The Fate of Autologous Endometrial Mesenchymal Stromal Cells After Application in the Healthy Equine Uterus

In-utero transfer of decidualized endometrial stromal cells increases the frequency of regulatory T cells and normalizes the abortion rate in the CBA/J × DBA/2 abortion model

Introduction

Failure to adequate decidualization leads to adverse pregnancy outcomes including pregnancy loss. Although there are plenty of reports underscoring immune dysfunction as the main cause of abortion in CBA/J females mated with DBA/2 males (CBA/J × DBA/2), little is known about the potential role of impaired endometrial decidualization.

Methods

Endometrial stromal cells (ESCs) from CBA/J mice were in-vitro decidualized, and the proteome profile of the secretome was investigated by membrane-based array. CBA/J mice were perfused In-utero with either decidualized ESCs (C×D/D), undecidualized ESCs (C×D/ND), or PBS (C×D/P) 12 days before mating with DBA/2 males. Control mice were not manipulated and were mated with male DBA/2 (C×D) or Balb/c (C×B) mice. On day 13.5 of pregnancy, reproductive parameters were measured. In-vivo tracking of EdU-labeled ESCs was performed using fluorescence microscopy. The frequency of regulatory T cells (Tregs) in paraaortic/renal and inguinal lymph nodes was measured by flow cytometry. The proliferation of pregnant CBA/J splenocytes in response to stimulation with DBA/2 splenocytes was assessed by 5,6-carboxyfluorescein diacetate succinimidyl ester (CFSE) flow cytometry.

Results

In C×D/D mice, the resorption rate was reduced to match that seen in the C×B group. Intrauterine perfused ESCs appeared in uterine stroma after 2 days, which remained there for at least 12 days. There was no difference in the number of implantation sites and embryo weight across all groups. The frequency of Tregs in the inguinal lymph nodes was similar across all groups, but it increased in the paraaortic/renal lymph nodes of C×D/D mice to the level found in C×B mice. No significant changes were observed in the proliferation of splenocytes from pregnant C×D/D compared to those of the C×D group in response to stimulation with DBA/2 splenocytes. Decidualization of ESCs was associated with a profound alteration in ESC secretome exemplified by alteration in proteins involved in extracellular matrix (ECM) remodeling, response to inflammation, senescence, and immune cell trafficking.

Discussion

Our results showed that the deficiency of Tregs is not the primary driver of abortion in the CBA/J × DBA/2 model and provided evidence that impaired endometrial decidualization probably triggers endometrial immune dysfunction and abortion in this model.

In mares resistant to endometrial infection, periovulatory treatment with ecbolic drugs does not influence uterine clearance or luteal development

We aimed to determine associations between experimentally impaired uterine clearance or treatment with ecbolic drugs on luteal development in estrous mares after insemination. In a crossover design, eight mares were treated with saline (CON), clenbuterol (CLEN), oxytocin (OXY) and carbetocin (CARB) from the day of first insemination until 2 days after ovulation. Between treatments, the mares rested for one cycle. Estrous mares were examined for the presence of free intrauterine fluid by transrectal ultrasound. Endometrial swabs for cytology and bacteriology were collected on days 1 and 14. Blood samples were collected daily before AI until day 14 after ovulation for determination of progesterone and PGF2α metabolites (PGFM). Differences between treatments were compared by a general linear model for repeated measures (SPSS 29). One mare was excluded because of a uterine infection in the control cycle. In all other mares, only minor amounts of free intrauterine fluid were present after insemination and decreased over time (P<0.05) with no treatment x time interaction. There was no effect of treatment on polymorphonucleated cells (PMN) in endometrial cytology after ovulation or PGFM secretion. Progesterone release from day 1-14 as well as pregnancy rate and conceptus size on day 14 was not influenced by treatment. In conclusion, treatment with clenbuterol does not impair uterine clearance in estrous mares resistant to endometritis. Repeated injection of the oxytocin analogue carbetocin during the early postovulatory period is not detrimental to corpus luteum function and can be recommended to enhance uterine clearance.

