Differences in extracellular matrix remodeling in the placenta of mares that retain fetal membranes and mares that deliver fetal membranes physiologically

[Initiation and endocrine control of parturition in domestic mammals - Part 1]

Endocrine regulation of parturition is based on an intense exchange of signals between the fetus, placenta and mother. Apart from sheep, our knowledge of the endocrine control of parturition is still very incomplete. However, current observations suggest significant differences between the species. For the maintenance of pregnancy, progesterone (P4) is the crucial superordinate regulatory factor, although in some species, such as the horse, functions of P4 are at least partially fulfilled by other progestogens. In general, prepartum P4 withdrawal is considered a prerequisite for the onset of physiological birth. In species with exclusive (dog) or predominant (e. g., cattle, goat, pig) luteal P4 at the end of gestation, luteolysis is the crucial event. In sheep, where P4 is of placental origin prior to parturition, the prepartum P4 decline is due to a switch in placental steroid metabolism. The mechanism of prepartum progestogen withdrawal in the mare is still largely unclear. In sheep, initiation of parturition proceeds from maturation of the fetal hypothalamic-pituitary-adrenal (HPA) axis, which leads to a steep prepartum rise in fetal cortisol concentrations stimulating the collapse of placental P4 production. In cattle, fetal cortisol probably triggers luteolysis via stimulation of placental prostaglandin secretion. In several other domestic mammalian species, there is also evidence that the initiation of parturition proceeds from maturation of the fetal HPA axis. However, the functional relationships between fetal cortisol and prepartum P4 withdrawal are largely unknown in nonruminant species.

Activities of matrix metalloproteinase-2 and -9 in amniotic fluid at parturition in mares with normal and high-risk pregnancy

The matrix metalloproteinases (MMPs) are a family of enzymes involved in extracellular matrix remodeling. MMPs are secreted in a latent form and activated by local and infiltrating cells. MMP-2 and -9 are the most studied in reproduction and have been detected in bovine, ovine, equine and human placenta. There is only one study on MMPs in the equine amniotic fluid (AF) reporting a decrease in the activity of MMP-2 in case of premature delivery. The aim of this study was focused on MMP-2 and -9 activity in AF collected at parturition from mares with normal or high-risk pregnancy. High-risk pregnancy was defined as a history of premature udder development/lactation, increase of combined thickness of the uterus and placenta, vulvar discharge and/or mare's systemic illness. The diagnosis of placental insufficiency was confirmed retrospectively after macroscopic and histopatologic examination of the placenta. AF was collected by needle puncture of the amnion within 5 min after its appearance through the vulva. The activity of MMP-2 and -9 was analyzed by in-gel zymography allowing the evaluation of both latent and active forms. Twenty mares with normal pregnancy (group 1) and 8 mares with high-risk pregnancy (group 2) were included. All mares in group 2 had a high-risk pregnancy with a diagnosis of placental insufficiency associated with placental villous hypoplasia, placentitis or placental edema. The bands relative to latent and active forms of MMP-2 were clearly visible in both groups and the activity of latent (P = 0.010) and active (P = 0.004) forms was lower in the AF samples of group 2. The band of the latent form of MMP-9 was visible in 17/20 samples of group 1, while it was completely absent in all samples of group 2. In contrast, the band of the active form was clearly visible and with a greater activity in AF samples of group 2 (P = 0.002). Placental dysfunction seems to induce a lower MMP-2 activity and a higher MMP-9 activity through the release of pro-inflammatory cytokines. Because fetal pulmonary secretions are a likely source of gelatinases in AF during late gestation, the increased MMP-9 activity could be related to fetal distress. These data provide a starting point to better understand the role of MMPs in equine pregnancy, although it should be confirmed in a larger and more homogeneous population of mares with high-risk pregnancy.

Determining MMP-2 and MMP-9 reductive activities of bovine and equine amniotic membranes homogenates using fluorescence resonance energy transfer

INTRODUCTION

Matrix metalloproteinases (MMPs)-2 and -9 are present in corneal ulcers, and an imbalance between MMPs and tissue inhibitors of metalloproteinases (TIMPs) leads to further corneal degradation. Amniotic membrane homogenate (AMH) has proteolytic properties beneficial for corneal healing, but it is unknown whether AMH possesses TIMPs or effectively inhibits MMP-2 and MMP-9 activity.

