Characterization of the equine placental microbial population during nocardioform placentitis.

Nocardioform placentitis is a poorly understood disease of equine late gestation. The presence of nocardioform, filamentous branching gram-positive bacteria, has been linked to the disease, with Crossiella equi, Amycolatopsis spp., and Streptomyces spp. being the most frequently identified bacteria. However, these bacteria are not found in all clinical cases in addition to being isolated from healthy, normal postpartum placentas. To better understand this form of placentitis, we analyzed the microbial composition in the equine placenta (chorioallantois) of both healthy postpartum (control; n = 11) and nocardioform-affected samples (n = 22) using 16S rDNA sequencing. We found a lower Shannon index in nocardioform samples, a higher Chao1 index in nocardioform samples, and a difference in beta diversity between control and nocardioform samples (p < 0.05), suggesting the presence of dysbiosis during the disease. In the majority of the NP samples (77 %), one of the following genera-Amycolatopsis, Crossiella, Lentzea, an unidentified member of the Pseudonocardiaceae family, Mycobacterium, or Enterococcus -represented over 70 % of the relative abundance. Overall, the data suggest that a broader spectrum of potential opportunistic pathogens could be involved in nocardioform placentitis, extending beyond the traditionally recognized bacteria, resulting in a similar histomorphological profile.

Using mycobacterium cell wall fraction to decrease equine chorionic gonadotropin after abortion.

BACKGROUND: Equine embryonic loss following the development of endometrial cups delays return to cyclicity due to the production of equine chorionic gonadotropin (eCG). Natural degradation of endometrial cups coincides with an influx of immune cells at 100-120 days of gestation, but therapeutic stimulation of reduced eCG production has been relatively unsuccessful. Recently, we observed an increase in pro-inflammatory cytokine production following the use of the immunostimulant mycobacterium cell wall fraction (MCWF). OBJECTIVES: To evaluate the efficacy of hysteroscopic-guided injection of MCWF on the accelerated decline of eCG secretion. STUDY DESIGN: In vivo experiment. METHODS: Mares were pharmacologically aborted at 40-45 days of gestation, and then divided into groups: MCWF-treated (6 mg MCWF suspended in 20 mL LRS; n = 10) and Control (20 mL LRS; n = 6). Five days after abortion, hysteroscopic-guided injection of endometrial cups was performed, with 1 mL of volume placed into each visible endometrial cup. This was repeated 7 days later. Trans-rectal ultrasonography was performed to monitor ovarian activity, and serum was obtained to assess eCG and cytokine concentrations. RESULTS: Concentrations of eCG decreased in the MCWF-treated group (p < 0.01) with a significant suppression noted as early as 14 days after onset of treatment and remained suppressed for the duration of the study. This coincided with an increase in peripheral IFN-γ (p < 0.01) and IL-1ß (p < 0.01) concentrations. Eight out of ten MCWF-treated mares (80%) developed pre-ovulatory follicles, in comparison to 2/6 controls (33%). A pre-ovulatory follicle was noted 23 ± 4 days after onset of treatment. MAIN LIMITATIONS: No pregnancy data was obtained following treatment. CONCLUSIONS: This is the first report of a treatment for the accelerated reduction of eCG following abortion. Stimulation of this process allowed mares to develop a pre-ovulatory follicle within a month of MCWF treatment onset, granting repeat attempts at breeding within the confines of a single breeding season.

Characterization of the equine placental microbial population in healthy pregnancies.

In spite of controversy, recent studies present evidence that a microbiome is present in the human placenta. However, there is limited information about a potential equine placental microbiome. In the present study, we characterized the microbial population in the equine placenta (chorioallantois) of healthy prepartum (280 days of gestation, n = 6) and postpartum (immediately after foaling, 351 days of gestation, n = 11) mares, using 16S rDNA sequencing (rDNA-seq). In both groups, the majority of bacteria belonged to the phyla Proteobacteria, Firmicutes, Actinobacteria, and Bacteroidota. The five most abundant genera were Bradyrhizobium, an unclassified Pseudonocardiaceae, Acinetobacter, Pantoea, and an unclassified Microbacteriaceae. Alpha diversity (p < 0.05) and beta diversity (p < 0.01) were significantly different between pre- and postpartum samples. Additionally, the abundance of 7 phyla and 55 genera was significantly different between pre- and postpartum samples. These differences suggest an effect of the caudal reproductive tract microbiome on the postpartum placental microbial DNA composition, since the passage of the placenta through the cervix and vagina during normal parturition had a significant influence on the composition of the bacteria found in the placenta when using 16S rDNA-seq. These data support the hypothesis that bacterial DNA is present in healthy equine placentas and opens the possibility for further exploration of the impact of the placental microbiome on fetal development and pregnancy outcome.