General and comparative aspects of endometritis in domestic species: A review

Endometritis is a leading cause of sub- and infertility in domestic animal species. The healthy uterus is colonized by commensal bacteria, viruses and yeast/fungi that represent the nonpathogenic microbiota. A shift in the number or type of organisms accompanied by immune dysfunction, however, may trigger uterine infection and inflammation. Metritis is associated with inflammation of all uterine layers (endometrium, myometrium and perimetrium), whereas endometritis is a more superficial inflammation involving solely the endometrium. Endometritis generally occurs at two time points in domestic animal species, postpartum and postmating. Postpartum endometritis may chronically persist, either as a low-grade disease that often manifests as a vaginal discharge but not a systemic illness (in some species termed clinical endometritis) or sometimes subclinical where features are only detected by endometrial sampling. Contamination of the uterus at the time of mating occurs by direct deposition of semen (ejaculated or artificially inseminated) into the uterus. Improper drainage of the ejaculatory fluid or an inadequate immune response may result in persistent mating-induced endometritis. Both postpartum and postmating endometritis interferes with fertility by creating a suboptimal environment for embryo development and placentation, and chronic endometritis may have an impact on sperm survival and fertilization ability. In the postpartum animal, there may also be changes in milk production and maternal behaviour, which can affect offspring health and survival. Preventive strategies for endometritis largely depend on monitoring their known risk factors, which are sometimes specific with regard to the species. Effective, nonantibiotic therapy for endometritis is not available to date. Overall, extensive research has been performed in cattle and horses to unravel key aspects of endometritis, but in sows and bitches, the available literature is scant. Thus, the need and opportunity to investigate the condition vary considerably among domestic species and necessitate their comparative assessment. This article reviews general and comparative aspects of the diagnosis and classification, pathogenesis, preventive strategies and therapeutics of endometritis in domestic species with a specific focus on cows, mares, sows and bitches.

Obesity Affects the Proliferative Potential of Equine Endometrial Progenitor Cells and Modulates Their Molecular Phenotype Associated with Mitochondrial Metabolism

The study aimed to investigate the influence of obesity on cellular features of equine endometrial progenitor cells (Eca EPCs), including viability, proliferation capacity, mitochondrial metabolism, and oxidative homeostasis. Eca EPCs derived from non-obese (non-OB) and obese (OB) mares were characterized by cellular phenotype and multipotency. Obesity-induced changes in the activity of Eca EPCs include the decline of their proliferative activity, clonogenic potential, mitochondrial metabolism, and enhanced oxidative stress. Eca EPCs isolated from obese mares were characterized by an increased occurrence of early apoptosis, loss of mitochondrial dynamics, and senescence-associated phenotype. Attenuated metabolism of Eca EPCs OB was related to increased expression of pro-apoptotic markers (CASP9, BAX, P53, P21), enhanced expression of OPN, PI3K, and AKT, simultaneously with decreased signaling stabilizing cellular homeostasis (including mitofusin, SIRT1, FOXP3). Obesity alters functional features and the self-renewal potential of endometrial progenitor cells. The impaired cytophysiology of progenitor cells from obese endometrium predicts lower regenerative capacity if used as autologous transplants.

Cell therapy in transplantation: A comprehensive review of the current applications of cell therapy in transplant patients with the focus on Tregs, CAR Tregs, and Mesenchymal stem cells

Organ transplantation is a practical treatment for patients with end-stage organ failure. Despite the advances in short-term graft survival, long-term graft survival remains the main challenge considering the increased mortality and morbidity associated with chronic rejection and the toxicity of immunosuppressive drugs. Since a novel therapeutic strategy to induce allograft tolerance seems urgent, focusing on developing novel and safe approaches to prolong graft survival is one of the main goals of transplant investigators. Researchers in the field of organ transplantation are interested in suppressing or optimizing the immune responses by focusing on immune cells including mesenchymal stem cells (MSCs), polyclonal regulatory Tcells (Tregs), and antigen-specific Tregs engineered with chimeric antigen receptors (CAR Tregs). We review the mechanistic pathways, phenotypic and functional characteristics of these cells, and their promising application in organ transplantation.

The Usefulness of Mesenchymal Stem Cells beyond the Musculoskeletal System in Horses

Simple Summary

The main target of mesenchymal stem cell therapy in horses has long been the locomotor system, because these athletic animals commonly suffer from tendon and joint lesions. Originally, mesenchymal stem cells were thought to act by just differentiating into the cells of the injured tissue. However, these cells are also able to regulate and stimulate the body’s own repair mechanisms, opening the door to many applications in inflammatory and immune-mediated disorders in both animals and humans. In horses, beyond their traditional application in the musculoskeletal system, these cells have been studied for ophthalmologic pathologies such as corneal ulcers or immune-mediated processes, and for reproductive disorders such as endometritis/endometrosis. Their potential has been explored for equine pathologies very similar to those affecting people, such as asthma, metabolic syndrome, aberrant wound healing, or endotoxemia, as well as for equine-specific pathologies such as laminitis. Current evidence is still preliminary, and further research is needed to clarify different aspects, although research performed so far shows the promising potential of mesenchymal stem cells to treat a wide variety of equine pathologies, some of which are analogous to human disorders. Therefore, advancements in this path will be beneficial for both animals and people.

