Effect of pregnancy on isolation efficiency and in vitro proliferation of equine peripheral-blood derived mesenchymal stromal cells

Mesenchymal stromal cells (MSCs) have regenerative and immunomodulatory potential and may be used to treat injured tissues. Pregnancy has been associated with increased MSCs in the peripheral circulation in multiple species, but to date, there are no reports on this matter in horses. This study aimed to evaluate the effect of pregnancy on isolation efficiency and proliferation capacity of equine MSCs derived from the peripheral blood (PB) of mares. Venous blood samples were collected at the 11th month of gestation and 1 month after delivery from clinically healthy Arabian mares that presented normal pregnancies. Blood samples were processed for in vitro cellular culture and hormonal and metabolic profiles. MSCs were isolated and characterized by trilineage differentiation potential, immunophenotyping, analyzed by gene sequencing and proliferation assays. The isolation of peripheral blood mononuclear cells (PBMCs) of pregnant mares were associated with higher isolation efficiency and proliferative capacity of MSCs derived from peripheral blood (PB-MSCs) recovered pre-partum than those isolated post-partum. Although fetal gender, parity, 5α-reduced pregnanes, insulin, and cortisol were shown to affect cellular proliferation, individual factors and the small population studied must be considered. This study suggests that PB-MSCs from pregnant mares could be a valuable alternative source of MSCs for therapeutic purposes.

Equine gamma herpesvirus presence and viral load are not associated with equine glandular gastric disease

OBJECTIVE

To investigate the role of equine herpesvirus-2 (EHV-2) and equine herpesvirus-5 (EHV-5) in equine glandular gastric disease (EGGD) by visualizing and quantifying these gamma herpesviruses in EGGD-affected and normal glandular gastric mucosa of horses. A secondary objective was to describe the histopathological abnormalities in the equine gastric glandular mucosa in horses with EGGD.

ANIMALS

29 horses (n = 21 postmortem and 8 gastroscopy) categorized as normal (11), EGGD (12), or both EGGD and equine squamous gastric disease (6).

METHODS

Glandular gastric mucosal samples were collected from horses by gastroscopy or postmortem. Histopathology and in situ hybridization targeting EHV-2 and EHV-5 were performed on grossly normal and abnormal glandular gastric mucosa. The number of in situ hybridization-positive cells per millimeter squared of tissue was calculated. Evaluators were blinded to groups.

RESULTS

Glandular gastric tissues from horses without EGGD had higher viral loads in the mucosa than normal or abnormal tissues from EGGD horses. There was no difference in viral loads for EHV-2 or EHV-5 between grossly or endoscopically normal to abnormal gastric tissues within horses with EGGD. Lymphocytic plasmacytic gastritis was the most common histopathological abnormality, with only 3 horses having mucosal disruption (glandular ulcer or erosion).

CLINICAL RELEVANCE

Equine gamma herpesviruses are unlikely to play a role in the pathophysiology of EGGD. EGGD is frequently inflammatory with occasional mucosal disruption (ulcer or erosion).

A xenotransplantation mouse model to study physiology of the mammary gland from large mammals

Although highly conserved in structure and function, many (patho)physiological processes of the mammary gland vary drastically between mammals, with mechanisms regulating these differences not well understood. Large mammals display variable lactation strategies and mammary cancer incidence, however, research into these variations is often limited to in vitro analysis due to logistical limitations. Validating a model with functional mammary xenografts from cryopreserved tissue fragments would allow for in vivo comparative analysis of mammary glands from large and/or rare mammals and would improve our understanding of postnatal development, lactation, and premalignancy across mammals. To this end, we generated functional mammary xenografts using mammary tissue fragments containing mammary stroma and parenchyma isolated via an antibody-independent approach from healthy, nulliparous equine and canine donor tissues to study these species in vivo. Cryopreserved mammary tissue fragments were xenotransplanted into de-epithelialized fat pads of immunodeficient mice and resulting xenografts were structurally and functionally assessed. Preimplantation of mammary stromal fibroblasts was performed to promote ductal morphogenesis. Xenografts recapitulated mammary lobule architecture and contained donor-derived stromal components. Mammatropic hormone stimulation resulted in (i) upregulation of lactation-associated genes, (ii) altered proliferation index, and (iii) morphological changes, indicating functionality. Preimplantation of mammary stromal fibroblasts did not promote ductal morphogenesis. This model presents the opportunity to study novel mechanisms regulating unique lactation strategies and mammary cancer induction in vivo. Due to the universal applicability of this approach, this model serves as proof-of-concept for developing mammary xenografts for in vivo analysis of virtually any mammals, including large and rare mammals.