Dynamics of the Equine Placental DNA Methylome and Transcriptome from Mid- to Late Gestation.

The placenta is a temporary organ that is essential for the survival of the fetus, with a lifelong effect on the health of both the offspring and the dam. The functions of the placenta are controlled by its dynamic gene expression during gestation. In this study, we aimed to investigate the equine placental DNA methylome as one of the fundamental mechanisms that controls the gene expression dynamic. Chorioallantois samples from four (4M), six (6M), and ten (10M) months of gestation were used to map the methylation pattern of the placenta. Globally, methylation levels increased toward the end of gestation. We identified 921 differentially methylated regions (DMRs) between 4M and 6M, 1225 DMRs between 4M and 10M, and 1026 DMRs between 6M and 10M. A total of 817 genes carried DMRs comparing 4M and 6M, 978 comparing 4M and 10M, and 804 comparing 6M and 10M. We compared the transcriptomes between the samples and found 1381 differentially expressed genes (DEGs) when comparing 4M and 6M, 1428 DEGs between 4M and 10M, and 741 DEGs between 6M and 10M. Finally, we overlapped the DEGs and genes carrying DMRs (DMRs-DEGs). Genes exhibiting (a) higher expression, low methylation and (b) low expression, high methylation at different time points were identified. The majority of these DMRs-DEGs were located in introns (48.4%), promoters (25.8%), and exons (17.7%) and were involved in changes in the extracellular matrix; regulation of epithelial cell migration; vascularization; and regulation of minerals, glucose, and metabolites, among other factors. Overall, this is the first report highlighting the dynamics in the equine placenta methylome during normal pregnancy. The findings presented serve as a foundation for future studies on the impact of abnormal methylation on the outcomes of equine pregnancies.

Transcriptomic analysis of the chorioallantois in equine premature placental separation.

BACKGROUND: Equine premature placental separation (PPS) is poorly understood and represents an important risk factor for fetal/neonatal hypoxia. OBJECTIVES: To examine transcriptomic changes in the chorioallantois (CA) from mares with clinical PPS compared with the CA from normal foaling mares. Differential gene expression was determined and gene ontology as well as molecular pathways related to PPS were characterised. STUDY DESIGN: Retrospective case: control study. METHODS: CA were collected from Thoroughbred mares with a clinical history of PPS (n = 33) and from control Thoroughbred mares (n = 4) with normal parturition for examination of transcriptional changes in the placenta associated with PPS. Transcriptomic changes in the villous CA near the cervical star were determined by Illumina® sequencing and subsequent bioinformatic analysis. PPS samples were divided by k-means clustering, and differentially expressed genes (DEGs) in each PPS cluster were identified by comparing to controls. Shared DEGs between PPS clusters were used for gene ontology analysis and pathway analysis. RESULTS: A total of 1204 DEGs were identified between PPS and control. Gene ontology revealed extracellular matrix (ECM) and cell adhesion, and pathway analysis revealed fatty acid, p-53, hypoxia and inflammation. Eleven key regulator genes of PPS including growth factors (IGF1, TGFB2, TGFB3), transcription factors (HIF1A, JUNB, SMAD3), and transmembrane receptors (FGFR1, TNFRSF1A, TYROBP) were also identified. MAIN LIMITATIONS: The use of clinical history of PPS, in the absence of other criteria, may have led to misidentification of some cases as PPS. CONCLUSIONS: Transcriptomic analysis indicated that changes in ECM and cell adhesion were important factors in equine PPS. Key predicted upstream events include genes associated with hypoxia, inflammation and growth factors related to the pathogenesis of equine PPS.

