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Köhne M, Diel E, Packeiser EM, Böttcher D, Tönissen A, Unruh C, Goericke-Pesch S, Ulrich R, Sieme H. Analysis of gene and protein expression in the endometrium for validation of an ex vivo model of the equine uterus using PCR, digital and visual histopathology. Theriogenology 2024; 221:38-46. [PMID: 38537320 DOI: 10.1016/j.theriogenology.2024.03.015] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/03/2024] [Revised: 03/21/2024] [Accepted: 03/23/2024] [Indexed: 04/09/2024]
Abstract
In the past, most research in equine reproduction has been performed in vivo but the use of in vitro and ex vivo models has recently increased. This study aimed to evaluate the functional stability of an ex vivo hemoperfused model for equine uteri with molecular characterization of marker genes and their proteins. In addition, the study validated the respective protein expression and the aptness of the software QuPath for identifying and scoring immunohistochemically stained equine endometrium. After collection, uteri (n = 12) were flushed with preservation solution, transported to the laboratory on ice, and perfused with autologous blood for 6 h. Cycle stage was determined by examination of the ovaries for presence of Graafian follicles or corpora lutea and analysis of plasma progesterone concentration (estrus: n = 4; diestrus: n = 4; anestrus: n = 4). Samples were obtained directly after slaughter, after transportation, and during perfusion (240, 300, 360 min). mRNA expression levels of progesterone (PGR), estrogen (ESR1) and oxytocin (OXTR) receptor as well as of MKI67 (marker of cell growth) and CASP3 (marker of apoptosis) were analyzed by RT-qPCR, and correlation to protein abundance was validated by immunohistochemical staining. Endometrial samples were analyzed by visual and computer-assisted evaluation of stained antigens via QuPath. For PGR, effects of the perfusion and cycle stage on expression were found (P < 0.05), while ESR1 was affected only by cycle stage (P < 0.05) and OXTR was unaffected by perfusion and cycle stage. MKI67 was lower after 360 min of perfusion as compared to samples collected before perfusion (P < 0.05). For CASP3, differences in gene expression were found after transport and samples taken after 240 min (P < 0.05). Immunohistochemical staining revealed effects of perfusion on stromal and glandular cells for steroid hormone receptors, but not for Ki-67 and active Caspase 3. OXTR was visualized in all layers of the endometrium and was unaffected by perfusion. Comparison of QuPath and visual analysis resulted in similar results. For most cell types and stained antigens, the correlation coefficient was r > 0.5. In conclusion, the isolated hemoperfused model of the equine uterus was successfully validated at the molecular level, demonstrating stability of key marker gene expression. The utility of computer-assisted immunohistochemical analysis of equine endometrial samples was also confirmed.
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Affiliation(s)
- Martin Köhne
- Unit for Reproductive Medicine, Clinic for Horses, University of Veterinary Medicine, Foundation, 30559, Hannover, Germany.
| | - Emilia Diel
- Unit for Reproductive Medicine, Clinic for Horses, University of Veterinary Medicine, Foundation, 30559, Hannover, Germany
| | - Eva-Maria Packeiser
- Unit for Reproductive Medicine, Clinic for Small Animals, University of Veterinary Medicine, Foundation, 30559, Hannover, Germany
| | - Denny Böttcher
- Institute of Veterinary Pathology, Faculty of Veterinary Medicine, Leipzig University, 04103, Leipzig, Germany
| | - Anna Tönissen
- Unit for Reproductive Medicine, Clinic for Horses, University of Veterinary Medicine, Foundation, 30559, Hannover, Germany
| | - Christin Unruh
- Unit for Reproductive Medicine, Clinic for Horses, University of Veterinary Medicine, Foundation, 30559, Hannover, Germany
| | - Sandra Goericke-Pesch
- Unit for Reproductive Medicine, Clinic for Small Animals, University of Veterinary Medicine, Foundation, 30559, Hannover, Germany
| | - Reiner Ulrich
- Institute of Veterinary Pathology, Faculty of Veterinary Medicine, Leipzig University, 04103, Leipzig, Germany
| | - Harald Sieme
- Unit for Reproductive Medicine, Clinic for Horses, University of Veterinary Medicine, Foundation, 30559, Hannover, Germany
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2
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de Castro T, van Heule M, Domingues RR, Jacob JCF, Daels PF, Meyers SA, Conley AJ, Dini P. Embryo-endometrial interaction associated with the location of the embryo during the mobility phase in mares. Sci Rep 2024; 14:3151. [PMID: 38326534 PMCID: PMC10850102 DOI: 10.1038/s41598-024-53578-z] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/06/2023] [Accepted: 02/02/2024] [Indexed: 02/09/2024] Open
Abstract
Embryo-maternal crosstalk is essential to establish pregnancy, with the equine embryo moving throughout the uterus on days 9-15 (ovulation = day 0) as part of this interaction. We hypothesized that the presence of a mobile embryo induces local changes in the gene expression of the endometrium. On Day 12, the endometrial transcripts were compared among three groups: uterine horn with an embryo (P+, n = 7), without an embryo (P-, n = 7) in pregnant mares, and both uterine horns of nonbred mares (NB, n = 6). We identified 1,101 differentially expressed genes (DEGs) between P+ vs. NB and 1,229 DEGs between P- vs. NB. The genes upregulated in both P+ and P- relative to NB were involved in growth factor pathway and fatty acid activation, while downregulated genes were associated with oxytocin signaling pathway and estrogen receptor signaling. Comparing the transcriptome of P+ to that of P-, we found 59 DEGs, of which 30 genes had a higher expression in P+. These genes are associated with regulating vascular growth factors and the immune system, all known to be essential in early pregnancy. Overall, this study suggests that the mobile embryo influences the endometrial gene expression locally.
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Affiliation(s)
- Thadeu de Castro
- Department of Population Health and Reproduction, School of Veterinary Medicine, University of California, Davis, CA, 95616, USA
| | - Machteld van Heule
- Department of Population Health and Reproduction, School of Veterinary Medicine, University of California, Davis, CA, 95616, USA
- Department of Morphology, Imaging, Orthopedics, Rehabilitation and Nutrition, Faculty of Veterinary Medicine, University of Ghent, 9820, Merelbeke, Belgium
| | - Rafael R Domingues
- Department of Animal and Dairy Sciences, The Ohio State University, Columbus, OH, 43210, USA
| | - Julio C F Jacob
- Departmento de Reprodução E Avalição Animal, Universidade Federal Rural Do Rio de Janeiro, Seropédica, Rio de Janiro, 23897-000, Brazil
| | - Peter F Daels
- Department of Morphology, Imaging, Orthopedics, Rehabilitation and Nutrition, Faculty of Veterinary Medicine, University of Ghent, 9820, Merelbeke, Belgium
| | - Stuart A Meyers
- Department of Anatomy, Physiology and Cell Biology, School of Veterinary Medicine, University of California, Davis, CA, 95616, USA
| | - Alan J Conley
- Department of Population Health and Reproduction, School of Veterinary Medicine, University of California, Davis, CA, 95616, USA
| | - Pouya Dini
- Department of Population Health and Reproduction, School of Veterinary Medicine, University of California, Davis, CA, 95616, USA.
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Newcombe JR, Cuervo-Arango J, Wilsher S. The Timing of the Maternal Recognition of Pregnancy Is Specific to Individual Mares. Animals (Basel) 2023; 13:ani13101718. [PMID: 37238148 DOI: 10.3390/ani13101718] [Citation(s) in RCA: 1] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/27/2023] [Revised: 05/16/2023] [Accepted: 05/19/2023] [Indexed: 05/28/2023] Open
Abstract
The present experiment aimed at determining whether the timing of the maternal recognition of pregnancy (MRP) was specific to individual mares by determining when luteostasis, a failure to return to oestrus, reliably occurred in individuals following embryo reduction. Singleton (n = 150) and synchronous twin pregnancies (n = 9) were reduced in 10 individuals (5-29 reductions/mare) at pre-determined time points within days 10 (n = 20), 11 (n = 65), 12 (n = 47), 13 (n = 12) or 14 (n = 15) of pregnancy. Prior to embryo reduction, the vesicle diameter was measured in 71% (106/150) of the singleton pregnancies. The interovulatory interval (IOI) was recorded on 78 occasions in seven of the mares in either non-pregnant cycles (n = 37) or those in which luteolysis followed embryo reduction (n = 41). The earliest time post-ovulation at which the embryo reduction resulted in luteostasis in an individual was 252 h (mid-Day 10). Consistency in luteostasis following embryo reduction showed individual variation between mares (272-344 h). Binary logistic regression analysis showed an individual mare effect (p < 0.001) and an effect of the interval post-ovulation at which embryo reduction was undertaken (p < 0.001). However, there was no significant effect of vesicle diameter at the time of embryo reduction (p = 0.099), nor a singleton or twin pregnancy (p = 0.993), on the dependent of luteolysis or luteostasis. The median IOI between individual mares varied significantly (p < 0.05) but was not correlated to the timing of MRP. The timing of MRP varied between the mares but was repeatable in each individual. The factors and mechanisms underlying the individuality in the timing of MRP were not determined and warrant further study.