Abstract

The differentiation ability of mesenchymal stem cells (MSCs) initially raised interest for treating musculoskeletal injuries in horses, but MSC paracrine activity has widened their scope for inflammatory and immune-mediated pathologies in both equine and human medicine. Furthermore, the similar etiopathogenesis of some diseases in both species has advanced the concept of “One Medicine, One Health”. This article reviews the current knowledge on the use of MSCs for equine pathologies beyond the locomotor system, highlighting the value of the horse as translational model. Ophthalmologic and reproductive disorders are among the most studied for MSC application. Equine asthma, equine metabolic syndrome, and endotoxemia have been less explored but offer an interesting scenario for human translation. The use of MSCs in wounds also provides a potential model for humans because of the healing particularities in both species. High-burden equine-specific pathologies such as laminitis have been suggested to benefit from MSC-therapy, and MSC application in challenging disorders such as neurologic conditions has been proposed. The available data are preliminary, however, and require further development to translate results into the clinic. Nevertheless, current evidence indicates a significant potential of equine MSCs to enlarge their range of application, with particular interest in pathologies analogous to human conditions.

Mesenchymal stem cells for restoring endometrial function: An infertility perspective

BACKGROUND

Mesenchymal stem cells (MSCs) can be derived from several tissues such as bone marrow, placenta, adipose tissue, or endometrial tissue. MSCs gain a lot of attention for cell-based therapy due to their characteristics including differentiation ability and immunomodulatory effect. Preclinical and clinical studies demonstrated that MSCs can be applied to treat female infertility by improving of the functions of ovary and uterus. This mini- review focuses on the current study of treatment of endometrial infertility by using MSCs.

METHODS

The present study performed a literature review focusing on the effect of MSCs for treatment of women infertility caused by endometrial dysfunction.

RESULTS

Bone marrow-, umbilical cord-, adipose-, amniotic-, and menstruation-derived MSCs enhance endometrial cell proliferation, injury repairs as well as reducing scar formation. The beneficial mechanism probably via immunomodulatory, cell differentiation, stimulates endometrial cell proliferation and down-regulation of fibrosis genes. The major advantage of using MSCs is to improve endometrial functions resulting in increased implantation and pregnancy.

CONCLUSIONS

MSCs exhibit a potential for endometrial infertility treatment. Adipose- and menstruation-derived stem cells show advantages over other sources because the cells can be derived easily and do not causes graft rejection after autologous transplantation.

Endometrial and Menstrual Blood Mesenchymal Stem/Stromal Cells: Biological Properties and Clinical Application

A highly proliferative mesenchymal stem/stromal cell (MSC) population was recently discovered in the dynamic, cyclically regenerating human endometrium as clonogenic stromal cells that fulfilled the International Society for Cellular Therapy (ISCT) criteria. Specific surface markers enriching for clonogenic endometrial MSC (eMSC), CD140b and CD146 co-expression, and the single marker SUSD2, showed their perivascular identity in the endometrium, including the layer which sheds during menstruation. Indeed, cells with MSC properties have been identified in menstrual fluid and commonly termed menstrual blood stem/stromal cells (MenSC). MenSC are generally retrieved from menstrual fluid as plastic adherent cells, similar to bone marrow MSC (bmMSC). While eMSC and MenSC share several biological features with bmMSC, they also show some differences in immunophenotype, proliferation and differentiation capacities. Here we review the phenotype and functions of eMSC and MenSC, with a focus on recent studies. Similar to other MSC, eMSC and MenSC exert immunomodulatory and anti-inflammatory impacts on key cells of the innate and adaptive immune system. These include macrophages, T cells and NK cells, both in vitro and in small and large animal models. These properties suggest eMSC and MenSC as additional sources of MSC for cell therapies in regenerative medicine as well as immune-mediated disorders and inflammatory diseases. Their easy acquisition via an office-based biopsy or collected from menstrual effluent makes eMSC and MenSC attractive sources of MSC for clinical applications. In preparation for clinical translation, a serum-free culture protocol was established for eMSC which includes a small molecule TGFβ receptor inhibitor that prevents spontaneous differentiation, apoptosis, senescence, maintains the clonogenic SUSD2+ population and enhances their potency, suggesting potential for cell-therapies and regenerative medicine. However, standardization of MenSC isolation protocols and culture conditions are major issues requiring further research to maximize their potential for clinical application. Future research will also address crucial safety aspects of eMSC and MenSC to ensure these protocols produce cell products free from tumorigenicity and toxicity. Although a wealth of data on the biological properties of eMSC and MenSC has recently been published, it will be important to address their mechanism of action in preclinical models of human disease.