Comparative transcriptomic analysis of bovine mesenchymal stromal cells reveals tissue-source and species-specific differences

Mesenchymal stromal cells (MSCs) have the potential to be used as therapeutics, but their efficacy varies due to cellular heterogeneity, which is not fully understood. After characterizing donor-matched bovine MSC from adipose tissue (AT), bone marrow (BM), and peripheral blood (PB), we performed single-cell RNA sequencing (scRNA-seq) to evaluate overarching similarities and differences across these three tissue-derived MSCs. Next, the transcriptomic profiles of the bovine MSCs were compared to those of equine MSCs, derived from the same tissue sources and previously published by our group, and revealed species-specific differences. Finally, the transcriptomic profile from bovine BM-MSCs was compared to mouse and human BM-MSCs and demonstrated that bovine BM-MSCs share more common functionally relevant gene expression profiles with human BM-MSCs than compared to murine BM-MSCs. Collectively, this study presents the cow as a potential non-traditional animal model for translational MSC studies based on transcriptomic profiles similar to human MSCs.

Use of Biologics and Stem Cells for Wound Healing in the Horse

Treatment of skin wounds is a high priority in veterinary medicine because healthy uncompromised skin is essential for the well-being of horses. Stem cells and other biologic therapies offer benefits by reducing the need for surgical procedures and conventional antibiotics. Evidence from in vitro studies and small in vivo trials supports the use of equine stem cells and biologics for the treatment of acute and chronic cutaneous wounds. Larger clinical trials are warranted to better evaluate the regenerative and immunological responses to these treatments. Additionally, delivery methods and treatment schedules should be optimized to improve efficacy of these novel therapies.

miRNA-214-3p stimulates carcinogen-induced mammary epithelial cell apoptosis in mammary cancer-resistant species

Mammary cancer incidence varies greatly across species and underlying mechanisms remain elusive. We previously showed that mammosphere-derived epithelial cells from species with low mammary cancer incidence, such as horses, respond to carcinogen 7, 12-Dimethylbenz(a)anthracene-induced DNA damage by undergoing apoptosis, a postulated anti-cancer mechanism. Additionally, we found that miR-214-3p expression in mammosphere-derived epithelial cells is lower in mammary cancer-resistant as compared to mammary cancer-susceptible species. Here we show that increasing miR-214 expression and decreasing expression of its target gene nuclear factor kappa B subunit 1 in mammosphere-derived epithelial cells from horses abolishes 7,12-Dimethylbenz(a)anthracene-induced apoptosis. A direct interaction of miR-214-3p with another target gene, unc-5 netrin receptor A, is also demonstrated. We propose that relatively low levels of miR-214 in mammosphere-derived epithelial cells from mammals with low mammary cancer incidence, allow for constitutive gene nuclear factor kappa B subunit 1 expression and apoptosis in response to 7, 12-Dimethylbenz(a)anthracene. Better understanding of the mechanisms regulating cellular responses to carcinogens improves our overall understanding of mammary cancer resistance mechanisms.

Bovine milk-derived cells express transcriptome markers of pluripotency and secrete bioactive factors with regenerative and antimicrobial activity

The bovine mammary stem/progenitor cell secretome stimulates regeneration in vitro and contains proteins associated with antimicrobial defense. This has led to the exploration of the secretome as a biologic treatment for mastitis, a costly inflammation of the udder commonly caused by bacteria. This study reports on a population of bovine mammary stem/progenitor cells isolated non-invasively from milk (MiDCs). MiDCs were characterized by immunophenotyping, mammosphere formation assays, and single cell RNA sequencing. They displayed epithelial morphology, exhibited markers of mammary stem/progenitor cells, and formed mammospheres, like mammary gland tissue-isolated stem/progenitor cells. Single cell RNA sequencing revealed two sub-populations of MiDCs: epithelial cells and macrophages. Functionally, the MiDC secretome increased fibroblast migration, promoted angiogenesis of endothelial cells, and inhibited the growth of mastitis-associated bacteria, including antibiotic-resistant strains, in vitro. These qualities of MiDCs render them a source of stem cells and stem cell products that may be used to treat diseases affecting the dairy industry, including mastitis.