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Affiliation(s)
- John R Newcombe
- Warren House Farm, Equine Fertility Clinic, Brownhills WS8 6LU, West Midlands, UK
| | - Juan Cuervo-Arango
- Departamento de Medicina y Cirugía Animal, Facultad de Veterinaria, Universidad Cardenal Herrera-CEU, CEU Universities, 46115 Alfara del Patriarca, Spain
| | - Sandra Wilsher
- Sharjah Equine Hospital, Sharjah 61313, United Arab Emirates
- The Paul Mellon Laboratory of Equine Reproduction, "Brunswick", Newmarket CB8 9BJ, Suffolk, UK
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Expression profile of genes related to pregnancy maintenance in Dromedary Camel during the first trimester. Anim Reprod Sci 2023; 251:107211. [PMID: 36990016 DOI: 10.1016/j.anireprosci.2023.107211] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/02/2022] [Revised: 02/27/2023] [Accepted: 03/06/2023] [Indexed: 03/18/2023]
Abstract
So far, few signals involved in embryo-maternal dialogue have been identified in pregnant she-camel. Our objective was to investigate expression profiles of genes relevant to uterine extracellular matrix remodeling (ITGB4, SLCO2A1, FOS, and JUN), uterine tissue vascularization, and placental formation (VEGFA, PGF, and PDGFA), embryonic growth and development (IGF1 and PTEN), plus cell death of uterine tissue (BCL2) in early pregnant versus non-pregnant she-camels. Forty genital tracts (20 pregnant and 20 non-pregnant) and blood samples were collected from abattoirs. Total RNA was extracted from uterine tissues and qRT-PCR was conducted for candidate genes. Serum concentrations of progesterone (P4) and estradiol17-β (E2) were measured. Expression of ITGB4, FOS, and PGF genes increased (P < 0.001) in the right uterine horn of pregnant versus non-pregnant she-camels. Moreover, JUN, SLCO2A1, VEGFA, and PTEN mRNAs were up-regulated (P < 0.001) in various segments of uterine tissues in pregnant groups. The PDGFA transcript was over-expressed (P < 0.001) in both uterine horns of pregnant groups. Additionally, IGF1 was higher (P < 0.001) in the right horn and the uterine body of pregnant groups, and expression of BCL2 was increased (P < 0.001) in the pregnant uterine body. Moreover, serum concentrations of P4 were higher (P < 0.001) and E2 lower (P < 0.05) in pregnant she-camels. Taken together, the fine-tuning of genes related to implantation, matrix formation, vascularization, and placental formation is highly required for successful pregnancy in she-camels.
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Diel de Amorim M, Bramer SA, Rajamanickam GD, Klein C, Card C. Endometrial and luteal gene expression of putative gene regulators of the equine maternal recognition of pregnancy. Anim Reprod Sci 2022; 245:107064. [DOI: 10.1016/j.anireprosci.2022.107064] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/23/2022] [Revised: 08/16/2022] [Accepted: 08/28/2022] [Indexed: 11/16/2022]
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6
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Wilsher S, Newcombe JR, Ismer A, Duarte L, Kovacsy S, (Twink) Allen W. The effect of embryo reduction and transfer on luteostasis in the mare. Anim Reprod Sci 2022; 242:107002. [DOI: 10.1016/j.anireprosci.2022.107002] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/08/2022] [Revised: 05/06/2022] [Accepted: 05/13/2022] [Indexed: 11/01/2022]
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Diel de Amorim M, Klein C, Foster R, Dong L, Lopez-Rodriguez MF, Card C. Expression of Oxytocin/Neurophysin I and Oxytocinase in the Equine Conceptus from Day 8 to Day 21 Post-Ovulation. Animals (Basel) 2022; 12:799. [PMID: 35405789 PMCID: PMC8996865 DOI: 10.3390/ani12070799] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/23/2022] [Revised: 03/16/2022] [Accepted: 03/20/2022] [Indexed: 11/17/2022] Open
Abstract
Leucyl and cystinyl aminopeptidase (LNPEP/oxytocinase) is an enzyme that metabolizes oxytocin in serum and tissues. The presence of oxytocin/neurophysin I (OXT), oxytocin and LNPEP and their relationship to other genes is unknown in the equine conceptus. Our objective was to characterize gene expression of LNPEP and OXT on D8, 10, 12, 14, 15, 16 and 21 conceptuses in relationship to other genes. Immunohistochemistry, western blot and liquid chromatography with tandem mass spectrometry (LC-MS/MS) were used for identification of oxytocin and LNPEP in D15, 16 and 18 conceptuses. LNPEP was increased at D15 compared to D10, was immunolocalized in the equine trophectoderm and endoderm, and protein was confirmed by LC-MS/MS. Maximal abundance of OXT was at D21, and lowest on D12 and D14, but no protein was identified. OXTR abundance was highest on D14 and D21. LNPEP was correlated with PTGFR and PTGES on D12 and D14-D15, and high expression of PTGES, PTGS2 was found on D14, D15 and D21; PTGFR was found on D8 and D12-21. LNPEP may have a role in prostaglandin regulation and conceptus fixation by decreasing the availability of oxytocin. Further investigation on the role embryonic LNPEP during pregnancy is warranted.
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Affiliation(s)
- Mariana Diel de Amorim
- Department of Clinical Sciences, Cornell University, 930 Campus Rd, Ithaca, NY 14853, USA
| | - Claudia Klein
- Department of Veterinary Clinical and Diagnostic Science, University of Calgary, 2500 University Drive NW, Calgary, AB T2N 1N4, Canada;
| | - Robert Foster
- Department of Pathobiology, Ontario Veterinary College, University of Guelph, 50 Stone Road E, Guelph, ON N1G 2W1, Canada;
| | - Lynn Dong
- Immunopathology Research and Development Laboratory, Department of Biomedical Sciences, Cornell University, 930 Campus Rd, Ithaca, NY 14853, USA;
| | - Maria Fernanda Lopez-Rodriguez
- Department of Large Animal Clinical Sciences, Western College of Veterinary Medicine, 52 Campus Drive, Saskatoon, SK S7N 5B4, Canada;
| | - Claire Card
- Department of Large Animal Clinical Sciences, Western College of Veterinary Medicine, 52 Campus Drive, Saskatoon, SK S7N 5B4, Canada;
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8
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Domingues RR, Ginther OJ, Gomez-Leon V, Castro T, Wiltbank MC. Endometrial and luteal responses to a prostaglandin F2alpha pulse: A comparison between heifers and mares. Biol Reprod 2022; 106:979-991. [DOI: 10.1093/biolre/ioac025] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/30/2021] [Revised: 12/28/2021] [Accepted: 01/25/2022] [Indexed: 11/13/2022] Open
Abstract
Abstract
In heifers and mares, multiple pulses of prostaglandin F2alpha (PGF) are generally associated with complete luteal regression. Although PGF pulses occur before and during luteolysis, little is known about the role of minor PGF pulses during preluteolysis on subsequent luteal and endometrial PGF production that may initiate luteolysis. Heifers (n = 7/group) and mares (n = 6/group) were treated with a single minor dose of PGF (3.0 and 0.5 mg, respectively) during mid-luteal phase (12 and 10 days postovulation in heifers and mares, respectively). After treatment, a transient decrease in progesterone (P4) concentrations occurred in heifers between Hours 0–2 but at Hour 4 P4 was not different from pre-treatment. In mares, P4 was unaltered between Hours 0 and 4. Concentrations of P4 decreased in both species by Hour 24 and complete luteolysis occurred in mares by Hour 48. Luteal and endometrial gene expression were evaluated 4 hours post-treatment. In heifers, luteal mRNA abundance of PGF receptor and PGF dehydrogenase were decreased while PTGS2, PGF transporter, and oxytocin receptor were increased. In the heifer endometrium, receptors for oxytocin, P4, and estradiol were upregulated. In mares, luteal expression of PGF receptor was decreased while PGF transporter and oxytocin receptor were increased. The decrease in P4 between Hours 4 and 24 and changes in gene expression were consistent with upregulation of endogenous synthesis of PGF. The hypotheses were supported that a single minor PGF treatment upregulates endogenous machinery for PGF synthesis in heifers and mares stimulating endogenous PGF synthesis through distinct regulatory mechanisms in heifers and mares.