Transcriptomic and histochemical analysis reveal the complex regulatory networks in equine chorioallantois during spontaneous term labor†.

The equine chorioallantois (CA) undergoes complex physical and biochemical changes during labor. However, the molecular mechanisms controlling these changes are still unclear. Therefore, the current study aimed to characterize the transcriptome of equine CA during spontaneous labor and compare it with that of normal preterm CA. Placental samples were collected postpartum from mares with normal term labor (TL group, n = 4) and from preterm not in labor mares (330 days GA; PTNL group, n = 4). Our study identified 4137 differentially expressed genes (1820 upregulated and 2317 downregulated) in CA during TL as compared with PTNL. TL was associated with the upregulation of several proinflammatory mediators (MHC-I, MHC-II, NLRP3, CXCL8, and MIF). Also, TL was associated with the upregulation of matrix metalloproteinase (MMP1, MMP2, MMP3, and MMP9) with subsequent extracellular matrix degradation and apoptosis, as reflected by upregulation of several apoptosis-related genes (ATF3, ATF4, FAS, FOS, and BIRC3). In addition, TL was associated with downregulation of 21 transcripts coding for collagens. The upregulation of proteases, along with the downregulation of collagens, is believed to be implicated in separation and rupture of the CA during TL. Additionally, TL was associated with downregulation of transcripts coding for proteins essential for progestin synthesis (SRD5A1 and AKR1C1) and angiogenesis (VEGFA and RTL1), as well as upregulation of prostaglandin synthesis-related genes (PTGS2 and PTGES), which could reflect the physiological switch in placental endocrinology and function during TL. In conclusion, our findings revealed the equine CA gene expression signature in spontaneous labor at term, which improves our understanding of the molecular mechanisms triggering labor.

Comparison of the host response to larvicidal and nonlarvicidal treatment of naturally acquired cyathostomin infections in horses.

This study aimed to collect information on local and systemic inflammatory responses, and goblet cell-associated components, following anthelmintic treatment with moxidectin and ivermectin in horses naturally infected with cyathostomin parasites. Thirty-six horses aged 2-5 years of age were randomly allocated to three groups. Group 1 received ivermectin/praziquantel (0.2 mg/kg), Group 2 received moxidectin/praziquantel (0.4 mg/kg) and Group 3 were untreated controls. Tissue samples from the Cecum, Dorsal and Ventral Colons were used for histopathological evaluation and preserved for RNA isolation and gene expression analysis. Whole blood was collected weekly for gene expression analysis as well. The control group had significantly higher inflammation associated with higher larval scores. The treatment groups displayed no differences in larval counts and inflammatory cell populations (p > .05). Mucosal larval counts were positively correlated with goblet cell hyperplasia scores (p = .047). The moxidectin-treated group had a significantly lower expression of IFN-γ (p < .05). The data suggest that removal of cyathostomins reduced the pro-inflammatory response associated with cyathostomin infections. Pro-inflammatory reactions associated with anthelmintic treatment were minimal, but lowest for moxidectin-treated horses. Results suggested that cecum, ventral and dorsal colons responded differently to cyathostomin larvae, which may have implications in the disease process.

Tumor necrosis factor signaling during equine placental infection leads to pro-apoptotic and necroptotic outcomes.

Ascending placentitis is the leading cause of abortion in the horse. The pleiotropic cytokine tumor necrosis factor (TNF) is an upstream regulator of this disease, but little is understood regarding its function in pregnancy maintenance or placental infection. To assess this, RNA sequencing was performed on chorioallantois and endometrium of healthy pregnant mares at various gestational lengths (n = 4/gestational age), in addition to postpartum chorioallantois, and diestrus endometrium to assess expression of TNF, TNFR-1, and TNFR-2. Additionally, ascending placentitis was induced via trans-cervical inoculation of S. equi spp. zooepidemicus in pregnant mares (n = 6 infected / n = 6 control) and tissues and serum were collected to evaluate TNF-related transcripts. IHC was performed to confirm protein localization of TNFR-1 and TNFR-2. In healthy pregnancy, TNFR-1 appears to be the predominant TNF-related receptor. Following induction of disease, TNF concentrations increased in maternal serum, but expression did not alter at the tissue level. While both TNFR-1 and TNFR-2 increased following induction of disease, alterations in downstream pathways indicate that TNFR-1 is the dominant receptor in ascending placentitis, and is primarily activated within the chorioallantois, with minimal signaling occurring within the endometrium. In conclusion, TNF appears to be involved in the pathophysiology of ascending placentitis. An increase in this cytokine during disease progression is believed to activate TNFR-1 within the chorioallantois, leading to various pro-apoptotic and necroptotic outcomes, all of which may signal for fetal demise and impending abortion.