Induced pluripotent stem cells from domesticated ruminants and their potential for enhancing livestock production

Ruminant livestock, including cattle, sheep, goat, and buffalo, are essential for global food security and serve valuable roles in sustainable agricultural systems. With the limited availability of embryonic stem cells (ESCs) from these species, ruminant induced pluripotent stem cells (iPSCs) and iPSC-like cells provide a valuable research tool for agricultural, veterinary, biomedical, and pharmaceutical applications, as well as for the prospect of translation to human medicine. iPSCs are generated by reprogramming of adult or fetal cells to an ESC-like state by ectopic expression of defined transcription factors. Despite the slow pace the field has evolved in livestock species compared to mice and humans, significant progress has been made over the past 15 years in using different cell sources and reprogramming protocols to generate iPSCs/iPSC-like cells from ruminants. This mini review summarizes the current literature related to the derivation of iPSCs/iPSC-like cells from domesticated ruminants with a focus on reprogramming protocols, characterization, associated limitations, and potential applications in ruminant basic science research and production.

Comparative Analysis of microRNAs that Stratify in vitro Mammary stem and Progenitor Activity Reveals Functionality of Human miR-92b-3p

Mammary stem/progenitor cells are fundamental for mammary gland development and function. However, much remains to be elucidated regarding their function in mammals beyond the traditionally studied rodents, human, and to a lesser extent, ruminants. Due to the growing appreciation for microRNAs (miRNAs) as regulators of stem cells and their progenitors, we compared miRNA expression in mammary stem/progenitor cells from mammals with varying mammary stem/progenitor activity in vitro, in order to identify miRNA candidates that regulate stem/progenitor self-renewal and function. Mammosphere-derived epithelial cells (MDECs), which are primary cell lines enriched in mammary stem and progenitor cells, were generated from six mammalian species (i.e., cow, human, pig, horse, dog, and rat) and small RNA sequencing was performed. We identified 9 miRNAs that were significantly differentially expressed in MDEC cultures with a low versus high mammary stem/progenitor activity. miR-92b-3p was selected for functional follow-up studies, as this miRNA is understudied in primary mammary cells but has well-described gene targets that are known to regulate mammary stem/progenitor activity. Altering the expression of miR-92b-3p in MDECs from species with low stem/progenitor activity (human and cow) and those with high stem/progenitor activity (dog and rat) via inhibition and overexpression, respectively, resulted in significantly decreased mammosphere formation of human MDECs, but showed no significant effects in cow, dog, or rat MDECs. This study is the first to perform small RNA sequencing in MDECs from various mammals and highlights that conserved miRNAs can have different functions in mammary stem/progenitor cells across species.

Prevalence and pathology of equine parvovirus-hepatitis in racehorses from New York racetracks

BACKGROUND

Theiler's disease, a.k.a. equine serum hepatitis, is a devastating, highly fatal disease of horses. Equine parvovirus-hepatitis (EqPV-H) has been identified as the likely cause of this disease. While the incidence of Theiler's disease is low, the prevalence of EqPV-H DNA in horses is high, with up to 37% in some regions, suggesting that subclinical or persistent infection is common.

METHODS

To determine the prevalence and pathogenicity of EqPV-H infection at New York racetracks, DNA was extracted from archived formalin-fixed, paraffin-embedded liver tissues from racehorses submitted for necropsy to the Animal Health Diagnostic Center as part of the New York State Gaming Commission-Cornell University postmortem examination program. A total of 191 liver samples from horses between 2 and 13 years old were evaluated. Extracted DNA was tested for EqPV-H using PCR and gel electrophoresis. PCR-positive samples were further assessed for tissue morphology using histology and detection of viral nucleic acid using in situ hybridization.

