Developmental biology in horses involves the study of the processes by which horses grow and develop from a single fertilized egg into a fully formed organism. This field encompasses various stages, including embryonic development, fetal growth, and postnatal maturation. Researchers in this area examine cellular differentiation, gene expression, and morphogenetic movements that contribute to the formation of tissues and organs in equine species. Key topics include the molecular mechanisms that regulate developmental pathways, the influence of genetic and environmental factors on development, and the identification of developmental disorders. This page compiles peer-reviewed research studies and scholarly articles that explore the fundamental aspects of equine developmental biology, offering insights into the mechanisms driving normal and abnormal development in horses.
Normélia P Morais A, Gastal GDA, Aguiar FLN, Hyde KA, Gastal MO, Lima LF, Ñaupas LVS, Flávia B Silva A, Becerra VAB, Gheno L, Curcio BR....Understanding how to effectively isolate a large number of healthy follicles is essential for increasing success rates in ARTs, such as in vitro culture and cryopreservation. Late secondary (preantral) and early tertiary (antral) follicles isolated from the intermediary portion of equine ovarian tissue sliced at two different thicknesses (0.25 mm vs. 0.50 mm) were characterized according to regional distribution (dorsal, medial, and ventral), morphofunctional features, and epigenetic profiles. After isolation via microdissection, follicles were evaluated for membrane integrity (trypan blue), v...
Mendes RP, Gonzaga MS, Matheus MM, Bittar MJ, Doria RGS, Corrêa RR.Developmental and eruption abnormalities are common and can result in progressive dental diseases. Ectopic eruption of the affected tooth may be the result of these processes. This study aims to report the occurrence of a permanent mandibular tooth in a horizontal position, with retention of the corresponding deciduous tooth, in a miniature horse. A 2-year-old female miniature horse was admitted to the veterinary hospital with a hard swelling on the left mandibular ramus, which had been growing continuously for three months. After a complete evaluation, it was concluded that the swelling was t...
Tsopp E, Kilk K, Gambini A, Tvrdà E, Viljaste-Seera A, Tuppits U, Jaakma Ü.Equine in vitro embryo production (IVP) via ovum pick-up (OPU) and intracytoplasmic sperm injection (ICSI) has gained prominence in sport-horse breeding due to high success rates, efficient semen utilization, and year-round embryo production, including from mares with fertility challenges or postmortem. However, assessing viability of early-stage ICSI-produced equine embryos remains challenging due to subjective morphological evaluations and limited visibility of developmental features. Non-invasive metabolomic analysis of culture media offers a promising alternative to enhance embryo selectio...
Verstraete MH, Norris JK, Loux SC, De Spiegelaere W, Carossino M, Daels P, Dini P.The placenta mediates critical interactions between mother and offspring that guide development and impact long-term health. Despite its importance, the cellular organization of the equine (Equus caballus) placenta remains poorly defined. The equine epitheliochorial placenta, characterized by the absence of trophoblast invasion and prominent endocrine activity, provides a unique comparative model for studying placental cellular composition and development. Methods: We applied single-cell RNA sequencing to chorioallantois tissue collected from first-trimester (n = 1) and term (n = 2) equine...
Cortez JV, Cervi D, Ruiz AJ, Grupen CG.Nicotinic acid (NA) treatment during in vitro maturation (IVM) has been shown to elevate nicotinamide adenine dinucleotide (NAD) levels and improve oocyte developmental competence. Suboptimal equine oocyte IVM systems currently limit the efficiency of viable embryo in vitro production. This study evaluated NA supplementation during IVM for cloned equine embryo production, using oocytes from abattoir-sourced ovaries and live mares via ovum pick-up (OPU). Abattoir-derived oocytes (n = 694) were treated without or with 50 or 200 μM NA during the 18 h holding period (Pre-IVM). Next, OPU-deriv...
de Castro Sasahara TH, Gomes SP, Abdala FCM, Schimming BC, Miglino MA.Sexual differentiation in the equine fetus involves coordinated morphogenetic processes that shape both the gonads and the genital ducts. Although the formation of testes and ovaries has been relatively well documented, the temporal dynamics and morphometric patterns of the mesonephric (Wolffian) and paramesonephric (Müllerian) ducts remain insufficiently characterized. This study aimed to detail the timeline of gonadal and ductal differentiation in male and female equine fetuses during the critical developmental window between 60 and 80 days of gestation. Gross anatomical evaluation, histo...