Edition of Prostaglandin E2 Receptors EP2 and EP4 by CRISPR/Cas9 Technology in Equine Adipose Mesenchymal Stem Cells

In mesenchymal stem cells (MSCs), it has been reported that prostaglandin E2 (PGE2) stimulation of EP2 and EP4 receptors triggers processes such as migration, self-renewal, survival, and proliferation, and their activation is involved in homing. The aim of this work was to establish a genetically modified adipose (aMSC) model in which receptor genes EP2 and EP4 were edited separately using the CRISPR/Cas9 system. After edition, the genes were evaluated as to if the expression of MSC surface markers was affected, as well as the migration capacity in vitro of the generated cells. Adipose MSCs were obtained from Chilean breed horses and cultured in DMEM High Glucose with 10% fetal bovine serum (FBS). sgRNA were cloned into a linearized LentiCRISPRv2GFP vector and transfected into HEK293FT cells for producing viral particles that were used to transduce aMSCs. GFP-expressing cells were separated by sorting to obtain individual clones. Genomic DNA was amplified, and the site-directed mutation frequency was assessed by T7E1, followed by Sanger sequencing. We selected 11 clones of EP2 and 10 clones of EP4, and by Sanger sequencing we confirmed 1 clone knock-out to aMSC/EP2 and one heterozygous mutant clone of aMSC/EP4. Both edited cells had decreased expression of EP2 and EP4 receptors when compared to the wild type, and the edition of EP2 and EP4 did not affect the expression of MSC surface markers, showing the same pattern in filling the scratch. We can conclude that the edition of these receptors in aMSCs does not affect their surface marker phenotype and migration ability when compared to wild-type cells.

Case Report: Use of Amniotic Microvesicles for Regenerative Medicine Treatment of a Mare With Chronic Endometritis

Chronic endometritis is an inflammation in the inner layer of uterine mucosa, with or without an infectious process, which affects the animal's fertility but not its general health. A variety of treatments has been adopted over the years but to date, no effective cures have been able to renew the injured tissue. Since the defects in the fetal-maternal communication are caused by degenerative changes due to chronic endometrial inflammation, our working hypothesis was a new approach to this disease by the regenerative medicine using amniotic derived microvesicles (MVs) for their anti-inflammatory and regenerative effects. The MVs are responsible for horizontal transfer of genetic materials, including microRNA (miRNAs) that are involved in paracrine communication between origin cells and target cells. Thus, intrauterine MV infusion may be beneficial in degenerative chronic endometritis and in the fetal–maternal talk. The selected mare was an 11-year-old Friesian, with a history of failed pregnancies despite numerous insemination attempts. Punctual and evident heats characterized the reproductive history, but no insemination attempts had been made for many years. The first (failed) insemination was when the mare was 9-years-old. In the next two reproductive seasons, other attempts were made at regular intervals but none was successful. After a final insemination attempt using a stallion of proven fertility, the collection of an 8-day old embryo suggested that the mare was affected by implantation failure related to endometritis. The mare was treated with two cycles of intrauterine administration of amniotic-derived MVs. The success of the intrauterine administration of MVs was demonstrated by an improvement in the classification of endometritis and in a successful artificial insemination (AI) with implantation of an embryo, as detected at day 14 and with a pregnancy that is still ongoing. Probably, MVs were able to restore the injured endometrium and re-establish the proper communication for a successful embryo implantation.