RESULTS

Forty-two samples were PCR positive (22%). Of those, 31 samples had positive viral nucleic acid hybridization in hepatocytes with 11 samples showing positive hybridization in necrotic hepatocytes associated with inflammatory cells, indicating active hepatitis. Both individual hepatocyte necrosis and hepatitis were positively associated with EqPV-H detection (p < 0.0001 and p = 0.0005, respectively).

CONCLUSION

These findings indicate that presence of EqPV-H in the liver and parvoviral-associated hepatitis are prevalent in racehorses from New York racetracks, thus warranting additional studies examining potential associations between EqPV-H infection and racehorse performance.

Nasal transmission of equine parvovirus hepatitis

BACKGROUND

Equine parvovirus hepatitis (EqPV-H) is highly prevalent and causes subclinical to fatal hepatitis, which can occur in outbreaks. Whereas iatrogenic transmission is well documented, the mode of horizontal transmission is not known. The virus is shed in nasal, oral and fecal secretions, and PO transmission has been reported in a single horse.

HYPOTHESIS/OBJECTIVE

Investigate the efficiency of PO and nasal transmission of EqPV-H in a larger cohort.

METHODS

Prospective experimental transmission study. Eleven EqPV-H-negative horses were inoculated with 5 × 10⁶ genome equivalents EqPV-H. Serum PCR and serology for EqPV-H were performed weekly and monthly, respectively. Horses first were inoculated PO, and then intranasally 8 weeks later.

RESULTS

No horse became viremic or seroconverted within 8 weeks after PO inoculation. After intranasal inoculation, 5 horses became viremic within 6 to 12 weeks and seroconverted within 10 to 19 weeks. After a period without monitoring from 12 to 19 weeks postinoculation, another 5 horses were found to be viremic at 19 to 22 weeks. The second set of 5 horses could have been infected by horizontal transmission from the first 5 because of cohousing.

CONCLUSIONS AND CLINICAL IMPORTANCE

We demonstrated that EqPV-H can be transmitted nasally. The prolonged eclipse phase before detectable viremia indicates biosecurity measures to control spread could be impractical.

Mesenchymal stromal cells isolated from chicken peripheral blood secrete bioactive factors with antimicrobial and regenerative properties

Mesenchymal stromal cells (MSCs) are adult multipotent progenitor cells that have been isolated from various tissue sources of many species, primarily mammals. Generally, these cells proliferate extensively in culture and have been shown to secrete bioactive factors that contribute to healing processes by regulating inflammation, modulating immune responses, inhibiting bacterial growth, and promoting tissue regeneration. The present study reports on the isolation and characterization of MSCs from the peripheral blood (PB) of chickens. Chicken PBMSCs were characterized based on their trilineage differentiation potential and gene and protein expression of MSC-specific cell surface markers. To determine functionality, conditioned medium (CM), which contains all bioactive factors secreted by MSCs, was collected from chicken PBMSCs, and used in in vitro antimicrobial, migration, and angiogenesis assays. Chicken PBMSC CM was found to (i) inhibit the growth of planktonic Staphylococcus aureus (S. aureus), and even more significantly the methicillin-resistant S. aureus (MRSA), (ii) decrease adhesion and promote migration of fibroblasts, and (iii) support endothelial cell tube formation. Collectively, these data indicate that chicken PBMSCs secrete bioactive factors with antimicrobial and regenerative properties, and as such, provide a novel source of cell-based therapies for the poultry industry.

Induced mammary cancer in rat models: pathogenesis, genetics, and relevance to female breast cancer

