energy production. Lipogenic activity is switched off and lipolytic mechanisms in adipose tissue increase through changes in the expression of several key enzymes. This results in a loss of body condition, together with high circulating concentrations of non-esterified fatty acids. Changes in the synthesis, secretion and signalling pathways of somatotrophic hormones (insulin, growth hormone, insulin-like growth factor 1) and adipokines (e.g. leptin) are central to the regulation of these processes. A high reliance on fatty acids as an energy source in the peripartum period causes oxidative damage to mitochondria in metabolically active tissues, including the liver and reproductive tract. The expression of genes involved in insulin resistance (PDK4, AHSG) is increased, together with expression of TIEG1, a transcription factor that can induce apoptosis via the mitochondrial pathway. Polymorphisms in TFAM and UCP2, two autosomal mitochondrial genes, have been associated with longevity in dairy cows. Polymorphisms in many other genes that affect lipid metabolism also show some associations with fertility traits. These include DGAT1, SCD1, DECR1, CRH, CBFA2T1, GH, LEP and NPY. Excess lipid accumulation in oocytes and the regenerating endometrium reduces fertility via reductions in embryo survival and increased inflammatory changes, respectively.

Global endometrial transcriptomic profiling: transient immune activation precedes tissue proliferation and repair in healthy beef cows

BACKGROUND

All cows experience bacterial contamination and tissue injury in the uterus postpartum, instigating a local inflammatory immune response. However mechanisms that control inflammation and achieve a physiologically functioning endometrium, while avoiding disease in the postpartum cow are not succinctly defined. This study aimed to identify novel candidate genes indicative of inflammation resolution during involution in healthy beef cows. Previous histological analysis of the endometrium revealed elevated inflammation 15 days postpartum (DPP) which was significantly decreased by 30 DPP. The current study generated a genome-wide transcriptomic profile of endometrial biopsies from these cows at both time points using mRNA-Seq. The pathway analysis tool GoSeq identified KEGG pathways enriched by significantly differentially expressed genes at both time points. Novel candidate genes associated with inflammatory resolution were subsequently validated in additional postpartum animals using quantitative real-time PCR (qRT-PCR).

RESULTS

mRNA-Seq revealed 1,107 significantly differentially expressed genes, 73 of which were increased 15 DPP and 1,034 were increased 30 DPP. Early postpartum, enriched immune pathways (adjusted P < 0.1) included the T cell receptor signalling pathway, graft-versus-host disease and cytokine-cytokine receptor interaction pathways. However 30 DPP, where the majority of genes were differentially expressed, the enrichment (adjusted P < 0.1) of tissue repair and proliferative activity pathways was observed. Nineteen candidate genes selected from mRNA-Seq results, were independently assessed by qRT-PCR in additional postpartum cows (5 animals) at both time points. SAA1/2, GATA2, IGF1, SHC2, and SERPINA14 genes were significantly elevated 30 DPP and are functionally associated with tissue repair and the restoration of uterine homeostasis postpartum.

CONCLUSIONS

The results of this study reveal an early activation of the immune response which undergoes a temporal functional change toward tissue proliferation and regeneration during endometrial involution in healthy postpartum cows. These molecular changes mirror the activation and resolution of endometrial inflammation during involution previously classified by the degree of neutrophil infiltration. SAA1/2, GATA2, IGF1, SHC2, and SERPINA14 genes may become potential markers for resolution of endometrial inflammation in the postpartum cow.

Temporal changes in endometrial gene expression and protein localization of members of the IGF family in cattle: effects of progesterone and pregnancy

In the study presented, the hypothesis that ligands of the insulin-like growth factor (IGF) family, as well as their binding proteins (BPs), are temporally regulated and are altered by elevated progesterone (P4) and/or pregnancy was tested. Heifers detected in standing estrus following synchronization (n = 210, day 0), were artificially inseminated (n = 140) or left as noninseminated cyclic controls (n = 70). On day 3, half of each group were randomly assigned to receive a P4-releasing intravaginal device resulting in four treatment groups, pregnant and cyclic heifers with high and normal P4 concentrations on either day 5, 7, 13, or 16 of the estrous cycle/early pregnancy. Quantitative real-time PCR and immunohistochemistry were performed on endometrial homogenate and uterine cross sections to measure transcript abundance and protein localization respectively (n = 5 per treatment per time point). No effect of day, treatment, or their interactions was observed for IGF2, IGFBP4, and -5 (P > 0.05). IGF1 and IGFBP6 expression decreased, while IGF1R and IGFBP2 expression increased (P < 0.05) as the days of the cycle or pregnancy progressed. The expression of IGFBP2 was increased by elevated P4; in addition, localization of both IGF2 and IGFBP2 protein in the luminal and superficial glandular epithelium displayed a P4 × day interaction. In conclusion it is proposed that decreased IGF1 and IGFBP6 expression with a coordinate increase in IGF1R and IGFBP2 as the estrous cycle/early pregnancy progresses, along with other factors, are required to establish a uterine environment that promotes the growth and development of the conceptus prior to implantation. In addition, the increased protein abundance of both IGF2 and IGFBP2 observed in heifers supplemented with P4 contributes to the enhanced conceptus elongation observed in this model.