Assessment of the anti-inflammatory and engraftment potential of horse endometrial and adipose mesenchymal stem cells in an in vivo model of post breeding induced endometritis

Horse mesenchymal stem cells (MSC) are potential anti-inflammatory tools for post-breeding induced endometritis (PBIE). In this research MSCs isolated from the endometrium or subcutaneous fat of the same donors were infused iu into mares with PBIE for assessment of their anti-inflammatory action and engraftment. PBIE was induced in nine gynecologically healthy mares by iu infusion of 500 million dead sperm in saline. Inflammatory markers were analyzed in uterine lavages and biopsies immediately before (phase I) and 3 h after infusion of sperm (phase II). Measurements: polymorph nuclear cells (PMN), proteins IL-6 and TNFα (ELISA in the lavages) and immunostaining in biopsies, transcripts of IL-1α, 6, 8, 10, TNFα and COX2 (qPCR of pelleted lavages). At 24 h after sperm deposition (phase III), mares were instilled iu with 20 ml of saline containing 2 × 10⁷ adipose MSCs (n = 3, group 1) or endometrial MSCs (n = 3, group 2). Cells were labeled previously with carboxyfluorescein diacetate succinimidyl ester (CFDA SE). A third group (n = 3) received 20 mL of sterile saline alone. After 48 h another biopsy/lavage were done and the same parameters analyzed. For engraftment, additional biopsies were taken at days 10 and 30 of sperm infusion and analyzed by confocal microscopy. Dead sperm in saline markedly increased PMNs counts, IL-6 and TNFα expression in the ELISA (p < 0.05) and immunostaining. In phase III a significant reduction (p < 0.0001) of PMN was found in all samples, including control mares. A decrease (p < 0.05) of IL-6 and TNF-α was detected by ELISA, in the groups that received MSC, but not in control group. In the aMSC-treated group, a significant decrease was found in the expression of (IL1α, p = 0.0003; IL-6 p 0.04; IL-8, p = 0.006, TNFα p = 0.004). Expression of IL-10 and COX2 remained unchanged (p = 0.08). In the mares that received eMSC, IL-6 and 8 decreased significantly (p = 0.01), IL-10 increased (p = 0.009), while TNFα, COX2 and IL1α did not significantly change their expression. In the engraftment experiment CFDA label was found sparingly in all the samples analyzed until day 30, mainly at the stromal compartment of the endometrium. No differences in the engraftment pattern was found among cell origins. We conclude that inoculation of MSCs significantly reduced inflammation independently of the origin of the cells and that cells perform limited engraftment detectable after one month of infusion. These findings can be of help for the design of new anti-inflammatory therapies of uterine diseases in mares.

Persistent Breeding-Induced Endometritis in Mares - a Multifaceted Challenge: From Clinical Aspects to Immunopathogenesis and Pathobiology

Post-breeding endometritis (i.e., inflammation/infection of the endometrium), is a physiological reaction taking place in the endometrium of mares within 48 hours post-breeding, aimed to clear seminal plasma, excess sperm, microorganisms, and debris from the uterine lumen in preparation for the arrival of an embryo. Mares are classified as susceptible or resistant to persistent breeding-induced endometritis (PBIE) based on their ability to clear this inflammation/infection by 48 hours post-breeding. Mares susceptible to PBIE, or those with difficulty clearing infection/inflammation, have a deficient immune response and compromised physical mechanisms of defense against infection. Molecular pathways of the innate immune response known to be involved in PBIE are discussed herein. The role of the adaptive uterine immune response on PBIE remains to be elucidated in horses. Advances in the pathobiology of microbes involved in PBIE are also revised here. Traditional and non-traditional therapeutic modalities for endometritis are contrasted and described in the context of clinical and molecular aspects. In recent years, the lack of efficacy of traditional therapeutic modalities, alongside the ever-increasing incidence of antibiotic-resistant microorganisms, has enforced the development of non-traditional therapies. Novel biological products capable of modulating the endometrial inflammatory response are also discussed here as part of the non-traditional therapies for endometritis.

Endometrial Regeneration in Asherman's Syndrome: Clinical and Translational evidence of Stem Cell Therapies

Asherman's Syndrome or Intrauterine adhesions is an acquired uterine condition where fibrous scarring forms within the uterine cavity, resulting in reduced menstrual flow, pelvic pain and infertility. Until recently, the molecular mechanisms leading to the formation of fibrosis were poorly understood, and the treatment of Asherman's syndrome has largely focused on hysteroscopic resection of adhesions, hormonal therapy, and physical barriers. Numerous studies have begun exploring the molecular mechanisms behind the fibrotic process underlying Asherman's Syndrome as well as the role of stem cells in the regeneration of the endometrium as a treatment modality. The present review offers a summary of available stem cell-based regeneration studies, as well as highlighting current gaps in research.