Mammary cancer, or breast cancer in women, is a polygenic disease with a complex etiopathogenesis. While much remains elusive regarding its origin, it is well established that chemical carcinogens and endogenous estrogens contribute significantly to the initiation and progression of this disease. Rats have been useful models to study induced mammary cancer. They develop mammary tumors with comparable histopathology to humans and exhibit differences in resistance or susceptibility to mammary cancer depending on strain. While some rat strains (e.g., Sprague-Dawley) readily form mammary tumors following treatment with the chemical carcinogen, 7,12-dimethylbenz[a]-anthracene (DMBA), other strains (e.g., Copenhagen) are resistant to DMBA-induced mammary carcinogenesis. Genetic linkage in inbred strains has identified strain-specific quantitative trait loci (QTLs) affecting mammary tumors, via mechanisms that act together to promote or attenuate, and include 24 QTLs controlling the outcome of chemical induction, 10 QTLs controlling the outcome of estrogen induction, and 4 QTLs controlling the outcome of irradiation induction. Moreover, and based on shared factors affecting mammary cancer etiopathogenesis between rats and humans, including orthologous risk regions between both species, rats have served as useful models for identifying methods for breast cancer prediction and treatment. These studies in rats, combined with alternative animal models that more closely mimic advanced stages of breast cancer and/or human lifestyles, will further improve our understanding of this complex disease.

Comparative Efficacy of Topical Ophthalmic Ganciclovir and Oral Famciclovir in Cats with Experimental Ocular Feline Herpesvirus-1 Epithelial Infection

Purpose: To determine the comparative efficacy of ganciclovir ophthalmic gel and famciclovir oral tablets in cats with experimentally induced ocular feline herpesvirus-1 (FHV-1) epithelial infection. Methods: A randomized, placebo-controlled trial was performed using 16 nonvaccinated, specific pathogen-free cats with experimental FHV-1 infection induced by topical ocular inoculation. Cats received topical ganciclovir 0.15% ophthalmic gel (1 drop 3 times daily, n = 6 cats), oral famciclovir (90 mg/kg twice daily, n = 6), or topical artificial tear gel (1 drop 3 times daily, n = 4) for 14 days. Cats were monitored after inoculation for 30 days. Ophthalmic examinations were performed every 2 days and ocular disease scores calculated. In vivo confocal microscopy was performed, and corneal leukocyte infiltrates quantified. Ocular samples for FHV-1 quantitative polymerase chain reaction (qPCR) and virus isolation assays were collected every 3 days. Hemograms and serum biochemistry panels were performed at intervals. Results: Clinical ocular disease scores and corneal leukocyte infiltrates were significantly lower in the ganciclovir and famciclovir groups compared with placebo, but no significant differences were detected between the antiviral treatment groups. Ocular viral loads determined by qPCR were significantly lower in the ganciclovir group compared with the placebo group, but there were no significant differences between the other study groups. Hemograms and biochemistry panels were unremarkable. Conclusion: Topical application of ganciclovir gel 3 times daily was well-tolerated and displayed similar efficacy at reducing clinical ocular disease scores and corneal inflammation as twice daily oral famciclovir treatment in cats with experimental ocular FHV-1 infection.

A TMPRSS2 inhibitor acts as a pan-SARS-CoV-2 prophylactic and therapeutic

The COVID-19 pandemic caused by the SARS-CoV-2 virus remains a global public health crisis. Although widespread vaccination campaigns are underway, their efficacy is reduced owing to emerging variants of concern1,2. Development of host-directed therapeutics and prophylactics could limit such resistance and offer urgently needed protection against variants of concern3,4. Attractive pharmacological targets to impede viral entry include type-II transmembrane serine proteases (TTSPs) such as TMPRSS2; these proteases cleave the viral spike protein to expose the fusion peptide for cell entry, and thus have an essential role in the virus lifecycle5,6. Here we identify and characterize a small-molecule compound, N-0385, which exhibits low nanomolar potency and a selectivity index of higher than 106 in inhibiting SARS-CoV-2 infection in human lung cells and in donor-derived colonoids7. In Calu-3 cells it inhibits the entry of the SARS-CoV-2 variants of concern B.1.1.7 (Alpha), B.1.351 (Beta), P.1 (Gamma) and B.1.617.2 (Delta). Notably, in the K18-human ACE2 transgenic mouse model of severe COVID-19, we found that N-0385 affords a high level of prophylactic and therapeutic benefit after multiple administrations or even after a single administration. Together, our findings show that TTSP-mediated proteolytic maturation of the spike protein is critical for SARS-CoV-2 infection in vivo, and suggest that N-0385 provides an effective early treatment option against COVID-19 and emerging SARS-CoV-2 variants of concern.