Development and Use of an Enzyme-Linked Immunosorbent Assay to Determine Temporal Exposure Patterns to Putative Agents of Nocardioform Placentitis.

Cases of nocardioform placentitis are characterized by focal, mucoid placentitis resulting in late-term abortion, premature birth, or small, full-term foals, occur sporadically, and are most commonly associated with Crossiella equi and Amycolatopsis spp. infection. The goal of this project was to develop an enzyme-linked immunosorbent assay (ELISA) for quantifying antibodies against Crossiella equi and Amycolatopsis spp. and utilize the ELISA to determine when exposure occurs. Serum samples collected during the 2020 foaling season from Crossiella equi (n = 8) and Amycolatopsis spp. (n = 32) infected mares, as well as nonaffected mares (n = 51 mares), were used to develop and optimize bacteria-specific ELISAs. Following development of the ELISAs, banked serum samples from a single, central Kentucky Thoroughbred farm collected during 2012 to 2013 (n = 104 mares) and 2013-14 (n = 82 mares) were analyzed. Differences in various groups were analyzed using one-way analysis of variance (ANOVA). Crossiella equi-infected mares had significantly higher ELISA unit (EU) values on the Crossiella equi ELISA near parturition when compared to the other two groups (P < .001). Using the Amycolatopsis spp. ELISA, EU values were not significantly different between Amycolatopsis spp. infected and non-affected mares, suggesting this ELISA is not specific for Amycolatopsis spp. During 2013 to 2014, there were significant increases in EU values between June and late September for the Crossiella equi ELISA, suggesting exposure in the summer and early fall months. Data from the Crossiella equi ELISA may help provide a better understanding of the epidemiology of nocardioform placentitis, guide the development of a successful experimental challenge model, and allow for further refinement of these ELISAs.

Binding of Equine Seminal Lactoferrin/Superoxide Dismutase (SOD-3) Complex Is Biased towards Dead Spermatozoa.

Sperm-neutrophil binding is an important facet of breeding and significantly impacts fertility. While a specific seminal plasma protein has been found to reduce this binding and improve fertility (CRISP-3), additional molecule(s) appear to promote binding between defective sperm and neutrophils. Recent work has suggested one of these proteins is lactoferrin (LF), an 80 kDa iron-binding protein found throughout the body, but the purity of the protein was not confirmed. It is unknown if LF binds to sperm selectively based on viability, and if receptors for LF are located on equine sperm. To evaluate this, we attempted to purify equine seminal LF from five stallions (n = 5), biotinylate LF, and evaluate potential binding site(s) on spermatozoa. LF was consistently associated with superoxide dismutase (SOD-3), and all attempts to separate the two proteins were unsuccessful. Flow cytometric and microscopic analyses were used to compare LF/SOD-3 binding to viable and nonviable spermatozoa. Additionally, various methods of biotinylation were assessed to optimize this methodology. Biotinylation of seminal plasma protein was an effective and efficient method to study seminal plasma protein properties, and the binding site for LF/SOD-3 was found to be broadly localized to the entire sperm cell surface as well as selective towards nonviable/defective sperm. Although we were not able to determine if the binding to equine spermatozoa was through LF or SOD-3, we can conclude that equine seminal LF is tightly bound to SOD-3 and this protein complex binds selectively to nonviable spermatozoa, possibly to mark them for elimination by neutrophil phagocytosis.

Transcriptional and Histochemical Signatures of Bone Marrow Mononuclear Cell-Mediated Resolution of Synovitis.