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Affiliation(s)
- Rafael R Domingues
- Department of Animal and Dairy Sciences, University of Wisconsin-Madison, Madison, WI, USA
- Endocrinology and Reproductive Physiology Program, University of Wisconsin-Madison, Madison, WI, USA
- Eutheria Foundation, Cross Plains, WI, USA
| | - O J Ginther
- Eutheria Foundation, Cross Plains, WI, USA
- Department of Pathobiological Sciences, School of Veterinary Medicine, University of Wisconsin-Madison, Madison, WI, USA
| | - Victor Gomez-Leon
- Department of Animal and Dairy Sciences, University of Wisconsin-Madison, Madison, WI, USA
- Eutheria Foundation, Cross Plains, WI, USA
| | - Thadeu Castro
- Eutheria Foundation, Cross Plains, WI, USA
- Department of Veterinary Medicine, Universidade Federal Rural do Rio de Janeiro, Seropédica, RJ, Brazil
| | - Milo C Wiltbank
- Department of Animal and Dairy Sciences, University of Wisconsin-Madison, Madison, WI, USA
- Endocrinology and Reproductive Physiology Program, University of Wisconsin-Madison, Madison, WI, USA
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9
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Local embryo-mediated changes in endometrial gene expression during embryo mobility in mares. Theriogenology 2022; 182:78-84. [DOI: 10.1016/j.theriogenology.2022.01.032] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/03/2021] [Revised: 01/26/2022] [Accepted: 01/27/2022] [Indexed: 10/19/2022]
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10
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Spatiotemporal endometrial transcriptome analysis revealed the luminal epithelium as key player during initial maternal recognition of pregnancy in the mare. Sci Rep 2021; 11:22293. [PMID: 34785745 PMCID: PMC8595723 DOI: 10.1038/s41598-021-01785-3] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/22/2021] [Accepted: 11/03/2021] [Indexed: 12/13/2022] Open
Abstract
During the period of maternal recognition of pregnancy (MRP) in the mare, the embryo needs to signal its presence to the endometrium to prevent regression of the corpus luteum and prepare for establishment of pregnancy. This is achieved by mechanical stimuli and release of various signaling molecules by the equine embryo while migrating through the uterus. We hypothesized that embryo's signals induce changes in the endometrial gene expression in a highly cell type-specific manner. A spatiotemporal transcriptomics approach was applied combining laser capture microdissection and low-input-RNA sequencing of luminal and glandular epithelium (LE, GE), and stroma of biopsy samples collected from days 10-13 of pregnancy and the estrous cycle. Two comparisons were performed, samples derived from pregnancies with conceptuses ≥ 8 mm in diameter (comparison 1) and conceptuses ≤ 8 mm (comparison 2) versus samples from cyclic controls. The majority of gene expression changes was identified in LE and much lower numbers of differentially expressed genes (DEGs) in GE and stroma. While 1253 DEGs were found for LE in comparison 1, only 248 were found in comparison 2. Data mining mainly focused on DEGs in LE and revealed regulation of genes related to prostaglandin transport, metabolism, and signaling, as well as transcription factor families that could be involved in MRP. In comparison to other mammalian species, differences in regulation of genes involved in epithelial barrier formation and conceptus attachment and implantation reflected the unique features of equine reproduction at the time of MRP at the molecular level.
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Klein C, Bruce P, Hammermueller J, Hayes T, Lillie B, Betteridge K. Transcriptional profiling of equine endometrium before, during and after capsule disintegration during normal pregnancy and after oxytocin-induced luteostasis in non-pregnant mares. PLoS One 2021; 16:e0257161. [PMID: 34614002 PMCID: PMC8494348 DOI: 10.1371/journal.pone.0257161] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/16/2021] [Accepted: 08/24/2021] [Indexed: 11/17/2022] Open
Abstract
The current study used RNA sequencing to determine transcriptional profiles of equine endometrium collected 14, 22, and 28 days after ovulation from pregnant mares. In addition, the transcriptomes of endometrial samples obtained 20 days after ovulation from pregnant mares, and from non-pregnant mares which displayed and failed to display extended luteal function following the administration of oxytocin, were determined and compared in order to delineate genes whose expressions depend on the presence of the conceptus as opposed to elevated progesterone alone. A mere fifty-five transcripts were differentially expressed between samples collected from mares at Day 22 and Day 28 of pregnancy. This likely reflects the longer-term exposure to a relatively constant, progesterone-dominated environment with little change in factors secreted by the conceptus that would affect endometrial gene expression. The complement system was amongst the canonical pathways significantly enriched in transcripts differentially expressed between Day 14 and Day 22/28 of pregnancy. The expression of complement components 7 and 8 was confirmed using in situ hybridization. The expression of SERPING1, an inhibitor of the complement system, was confirmed by immunohistochemistry. In line with the resumed capacity of the endometrium to produce prostaglandin, prostaglandin G/H synthase 1 was expressed at higher levels at Days 22 and 28 than at Day 14 of pregnancy. Our data suggest that this up-regulation is enhanced by the presence of the conceptus; samples obtained from mares at Day 20 of pregnancy had significantly higher levels of prostaglandin G/H synthase 1 transcript than mares with extended luteal function.
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Affiliation(s)
- Claudia Klein
- Friedrich-Loeffler-Institute, Institute of Farm Animal Genetics, Mariensee, Germany
| | - Phoebe Bruce
- Department of Pathobiology, Ontario Veterinary College, University of Guelph, Guelph, Ontario, Canada
| | - Jutta Hammermueller
- Department of Pathobiology, Ontario Veterinary College, University of Guelph, Guelph, Ontario, Canada
| | - Tony Hayes
- Department of Pathobiology, Ontario Veterinary College, University of Guelph, Guelph, Ontario, Canada
| | - Brandon Lillie
- Department of Pathobiology, Ontario Veterinary College, University of Guelph, Guelph, Ontario, Canada
| | - Keith Betteridge
- Department of Biomedical Sciences, Ontario Veterinary College, University of Guelph, Guelph, Ontario, Canada
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12
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Rebordão MR, Amaral A, Fernandes C, Silva E, Lukasik K, Szóstek-Mioduchowska A, Pinto-Bravo P, Galvão A, Skarzynski DJ, Ferreira-Dias G. Enzymes Present in Neutrophil Extracellular Traps May Stimulate the Fibrogenic PGF 2α Pathway in the Mare Endometrium. Animals (Basel) 2021; 11:ani11092615. [PMID: 34573581 PMCID: PMC8469524 DOI: 10.3390/ani11092615] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/23/2021] [Revised: 09/02/2021] [Accepted: 09/02/2021] [Indexed: 12/23/2022] Open
Abstract
Simple Summary Endometrosis is a fibrotic disease in mare endometrium whose pathological mechanisms remain obscure. Prostaglandin (PG)F2α, despite modulating reproductive physiological processes, may also provoke local pathological collagen deposition (fibrogenesis). Neutrophil extracellular traps (NETs) released during inflammation have been linked to fibrogenesis in several tissues. We have previously shown that enzymes found in NETs increase in vitro collagen production in mare endometrium. In this study, activation of PGF2α-pathway in equine endometrial explants challenged in vitro by enzymes found in NETs is shown. Our results indicate that both endocrine microenvironment (estrous cycle phase) and healthy or pathological conditions of endometrial tissues play an important role in PGF2α-pathway activation. In the endometrium of the follicular phase, we have observed both high production of PGF2α and/or PGF2α receptor gene transcription under the action of enzymes found in NETs, both conditions associated with fibrogenesis in other tissues. Nevertheless, transcription of the PGF2α receptor gene does not appear to be hormone-dependent, albeit their levels seem to be dependent on endometrial category in the mid-luteal phase. This study suggests that enzymes existing in NETs may instigate changes on PGF2α mediators, which may become an additional mechanism of fibrogenesis in mare endometrium. Abstract Endometrosis, a fibrotic disease of mare endometrium, impairs uterine function. Prostaglandins (PG), despite modulating reproductive physiological functions, may also cause local pathological collagen deposition (fibrogenesis). We have previously shown that neutrophil extracellular traps (NETs) may also favor mare endometrosis. The aim of this study was to investigate the effect of enzymes present in NETs on PGF2α-pathway activation. Kenney and Doig’s type I/IIA and IIB/III mare endometria, from follicular phase (FLP) and mid-luteal (MLP) phase, were cultured in vitro in the presence of NETs enzymes (elastase, cathepsin-G or myeloperoxidase). Production of PGF2α (EIA) and transcription (qPCR) of its synthases (PTGS2, AKR1C3) and receptor (PTGFR) genes were evaluated. PGF2α and PTGFR were influenced by endometrial category and estrous cycle phase. In FLP endometrium, NETs enzymes induced both high PGF2α production and/or PTGFR transcription. In MLP type I/IIA tissues, down-regulation of PTGFR transcripts occurred. However, in MLP type IIB/III endometrium, high levels of PTGFR transcripts were induced by NETs enzymes. As PGF2α-pathway activation facilitates fibrogenesis in other tissues, PGF2α may be involved in endometrosis pathogenesis. In the mare, the endocrine microenvironment of healthy and pathological endometrium might modulate the PGF2α pathway, as well as fibrosis outcome on endometrium challenged by NETs enzymes.