Establishment and characterization of equine mammary organoids using a method translatable to other non-traditional model species

Mammary organoid (MaO) models are only available for a few traditional model organisms, limiting our ability to investigate mammary gland development and cancer across mammals. This study established equine mammary organoids (EqMaOs) from cryopreserved mammary tissue, in which mammary tissue fragments were isolated and embedded into a 3D matrix to produce EqMaOs. We evaluated viability, proliferation and budding capacity of EqMaOs at different time points during culture, showing that although the number of proliferative cells decreased over time, viability was maintained and budding increased. We further characterized EqMaOs based on expression of stem cell, myoepithelial and luminal markers, and found that EqMaOs expressed these markers throughout culture and that a bilayered structure as seen in vivo was recapitulated. We used the milk-stimulating hormone prolactin to induce milk production, which was verified by the upregulation of milk proteins, most notably β-casein. Additionally, we showed that our method is also applicable to additional non-traditional mammalian species, particularly domesticated animals such as cats, pigs and rabbits. Collectively, MaO models across species will be a useful tool for comparative developmental and cancer studies.

The equine mesenchymal stromal cell secretome inhibits equid herpesvirus type 1 strain Ab4 in epithelial cells

Equid herpesvirus 1 (EHV-1) outbreaks occur when virus spreads from infected horses to in-contact horses, primarily via nasal shedding. This study evaluated the efficacy of factors secreted by equine peripheral blood derived mesenchymal stromal cells (PB-MSCs), collectively named the secretome, to inhibit the growth of EHV-1 in (i) 2D epithelial cell cultures (RK-13) in vitro, (ii) 3D equine nasal explants in vitro and (iii) an EHV-1 infection mouse model in vivo. The PB-MSC secretome was found to inhibit EHV-1 in RK-13 cells as well as in the epithelium of equine nasal explants. Although the PB-MSC secretome did not decrease overall severity of EHV-1 infection in mice, as determined by weight loss and viral titers in lungs, histological analyses indicated local reduction of EHV-1 infection in nasal epithelium. These results indicate that the PB-MSC secretome inhibits EHV-1 in epithelial cells in a context-dependent manner.

Mesenchymal stromal cell-secreted CCL2 promotes antibacterial defense mechanisms through increased antimicrobial peptide expression in keratinocytes

Mesenchymal stromal cells (MSCs) from both humans and horses, which represent a clinically relevant translation animal model for human cutaneous wound healing, were recently found to possess antimicrobial properties against planktonic bacteria, and in the case of equine MSCs, also against biofilms. This, together with previous findings that human and equine MSCs promote angiogenesis and wound healing, makes these cells an attractive approach to treat infected cutaneous wounds in both species. The anti-biofilm activities of equine MSC, via secretion of cysteine proteases, have only been demonstrated in vitro, thus lacking information about in vivo relevance. Moreover, the effects of the equine MSC secretome on resident skin cells have not yet been explored. The goals of this study were to (a) test the efficacy of the MSC secretome in a physiologically relevant ex vivo equine skin biofilm explant model and (b) explore the impact of the MSC secretome on the antimicrobial defense mechanisms of resident skin cells. Our salient findings were that secreted factors from equine MSCs significantly decreased viability of methicillin-resistant Staphylococcus aureus bacteria in mature biofilms in this novel skin biofilm explant model. Moreover, we demonstrated that equine MSCs secrete CCL2 that increases the antimicrobial activity of equine keratinocytes by stimulating expression of antimicrobial peptides. Collectively, these data contribute to our understanding of the MSC secretome's antimicrobial properties, both directly by killing bacteria and indirectly by stimulating immune responses of surrounding resident skin cells, thus further supporting the value of MSC secretome-based treatments for infected wounds.