Osteoarthritis (OA) may result from impaired ability of synovial macrophages to resolve joint inflammation. Increasing macrophage counts in inflamed joints through injection with bone marrow mononuclear cells (BMNC) induces lasting resolution of synovial inflammation. To uncover mechanisms by which BMNC may affect resolution, in this study, differential transcriptional signatures of BMNC in response to normal (SF) and inflamed synovial fluid (ISF) were analyzed. We demonstrate the temporal behavior of co-expressed gene networks associated with traits from related in vivo and in vitro studies. We also identified activated and inhibited signaling pathways and upstream regulators, further determining their protein expression in the synovium of inflamed joints treated with BMNC or DPBS controls. BMNC responded to ISF with an early pro-inflammatory response characterized by a short spike in the expression of a NF-ƙB- and mitogen-related gene network. This response was associated with sustained increased expression of two gene networks comprising known drivers of resolution (IL-10, IGF-1, PPARG, isoprenoid biosynthesis). These networks were common to SF and ISF, but more highly expressed in ISF. Most highly activated pathways in ISF included the mevalonate pathway and PPAR-γ signaling, with pro-resolving functional annotations that improve mitochondrial metabolism and deactivate NF-ƙB signaling. Lower expression of mevalonate kinase and phospho-PPARγ in synovium from inflamed joints treated with BMNC, and equivalent IL-1ß staining between BMNC- and DPBS-treated joints, associates with accomplished resolution in BMNC-treated joints and emphasize the intricate balance of pro- and anti-inflammatory mechanisms required for resolution. Combined, our data suggest that BMNC-mediated resolution is characterized by constitutively expressed homeostatic mechanisms, whose expression are enhanced following inflammatory stimulus. These mechanisms translate into macrophage proliferation optimizing their capacity to counteract inflammatory damage and improving their general and mitochondrial metabolism to endure oxidative stress while driving tissue repair. Such effect is largely achieved through the synthesis of several lipids that mediate recovery of homeostasis. Our study reveals candidate mechanisms by which BMNC provide lasting improvement in patients with OA and suggests further investigation on the effects of PPAR-γ signaling enhancement for the treatment of arthritic conditions.

Estrogens Regulate Placental Angiogenesis in Horses.

A sufficient vascular network within the feto-maternal interface is necessary for placental function. Several pregnancy abnormalities have been associated with abnormal vascular formations in the placenta. We hypothesized that growth and expansion of the placental vascular network in the equine (Equus caballus) placenta is regulated by estrogens (estrogen family hormones), a hormone with a high circulating concentration during equine gestation. Administration of letrozole, a potent and specific inhibitor of aromatase, during the first trimester (D30 to D118), decreased circulatory estrone sulfate concentrations, increased circulatory testosterone and androstenedione concentrations, and tended to reduce the weight of the fetus (p < 0.1). Moreover, the gene expression of CYP17A1 was increased, and the expression of androgen receptor was decreased in the D120 chorioallantois (CA) of letrozole-treated mares in comparison to that of the control mares. We also found that at D120, the number of vessels tended to decrease in the CAs with letrozole treatment (p = 0.07). In addition, expression of a subset of angiogenic genes, such as ANGPT1, VEGF, and NOS2, were altered in the CAs of letrozole-treated mares. We further demonstrated that 17ß-estradiol increases the expression of ANGPT1 and VEGF and increases the angiogenic activity of equine endothelial cells in vitro. Our results from the estrogen-suppressed group demonstrated an impaired placental vascular network, suggesting an estrogen-dependent vasculogenesis in the equine CA during the first trimester.

Steroidogenic Enzyme and Steroid Receptor Expression in the Equine Accessory Sex Glands.