Stem cells on regenerative and reproductive science in domestic animals

Stem cells are undifferentiated and self-renewable cells that present new possibilities for both regenerative medicine and the understanding of early mammalian development. Adult multipotent stem cells are already widely used worldwide in human and veterinary medicine, and their therapeutic signalling, particularly with respect to immunomodulation, and their trophic properties have been intensively studied. The derivation of embryonic stem cells (ESCs) from domestic species, however, has been challenging, and the poor results do not reflect the successes obtained in mouse and human experiments. More recently, the generation of induced pluripotent stem cells (iPSCs) via the forced expression of specific transcription factors has been demonstrated in domestic species and has introduced new potentials in regenerative medicine and reproductive science based upon the ability of these cells to differentiate into a variety of cells types in vitro. For example, iPSCs have been differentiated into primordial germ-like cells (PGC-like cells, PGCLs) and functional gametes in mice. The possibility of using iPSCs from domestic species for this purpose would contribute significantly to reproductive technologies, offering unprecedented opportunities to restore fertility, to preserve endangered species and to generate transgenic animals for biomedical applications. Therefore, this review aims to provide an updated overview of adult multipotent stem cells and to discuss new possibilities introduced by the generation of iPSCs in domestic animals, highlighting the possibility of generating gametes in vitro via PGCL induction.

Endometrial Stem Cells in Farm Animals: Potential Role in Uterine Physiology and Pathology

The endometrium is an accessible source of mesenchymal stem cells. Most investigations of endometrial mesenchymal stem cells (eMSCs) have been conducted in humans. In animals, particularly in livestock, eMSC research is scarce. Such cells have been described in the bovine, ovine, caprine, porcine, and equine endometrium. Here we provide the state of the art of eMSCs in farm animals with a focus on the bovine species. In bovines, eMSCs have been identified during the phases of the estrous cycle, during which their functionality and the presence of eMSC-specific markers has been shown to change. Moreover, postpartum inflammation related to endometritis affects the presence and functionality of eMSCs, and prostaglandin E₂ (PGE₂) may be the mediator of such changes. We demonstrated that exposure to PGE₂ in vitro modifies the transcriptomic profile of eMSCs, showing its potential role in the fate of stem cell activation, migration, and homing during pathological uterine inflammation in endometritis and in healthy puerperal endometrium. Farm animal research on eMSCs can be of great value in translational research for certain uterine pathologies and for immunomodulation of local responses to pathogens, hormones, and other substances. Further research is necessary in areas such as in vivo location of the niches and their immunomodulatory and anti-infective properties.

Comparison of Antibacterial and Immunological Properties of Mesenchymal Stem/Stromal Cells from Equine Bone Marrow, Endometrium, and Adipose Tissue

Equine mesenchymal stem/stromal cells (MSCs) are multipotent cells that are widely used for treatment of musculoskeletal injuries, and there is significant interest in expanding their application to nonorthopedic conditions. MSCs possess antibacterial and immunomodulatory properties that may be relevant for combating infection; however, comparative studies using MSCs from different origins have not been carried out in the horse, and this was the focus of this study. Our results showed that MSC-conditioned media attenuated the growth of Escherichia coli, and that this effect was, on average, more pronounced for endometrium (EM)-derived and adipose tissue (AT)-derived MSCs than for bone marrow (BM)-derived MSCs. In addition, the antimicrobial lipocalin-2 was expressed at mean higher levels in EM-MSCs than in AT-MSCs and BM-MSCs, and the bacterial component lipopolysaccharide (LPS) stimulated its production by all three MSC types. We also showed that MSCs express interleukin-6 (IL-6), IL-8, monocyte chemoattractant protein-1, chemokine ligand-5, and Toll-like receptor 4, and that, in general, these cytokines were induced in all cell types by LPS. Low expression levels of the macrophage marker colony-stimulating factor 1 receptor were detected in BM-MSCs and EM-MSCs but not in AT-MSCs. Altogether, these findings suggest that equine MSCs from EM, AT, and BM have both direct and indirect antimicrobial properties that may vary between MSCs from different origins and could be exploited toward improvement of regenerative therapies for horses.