Ver Goltz L, Gomes SP, Schimming BC, Abdala FCM, Miglino MA, de Castro Sasahara TH.The equine ovary exhibits unique structural and developmental features that distinguish it from those of other domestic species, including the presence of an ovulation fossa and an inversion of cortical and medullary layers. This study aimed to investigate the morphostructural development of the equine fetal ovary, with particular emphasis on the formation of the ovulation fossa. Fourteen female equine fetuses, ranging from 70 to 200 days of gestation, were collected from a commercial abattoir. Results revealed a progressive increase in ovarian volume and marked histological changes througho...
Bertuglia A, Cantatore F, Pallante M, Manassero L, Bergamini L, Riccio B, Pagliara E.To report the incidence, and clinical and pathological findings of developmental lateral patellar luxation in Standardbred yearlings diagnosed with femoropatellar dysplasia (FPD) and demonstrate that osteochondral lesions in the lateral trochlear ridge (LTR) of the femur observed in the affected horses are osteochondral lesions related to patellar maltracking.Retrospective case series. Medical records were retrospectively reviewed for Standardbreds <12 months of age diagnosed with FPD between 2017 and 2023.A total of 10 Standardbred yearlings developed FPD (incidence 6.4 cases per 1,000 foals)...
Liu J, Yang Y, Wen L, Wen M, Zeng Y, Ren W, Yao X.The Kazakh horse is an outstanding dual-purpose dairy and meat breed in China, characterized by early maturity, tolerance to coarse feed, and strong stress resistance. Previous studies have examined gene expression patterns in the testicular tissues of Kazakh horses at different age stages, but the molecular mechanisms regulating testicular sexual maturation remain unclear. To address this gap, this study conducted HE staining and in-depth transcriptome sequencing analysis of Kazakh horse testicular tissue before and after sexual maturity. HE staining showed that the G3 group had well-formed s...
Liu X, Liu A, Khan MZ, Zhu Q, Zheng Y, Chen W, Cai B, Yan Z, Peng Y, Wang C.The gene family plays an indispensable role in regulating embryonic development, cell differentiation, and morphogenesis. This study employed bioinformatics approaches for systematic analysis, ultimately identifying 33 gene family members from the donkey genome. Physicochemical property analysis revealed that the number of amino acids encoded ranged from 94 to 444, with 31 members classified as alkaline proteins. Their secondary structure was predominantly composed of random coils and alpha helices, and all members were localized to the nucleus. Conserved motif analysis further demonstrated ...
Feng M, Hall TJ, MacHugh DE, Katz LM, Hill EW.Early skeletal muscle development is critical for young racehorses, yet research on the transcriptional changes during this period is limited. Additionally, the impact of age on the transcriptional response to exercise training in equine athletes is not well understood. A transcriptome-wide analysis of differential gene expression in skeletal muscle was performed for five untrained Thoroughbred horses sampled at rest at two years old (UR2) and three years old (UR3). A total of 136 differentially expressed genes (DEGs) were identified, with 95 increased and 41 decreased in expression. GO enrich...
Gugole PM, Zannoni A, Iacono E, Merlo B.Cryopreservation of equine mature oocytes remains a major challenge in assisted reproduction, mainly due to the limited availability of material and logistical constraints requiring a holding phase. To address these issues, this study evaluated whether naloxone (NX), an opioid receptor antagonist with reported antioxidant properties, could improve vitrification outcomes and whether bovine oocytes could serve as a suitable preliminary and supportive model. Two experiments were conducted. In experiment 1, immature (bGV) and mature (bMII) bovine oocytes were vitrified without (VIT) or with NX (VI...
Kawamura N, Sakamoto M, Hashimoto C, Ozeki Y, Machida K.Children with autism spectrum disorder (ASD) often experience challenges in social communication, behavioral regulation, and daily life adaptation. Equine-assisted activities and therapies (EAATs) have been implemented as complementary approaches to support psychosocial development. However, little is known about the experiences of parents in Japan whose children participate in EAATs. Unassigned: The study aims to qualitatively explore how parents in Japan perceive the psychosocial outcomes of EAATs for their children with ASD. By focusing on parental perspectives, this study seeks to clarify ...