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Affiliation(s)
- Maria Rosa Rebordão
- CIISA—Centro de Investigação Interdisciplinar em Sanidade Animal, Faculdade de Medicina Veterinária, Universidade de Lisboa, 1300-477 Lisboa, Portugal; (M.R.R.); (A.A.); (C.F.); (E.S.)
- Polytechnic Institute of Coimbra, College of Agriculture, 3045-601 Coimbra, Portugal;
| | - Ana Amaral
- CIISA—Centro de Investigação Interdisciplinar em Sanidade Animal, Faculdade de Medicina Veterinária, Universidade de Lisboa, 1300-477 Lisboa, Portugal; (M.R.R.); (A.A.); (C.F.); (E.S.)
| | - Carina Fernandes
- CIISA—Centro de Investigação Interdisciplinar em Sanidade Animal, Faculdade de Medicina Veterinária, Universidade de Lisboa, 1300-477 Lisboa, Portugal; (M.R.R.); (A.A.); (C.F.); (E.S.)
| | - Elisabete Silva
- CIISA—Centro de Investigação Interdisciplinar em Sanidade Animal, Faculdade de Medicina Veterinária, Universidade de Lisboa, 1300-477 Lisboa, Portugal; (M.R.R.); (A.A.); (C.F.); (E.S.)
| | - Karolina Lukasik
- Department of Reproductive Immunology and Pathology, Institute of Animal Reproduction and Food Research of PAS, 10-748 Olsztyn, Poland; (K.L.); (A.S.-M.); (A.G.); (D.J.S.)
| | - Anna Szóstek-Mioduchowska
- Department of Reproductive Immunology and Pathology, Institute of Animal Reproduction and Food Research of PAS, 10-748 Olsztyn, Poland; (K.L.); (A.S.-M.); (A.G.); (D.J.S.)
| | - Pedro Pinto-Bravo
- Polytechnic Institute of Coimbra, College of Agriculture, 3045-601 Coimbra, Portugal;
| | - António Galvão
- Department of Reproductive Immunology and Pathology, Institute of Animal Reproduction and Food Research of PAS, 10-748 Olsztyn, Poland; (K.L.); (A.S.-M.); (A.G.); (D.J.S.)
| | - Dariusz J. Skarzynski
- Department of Reproductive Immunology and Pathology, Institute of Animal Reproduction and Food Research of PAS, 10-748 Olsztyn, Poland; (K.L.); (A.S.-M.); (A.G.); (D.J.S.)
| | - Graça Ferreira-Dias
- CIISA—Centro de Investigação Interdisciplinar em Sanidade Animal, Faculdade de Medicina Veterinária, Universidade de Lisboa, 1300-477 Lisboa, Portugal; (M.R.R.); (A.A.); (C.F.); (E.S.)
- Correspondence: ; Tel.: +351-213-652-859
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13
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Swegen A. Maternal recognition of pregnancy in the mare: does it exist and why do we care? Reproduction 2021; 161:R139-R155. [PMID: 33957605 PMCID: PMC8183633 DOI: 10.1530/rep-20-0437] [Citation(s) in RCA: 13] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/05/2020] [Accepted: 04/09/2021] [Indexed: 12/27/2022]
Abstract
Maternal recognition of pregnancy (MRP) is a process by which an early conceptus signals its presence to the maternal system and prevents the lysis of the corpus luteum, thus ensuring a maternal milieu supportive of pregnancy continuation. It is a fundamental aspect of reproductive biology, yet in the horse, the mechanism underlying MRP remains unknown. This review seeks to address some of the controversies surrounding the evidence and theories of MRP in the equine species, such as the idea that the horse does not conform to the MRP paradigm established in other species or that equine MRP involves a mechanical, rather than chemical, signal. The review examines the challenges of studying this particularly clandestine phenomenon along with the new tools in scientific research that will drive this quest forward in coming years, and discusses the value of knowledge gleaned along this path in the context of clinical applications for improving breeding outcomes in the horse industry.
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Affiliation(s)
- Aleona Swegen
- Nuffield Department of Women's and Reproductive Health, University of Oxford, Oxford, UK.,Priority Research Centre for Reproductive Science, University of Newcastle, Callaghan, New South Wales, Australia
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14
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Kalpokas I, Martínez MN, Cavestany D, Perdigón F, Mattos RC, Meikle A. Equine early pregnancy endocrine profiles and ipsilateral endometrial immune cell, gene expression and protein localisation response. Reprod Fertil Dev 2021; 33:410-426. [PMID: 33752795 DOI: 10.1071/rd21001] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/01/2021] [Accepted: 02/12/2021] [Indexed: 12/12/2022] Open
Abstract
We investigated the early effects of the equine embryo on maternal serum concentrations of insulin-like growth factor 1 (IGF1), leptin and adiponectin, uterine immune cells and genes and proteins related to embryo development and the maintenance of pregnancy. Ipsilateral endometrial expression was assessed on Days 7 and 13 after ovulation for the following transcripts: oestrogen receptor ERα (ESR1), progesterone receptor (PGR), progestin and adipoQ receptor family member 5 (PAQR5), oxytocin receptor (OXTR), prostaglandin-endoperoxide synthase 2 (PTGS2), raf-1 proto-oncogene serine/threonine kinase (RAF1), p21-activated kinase 6 (PAK6), fibroblast growth factor family member 9 (FGF9), IGF1 and its receptor (IGF1R), mucin 1 (MUC1), osteopontin (OPN), leptin receptor (LEPR) and adiponectin receptors 1 and 2 (ADIPOR1 and ADIPOR2). Ipsilateral endometrial immunological cell infiltration and immunohistochemical protein localisation were evaluated on Days 7, 10 and 13 after ovulation for ERα, PGR, OXTR, PTGS2, IGF1, IGF1R, IGF2 and MUC1. Serum hormone concentrations were not affected by reproductive status. Pregnancy downregulated ESR1 and PGR mRNA levels, upregulated the expression of all other genes and affected the expression of all genes, except PGR, on Day 7 (compared with eight genes affected at Day 13). Proteins were affected by pregnancy or by its interaction with other variables (day of extraction and endometrial compartment). Pregnant mares had a higher lymphocyte count, which decreased towards Day 13. The effect of pregnancy on leucocytes and proteins was more evident in superficial endometrial compartments. The results of this study suggest that the equine embryo exerts prompt paracrine regulation of critical biological processes.
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Affiliation(s)
- Irene Kalpokas
- Laboratory of Animal Endocrinology and Metabolism, Veterinary Faculty, Montevideo, Uruguay; and Corresponding author.
| | - María Noel Martínez
- Laboratory of Animal Endocrinology and Metabolism, Veterinary Faculty, Montevideo, Uruguay
| | - Daniel Cavestany
- Department of Reproduction, Veterinary Faculty, Montevideo, Uruguay
| | | | | | - Ana Meikle
- Laboratory of Animal Endocrinology and Metabolism, Veterinary Faculty, Montevideo, Uruguay
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15
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Thompson RE, Premanandan C, Pukazhenthi BS, Whitlock BK. A review of in vivo and in vitro studies of the mare endometrium. Anim Reprod Sci 2020; 222:106605. [PMID: 32987223 DOI: 10.1016/j.anireprosci.2020.106605] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/24/2020] [Revised: 09/09/2020] [Accepted: 09/10/2020] [Indexed: 11/29/2022]
Abstract
The inner layer of the uterus, the endometrium, is responsible and necessary for many reproductive functions. Normal reproductive cyclicity, maternal recognition of pregnancy, maternal interaction with the embryo, and interaction of the reproductive tract with pathogens are dependent on the endometrium. Although most studies have been conducted in vivo using live animals, recent advances in in vitro approaches could facilitate future research in a laboratory setting with minimal effect on animals. Many reproductive studies have been performed in vivo and in vitro in equids, but new in vitro methods to study the endometrium of mares remain unexplored. In this review, there is a description of the normal anatomy and physiology of the mare endometrium in vivo, in vitro endometrial cell culture techniques that have been previously described for the mare, and opportunities for future reproductive research using in vitro methods.