The expression pattern and distribution of sex steroid receptors and steroidogenic enzymes during development of the equine accessory sex glands has not previously been described. We hypothesized that equine steroidogenic enzyme and sex steroid receptor expression is dependent on reproductive status. Accessory sex glands were harvested from mature stallions, pre-pubertal colts, geldings, and fetuses. Expression of mRNA for estrogen receptor 1 (ESR1), estrogen receptor 2 (ESR2), androgen receptor (AR), 3ß-Hydroxysteroid dehydrogenase/Δ5-4 isomerase (3ßHSD), P450,17α hydroxylase, 17-20 lyase (CYP17), and aromatase (CYP19) were quantified by RT-PCR, and protein localization of AR, ER-α, ER-ß, and 3ßHSD were investigated by immunohistochemistry. Expression of AR, ESR2, CYP17, or CYP19 in the ampulla was not different across reproductive statuses (p > 0.1), while expression of ESR1 was higher in the ampulla of geldings and fetuses than those of stallions or colts (p < 0.05). AR, ESR1 and ESR2 expression were decreased in stallion vesicular glands compared to the fetus or gelding, while AR, ESR1, and CYP17 expression were decreased in the bulbourethral glands compared to other glands. ESR1 expression was increased in the prostate compared to the bulbourethral glands, and no differences were seen with CYP19 or 3ß-HSD. In conclusion, sex steroid receptors are expressed in all equine male accessory sex glands in all stages of life, while the steroidogenic enzymes were weakly and variably expressed.

Use of Tubo-Ovarian Ligation Via Colpotomy as A Potential Method for Sterilization in Mares.

The goal of this study was to develop a safe, effective, and economical method for permanent sterilization of mares based upon tubo-ovarian ligation performed via colpotomy. In this study, we evaluated the application of a nylon cable tie (zip-tie) to the ovarian pedicle and oviduct of mares to induce ovarian ischemia and tubal ligation without removal of ovaries. Initially, efficiency of zip-ties on the ovarian pedicle was tested in vitro and in vivo. Based on the absence of leakage through the zip-tie ligated vessels in anatomic specimens, we confirmed the potential efficacy of the technique. Next, ligation of the ovarian pedicle via a standing colpotomy was conducted in five mares. Although the surgical procedure in these mares appeared to be quick and efficient, all five mares were noted to develop ovarian adhesions to surrounding abdominal viscera in either one or both ovaries postoperatively. Ovarian ischemia led to loss of ovarian activity based upon ultrasound examination, which was confirmed by a low plasma progesterone concentration in four of the five mares. During the postoperative period, four mares demonstrated clinical signs related to the ovarian adhesions and were euthanized. The postoperative complications associated with ovarian adhesions to abdominal viscera presented significant challenges, limiting the success of this study. While this technique resulted in ovarian ischemia and atrophy in four out of the five mares, we were unable to assess long-term effects on the health and reproduction of the mares due to the ovarian adhesions to the surrounding tissues and the potential for secondary complications. Although technically feasible, tubo-ovarian ligation via colpotomy does not appear to be a viable option for sterilization of mares using the described technique due to ovarian adhesions post procedure.

Transcriptomic analysis of equine chorioallantois reveals immune networks and molecular mechanisms involved in nocardioform placentitis.

Nocardioform placentitis (NP) continues to result in episodic outbreaks of abortion and preterm birth in mares and remains a poorly understood disease. The objective of this study was to characterize the transcriptome of the chorioallantois (CA) of mares with NP. The CA were collected from mares with confirmed NP based upon histopathology, microbiological culture and PCR for Amycolatopsis spp. Samples were collected from the margin of the NP lesion (NPL, n = 4) and grossly normal region (NPN, n = 4). Additionally, CA samples were collected from normal postpartum mares (Control; CRL, n = 4). Transcriptome analysis identified 2892 differentially expressed genes (DEGs) in NPL vs. CRL and 2450 DEGs in NPL vs. NPN. Functional genomics analysis elucidated that inflammatory signaling, toll-like receptor signaling, inflammasome activation, chemotaxis, and apoptosis pathways are involved in NP. The increased leukocytic infiltration in NPL was associated with the upregulation of matrix metalloproteinase (MMP1, MMP3, and MMP8) and apoptosis-related genes, such as caspases (CASP3 and CASP7), which could explain placental separation associated with NP. Also, NP was associated with downregulation of several placenta-regulatory genes (ABCG2, GCM1, EPAS1, and NR3C1), angiogenesis-related genes (VEGFA, FLT1, KDR, and ANGPT2), and glucose transporter coding genes (GLUT1, GLUT10, and GLUT12), as well as upregulation of hypoxia-related genes (HIF1A and EGLN3), which could elucidate placental insufficiency accompanying NP. In conclusion, our findings revealed for the first time, the key regulators and mechanisms underlying placental inflammation, separation, and insufficiency during NP, which might lead to the development of efficacious therapies or diagnostic aids by targeting the key molecular pathways.