Broothaers K, Jouneau A, Angel-Velez D, De Coster T, Festuccia N, Archilla C, Calderari S, Jouneau L, Van den Branden E, Peere S, Polfliet E....In vitro production of equine embryos has been performed using intracytoplasmic sperm injection (ICSI) for the last two decades. Since 2022, a repeatable protocol for conventional in vitro fertilization (IVF) provides a successful alternative. However, little is known about the influence of the fertilization method on embryo quality and the transcriptomic profile. In this study, we aimed to examine differentially expressed genes (DEGs) between ICSI and IVF embryos in the horse. Therefore, ten equine sibling blastocysts, produced in vitro by either ICSI or IVF from three different mares, were s...
Barrachina L, Ivanovska A, Eslami Arshaghi T, O'Brien A, Cequier A, Murphy M, Hollinshead F, Rodellar C, Barry F.Regenerative therapies are quickly expanding to application in equine patients because of their importance as sporting and companion animals. Furthermore, aligning with a One Health concept, veterinary medicine offers a unique platform for preclinical studies. While mesenchymal stem/stromal cells (MSCs) therapies are already used in treating horses, strategies involving induced pluripotent stem cells (iPSCs) are poorly developed. iPSCs present great potential for therapy and disease modelling, but their consistent generation in horses requires further investigation into the source of somatic c...
Riahi Z, Naeini AT, Zare R.Dareshuri horses are the predominant breed in Fars Province, Iran. Although disorders affecting their maxillary cheek teeth and maxillary sinuses are relatively common, limited fundamental data are available on the dimensions and relationships of these structures at different ages. Given the significant anatomical changes in the heads of young horses as they mature, this study aimed to evaluate age-related changes in the position and anatomical relationships of individual maxillary cheek teeth within the rostral and caudal maxillary sinuses (RMS and CMS, respectively), as well as changes in th...
Cullen JN, Cieslak J, Petersen JL, Bellone RR, Finno CJ, Kalbfleisch TS, Calloe K, Capomaccio S, Cappelli K, Coleman SJ, Distl O, Durward-Akhurst SA....MicroRNAs (miRNAs) are essential regulators of gene expression, yet few comprehensive databases exist for miRNA expression in non-model species, limiting our ability to characterize their roles in gene regulation, development, and disease. Similarly, isomiRs - length and sequence isoforms of canonical miRNAs with potentially altered regulatory targets and functions - have received even less attention in non-model species, including the horse, leaving a critical gap in our understanding of their biological significance. To address these challenges, we developed an open-source, containerized pip...
Mouncey R, de Mestre AM, Arango-Sabogal JC, Verheyen KL.Gestational and early-life exposures may modulate development during growth and influence future athletic performance. Objective: To investigate associations between gestational and early-life exposures in Thoroughbreds and (i) likelihood of racing, (ii) total number of runs and (iii) total prizemoney by the end of the 3-year-old year. Methods: Prospective cohort. Methods: Daily records were kept on the location and duration of turnout, management and veterinary-attended episodes of disease or injury from birth until leaving the farm or study exit for 129 Thoroughbred foals on six stud farms. ...
Martínez Moreno CM, Hernández Garre JM, Echevarría Pérez P, Morales Moreno I, Vegue Parra E, Valero Merlos E.: This study examines the effectiveness of equine-assisted intervention (EAI) in improving adaptive behaviour and motor skills in children with autism spectrum disorder (ASD). : To that effect, a self-controlled experimental analytical study has been designed, which is longitudinal and prospective in nature, with pre- and post-intervention measures, using the Vineland Adaptive Behavior Scale II (VABS-II) as the assessment instrument. The sample consists of 19 children who participated in weekly therapeutic sessions involving horses for eight months; these sessions included horseback riding, gr...
Bazvand B, Rashidi A, Zandi MB, Moradi MH, Rostamzadeh J, Mahmoudi P.Iran is home to genetically distinct horse breeds shaped by geography and history. Breeds like the Kurdish, Caspian pony, and Turkmen reflect deep-rooted diversity and unique adaptive traits. Objective: This study aimed to identify genomic regions exhibiting signatures of selection and to detect candidate genes and biological pathways related to body size that may influence performance in various Iranian and exotic horse breeds. Methods: Samples were collected from three Iranian native breeds (Caspian pony, Turkmen, and Kurdish) and three exotic breeds (Fell pony, Arabian, and Akhal-Teke) orig...