Influence of energy balance on the somatotrophic axis and matrix metalloproteinase expression in the endometrium of the postpartum dairy cow

Postpartum dairy cows enter a period of negative energy balance (NEB) associated with low circulating IGF1, during which the uterus must undergo extensive repair following calving. This study investigated the effects of NEB on expression of IGF family members and related genes in the involuting uterus. Cows were allocated to two treatments using differential feeding and milking regimes to produce mild NEB or severe NEB (SNEB). Uterine endometrial samples collected 2 weeks post partum were analysed by quantitative PCR. The expression of IGF-binding protein 4 (IGFBP4) mRNA increased in the endometrium of SNEB cows, with trends towards increased IGFBP1 and reduced IGFBP6 expression. There were no significant differences between treatments in mRNA expression of IGF1, IGF2 or of any hormone receptor studied, but significant correlations across all cows in the expression levels of groups of receptors suggested common regulatory mechanisms: type 1 IGF receptor (IGF1R), IGF2R and insulin receptor (INSR); GHR with ESR1; and ESR2 with NR3C1. The expression of IGF1R and INSR also positively correlated with the circulating urea concentration. Matrix metalloproteinases (MMPs) are important in tissue remodelling and can affect IGF signalling via interaction with IGFBPs. The expression levels of MMP1, MMP3, MMP9 and MMP13 mRNAs all showed major upregulation in the endometrium of cows in SNEB and all except MMP9 were highly correlated with expression of IGFBP4. Alpha(2)-HS-glycoprotein (AHSG) and PDK4, two genes implicated in insulin resistance, were also highly expressed in SNEB. These results suggest that cows in SNEB experience alterations to the IGF and insulin signalling pathways in the postpartum endometrium. This may affect the rate of tissue repair with a possible negative impact on subsequent fertility.

Effect of dietary n-3 polyunsaturated fatty acid supplementation on bovine uterine endometrial and hepatic gene expression of the insulin-like growth factor system

Supplementation of cattle diets with n-3 polyunsaturated fatty acids (n-3 PUFA) has been suggested to have positive effects on fertility. In addition, the actions of the insulin-like growth factor (IGF) system both systemically and locally have been shown to influence reproductive processes. The objective of this study was to evaluate the effect of dietary n-3 PUFA supplementation on hepatic and endometrial expression of IGF signalling genes in cattle. Beef heifers were supplemented with a rumen protected source of either a saturated fatty acid (palmitic acid; CON) or high n-3 PUFA diet (n-3 PUFA) for 45 days before slaughter and tissue recovery. Transcription level of candidate IGF signalling genes was measured by reverse transcription quantitative real-time PCR (RT-qPCR) in total RNA isolated from uterine endometrial and liver tissue from seven CON and seven n-3 PUFA supplemented animals. Compared to controls, mRNA abundance in n-3 PUFA liver tissues was higher for IGF-2R, IGFBP-1 and IGFBP-5 (P < 0.05); lower for GHR-1A (P < 0.05); and unchanged for IGF-1, IGF-2, IGF-1R, IGFBP-2, IGFBP-3, IGFBP-4, IGFBP-6, ALS and GHR(total) (P > 0.05). Compared to controls, mRNA abundance in n-3 PUFA endometrial tissues was higher for IGF-2, IGF-1R, IGF-2R and IGFBP-2 (P < 0.05); lower for IGF-1, IGFBP-3 and IGFBP-6 (P < 0.05); and unchanged for IGFBP-1, IGFBP-4, IGFBP-5 and GHR(total) (P > 0.05). Thus, dietary supplementation of cattle with n-3 PUFA affects transcription of genes involved in IGF signalling, in a tissue dependent fashion.

Endometrial biopsy: a valuable clinical and research tool in bovine reproduction

Studies of postpartum endometrial physiologic and immune mechanisms in cows are compromised by the difficulty in acquiring tissue of suitable quality and in sufficient quantity (Bos taurus). Endometrial biopsy sampling has attracted concern regarding potential animal ill-health and perturbed subsequent fertility. Here, we describe a method of endometrial biopsy that obtains high-quality tissue samples and does not compromise fertility. Using a Hauptner instrument, endometrial biopsies were taken at 15, 30, and 60 d postpartum from 13 mixed-breed beef cows. The effects of repeat biopsy on health (heart rate, respiration rate, color of mucous membranes, rectal temperature), onset of estrous cyclicity, and first service conception rate were monitored. Extensive daily clinical examinations revealed no signs of ill-health. All cows had resumed estrous cyclicity at 60 d postpartum. A conception rate of 77% was achieved after estrus synchronization and artificial insemination. Each biopsy yielded intact endometrial tissue and nucleic acid suitable for extensive histologic and molecular analysis, respectively. We conclude that when carried out appropriately, bovine endometrial biopsy is a safe and reliable technique for assessing postpartum uterine function or health.