OBJECTIVE

To determine if bovine and equine AMH reduce in vitro MMP-2 and MMP-9 activities associated with the presence of TIMPs.

PROCEDURES

Undiluted and diluted twofold series (0-fold to 16-fold dilutions) of equine amniotic membrane homogenates (EAMH, n = 8) and bovine amniotic membrane homogenates (BAMH, n = 8) were subjected to fluorescence resonance energy transfer, and the fluorescence emitted was recorded over time. Average fluorescence was calculated versus recombinant concentration. Enzyme-linked immunosorbent assays for TIMPs 1-4 were applied to quantify TIMPs in the samples.

RESULTS

AMH from both species were able to inhibit MMP-2 and MMP-9 activities in vitro, and the inhibition efficacy decreased gradually with dilution. BAMH was significantly more effective than EAMH at inhibiting MMP-2 and MMP-9 in vitro. TIMPs -2 and -3 were present in EAMH and BAMH. TIMP-1 was detected only in BAMH, and TIMP-4 was not detected in any samples.

CONCLUSION

Both EAMH and BAMH directly inhibited MMP-2 and MMP-9 in vitro without dilution, and BAMH showed better inhibition of MMP-2 and MMP-9 before and after dilution compared to EAMH.

Transcriptome Profiling of the Retained Fetal Membranes-An Insight in the Possible Pathogenesis of the Disease

Simple Summary

Retained fetal membranes (RFM) in mares is a disease of a multifactorial etiology with not fully understood pathogenesis. Profound analysis of genes expressed in the placenta may reveal pathways and processes which might be comprised in mares with this disease and hence help to explain the pathogenesis of RFM. This work employed RNA sequencing to identify and compare genes differentially expressed (DEGs) in the placenta of mares that retained fetal membranes and those that released them physiologically. Results showed that within DEGs genes important for apoptosis, inflammatory-related processes, and metabolism of extracellular matrix were identified.

Abstract

Retained fetal membranes (RFM) is one of the most common post-partum diseases of a complex etiology. Moreover, its pathogenesis is still not elucidated. Detailed transcriptomic analysis of physiological and retained placenta may bring profound insight in the pathogenesis of the disease. The aim of the study was to compare the transcriptome of the retained and physiologically released placenta as well as biological pathways and processes in order to determine the possible pathogenesis of the disease. Samples of the endometrium and the allantochorion were taken within 2 h after parturition from control mares (n = 3) and mares with RFM (n = 3). RNA sequencing was performed with the use of all samples and mRNA expression of chosen genes was validated with Real Time PCR. Analysis of RNA-seq identified 487 differentially expressed genes in the allantochorion and 261 in the endometrium of control and RFM mares (p < 0.0001). Within genes that may be important in the release of fetal membranes and were differentially expressed, our report pinpointed BGN, TIMP1, DRB, CD3E, C3, FCN3, CASP3, BCL2L1. Gene ontology analysis showed possible processes which were altered in RFM that are apoptosis, inflammatory-related processes, and extracellular matrix metabolism and might be involved in the pathogenesis of RFM. This is the first report on the transcriptome of RFM and physiologically released placenta in mares.

MMP-9 Concentration in Peritoneal Fluid Is a Valuable Biomarker Associated with Endotoxemia in Equine Colic