Cortez JV, Hardwicke K, Méndez-Calderón CE, Grupen CG.The asynchrony of cytoplasmic and nuclear maturation in cumulus-oocyte complexes (COCs) due to prematurely declining concentrations of cyclic adenosine monophosphate (cAMP) has been shown to result in reduced oocyte developmental competence. The objective of this study was to evaluate the effect of pre-IVM treatment with cAMP modulators for different durations on the developmental potential of equine oocytes used for cloned embryo production. Collected COCs were transferred to cryovials filled with transport medium at 20-22 °C. Within the cryovials, the COCs were either untreated (Control) fo...
Koch DW.Our understanding of tendon homeostasis and repair following injury has made great strides through basic science, clinical veterinary medicine, and preclinical translational research. We have now gleaned a greater understanding of the cellular and matrix dynamics that are being orchestrated within the tendon, which provide therapeutic opportunities. This article will focus on how utilizing the horse and equine tissues have advanced our understanding of tendinopathy and the cellular and matrix dynamics at play while also identifying continued gaps in our knowledge where the horse as a veterinar...
Ishimaru M, Kume K, Murase H, Sato F, Matsui A, Ohmura H, Taya K.Thoroughbreds born early in the year are believed to have an advantage in racing. However, the development of endocrine functions in early-born foals in the cold winter climate is unclear. The present study was conducted to elucidate the effect of birth month on the development of endocrine function in Thoroughbred foals born from February to May in Hokkaido by comparing hypothalamic-pituitary axis, adrenal and thyroid functions from birth to 24 weeks of age. Eighty-seven Thoroughbred foals were used to compare the changes in circulating luteinizing hormone (LH), follicle-stimulating hormone (...
Bouquet A, Nicol C, Díez-León M.The natural behaviour of wood-chewing (WC) in horses may, under certain conditions, become excessive or it may precede crib-biting . However, the potential causes of WC, including frustrated foraging motivation) or developmental exploratory or teething behavior are poorly understood. We studied WC in 31 mares and their foals, examining associations with browsing access, stocking density, foal sex and performance of other non-nutritive oral behaviors. Behaviors (counts/hour) were recorded by all-occurrences sampling during focal, continuous observations of grazing,resting and suckling for 20 ...
Martinez-Saez L, Marín-García PJ, Llobat ML.Osteochondrosis (OC) is a frequent manifestation of developmental orthopaedic disease, and its severe clinical presentation is known as OC dissecans (OCD). OC is defined as a disruption of the endochondral ossification process in the epiphyseal cartilage, and this disease has been reported in different mammalian species, including humans, dogs, pigs, and horses. OCD is an important cause of lameness in sport horses and is a common cause of impaired orthopaedic potential, whose clinical signs may be of minimal magnitude or manifest as severe joint effusion or clinically noticeable lameness. The...
Trauner AM, McCoski SR, Satterfield MC, Bradbery AN.Reproductive health of male offspring following perturbations in maternal nutrition is not well-described in the horse; therefore, the objective of this study was to determine the effects of maternal overnutrition on neonatal foal testicular development. Sixteen Quarter Horse mares were used in a completely randomized design and stratified by expected foaling date, body weight, and body condition score into 1 of 2 dietary treatments beginning on gestational day 235: control (CON; n = 8) fed to meet nutrient requirements and overfed (HIGH; n = 8) fed 40% above CON. At 5 h postpartum, f...
Dubeibe-Marin DF, Borraez DF, Gomez-López DL, Velasco-Acosta DA.This study evaluated the effect of the presence and location of the corpus luteum (CL) on quantity and competence of equine cumulus-oocyte complexes (COCs). Pairs of ovaries were collected at the slaughterhouse and classified into three groups: ovaries with CL (CL+); ovaries with CL in the contralateral ovary (CL-) and ovaries without a CL (NCL). Were evaluated COC quantity, morphology, nuclear maturation rate, and intrafollicular progesterone concentration and gene expression (BAX, BMP-15, ODC1, GDF9, AURKA) in both cumulus cells and oocytes after in vitro maturation. Results showed a lower r...