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Affiliation(s)
- Riley E Thompson
- Department of Large Animal Clinical Sciences, University of Tennessee, Knoxville, TN, USA; Center for Species Survival, Smithsonian Conservation Biology Institute, Front Royal, VA, USA
| | | | - Budhan S Pukazhenthi
- Center for Species Survival, Smithsonian Conservation Biology Institute, Front Royal, VA, USA.
| | - Brian K Whitlock
- Department of Large Animal Clinical Sciences, University of Tennessee, Knoxville, TN, USA.
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16
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Gibson C, de Ruijter-Villani M, Bauersachs S, Stout TA. Asynchronous Embryo Transfer Followed by Comparative Transcriptomic Analysis of Conceptus Membranes and Endometrium Identifies Processes Important to the Establishment of Equine Pregnancy. Int J Mol Sci 2020; 21:E2562. [PMID: 32272720 PMCID: PMC7177982 DOI: 10.3390/ijms21072562] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/06/2020] [Revised: 04/01/2020] [Accepted: 04/03/2020] [Indexed: 12/27/2022] Open
Abstract
Preimplantation horse conceptuses require nutrients and signals from histotroph, the composition of which is regulated by luteal progesterone and conceptus-secreted factors. To distinguish progesterone and conceptus effects we shortened the period of endometrial progesterone-priming by asynchronous embryo transfer. Day 8 embryos were transferred to synchronous (day 8) or asynchronous (day 3) recipients, and RNA sequencing was performed on endometrium and conceptuses recovered 6 and 11 days later (embryo days 14 and 19). Asynchrony resulted in many more differentially expressed genes (DEGs) in conceptus membranes (3473) than endometrium (715). Gene ontology analysis identified upregulation in biological processes related to organogenesis and preventing apoptosis in synchronous conceptuses on day 14, and in cell adhesion and migration on day 19. Asynchrony also resulted in large numbers of DEGs related to 'extracellular exosome'. In endometrium, genes involved in immunity, the inflammatory response, and apoptosis regulation were upregulated during synchronous pregnancy and, again, many genes related to extracellular exosome were differentially expressed. Interestingly, only 14 genes were differentially expressed in endometrium recovered 6 days after synchronous versus 11 days after asynchronous transfer (day 14 recipient in both). Among these, KNG1 and IGFBP3 were consistently upregulated in synchronous endometrium. Furthermore bradykinin, an active peptide cleaved from KNG1, stimulated prostaglandin release by cultured trophectoderm cells. The horse conceptus thus responds to a negatively asynchronous uterus by extensively adjusting its transcriptome, whereas the endometrial transcriptome is modified only subtly by a more advanced conceptus.
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Affiliation(s)
- Charlotte Gibson
- Department of Clinical Sciences, Faculty of Veterinary Medicine, Utrecht University, 3584CM Utrecht, The Netherlands; (C.G.); (M.d.R.-V.)
| | - Marta de Ruijter-Villani
- Department of Clinical Sciences, Faculty of Veterinary Medicine, Utrecht University, 3584CM Utrecht, The Netherlands; (C.G.); (M.d.R.-V.)
| | - Stefan Bauersachs
- Institute of Veterinary Anatomy, Vetsuisse Faculty Zurich, University of Zurich, 8315 Lindau (ZH), Switzerland;
| | - Tom A.E. Stout
- Department of Clinical Sciences, Faculty of Veterinary Medicine, Utrecht University, 3584CM Utrecht, The Netherlands; (C.G.); (M.d.R.-V.)
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17
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Rapacz-Leonard A, Leonard M, Chmielewska-Krzesińska M, Siemieniuch M, Janowski TE. The oxytocin-prostaglandins pathways in the horse (Equus caballus) placenta during pregnancy, physiological parturition, and parturition with fetal membrane retention. Sci Rep 2020; 10:2089. [PMID: 32034259 PMCID: PMC7005845 DOI: 10.1038/s41598-020-59085-1] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/24/2019] [Accepted: 01/23/2020] [Indexed: 11/18/2022] Open
Abstract
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.
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Affiliation(s)
- Anna Rapacz-Leonard
- Department of Animal Reproduction with Clinic, Faculty of Veterinary Medicine, University of Warmia and Mazury in Olsztyn, Olsztyn, Poland.
| | - Mark Leonard
- University of Warmia and Mazury in Olsztyn, Olsztyn, Poland
| | - Małgorzata Chmielewska-Krzesińska
- Department of Pathophysiology, Forensic Veterinary and Administration, Faculty of Veterinary Medicine, University of Warmia and Mazury in Olsztyn, Olsztyn, Poland
| | - Marta Siemieniuch
- Research Station in Popielno/Department of Immunology and Pathology of Reproduction, Polish Academy of Science, Olsztyn, Poland
| | - Tomasz E Janowski
- Department of Animal Reproduction with Clinic, Faculty of Veterinary Medicine, University of Warmia and Mazury in Olsztyn, Olsztyn, Poland
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18
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Smits K, Gansemans Y, Tilleman L, Van Nieuwerburgh F, Van De Velde M, Gerits I, Ververs C, Roels K, Govaere J, Peelman L, Deforce D, Van Soom A. Maternal Recognition of Pregnancy in the Horse: Are MicroRNAs the Secret Messengers? Int J Mol Sci 2020; 21:ijms21020419. [PMID: 31936511 PMCID: PMC7014256 DOI: 10.3390/ijms21020419] [Citation(s) in RCA: 10] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/29/2019] [Revised: 12/26/2019] [Accepted: 01/07/2020] [Indexed: 01/22/2023] Open
Abstract
The signal for maternal recognition of pregnancy (MRP) has still not been identified in the horse. High-throughput molecular biology at the embryo-maternal interface has substantially contributed to the knowledge on pathways affected during MRP, but an integrated study in which proteomics, transcriptomics and miRNA expression can be linked directly is currently lacking. The aim of this study was to provide such analysis. Endometrial biopsies, uterine fluid, embryonic tissues, and yolk sac fluid were collected 13 days after ovulation during pregnant and control cycles from the same mares. Micro-RNA-Sequencing was performed on all collected samples, mRNA-Sequencing on the same tissue samples and mass spectrometry was conducted previously on the same fluid samples. Differential expression of miRNA, mRNA and proteins showed high conformity with literature and confirmed involvement in pregnancy establishment, embryo quality, steroid synthesis and prostaglandin regulation, but the link between differential miRNAs and their targets was limited and did not indicate the identity of an unequivocal signal for MRP in the horse. Differential expression at the embryo-maternal interface was prominent, highlighting a potential role of miRNAs in embryo-maternal communication during early pregnancy in the horse. These data provide a strong basis for future targeted studies.