Parental bias in expression and interaction of genes in the equine placenta.

Most autosomal genes in the placenta show a biallelic expression pattern. However, some genes exhibit allele-specific transcription depending on the parental origin of the chromosomes on which the copy of the gene resides. Parentally expressed genes are involved in the reciprocal interaction between maternal and paternal genes, coordinating the allocation of resources between fetus and mother. One of the main challenges of studying parental-specific allelic expression (allele-specific expression [ASE]) in the placenta is the maternal cellular remnant at the fetomaternal interface. Horses (Equus caballus) have an epitheliochorial placenta in which both the endometrial epithelium and the epithelium of the chorionic villi are juxtaposed with minimal extension into the uterine mucosa, yet there is no information available on the allelic gene expression of equine chorioallantois (CA). In the current study, we present a dataset of 1,336 genes showing ASE in the equine CA (https://pouya-dini.github.io/equine-gene-db/) along with a workflow for analyzing ASE genes. We further identified 254 potentially imprinted genes among the parentally expressed genes in the equine CA and evaluated the expression pattern of these genes throughout gestation. Our gene ontology analysis implies that maternally expressed genes tend to decrease the length of gestation, while paternally expressed genes extend the length of gestation. This study provides fundamental information regarding parental gene expression during equine pregnancy, a species with a negligible amount of maternal cellular remnant in its placenta. This information will provide the basis for a better understanding of the role of parental gene expression in the placenta during gestation.

Paternally expressed retrotransposon Gag-like 1 gene, RTL1, is one of the crucial elements for placental angiogenesis in horses†.

RTL1 (retrotransposon Gag-like 1) is an essential gene in the development of the human and murine placenta. Several fetal and placental abnormalities such as intrauterine growth restriction (IUGR) and hydrops conditions have been associated with altered expression of this gene. However, the function of RTL1 has not been identified. RTL1 is located on a highly conserved region in eutherian mammals. Therefore, the genetic and molecular analysis in horses could hold important implications for other species, including humans. Here, we demonstrated that RTL1 is paternally expressed and is localized within the endothelial cells of the equine (Equus caballus) chorioallantois. We developed an equine placental microvasculature primary cell culture and demonstrated that RTL1 knockdown leads to loss of the sprouting ability of these endothelial cells. We further demonstrated an association between abnormal expression of RTL1 and development of hydrallantois. Our data suggest that RTL1 may be essential for placental angiogenesis, and its abnormal expression can lead to placental insufficiency. This placental insufficiency could be the reason for IUGR and hydrops conditions reported in other species, including humans.

Equine cervical remodeling during placentitis and the prepartum period: a transcriptomic approach.

Cervical remodeling is a critical component in both term and preterm labor in eutherian mammals. However, the molecular mechanisms underlying cervical remodeling remain poorly understood in the mare. The current study compared the transcriptome of the equine cervix (cervical mucosa (CM) and stroma (CS)) during placentitis (placentitis group, n = 5) and normal prepartum mares (prepartum group, n = 3) to normal pregnant mares (control group, n = 4). Transcriptome analysis identified differentially expressed genes (DEGs) during placentitis (5310 in CM and 907 in CS) and during the normal prepartum period (189 in CM and 78 in CS). Our study revealed that cervical remodeling during placentitis was dominated by inflammatory signaling as reflected by the overrepresented toll-like receptor signaling, interleukin signaling, T cell activation, and B cell activation pathways. These pathways were accompanied by upregulation of several proteases, including matrix metalloproteinases (MMP1, MMP2, and MMP9), cathepsins (CTSB, CTSC, and CTSD) and a disintegrin and metalloproteinase with thrombospondin type 1 motifs (ADAMTS1, ADAMTS4, and ADAMTS5), which are crucial for degradation of cervical collagens during remodeling. Cervical remodeling during placentitis was also associated with upregulation of water channel-related transcripts (AQP9 and RLN), angiogenesis-related transcripts (NOS3, ENG1, THBS1, and RAC2), and aggrecan (ACAN), a hydrophilic glucosaminoglycan, with subsequent cervical hydration. The normal prepartum cervix was associated with upregulation of ADAMTS1, ADAMTS4, NOS3 and THBS1, which might reflect an early stage of cervical remodeling taking place in preparation for labor. In conclusion, our findings revealed the possible key regulators and mechanisms underlying equine cervical remodeling during placentitis and the normal prepartum period.