Son JK, De Paz P, Kim J, Sanaei R, Ryu S, Bailey S, Davies HMS.Changes in the third metacarpal (MC3) mid-diaphyseal dimensions were measured radiographically in young Thoroughbred racehorses through race training and found to be associated with a higher risk of shin soreness. However, it is still unclear whether such negative MC3 morphologies are set congenitally or through development. Objective: To quantify MC3 bone dimensional changes through growth. Methods: Longitudinal. Methods: Twenty privately owned Thoroughbred foals were radiographed bimonthly from birth to 14 months of age. Four linear MC3 parameters (proximodistal MC3 length, mid-diaphyseal do...
Andersson LS, Larhammar M, Memic F, Wootz H, Schwochow D, Rubin CJ, Patra K, Arnason T, Wellbring L, Hjälm G, Imsland F, Petersen JL, McCue ME....Locomotion in mammals relies on a central pattern-generating circuitry of spinal interneurons established during development that coordinates limb movement. These networks produce left-right alternation of limbs as well as coordinated activation of flexor and extensor muscles. Here we show that a premature stop codon in the DMRT3 gene has a major effect on the pattern of locomotion in horses. The mutation is permissive for the ability to perform alternate gaits and has a favourable effect on harness racing performance. Examination of wild-type and Dmrt3-null mice demonstrates that Dmrt3 is exp...
Furukawa S, Kuroda Y, Sugiyama A.The primary function of the placenta is to act as an interface between the dam and fetus. The anatomic structure of the chorioallantoic placenta in eutherian mammals varies between different animal species. The placental types in eutherian mammals are classified from various standpoints based on the gross shape, the histological structure of the materno-fetal interface, the type of materno-fetal interdigitation, etc. Particularly, the histological structure is generally considered one of the most useful and instructive classifications for functionally describing placental type. In this system,...
Yu L, Wei Y, Sun HX, Mahdi AK, Pinzon Arteaga CA, Sakurai M, Schmitz DA, Zheng C, Ballard ED, Li J, Tanaka N, Kohara A, Okamura D, Mutto AA, Gu Y....Dynamic pluripotent stem cell (PSC) states are in vitro adaptations of pluripotency continuum in vivo. Previous studies have generated a number of PSCs with distinct properties. To date, however, no known PSCs have demonstrated dual competency for chimera formation and direct responsiveness to primordial germ cell (PGC) specification, a unique functional feature of formative pluripotency. Here, by modulating fibroblast growth factor (FGF), transforming growth factor β (TGF-β), and WNT pathways, we derived PSCs from mice, horses, and humans (designated as XPSCs) that are permissive for dire...
Nagy K, Sung HK, Zhang P, Laflamme S, Vincent P, Agha-Mohammadi S, Woltjen K, Monetti C, Michael IP, Smith LC, Nagy A.The domesticated horse represents substantial value for the related sports and recreational fields, and holds enormous potential as a model for a range of medical conditions commonly found in humans. Most notable of these are injuries to muscles, tendons, ligaments and joints. Induced pluripotent stem (iPS) cells have sparked tremendous hopes for future regenerative therapies of conditions that today are not possible to cure. Equine iPS (EiPS) cells, in addition to bringing promises to the veterinary field, open up the opportunity to utilize horses for the validation of stem cell based therapi...
Cooper KL, Sears KE, Uygur A, Maier J, Baczkowski KS, Brosnahan M, Antczak D, Skidmore JA, Tabin CJ.A reduction in the number of digits has evolved many times in tetrapods, particularly in cursorial mammals that travel over deserts and plains, yet the underlying developmental mechanisms have remained elusive. Here we show that digit loss can occur both during early limb patterning and at later post-patterning stages of chondrogenesis. In the 'odd-toed' jerboa (Dipus sagitta) and horse and the 'even-toed' camel, extensive cell death sculpts the tissue around the remaining toes. In contrast, digit loss in the pig is orchestrated by earlier limb patterning mechanisms including downregulation of...
Schroeder DI, Jayashankar K, Douglas KC, Thirkill TL, York D, Dickinson PJ, Williams LE, Samollow PB, Ross PJ, Bannasch DL, Douglas GC, LaSalle JM.Over the last 20-80 million years the mammalian placenta has taken on a variety of morphologies through both divergent and convergent evolution. Recently we have shown that the human placenta genome has a unique epigenetic pattern of large partially methylated domains (PMDs) and highly methylated domains (HMDs) with gene body DNA methylation positively correlating with level of gene expression. In order to determine the evolutionary conservation of DNA methylation patterns and transcriptional regulatory programs in the placenta, we performed a genome-wide methylome (MethylC-seq) analysis of hu...