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Affiliation(s)
- Katrien Smits
- Department of Reproduction, Obstetrics and Herd Health, Faculty of Veterinary Medicine, Ghent University, Salisburylaan 133, 9820 Merelbeke, Belgium
- Correspondence:
| | - Yannick Gansemans
- Laboratory of Pharmaceutical Biotechnology, Faculty of Pharmaceutical Sciences, Ghent University, Ottergemsesteenweg 460, 9000 Gent, Belgium
| | - Laurentijn Tilleman
- Laboratory of Pharmaceutical Biotechnology, Faculty of Pharmaceutical Sciences, Ghent University, Ottergemsesteenweg 460, 9000 Gent, Belgium
| | - Filip Van Nieuwerburgh
- Laboratory of Pharmaceutical Biotechnology, Faculty of Pharmaceutical Sciences, Ghent University, Ottergemsesteenweg 460, 9000 Gent, Belgium
| | - Margot Van De Velde
- Department of Reproduction, Obstetrics and Herd Health, Faculty of Veterinary Medicine, Ghent University, Salisburylaan 133, 9820 Merelbeke, Belgium
| | - Ilse Gerits
- Department of Reproduction, Obstetrics and Herd Health, Faculty of Veterinary Medicine, Ghent University, Salisburylaan 133, 9820 Merelbeke, Belgium
| | - Cyrillus Ververs
- Department of Reproduction, Obstetrics and Herd Health, Faculty of Veterinary Medicine, Ghent University, Salisburylaan 133, 9820 Merelbeke, Belgium
| | - Kim Roels
- Department of Reproduction, Obstetrics and Herd Health, Faculty of Veterinary Medicine, Ghent University, Salisburylaan 133, 9820 Merelbeke, Belgium
| | - Jan Govaere
- Department of Reproduction, Obstetrics and Herd Health, Faculty of Veterinary Medicine, Ghent University, Salisburylaan 133, 9820 Merelbeke, Belgium
| | - Luc Peelman
- Animal Genetics Lab, Faculty of Veterinary Medicine, Ghent University, Heidestraat 19, 9820 Merelbeke, Belgium
| | - Dieter Deforce
- Laboratory of Pharmaceutical Biotechnology, Faculty of Pharmaceutical Sciences, Ghent University, Ottergemsesteenweg 460, 9000 Gent, Belgium
| | - Ann Van Soom
- Department of Reproduction, Obstetrics and Herd Health, Faculty of Veterinary Medicine, Ghent University, Salisburylaan 133, 9820 Merelbeke, Belgium
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19
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Scaravaggi I, Borel N, Romer R, Imboden I, Ulbrich SE, Zeng S, Bollwein H, Bauersachs S. Cell type-specific endometrial transcriptome changes during initial recognition of pregnancy in the mare. Reprod Fertil Dev 2019; 31:496-508. [PMID: 30253121 DOI: 10.1071/rd18144] [Citation(s) in RCA: 14] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/17/2018] [Accepted: 08/27/2018] [Indexed: 12/11/2022] Open
Abstract
Previous endometrial gene expression studies during the time of conceptus migration did not provide final conclusions on the mechanisms of maternal recognition of pregnancy (MRP) in the mare. This called for a cell type-specific endometrial gene expression analysis in response to embryo signals to improve the understanding of gene expression regulation in the context of MRP. Laser capture microdissection was used to collect luminal epithelium (LE), glandular epithelium and stroma from endometrial biopsies from Day 12 of pregnancy and Day 12 of the oestrous cycle. RNA sequencing (RNA-Seq) showed greater expression differences between cell types than between pregnant and cyclic states; differences between the pregnant and cyclic states were mainly found in LE. Comparison with a previous RNA-Seq dataset for whole biopsy samples revealed the specific origin of gene expression differences. Furthermore, genes specifically differentially expressed (DE) in one cell type were found that were not detectable as DE in biopsies. Overall, this study revealed spatial information about endometrial gene expression during the phase of initial MRP. The conceptus induced changes in the expression of genes involved in blood vessel development, specific spatial regulation of the immune system, growth factors, regulation of prostaglandin synthesis, transport prostaglandin receptors, specifically prostaglandin F receptor (PTGFR) in the context of prevention of luteolysis.
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Affiliation(s)
- Iside Scaravaggi
- Clinic of Reproductive Medicine, Department for Farm Animals, University of Zurich, Winterthurerstrasse 260, 8057 Zurich, Switzerland
| | - Nicole Borel
- Institute of Veterinary Pathology, University of Zurich, Winterthurerstrasse 260, 8057 Zurich, Switzerland
| | - Rebekka Romer
- Clinic of Reproductive Medicine, Department for Farm Animals, University of Zurich, Winterthurerstrasse 260, 8057 Zurich, Switzerland
| | - Isabel Imboden
- Clinic of Reproductive Medicine, Department for Farm Animals, University of Zurich, Winterthurerstrasse 260, 8057 Zurich, Switzerland
| | - Susanne E Ulbrich
- Animal Physiology, Institute of Agricultural Sciences, ETH Zurich, Universitätstrasse 2, 8092 Zurich, Switzerland
| | - Shuqin Zeng
- Clinic of Reproductive Medicine, Department for Farm Animals, University of Zurich, Winterthurerstrasse 260, 8057 Zurich, Switzerland
| | - Heinrich Bollwein
- Clinic of Reproductive Medicine, Department for Farm Animals, University of Zurich, Winterthurerstrasse 260, 8057 Zurich, Switzerland
| | - Stefan Bauersachs
- Clinic of Reproductive Medicine, Department for Farm Animals, University of Zurich, Winterthurerstrasse 260, 8057 Zurich, Switzerland
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20
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Gibson C, de Ruijter-Villani M, Rietveld J, Stout TAE. Amino acid transporter expression in the endometrium and conceptus membranes during early equine pregnancy. Reprod Fertil Dev 2019; 30:1675-1688. [PMID: 29903343 DOI: 10.1071/rd17352] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/05/2017] [Accepted: 05/07/2018] [Indexed: 12/29/2022] Open
Abstract
Maternally derived amino acids (AA) are essential for early conceptus development, and specific transporters enhance histotrophic AA content during early ruminant pregnancy. In the present study we investigated AA transporter expression in early equine conceptuses and endometrium, during normal pregnancy and after induction of embryo-uterus asynchrony. 'Normal' conceptuses and endometrium were recovered on Days 7, 14, 21 and 28 after ovulation. To investigate asynchrony, Day 8 embryos were transferred to recipient mares on Day 8 or Day 3, and conceptuses were recovered 6 or 11 days later. Endometrial expression of AA transporters solute carrier family 38 member 2 (SLC38A2), solute carrier family 1 members 4 and 5 (SLC1A4 and SLC1A5) increased during early pregnancy, whereas solute carrier family 7 member 8 (SLC7A8), solute carrier family 43 member 2 (SLC43A2) and solute carrier family 7 member 1 (SLC7A1) SLC7A8, SLC43A2 and SLC7A1 expression decreased and the expression of solute carrier family 1 member 1(SLC1A1) and solute carrier family 7 member 2 (SLC7A2) was unaffected. In conceptus membranes, most transporters studied were upregulated, either after Day 14 (solute carrier family 7 member 5 - SLC7A5, SLC38A2, SLC1A4, SLC1A5 and SLC7A1) or Day 21 (SLC43A2 and SLC7A2). Asynchronous ET indicated that endometrial SLC1A5, SLC1A1 and SLC7A8 are primarily regulated by conceptus factors and/or longer exposure to progesterone. In conclusion, AA transporters are expressed in early equine conceptus membranes and endometrium in specific spatiotemporal patterns. Because conceptuses express a wider range of transporters than the endometrium, we speculate that the equine yolk sac has recruited AA transporters to ensure adequate nutrient provision during an unusually long preimplantation period.
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Affiliation(s)
- Charlotte Gibson
- Department of Equine Sciences, Faculty of Veterinary Medicine, Utrecht University, Yalelaan 114, 3584CM Utrecht, Netherlands
| | - Marta de Ruijter-Villani
- Department of Equine Sciences, Faculty of Veterinary Medicine, Utrecht University, Yalelaan 114, 3584CM Utrecht, Netherlands
| | - Jolanda Rietveld
- Department of Equine Sciences, Faculty of Veterinary Medicine, Utrecht University, Yalelaan 114, 3584CM Utrecht, Netherlands
| | - Tom A E Stout
- Department of Equine Sciences, Faculty of Veterinary Medicine, Utrecht University, Yalelaan 114, 3584CM Utrecht, Netherlands
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21
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Srikanth K, Park W, Lim D, Lee KT, Jang GW, Choi BH, Ka H, Park JE, Kim JM. Serial gene co-expression network approach to mine biological meanings from integrated transcriptomes of the porcine endometrium during estrous cycle. Funct Integr Genomics 2019; 20:117-131. [PMID: 31396752 DOI: 10.1007/s10142-019-00703-1] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/11/2018] [Revised: 07/03/2019] [Accepted: 07/22/2019] [Indexed: 01/22/2023]
Abstract
The estrous cycle is a complex process regulated by several hormones. To understand the dynamic changes in gene expression that takes place in the swine endometrium during the estrous cycle relative to the day of estrus onset, we performed RNA-sequencing analysis on days 0, 3, 6, 9, 12, 15, and 18, resulting in the identification of 4495 differentially expressed genes (DEGs; Q ≤ 0.05 and |log2FC| ≥ 1) at various phases in the estrous cycle. These DEGs were integrated into multiple gene co-expression networks based on different fold changes and correlation coefficient (R2) thresholds and a suitable network, which included 899 genes (|log2FC| ≥ 2 and R2 ≥ 0.99), was identified for downstream analyses based on the biological relevance of the Gene Ontology (GO) terms enriched. The genes in this network were partitioned into 6 clusters based on the expression pattern. Several GO terms including cell cycle, apoptosis, hormone signaling, and lipid biosynthetic process were found to be enriched. Furthermore, we found 15 significant KEGG pathways, including cell adhesion molecules, cytokine-cytokine receptor signaling, steroid biosynthesis, and estrogen signaling pathways. We identified several genes and GO terms to be stage-specific. Moreover, the identified genes and pathways extend our understanding of porcine endometrial regulation during estrous cycle and will serve as a good resource for future studies.