The purpose of the study was to compare the results of sepsis scoring (clinical examination and clinical pathology) to the concentrations of matrix-metalloproteinases (MMPs) -2, -8, and -9; tissue-inhibitor of metalloproteinases (TIMPs) -1 and -2; and inflammatory chemokines interleukin (IL) 1β and tumor-necrosis-factor-alpha (TNF-α) in plasma and peritoneal fluid of equine colic patients. A modified sepsis scoring including general condition, heart and respiratory rate, rectal temperature, mucous membranes, white blood cell count (WBC), and ionized calcium was applied in 47 horses presented with clinical signs of colic. Using this scoring system, horses were classified as negative (n = 32, ≤6/19 points), questionable (n = 9, 7-9/19 points), or positive (n = 6, ≥10/19 points) for sepsis. MMPs, TIMPs, IL-1β, and TNF-α concentrations were evaluated in plasma and peritoneal fluid using species-specific sandwich ELISA kits. In a linear discriminant analysis, all parameters of sepsis scoring apart from calcium separated well between sepsis severity groups (P < 0.05). MMP-9 was the only biomarker of high diagnostic value, while all others remained insignificant. A significant influence of overall sepsis scoring on MMP-9 was found for peritoneal fluid (P = 0.005) with a regression coefficient of 0.092, while no association was found for plasma (P = 0.085). Using a MMP-9 concentration of >113 ng/ml in the peritoneal fluid was found to be the ideal cutoff to identify positive sepsis scoring (≥10/19 points; sensitivity of 83.3% and specificity of 82.9%). In conclusion, MMP-9 was found to be a biomarker of high diagnostic value for sepsis and endotoxemia in equine colic. The evaluation of peritoneal fluid seems preferable in comparison to plasma. As abdominocentesis is commonly performed in the diagnostic work-up of equine colic, a pen-side assay would be useful and easy-to-perform diagnostic support in the decision for therapeutic intervention.

Modifications of extracellular matrix features in the left and right uterine horns during the embryo pre-implantation period in Vicugna pacos

More than 98% of the pregnancies in South American camelids is carried out in the left uterine horn (LUH). Hence, embryos originated from right-ovary ovulations have to migrate to the contralateral or left uterine horn (LUH) to implant and survive. A reason for this unique pattern of embryo implantation has not been elucidated yet. In general, embryo implantation involves an extensive extracellular matrix (ECM) remodeling within the endometrium, in which collagen and matrix metalloproteinases (MMPs) play an essential role. Deregulation of collagen and MMPs has been related to embryo implantation failure, miscarriage, and infertility. Therefore, we hypothesized that ECM components in camelids could be involved in differential embryo implantation and consequently the high incidence of left horn gestations. The aim of this study was to describe and compare changes in ECM components in the left and right uterine horn of non-pregnant and 15 days pregnant alpacas. To test this hypothesis, the collagen content was evaluated by specific staining with Picrosirius Red and using ImageJ 1.42q software. Subsequently, gene expression of the following components of the MMP pathway was determined: MMP-2, -3, -7, -9, and -14, MMP substrates (COL1A2 and COL3A1), MMP inhibitors (TIMP1 and TIMP2), LGMN, an MMP activator, and EMMPRIN, an extracellular matrix metalloproteinase inducer. Uterine horns of pregnant alpacas exhibited a marked decrease in collagen content. In contrast, transcript expression of COL1A2 and COL3A1 was higher in the LUH of pregnant alpacas. Gene expression of MMP-3, -7, -9, -14, LGMN, and EMMPRIN were also higher in the LUH of pregnant animals, whereas MMP-2 gene expression was higher in the LUH of both pregnant and non-pregnant alpacas. Expression of TIMP1 and TIMP2 increased during pregnancy, with higher values in the LUH. In conclusion, expression of ECM components displayed a specific pattern depending on the uterine side and the physiological status (pregnant vs non-pregnant) of the animal. The increased expression of ECM transcripts in the left uterine horn during early pregnancy in alpacas suggests the involvement of these molecules in a highly regulated process leading to the implantation process.