Ezashi T, Yuan Y, Roberts RM.This review deals with the latest advances in the study of embryonic stem cells (ESC) and induced pluripotent stem cells (iPSC) from domesticated species, with a focus on pigs, cattle, sheep, goats, horses, cats, and dogs. Whereas the derivation of fully pluripotent ESC from these species has proved slow, reprogramming of somatic cells to iPSC has been more straightforward. However, most of these iPSC depend on the continued expression of the introduced transgenes, a major drawback to their utility. The persistent failure in generating ESC and the dependency of iPSC on ectopic genes probably s...
Rathi R, Honaramooz A, Zeng W, Turner R, Dobrinski I.Grafting of testis tissue from immature animals to immunodeficient mice results in complete spermatogenesis, albeit with varying efficiency in different species. The objectives of this study were to investigate if grafting of horse testis tissue would result in spermatogenesis, and to assess the effect of exogenous gonadotropins on xenograft development. Small fragments of testis tissue from 7 colts (2 week to 4 years of age) were grafted under the back skin of castrated male immunodeficient mice. For 2 donor animals, half of the mice were treated with gonadotropins. Xenografts were analyzed a...
Das PJ, McCarthy F, Vishnoi M, Paria N, Gresham C, Li G, Kachroo P, Sudderth AK, Teague S, Love CC, Varner DD, Chowdhary BP, Raudsepp T.Mature mammalian sperm contain a complex population of RNAs some of which might regulate spermatogenesis while others probably play a role in fertilization and early development. Due to this limited knowledge, the biological functions of sperm RNAs remain enigmatic. Here we report the first characterization of the global transcriptome of the sperm of fertile stallions. The findings improved understanding of the biological significance of sperm RNAs which in turn will allow the discovery of sperm-based biomarkers for stallion fertility. The stallion sperm transcriptome was interrogated by analy...
Imsland F, McGowan K, Rubin CJ, Henegar C, Sundström E, Berglund J, Schwochow D, Gustafson U, Imsland P, Lindblad-Toh K, Lindgren G, Mikko S....Dun is a wild-type coat color in horses characterized by pigment dilution with a striking pattern of dark areas termed primitive markings. Here we show that pigment dilution in Dun horses is due to radially asymmetric deposition of pigment in the growing hair caused by localized expression of the T-box 3 (TBX3) transcription factor in hair follicles, which in turn determines the distribution of hair follicle melanocytes. Most domestic horses are non-dun, a more intensely pigmented phenotype caused by regulatory mutations impairing TBX3 expression in the hair follicle, resulting in a more circu...
Breton A, Sharma R, Diaz AC, Parham AG, Graham A, Neil C, Whitelaw CB, Milne E, Donadeu FX.Pluripotent stem cells offer unprecedented potential not only for human medicine but also for veterinary medicine, particularly in relation to the horse. Induced pluripotent stem cells (iPSCs) are particularly promising, as they are functionally similar to embryonic stem cells and can be generated in vitro in a patient-specific manner. In this study, we report the generation of equine iPSCs from skin fibroblasts obtained from a foal and reprogrammed using viral vectors coding for murine Oct4, Sox2, c-Myc, and Klf4 sequences. The reprogrammed cell lines were morphologically similar to iPSCs rep...
Asher RJ, Bennett N, Lehmann T.An unprecedented level of confidence has recently crystallized around a new hypothesis of how living placental mammals share a pattern of common descent. The major groups are afrotheres (e.g., aardvarks, elephants), xenarthrans (e.g., anteaters, sloths), laurasiatheres (e.g., horses, shrews), and euarchontoglires (e.g., humans, rodents). Compared with previous hypotheses this tree is remarkably stable; however, some uncertainty persists about the location of the placental root, and (for example) the position of bats within laurasiatheres, of sea cows and aardvarks within afrotheres, and of der...