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Affiliation(s)
- Krishnamoorthy Srikanth
- Animal Genomics and Bioinformatics Division, National Institute of Animal Science, RDA, Wanju, 55365, Republic of Korea
| | - WonCheoul Park
- Animal Genomics and Bioinformatics Division, National Institute of Animal Science, RDA, Wanju, 55365, Republic of Korea
| | - Dajeong Lim
- Animal Genomics and Bioinformatics Division, National Institute of Animal Science, RDA, Wanju, 55365, Republic of Korea
| | - Kyung Tai Lee
- Animal Genetics and Breeding Division, National Institute of Animal Science, RDA, Wanju, 55365, Republic of Korea
| | - Gul Won Jang
- Animal Genomics and Bioinformatics Division, National Institute of Animal Science, RDA, Wanju, 55365, Republic of Korea
| | - Bong Hwan Choi
- Animal Genomics and Bioinformatics Division, National Institute of Animal Science, RDA, Wanju, 55365, Republic of Korea
| | - Hakhyun Ka
- Division of Biological Science and Technology, Yonsei University, Wonju, 26493, Republic of Korea.
| | - Jong-Eun Park
- Animal Genomics and Bioinformatics Division, National Institute of Animal Science, RDA, Wanju, 55365, Republic of Korea.
| | - Jun-Mo Kim
- Department of Animal Science and Technology, Chung-Ang University, Anseong, Gyeonggi-do, 17546, Republic of Korea.
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22
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Silva ESM, Cuervo-Arango J, de Ruijter-Villani M, Klose K, Oquendo PS, Stout TAE. Effect of the duration of estradiol priming prior to progesterone administration on endometrial gene expression in anestrous mares. Theriogenology 2019; 131:96-105. [PMID: 30959441 DOI: 10.1016/j.theriogenology.2019.03.025] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/07/2019] [Revised: 03/25/2019] [Accepted: 03/27/2019] [Indexed: 10/27/2022]
Abstract
Field data indicate that a longer period of estrus prior to ovulation correlates positively with fertility. To test the hypothesis that the duration of exposure to estrogens prior to progesterone dominance influences endometrial function, we used anestrous mares to simulate varying durations of estrus (3 groups of 5 mares): long (LE), short (SE), and no estrus (NE), as determined by the duration of estradiol priming prior to progesterone treatment: 7, 2 and 0 days for the LE, SE and NE, respectively. Endometrial biopsies were recovered 4 days after progesterone administration in all groups for real time quantitative reverse transcription PCR (RT-qPCR) and immunohistochemical analyses. A total of 17 genes believed to contribute to a "receptive endometrium" for embryo development and viability were evaluated by RT-qPCR. Of the genes evaluated, the expression of FGF-2 (fibroblast growth factor-2) decreased with increased length of preceding estrus, whereas P19 (uterocalin) expression was higher in the LE than in the SE or NE groups. In conclusion, a lower abundance of FGF-2 and higher abundance of uterocalin, a lipocalin protein known to play an important role in providing lipids to the embryo, could contribute to a more receptive endometrium in mares following a long estrus.
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Affiliation(s)
| | - Juan Cuervo-Arango
- Department of Equine Sciences, Faculty of Veterinary Medicine, Utrecht University, 3584CM Utrecht, the Netherlands.
| | - Marta de Ruijter-Villani
- Department of Equine Sciences, Faculty of Veterinary Medicine, Utrecht University, 3584CM Utrecht, the Netherlands
| | - Kristin Klose
- Institute of Pathology, Faculty of Veterinary Medicine, University of Leipzig, An den Tierkliniken 33, 04103 Leipzig, Germany
| | | | - Tom A E Stout
- Department of Equine Sciences, Faculty of Veterinary Medicine, Utrecht University, 3584CM Utrecht, the Netherlands
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23
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Proteins involved in embryo-maternal interaction around the signalling of maternal recognition of pregnancy in the horse. Sci Rep 2018; 8:5249. [PMID: 29588480 PMCID: PMC5869742 DOI: 10.1038/s41598-018-23537-6] [Citation(s) in RCA: 39] [Impact Index Per Article: 6.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/10/2017] [Accepted: 03/14/2018] [Indexed: 02/08/2023] Open
Abstract
During maternal recognition of pregnancy (MRP), a conceptus-derived signal leads to the persistence of the corpus luteum and the maintenance of gestation. In the horse, the nature of this signal remains to be elucidated. Several studies have focused on the changes in gene expression during MRP, but little information exists at the protein level. The aim of this study was to identify the proteins at the embryo-maternal interface around signalling of MRP in the horse (day 13) by means of mass spectrometry. A distinct influence of pregnancy was established, with 119 proteins differentially expressed in the uterine fluid of pregnant mares compared to cyclic mares and with upregulation of several inhibitors of the prostaglandin synthesis during pregnancy. By creating an overview of the proteins at the embryo-maternal interface in the horse, this study provides a solid foundation for further targeted studies of proteins potentially involved in embryo-maternal interactions, MRP and pregnancy loss in the horse.
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Effect of side of the corpus luteum and pregnancy on estrogen and progesterone receptor expression and localization in the endometrium of mares. Theriogenology 2017; 114:221-228. [PMID: 29655155 DOI: 10.1016/j.theriogenology.2017.12.034] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/06/2017] [Revised: 12/15/2017] [Accepted: 12/15/2017] [Indexed: 02/06/2023]
Abstract
The effect of side of corpus luteum on uterine gene expression and protein localization of estrogen receptor α (ERα) and progesterone receptor (PR) in healthy cyclic and pregnant mares 13 days after ovulation (day 0) was investigated. Transcervical biopsies were performed to collect endometrium ipsilateral and contralateral regarding the side of corpus luteum on day 13 post-ovulation in cyclic (n = 6) and pregnant (n = 6) mares. Blood samples were collected daily from day 0 until the day of biopsy for 17β-estradiol (E2) and progesterone (P4) determinations. Receptor expression was determined by immunohistochemistry and transcript expression by real time RT-PCR. Serum E2 and P4 concentrations were not affected by reproductive status. The contralateral horn presented higher percentage of positive cells for ERα than the ipsilateral horn (P < .05), but side did not affect PR. ERα showed low staining and no main effect of pregnancy was found, but pregnant mares had lower protein expression of PR (19.8 vs. 40.4 ± 5.3%, P < .01). The contralateral horn tended to present higher expression of ERα mRNA (1.33 vs. 0.97 ± 0.17, P < .10) and PR mRNA (1.96 vs. 1.57 ± 0.52, P < .09). ERα mRNA relative expression was lower in the pregnant group (0.88 vs. 1.44 ± 0.19, P < .05). The interaction of reproductive status and side of corpus luteum tended to affect PR mRNA expression as pregnant mares had a lower PR mRNA content in the ipsilateral horn than cyclic mares. To our knowledge, this is the first study that describes the behavior of steroid receptors in the endometrium of mares regarding side of corpus luteum.