The oxytocin-prostaglandins pathways in the horse (Equus caballus) placenta during pregnancy, physiological parturition, and parturition with fetal membrane retention

Despite their importance in mammalian reproduction, substances in the oxytocin-prostaglandins pathways have not been investigated in the horse placenta during most of pregnancy and parturition. Therefore, we quantified placental content of oxytocin (OXT), oxytocin receptor (OXTR), and prostaglandin E2 and F2 alpha during days 90-240 of pregnancy (PREG), physiological parturition (PHYS), and parturition with fetal membrane retention (FMR) in heavy draft horses (PREG = 13, PHYS = 11, FMR = 10). We also quantified OXTR and prostaglandin endoperoxide synthase-2 (PTGS2) mRNA expression and determined the immunolocalization of OXT, OXTR, and PTGS2. For relative quantification of OXT and OXTR, we used western blotting with densitometry. To quantify the prostaglandins, we used enzyme immunoassays. For relative quantification of OXTR and PTGS2, we used RT-qPCR. For immunolocalization of OXT, OXTR, and PTGS2, we used immunohistochemistry. We found that OXT was present in cells of the allantochorion and endometrium in all groups. PTGS2 expression in the allantochorion was 14.7-fold lower in FMR than in PHYS (p = 0.007). These results suggest that OXT is synthesized in the horse placenta. As PTGS2 synthesis is induced by inflammation, they also suggest that FMR in heavy draft horses may be associated with dysregulation of inflammatory processes.

Fetal Membrane Removal in the Mare: Proactive Versus Reactive Approaches

Retained fetal membranes are the most common postpartum condition in mares. Although the incidence of retained fetal membranes is low, the consequences for the health of the mare can be severe (metritis, endotoxemia, laminitis, death). Oxytocin administration is often the first line of therapy for management of retained fetal membranes. Removal of fetal membranes using umbilical vessel infusion and manual membrane removal are effective tools for reducing risks associated with abnormally heavy membranes, retained membranes, or for mares that are geographically limited for veterinary care.

The preliminary studies on protein profile in retained and not retained foetal membranes in heavy draft mares

Protein profile of the placenta expresses its function and maintenance. Any alterations can be reflected in qualitative and quantitative changes in this profile. The aim of the present study was the evaluation of protein profile in the placenta of mares suffering from the retention of foetal membranes (FMR) by two separation methods and the comparison with physiologically released tissues. Placentas from 14 healthy, heavy draft mares were collected immediately after the expulsion of newborn. Tissues after homogenization and staining with fluorescent dyes were subjected to electrophoretic as well as chromatographic separation. Electrophoretic gels were statistically analysed for the presence and abundance of examined proteins, while some proteins were identified in chromatographic fractions. Out of 248 spots detected in endometrium, 38 differed significantly between FMR and control animals, while in allantochorion, respective values reached 241 and 27 spots (p < .05). Among identified proteins that expressed higher abundance in endometrium of FMR mares than control animals were prostaglandin reductase, dehydrogenase/reductase SDR family, and placental growth factor. These proteins are involved in regulation of parturition. Additionally, the following proteins responsible for physiological activity of a cell-guanine methyl transferase, aspartyl/asparaginyl beta-hydroxylase and GTP-binding protein, were identified. These proteins expressed higher abundance in allantochorion of FMR mares than in controls. This preliminary study confirmed the disturbances in protein pattern between foetal membranes in FMR and healthy mares. Further qualitative and quantitative experiments are necessary to deepen our knowledge on the mechanisms of the retention of foetal membranes in mares.

Major histocompatibility complex class I in the horse (Equus caballus) placenta during pregnancy and parturition

BACKGROUND

Major histocompatibility protein class I (MHC-I) is believed to be expressed in the horse allantochorion only in limited areas at limited times. However, its expression has only been investigated in early pregnancy with non-quantitative techniques that cannot reliably detect small amounts of protein.

OBJECTIVE

To quantify the relative expression of MHC-I in the allantochorion and endometrium during days 90-240 of pregnancy (PREG), parturition with physiological delivery of fetal membranes (PHYS), and parturition with retention of these membranes (FMR). Also, to visualize protein expression and determine whether classical or non-classical MHC-I mRNA is expressed.

ANIMALS

Heavy draft horses.

SETTING

PREG horses (n = 12) were sampled postmortem at a slaughterhouse. PHYS (n = 6) and FMR (n = 5) horses were sampled at farms in the vicinity of Olsztyn, Poland.

METHODS

For relative quantification of MHC-I, western blotting with densitometry was used. To visualize MHC-I, immunohistochemistry was used. For mRNA identification, RT-PCR was performed.