Small but mighty: old and new parvoviruses of veterinary significance

In line with the Latin expression "sed parva forti" meaning "small but mighty," the family Parvoviridae contains many of the smallest known viruses, some of which result in fatal or debilitating infections. In recent years, advances in metagenomic viral discovery techniques have dramatically increased the identification of novel parvoviruses in both diseased and healthy individuals. While some of these discoveries have solved etiologic mysteries of well-described diseases in animals, many of the newly discovered parvoviruses appear to cause mild or no disease, or disease associations remain to be established. With the increased use of animal parvoviruses as vectors for gene therapy and oncolytic treatments in humans, it becomes all the more important to understand the diversity, pathogenic potential, and evolution of this diverse family of viruses. In this review, we discuss parvoviruses infecting vertebrate animals, with a special focus on pathogens of veterinary significance and viruses discovered within the last four years.

Pathogenesis, MicroRNA-122 Gene-Regulation, and Protective Immune Responses After Acute Equine Hepacivirus Infection

BACKGROUND AND AIMS

Equine hepacivirus (EqHV) is phylogenetically the closest relative of HCV and shares genome organization, hepatotropism, transient or persistent infection outcome, and the ability to cause hepatitis. Thus, EqHV studies are important to understand equine liver disease and further as an outbred surrogate animal model for HCV pathogenesis and protective immune responses. Here, we aimed to characterize the course of EqHV infection and associated protective immune responses.

APPROACH AND RESULTS

Seven horses were experimentally inoculated with EqHV, monitored for 6 months, and rechallenged with the same and, subsequently, a heterologous EqHV. Clearance was the primary outcome (6 of 7) and was associated with subclinical hepatitis characterized by lymphocytic infiltrate and individual hepatocyte necrosis. Seroconversion was delayed and antibody titers waned slowly. Clearance of primary infection conferred nonsterilizing immunity, resulting in shortened duration of viremia after rechallenge. Peripheral blood mononuclear cell responses in horses were minimal, although EqHV-specific T cells were identified. Additionally, an interferon-stimulated gene signature was detected in the liver during EqHV infection, similar to acute HCV in humans. EqHV, as HCV, is stimulated by direct binding of the liver-specific microRNA (miR), miR-122. Interestingly, we found that EqHV infection sequesters enough miR-122 to functionally affect gene regulation in the liver. This RNA-based mechanism thus could have consequences for pathology.

CONCLUSIONS

EqHV infection in horses typically has an acute resolving course, and the protective immune response lasts for at least a year and broadly attenuates subsequent infections. This could have important implications to achieve the primary goal of an HCV vaccine; to prevent chronicity while accepting acute resolving infection after virus exposure.

The Horse as a Model for the Study of Cutaneous Wound Healing

Significance: Cutaneous wounds are a major problem in both human and equine medicine. The economic cost of treating skin wounds and related complications in humans and horses is high, and in both species, particular types of chronic wounds do not respond well to current therapies, leading to suffering and morbidity. Recent Advances: Conventional methods for the treatment of cutaneous wounds are generic and have not changed significantly in decades. However, as more is learned about the mechanisms involved in normal skin wound healing, and how failure of these processes leads to chronic nonhealing wounds, novel therapies targeting the specific pathologies of hard-to-heal wounds are being developed and evaluated. Critical Issues: Physiologically relevant animal models are needed to (1) study the mechanisms involved in normal and impaired skin wound healing and (2) test newly developed therapies. Future Directions: Similarities in normal wound healing in humans and horses, and the natural development of distinct types of hard-to-heal chronic wounds in both species, make the horse a physiologically relevant model for the study of mechanisms involved in wound repair. Horses are also well-suited models to test novel therapies. In addition, studies in horses have the potential to benefit veterinary, as well as human medicine.

The Lack of a Representative Tendinopathy Model Hampers Fundamental Mesenchymal Stem Cell Research