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Swegen A, Grupen CG, Gibb Z, Baker MA, Ruijter‐Villani M, Smith ND, Stout TAE, Aitken RJ. From Peptide Masses to Pregnancy Maintenance: A Comprehensive Proteomic Analysis of The Early Equine Embryo Secretome, Blastocoel Fluid, and Capsule. Proteomics 2017; 17. [DOI: 10.1002/pmic.201600433] [Citation(s) in RCA: 21] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/07/2016] [Revised: 07/19/2017] [Indexed: 01/17/2023]
Affiliation(s)
- Aleona Swegen
- Priority Research Centre in Reproductive Science University of Newcastle Callaghan NSW Australia
| | - Christopher G. Grupen
- Faculty of Veterinary Science School of Life and Environmental Sciences University of Sydney Camden NSW Australia
| | - Zamira Gibb
- Priority Research Centre in Reproductive Science University of Newcastle Callaghan NSW Australia
| | - Mark A. Baker
- Priority Research Centre in Reproductive Science University of Newcastle Callaghan NSW Australia
| | - Marta Ruijter‐Villani
- Department of Equine Sciences Faculty of Veterinary Medicine Utrecht University Utrecht the Netherlands
| | - Nathan D. Smith
- Analytical and Biomolecular Research Facility University of Newcastle Callaghan NSW Australia
| | - Tom A. E. Stout
- Department of Equine Sciences Faculty of Veterinary Medicine Utrecht University Utrecht the Netherlands
| | - R. John Aitken
- Priority Research Centre in Reproductive Science University of Newcastle Callaghan NSW Australia
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Silva E, Ignácio F, Fritsch S, Zanoni D, Pantoja J, Oliveira-Filho J, Meira C. Administration of 2.5 mg of estradiol followed by 1,500 mg of progesterone to anovulatory mares promote similar uterine morphology, hormone concentrations and molecular dynamics to those observed in cyclic mares. Theriogenology 2017; 97:159-169. [DOI: 10.1016/j.theriogenology.2017.04.031] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/20/2016] [Revised: 04/21/2017] [Accepted: 04/21/2017] [Indexed: 12/29/2022]
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Endometrial prostaglandin synthases, ovarian steroids, and oxytocin receptors in mares with oxytocin-induced luteal maintenance. Theriogenology 2017; 87:193-204. [DOI: 10.1016/j.theriogenology.2016.08.028] [Citation(s) in RCA: 17] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/10/2016] [Revised: 08/12/2016] [Accepted: 08/25/2016] [Indexed: 11/22/2022]
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Embryo-maternal communication during the first 4 weeks of equine pregnancy. Theriogenology 2016; 86:349-54. [PMID: 27156682 DOI: 10.1016/j.theriogenology.2016.04.048] [Citation(s) in RCA: 21] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/30/2015] [Revised: 12/15/2015] [Accepted: 03/14/2016] [Indexed: 01/01/2023]
Abstract
The first month of equine pregnancy covers a period of rapid growth and development, during which the single-cell zygote metamorphoses into an embryo with a functional circulation and precursors of many important organs, enclosed within extraembryonic membranes responsible for nutrient uptake and gaseous exchange. After exiting the oviduct, the conceptus must influence uterine physiology to ensure adequate nutrition and preparation for implantation, while continued development results in the chorioallantois superseding the yolk sac as the primary interface for maternal interaction and exchange. Throughout the first month, pregnancy maintenance depends absolutely on progesterone secreted by the primary corpus luteum. However, although extension of luteal life span via maternal recognition of pregnancy is clearly essential, it is still not known how the horse conceptus signals its presence. On the other hand, our understanding of how luteolytic prostaglandin F2α release from the endometrium is averted has improved, and we are increasingly aware of the biological and practical significance of various events characteristic of early horse pregnancy, such as selective oviductal transport, the formation and dissolution of the blastocyst capsule, and prolonged intrauterine conceptus migration. It is also increasingly clear that embryo-maternal dialog during the first month is essential not only to conceptus survival but also has more profound and long-lasting implications. In this latter respect, it is now accepted that the maternal environment (e.g., metabolic or health status) may epigenetically alter gene expression capacity of the developing embryo and thereby permanently influence the health of the resulting foal right through adulthood.
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Kozai K, Tokuyama S, Szóstek AZ, Toishi Y, Tsunoda N, Taya K, Sakatani M, Takahashi M, Nambo Y, Skarzynski DJ, Yamamoto Y, Kimura K, Okuda K. Evidence for a PGF2α auto-amplification system in the endometrium in mares. Reproduction 2016; 151:517-26. [PMID: 26908917 DOI: 10.1530/rep-15-0617] [Citation(s) in RCA: 14] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/28/2014] [Accepted: 02/22/2016] [Indexed: 11/08/2022]
Abstract
In mares, prostaglandin F2α (PGF2α) secreted from the endometrium is a major luteolysin. Some domestic animals have an auto-amplification system in which PGF2α can stimulate its own production. Here, we investigated whether this is also the case in mares. In an in vivo study, mares at the mid-luteal phase (days 6-8 of estrous cycle) were injected i.m. with cloprostenol (250 µg) and blood samples were collected at fixed intervals until 72 h after treatment. Progesterone (P4) concentrations started decreasing 45 min after the injection and continued to decrease up to 24 h (P < 0.05). In turn, 13,14-dihydro-15-keto-PGF2α (PGFM) metabolite started to increase 4h after an injection and continued to increase up to 72 h (P < 0.05). PGF receptor (PTGFR) mRNA expression in the endometrium was significantly higher in the late luteal phase than in the early and regressed luteal phases (P < 0.05). In vitro, PGF2α significantly stimulated (P < 0.05) PGF2α production by endometrial tissues and endometrial epithelial and stromal cells and significantly increased (P < 0.05) the mRNA expression of prostaglandin-endoperoxide synthase-2 (PTGS2), an enzyme involved in PGF2α synthesis in endometrial cell. These findings strongly suggest the existence of an endometrial PGF2α auto-amplification system in mares.
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Affiliation(s)
- Keisuke Kozai
- Laboratory of Reproductive PhysiologyGraduate School of Environmental and Life Science, Okayama University, Okayama, Japan
| | - Shota Tokuyama
- Laboratory of Reproductive PhysiologyGraduate School of Environmental and Life Science, Okayama University, Okayama, Japan
| | - Anna Z Szóstek
- Laboratory of Reproductive PhysiologyGraduate School of Environmental and Life Science, Okayama University, Okayama, Japan Department of Reproductive ImmunologyInstitute of Animal Reproduction and Food Research, Polish Academy of Sciences, Olsztyn, Poland
| | | | | | | | - Miki Sakatani
- Kyushu Okinawa Agricultural Research CenterNational Agriculture and Food Research Organization (NARO), Kumamoto, Japan
| | - Masashi Takahashi
- Kyushu Okinawa Agricultural Research CenterNational Agriculture and Food Research Organization (NARO), Kumamoto, Japan Department of Animal ScienceHokkaido University, Hokkaido, Japan
| | - Yasuo Nambo
- Equine Science DivisionHidaka Training and Research Center, Japan Racing Association, Hokkaido, Japan Obihiro University of Agriculture and Veterinary MedicineObihiro, Japan
| | - Dariusz J Skarzynski
- Department of Reproductive ImmunologyInstitute of Animal Reproduction and Food Research, Polish Academy of Sciences, Olsztyn, Poland
| | - Yuki Yamamoto
- Laboratory of Reproductive PhysiologyGraduate School of Environmental and Life Science, Okayama University, Okayama, Japan
| | - Koji Kimura
- Laboratory of Reproductive PhysiologyGraduate School of Environmental and Life Science, Okayama University, Okayama, Japan
| | - Kiyoshi Okuda
- Laboratory of Reproductive PhysiologyGraduate School of Environmental and Life Science, Okayama University, Okayama, Japan Obihiro University of Agriculture and Veterinary MedicineObihiro, Japan
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Klein C. Pregnancy Recognition and Implantation of the Conceptus in the Mare. ADVANCES IN ANATOMY, EMBRYOLOGY, AND CELL BIOLOGY 2015; 216:165-88. [PMID: 26450499 DOI: 10.1007/978-3-319-15856-3_9] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/13/2022]
Abstract
Few, if any, biological processes are as diverse among domestic species as establishment of early pregnancy, in particular maternal recognition of pregnancy. Following fertilization and initial development in the mare oviduct, selective transport of the embryo through the uterotubal junction driven by embryo-derived PGE2 occurs. Upon arrival in the uterus, an acellular glycoprotein capsule is formed that covers the embryo, blastocyst, and conceptus (embryo and associated extraembryonic membranes) between the second and third weeks of pregnancy. Between Days 9 and 15/16 of pregnancy, the conceptus undergoes an extended phase of mobility. Conceptus mobility is driven by conceptus-derived PGF2α and PGE2 that stimulate uterine contractions which in turn propel migration of the conceptus within the uterine lumen. Cessation of conceptus mobility is referred to as fixation and appears to be attributable to increasing size of the conceptus, preferential thickening of the endometrium near the mesometrial attachment referred to as encroachment, and a reduction in sialic acid content of the capsule. During maternal recognition of pregnancy, endometrial PGF2α release is attenuated, a consequence of reduced expression of key enzymes involved in prostaglandin production. Oxytocin responsiveness is altered during early pregnancy, and reduced expression of the oxytocin receptor appears to be regulated at the posttranscriptional level rather than the transcriptional level. Prostaglandin release is attenuated temporarily only during early pregnancy; during the third week of pregnancy, the endometrium resumes the ability to secrete PGF2α. The equine conceptus initiates steroidogenesis as early as Day 6 and synthesizes estrogens, androgens, and progesterone. Estrogens are metabolized locally, presumably regulating their bioavailability and actions. Results of experiments attempting to prove that conceptus-derived estrogens are responsible for extension of corpus luteum function have been inconclusive. By the fourth week of pregnancy, the chorionic girdle becomes visible on the trophoblast. Subsequent invasion of chorionic girdle cells leads to formation of endometrial cups which secrete equine chorionic gonadotropin. Equine chorionic gonadotropin has luteinizing hormone functions in the mare, causing luteinization of follicles resulting in the formation of secondary corpora lutea essential to production of progesterone and maintenance of pregnancy.
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Affiliation(s)
- Claudia Klein
- Veterinary and Clinical Diagnostic Sciences, Faculty of Veterinary Medicine, University of Calgary, 3280 Hospital Dr NW, Calgary, AB, T2N 4Z6, Canada.
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