RESULTS

Although the quantity of MHC-I was lower during PREG than parturition, it was present in the allantochorion and endometrium during PREG. During parturition, MHC-I expression was upregulated in the allantochorion (PHYS vs. PREG: 2.7-times higher, 95% confidence interval, 1.3- to 5.7-times higher; FMR vs. PREG: 3.2-times higher, 95% confidence interval, 1.5- to 6.7-times higher). At parturition, staining for MHC-I was detected in the microcotyledons. Classical and non-classical MHC-I were expressed in both tissues during PREG, PHYS, and FMR.

CONCLUSION

MHC-I protein is present in the horse allantochorion and endometrium for at least the first two-thirds of pregnancy and at parturition.

Expression of proinflammatory cytokines IL-1β, IL-6 and TNFα in the retained placenta of mares

Retained fetal membranes (RFM) is a prevalent postpartum disease in mares. During parturition, various proinflammatory cytokines are released in the placenta, which further facilitates uterine contractions, expulsion of the fetus and fetal membranes. We hypothesized that an altered inflammatory response in mares results in retained fetal membranes. Samples of the endometrium and the allantochorion were collected from 15 mares with RFM and from 29 control mares within 2 h of foal delivery. Next, the mRNA expression of IL-1β, IL-6 and TNFα proteins was analyzed by Real Time PCR and Western blot. These cytokines were also localized by immunocytochemistry. In mares with RFM, the mRNA expression of IL-1β in the endometrium (p < 0.05) and IL-6 in the allantochorion (p < 0.0001) was higher than in mares that expelled fetal membranes physiologically. Higher expression of IL-6 in the allantochorion was confirmed by Western blot. In contrast, no changes in TNFα mRNA and protein expression were observed between the 2 groups of mares. Moreover, TNFα mRNA was barely detectable. The presence of all studied cytokine proteins in the allantochorion was confirmed by immunocytochemistry. The results suggest that the outbreak of inflammation is involved in the mechanism of placenta release in mares. Increased expression of IL-6 in the allantochorion and IL-1β in the endometrium could reflect a local immune response which leads to the detachment of fetal membranes. The low expression of TNFα mRNA might suggest that this cytokine is not involved in the expulsion of fetal membranes. Further work is needed to determine the exact role and timing of inflammatory activation in fetal membranes during equine parturition.

Treatment of Retained Fetal Membranes in the Mare-A Practitioner Survey

Retained fetal membranes (RFM) is a common post-partum problem in mares for which the treatment is highly variable. The aim of this study was (i) to investigate the different treatments used by equine practitioners for RFM and (ii) to determine if there is a difference between treatments used by reproductive specialists and general equine practitioners. Information regarding treatment of RFM was sought from veterinary practitioners via a survey and this was compared to recommendations in the current literature. The survey was sent out to equine veterinarians and mixed practitioners with a high equine case load. Most treatments of RFM were in line with current recommendations, while some obsolete practices are still routinely performed by a small number of practitioners. Treatment recommendations for RFM have changed over the last few decades, but there are no universally accepted guidelines. The vast variety of treatments reported by practitioners in the present survey reflect this lack of guidance. More extensive research is needed in this area to establish evidence-based, uniformly agreed upon protocols.

The contribution of total and free iodothyronines to welfare maintenance and management stress coping in Ruminants and Equines: Physiological ranges and reference values