Negative energy balance alters global gene expression and immune responses in the uterus of postpartum dairy cows

Most dairy cows suffer uterine microbial contamination postpartum. Persistent endometritis often develops, associated with reduced fertility. We used a model of differential feeding and milking regimes to produce cows in differing negative energy balance status in early lactation (mild or severe, MNEB or SNEB). Blood hematology was assessed preslaughter at 2 wk postpartum. RNA expression in endometrial samples was compared using bovine Affymetrix arrays. Data were mapped using Ingenuity Pathway Analysis. Circulating concentrations of IGF-I remained lower in the SNEB group, whereas blood nonesterified fatty acid and β-hydroxybutyrate concentrations were raised. White blood cell count and lymphocyte number were reduced in SNEB cows. Array analysis of endometrial samples identified 274 differentially expressed probes representing 197 recognized genes between the energy balance groups. The main canonical pathways affected related to immunological and inflammatory disease and connective tissue disorders. Inflammatory response genes with major upregulation in SNEB cows included matrix metalloproteinases, chemokines, cytokines, and calgranulins. Expression of several interferon-inducible genes including ISG20, IFIH1, MX1, and MX2 were also significantly increased in the SNEB cows. These results provide evidence that cows in SNEB were still undergoing an active uterine inflammatory response 2 wk postpartum, whereas MNEB cows had more fully recovered from their energy deficit, with their endometrium reaching a more advanced stage of repair. SNEB may therefore prevent cows from mounting an effective immune response to the microbial challenge experienced after calving, prolonging the time required for uterine recovery and compromising subsequent fertility.

Defining postpartum uterine disease and the mechanisms of infection and immunity in the female reproductive tract in cattle

Uterine microbial disease affects half of all dairy cattle after parturition, causing infertility by disrupting uterine and ovarian function. Infection with Escherichia coli, Arcanobacterium pyogenes, and bovine herpesvirus 4 causes endometrial tissue damage. Toll-like receptors on endometrial cells detect pathogen-associated molecules such as bacterial DNA, lipids, and lipopolysaccharide (LPS), leading to secretion of cytokines, chemokines, and antimicrobial peptides. Chemokines attract neutrophils and macrophages to eliminate the bacteria, although persistence of neutrophils is associated with subclinical endometritis and infertility. Cows with uterine infections are less likely to ovulate because they have slower growth of the postpartum dominant follicle in the ovary, lower peripheral plasma estradiol concentrations, and perturbation of hypothalamic and pituitary function. The follicular fluid of animals with endometritis contains LPS, which is detected by the TLR4/CD14/LY96 (MD2) receptor complex on granulosa cells, leading to lower aromatase expression and reduced estradiol secretion. If cows with uterine disease ovulate, the peripheral plasma concentrations of progesterone are lower than those in normal animals. However, luteal phases are often extended in animals with uterine disease, probably because infection switches the endometrial epithelial secretion of prostaglandins from the F series to the E series by a phospholipase A2-mediated mechanism, which would disrupt luteolysis. The regulation of endometrial immunity depends on steroid hormones, somatotrophins, and local regulatory proteins. Advances in knowledge about infection and immunity in the female genital tract should be exploited to develop new therapeutics for uterine disease.

Histopathological and molecular evaluation of Holstein-Friesian cows postpartum: toward an improved understanding of uterine innate immunity

Bovine uterine disease reduces milk yield, impairs fertility and has implications for animal welfare. During involution, the uterus is usually exposed to multiple potential bacterial pathogens which are cleared by successful orchestration of the local inflammatory response. Unsuccessful resolution leads to the development of disease. The aim of this study was to characterize the local innate immune response in the uterus during physiological involution using histopathological and molecular analyses in 9 cows, 2 weeks after calving (early postpartum, EPP), and 4 cows, 9 weeks after calving (late postpartum, LPP). Uterine biopsies taken from each cow were classified by histopathology, and RNA was extracted for molecular analysis. Two EPP cows were classified with a mild, 5 with a moderate and 2 with a severe inflammatory response. Relative gene expression analysis was then performed using quantitative real-time PCR (qRT-PCR) and specific primers for genes encoding Toll-like receptors (TLRs), chemokines, cytokines, acute phase proteins (APPs) and antimicrobial peptides (AMPs). TLR4, transcription factor NFKB1 and the inflammatory cytokines IFNG, IL1A, IL6, IL8, IL12A were all significantly increased in EPP cows (P<0.05). Increase in HP, SAA3, TAP and DEFB5 genes was particularly marked in cows with severe inflammation. These results reveal evidence of an inflammatory uterine environment in the early postpartum period with significant induction of both AMP and APP genes. Histopathological grades in EPP cows are underpinned by quantitative changes in gene expression. Understanding the molecular mechanisms contributing to uterine immunity in the early postpartum period may identify candidate genes associated with the resolution of inflammation.