Saito S, Ugai H, Sawai K, Yamamoto Y, Minamihashi A, Kurosaka K, Kobayashi Y, Murata T, Obata Y, Yokoyama K.Embryonic stem (ES) cells are pluripotent cells with the potential capacity to generate any type of cell. We describe here the isolation of pluripotent ES-like cells from equine blastocysts that have been frozen and thawed. Our two lines of ES-like cells (E-1 and E-2) appear to maintain a normal diploid karyotype indefinitely in culture in vitro and to express markers that are characteristic of ES cells from mice, namely, alkaline phosphatase, stage-specific embryonic antigen-1, STAT-3 and Oct 4. After culture of equine ES-like cells in vitro for more than 17 passages, some ES-like cells diffe...
Iqbal K, Chitwood JL, Meyers-Brown GA, Roser JF, Ross PJ.Formation of the inner cell mass (ICM) and trophectoderm (TE) marks the first differentiation event in mammalian development. These two cell types have completely divergent fates for the remainder of the developmental process. The molecular mechanisms that regulate ICM and TE formation are poorly characterized in horses. The objective of this study was to establish the transcriptome profiles of ICM and TE cells from horse blastocysts using RNA sequencing (RNA-seq). A total of 12 270 genes were found to be expressed in either lineage. Global analysis of the transcriptome profiles by unsupervi...
Galli C, Colleoni S, Duchi R, Lagutina I, Lazzari G.Development of assisted reproductive technologies in horses has been relatively slow compared to other domestic species, namely ruminants and pigs. The scarce availability of abattoir ovaries and the lack of interest from horse breeders and breed associations have been the main reasons for this delay. Progressively though, the technology of oocyte maturation in vitro has been established followed by the application of ICSI to achieve fertilization in vitro. Embryo culture was initially performed in vivo, in the mare oviduct or in the surrogate sheep oviduct, to achieve the highest embryo devel...
Riggs CM, Lanyon LE, Boyde A.A novel technique for determining the collagen fibre orientation pattern of cross-sections of cortical bone was used to study mid-diaphyseal sections from the equine radius. Several in vivo strain gauge studies have demonstrated that this bone is loaded in bending during locomotion in such a way that the cranial cortex is consistently subjected to longitudinal tensile strains and the caudal cortex to longitudinal compressive strains. Twenty-three radii from 17 horses were studied. All the bones obtained from adult horses exhibited a consistent pattern of collagen fibre orientation across the c...
Li X, Zhou SG, Imreh MP, Ahrlund-Richter L, Allen WR.Inner cell mass (ICM) cells were isolated immunosurgically from day 7-8 horse blastocysts and, after proliferation in vitro for 15-28 passages, three lines of cells were confirmed to be embryonic stem (ES) cells by their continued expression of alkaline phosphatase activity and their ability to bind antisera specific for the recognized stem cell markers, SSEA-1, TRA-1-60, TRA-1-81, and the key embryonic gene Oct-4. When maintained under feeder cell-free conditions in vitro, the three lines of cells differentiated into cells of ectodermal, endodermal, and mesodermal lineages. However, they did ...
Whitworth DJ, Ovchinnikov DA, Sun J, Fortuna PR, Wolvetang EJ.In this study we have reprogrammed dermal fibroblasts from an adult female horse into equine induced pluripotent stem cells (equiPSCs). These equiPSCs are dependent only on leukemia inhibitory factor (LIF), placing them in striking contrast to previously derived equiPSCs that have been shown to be co-dependent on both LIF and basic fibroblast growth factor (bFGF). These equiPSCs have a normal karyotype and have been maintained beyond 60 passages. They possess alkaline phosphatase activity and express eqNANOG, eqOCT4, and eqTERT mRNA. Immunocytochemistry confirmed that they produce NANOG, REX1,...
Betteridge KJ, Eaglesome MD, Mitchell D, Flood PF, Beriault R.Forty nine embryos, twenty unfertilized eggs and five other fresh eggs of 'doubtful' status have been recovered from 58 pony mares in 122 flushes up to 22 days after ovulation. The fresh egg or embryo recovery rate was 78% with surgical methods (or at slaughter) and 40-60% with non-surgical methods of recovery. The fertilization rate was about 70%. It has been confirmed that horse embryos normally enter the uterus as blastocysts 5-6 days after ovulation. Three features of early embryo morphology have become clearer upon comparison with unfertilized eggs of similar ages; early embryos are often...