Alterations of Circulating Biomarkers During Late Term Pregnancy Complications in the Horse Part II: Steroid Hormones and Alpha-Fetoprotein.

Preterm labor and/or abortion causes considerable economic impact on the equine industry. Unfortunately, few experimental models exist for the induction of various pregnancy-related complications, and therefore extrapolations are made from the experimental model for ascending placentits, although inferences may be minimal. Certain steroid hormones (progestogens, estrogens) and fetal proteins (alpha-fetoprotein; AFP) might improve the diagnostics for abnormal pregnancy, but the utility of these markers in the field is unknown. To assess this, thoroughbred mares (n = 702) were bled weekly beginning in December 2013 until parturition/abortion. Following parturition, fetal membranes were assessed histopathologically and classified as either ascending placentitis (n = 6), focal mucoid placentitis (n = 6), idiopathic abortion (n = 6) or no disease (n = 20). Weekly serum samples were analyzed for concentrations of progesterone, estradiol-17ß, and AFP. Samples were analyzed retrospectively from the week of parturition/abortion in addition to the preceding four weeks. For both ascending and focal mucoid placentitis, a significant increase in progesterone and AFP was noted, alongside a significant decrease in estradiol-17ß and the ratio of estradiol-17ß to progesterone in comparison to controls. In contrast, idiopathic abortions experienced a decrease in progesterone concentrations alongside an increase in AFP, and this was only noted in the week preceding parturition/abortion. In conclusion, spontaneous placental infection in the horse altered both endocrine and feto-secretory markers in maternal circulation, while minimal changes were noted preceding noninfectious idiopathic abortion. Additionally, this is the first study to report an alteration in steroid hormones and AFP during the disease process of focal mucoid placentitis, the etiology of which includes Nocardioform placentitis.

Transcriptomic analysis of equine placenta reveals key regulators and pathways involved in ascending placentitis†.

Improved understanding of the molecular mechanisms underlying ascending equine placentitis holds the potential for the development of new diagnostic tools and therapies to forestall placentitis-induced preterm labor. The current study characterized the equine placental transcriptome (chorioallantois [CA] and endometrium [EN]) during placentitis (placentitis group, n = 6) in comparison to gestationally-matched controls (control group, n = 6). Transcriptome analysis identified 2953 and 805 differentially expressed genes in CA and EN during placentitis, respectively. Upstream regulator analysis revealed the central role of toll-like receptors (TLRs) in triggering the inflammatory signaling, and consequent immune-cell chemotaxis. Placentitis was associated with the upregulation of matrix metalloproteinase (MMP1, MMP2, and MMP9) and apoptosis-related genes such as caspases (CASP3, CASP4, and CASP7) in CA. Also, placentitis was associated with downregulation of transcripts coding for proteins essential for placental steroidogenesis (SRD5A1 and AKR1C1), progestin signaling (PGRMC1 and PXR) angiogenesis (VEGFA, VEGFR2, and VEGFR3), and nutrient transport (GLUT12 and SLC1A4), as well as upregulation of hypoxia-related genes (HIF1A and EGLN3), which could explain placental insufficiency during placentitis. Placentitis was also associated with aberrant expression of several placenta-regulatory genes, such as PLAC8, PAPPA, LGALS1, ABCG2, GCM1, and TEPP, which could negatively affect placental functions. In conclusion, our findings revealed for the first time the key regulators and mechanisms underlying placental inflammation, separation, and insufficiency during equine placentitis, which might lead to the development of efficacious therapies or diagnostic aids by targeting the key molecular pathways.