In order to acquire a pattern of thyroid involvement in welfare maintenance in Ruminants and Equines, this review summarizes data concerning the reference values of total and free iodothyronines and their modifications in physiological conditions and in different management conditions (pregnancy, lactation, weaning, growth, isolation, restraint, shearing, confinement and transportation). Thyroidal and extrathyroidal tissues efficiently respond to management practices, giving a differentiated contribution to circulating iodothyronine changes. The hormonal response could be mainly attributed to the intracellular deiodination of T₄ to T_3. Triiodothyronine (T₃) and free iodothyronines (fT₃ and fT₄) result more responsive to management stress, showing different pattern with species and to various conditions, as to environmental conditions in which activities are performed. Intrinsic seasonal changes of iodothyronines and a significant pregnancy effect for T₃ were recorded in mares. Higher, although not significant, T₃ and T₄ concentrations in barren than pregnant mares were observed in donkeys. A positive significant correlation between T₃ and T₄ was described only in pregnant donkeys. Moreover, a significant effect of season on T₃ and fT₃ changes was observed both in pregnant and barren donkeys. A significant lactating effect compared with nonlactating stage for T₃ and T₄ was recorded in mares. In growing foals, body weight (BW) and age were positively correlated with T₃ and negatively correlated with T₄, fT₄ and fT₃. Weaning effects were shown for T₃ and fT₄ concentrations, indicating that weaning represents a severe stress and the presence of conspecific does not reduce psychological stress in this phase. Lambs showed significant decreased T₃ and elevated T₄ concentrations two weeks after weaning, with higher concentrations in both males and females compared to 24 h. Significant positive correlations were observed between BW and T₄, fT₃ and fT₄ concentrations in lambs. A T₃ decrease was detected after isolation, such as induced by confinement and weaning in lambs. Higher T₃ concentration after restraint and shearing than after isolation and significant increases in T₄, fT₃ and fT₄ values after restraint and shearing were recorded. The basal concentrations of fT₃ in both the inexperienced and experienced transported horses were significantly higher than in untransported experienced horses. Moreover, increases of T_3, T₄ and fT₄ after short road transportation, and significant correlations between T₃ and rectal temperature (RT), body weight (BW) and heart rate (HR), confirmed their important role in coping strategy. Thyroid responsiveness to short transport is similar in domestic donkeys and horses, with a preferential release of T₃ in horses. A greatest and constant release of T₃ and T₄, although differentiated, after simulated transportation and after conventional transport of horses confirmed that the degree of stress induced by confinement and additional stressful stimuli associated to road transportation could differently influence the iodothyronine release. Temperamental Limousin young beef bulls showed lower T₄ and fT₄ concentrations after prolonged transportation than calm subjects, and a concomitant decrease of circulating ACTH, cortisol, T₃ and fT₃ concentrations, probably induced by down regulation of HPA axis and cortisol negative feedback. These data reinforce the importance of taking into account the evaluation of iodothyronines, and notably of T₃, as markers of welfare and stress and their role in ensuring energy homeostasis and productive and reproductive performances in Ruminants and Equines.

The outcome of the first stages of pregnancy on mares' bloodstream thyroid hormones

The objective of this study was to compare in detail the total and free iodothyronines' pattern of mares from the first ovulation of the year over an extended period of 12 weeks. A total of 20 mares were used in the study. The mares were classified into two groups: mares mated at the ovulation (n = 10) used as observational group and mares unmated at the ovulation (n = 10) used as control group. Serum total and free triiodothyronine (T3, fT3) and thyroxine (T4, fT4) levels were measured in baseline conditions at the first ovulation of year and once a week until 12 weeks later. For the experimental group, the first week of postovulation mating was considered as the first week of gestation. One-way analysis of variance showed a significant effect of time over 12 weeks for T3 (F = 2.44; P = 0.007) in pregnant mares, with the higher levels at the seventh and 12th weeks (P < 0.05) than baseline values, and for fT3 (F = 2.36; P = 0.009), with the higher levels at the 11th week (P < 0.05) than baseline values. Two-way analysis of variance showed a significant pregnancy effect compared with nonpregnancy stage for T3 (F = 15.82; P = 0.009), with the higher levels at the seventh and 12th weeks (P < 0.05) of pregnancy than that in nonpregnant values. Thus, it appears that, under similar environment, management and nutritional regime, the first trimester of pregnancy plays a dynamic role on the thyroid patterns by their anabolic activity; therefore, significant effects of time points on the T3 and fT3 concentrations probably may contribute to the control of early embryonic growth and development, before the onset of fetal thyroid activity. Considerable additional research, outwith the aim of this study, will be required to elucidate the mechanisms by which gestational age affects the physiological thyroid function in mares and/or fetus ratio in the first pregnancy stage.