Allen WR, Stewart F.A tough, elastic glycoprotein capsule envelops the equine blastocyst between Days 6 and 23 after ovulation. It maintains the spherical configuration of, and provides physical support for, the embryo as it traverses the entire uterine lumen during Days 6-17, propelled by myometrial contractions that are stimulated by pulsatile release of prostaglandin F2alpha and prostaglandin E2. The capsule also accumulates constituents of the exocrine secretions of the endometrial glands ('uterine milk') as nutrients for the mobile embryo as it releases its antiluteolytic maternal recognition-of-pregnancy si...
Hoffman LH, Wooding FB.The cellular origin, structure, and function of trophoblastic giant cells (GC) and binucleate cells (BNC) are reviewed. Mammals in which these cells have received the greatest attention include rodents, rabbits, and humans (GCs), and ruminants and equids (BNCs). In almost all cases these cells arise from the cytotrophoblast. All are large cells and contain either two diploid nuclei (BNCs), multiple nuclei (human placental bed GCs), or single nuclei with amplified DNA content (rodent and rabbit GCs). Giant and binucleate cells typically exhibit the capacity for migration or invasion, although t...
Wilsher S, Allen WR.The normality of equine placentation is essential for fetal health and development. Substantial information exists on the gross morphological status of the placenta but few studies have addressed the problem of degenerative lesions that interfere with placental morphology and placental efficiency. Objective: Degenerative changes in the endometrium with increasing age and parity are reflected in the morphology and density of the placental microcotyledons. Objective: To assess placental efficiency on the basis of foal birthweight as a function of total microscopic area of fetomaternal contact. M...
Wang X, Miller DC, Clark AG, Antczak DF.In eutherian mammals, dosage compensation of X-linked genes is achieved by X chromosome inactivation. X inactivation is random in embryonic and adult tissues, but imprinted X inactivation (paternal X silencing) has been identified in the extra-embryonic membranes of the mouse, rat, and cow. Few other species have been studied for this trait, and the data from studies of the human placenta have been discordant or inconclusive. Here, we quantify X inactivation using RNA sequencing of placental tissue from reciprocal hybrids of horse and donkey (mule and hinny). In placental tissue from the equid...
Guest DJ, Allen WR.Embryonic stem-like (ES-like) cells have now been derived from the inner cell mass (ICM) of horse embryos at the blastocyst stage. Because they have been shown to express cell-surface antigens found in both human and mouse ES cells, the present study investigated gene expression patterns in day-7 horse blastocysts from which the horse ES-like cells had been derived originally. The genes studied included Oct-4, stage-specific embryonic antigen-1 (SSEA-1), SSEA-3, SSEA-4, tumor rejection antigen-1-60 (TRA-1-60), TRA-1-81, and alkaline phosphatase activity, and whereas all three of the SSEA antig...
Marck A, Berthelot G, Foulonneau V, Marc A, Antero-Jacquemin J, Noirez P, Bronikowski AM, Morgan TJ, Garland T, Carter PA, Hersen P, Di Meglio JM....Locomotion is one of the major physiological functions for most animals. Previous studies have described aging mechanisms linked to locomotor performance among different species. However, the precise dynamics of these age-related changes, and their interactions with development and senescence, are largely unknown. Here, we use the same conceptual framework to describe locomotor performances in Caenorhabditis elegans, Mus domesticus, Canis familiaris, Equus caballus, and Homo sapiens. We show that locomotion is a consistent biomarker of age-related changes, with an asymmetrical pattern througho...
Allen WR.The equine embryo takes 6 days to traverse the oviduct and, when it finally enters the uterus, it remains spherical in shape and moves continually throughout the uterine lumen until day 17 after ovulation to deliver its maternal recognition of pregnancy signal to the entire endometrium. Between day 25 and day 35 after ovulation, the trophoblast cells of a discrete annulate portion of the chorion multiply rapidly and acquire an invasive phenotype and, between day 36 and day 38, migrate deeply into the maternal endometrium to form the equine-unique endometrial protuberances known as endometrial ...
Carter AM, Enders AC.Epitheliochorial placentation is a derived condition and has evolved separately in strepsirrhine primates and laurasiatherians (pangolins, whales, and hoofed mammals). Usually it is associated with a long gestation period, small litters, and precocial young. Oxygen transfer is facilitated by indenting of the uterine and trophoblast epithelia by maternal and fetal capillaries, respectively. Histotrophic nutrition is important, and adaptations include areolas and hemophagous regions. In pigs and horses, for example, iron is transported as uteroferrin secreted from the uterine glands and taken up...