Overuse tendon injuries are a major cause of musculoskeletal morbidity in both human and equine athletes, due to the cumulative degenerative damage. These injuries present significant challenges as the healing process often results in the formation of inferior scar tissue. The poor success with conventional therapy supports the need to search for novel treatments to restore functionality and regenerate tissue as close to native tendon as possible. Mesenchymal stem cell (MSC)-based strategies represent promising therapeutic tools for tendon repair in both human and veterinary medicine. The translation of tissue engineering strategies from basic research findings, however, into clinical use has been hampered by the limited understanding of the multifaceted MSC mechanisms of action. In vitro models serve as important biological tools to study cell behavior, bypassing the confounding factors associated with in vivo experiments. Controllable and reproducible in vitro conditions should be provided to study the MSC healing mechanisms in tendon injuries. Unfortunately, no physiologically representative tendinopathy models exist to date. A major shortcoming of most currently available in vitro tendon models is the lack of extracellular tendon matrix and vascular supply. These models often make use of synthetic biomaterials, which do not reflect the natural tendon composition. Alternatively, decellularized tendon has been applied, but it is challenging to obtain reproducible results due to its variable composition, less efficient cell seeding approaches and lack of cell encapsulation and vascularization. The current review will overview pros and cons associated with the use of different biomaterials and technologies enabling scaffold production. In addition, the characteristics of the ideal, state-of-the-art tendinopathy model will be discussed. Briefly, a representative in vitro tendinopathy model should be vascularized and mimic the hierarchical structure of the tendon matrix with elongated cells being organized in a parallel fashion and subjected to uniaxial stretching. Incorporation of mechanical stimulation, preferably uniaxial stretching may be a key element in order to obtain appropriate matrix alignment and create a pathophysiological model. Together, a thorough discussion on the current status and future directions for tendon models will enhance fundamental MSC research, accelerating translation of MSC therapies for tendon injuries from bench to bedside.

Translational Animal Models Provide Insight Into Mesenchymal Stromal Cell (MSC) Secretome Therapy

The therapeutic potential of the mesenchymal stromal cell (MSC) secretome, consisting of all molecules secreted by MSCs, is intensively studied. MSCs can be readily isolated, expanded, and manipulated in culture, and few people argue with the ethics of their collection. Despite promising pre-clinical studies, most MSC secretome-based therapies have not been implemented in human medicine, in part because the complexity of bioactive factors secreted by MSCs is not completely understood. In addition, the MSC secretome is variable, influenced by individual donor, tissue source of origin, culture conditions, and passage. An increased understanding of the factors that make up the secretome and the ability to manipulate MSCs to consistently secrete factors of biologic importance will improve MSC therapy. To aid in this goal, we can draw from the wealth of information available on secreted factors from MSC isolated from veterinary species. These translational animal models will inspire efforts to move human MSC secretome therapy from bench to bedside.

Single-cell resolution landscape of equine peripheral blood mononuclear cells reveals diverse cell types including T-bet+ B cells

BACKGROUND

Traditional laboratory model organisms represent a small fraction of the diversity of multicellular life, and findings in any given experimental model often do not translate to other species. Immunology research in non-traditional model organisms can be advantageous or even necessary, such as when studying host-pathogen interactions. However, such research presents multiple challenges, many stemming from an incomplete understanding of potentially species-specific immune cell types, frequencies, and phenotypes. Identifying and characterizing immune cells in such organisms is frequently limited by the availability of species-reactive immunophenotyping reagents for flow cytometry, and insufficient prior knowledge of cell type-defining markers.

RESULTS

Here, we demonstrate the utility of single-cell RNA sequencing (scRNA-Seq) to characterize immune cells for which traditional experimental tools are limited. Specifically, we used scRNA-Seq to comprehensively define the cellular diversity of equine peripheral blood mononuclear cells (PBMC) from healthy horses across different breeds, ages, and sexes. We identified 30 cell type clusters partitioned into five major populations: monocytes/dendritic cells, B cells, CD3+PRF1+ lymphocytes, CD3+PRF1- lymphocytes, and basophils. Comparative analyses revealed many cell populations analogous to human PBMC, including transcriptionally heterogeneous monocytes and distinct dendritic cell subsets (cDC1, cDC2, plasmacytoid DC). Remarkably, we found that a majority of the equine peripheral B cell compartment is comprised of T-bet+ B cells, an immune cell subpopulation typically associated with chronic infection and inflammation in human and mouse.

CONCLUSIONS

Taken together, our results demonstrate the potential of scRNA-Seq for cellular analyses in non-traditional model organisms and form the basis for an immune cell atlas of horse peripheral blood.

Single-cell RNA sequencing of equine mesenchymal stromal cells from primary donor-matched tissue sources reveals functional heterogeneity in immune modulation and cell motility

BACKGROUND

The efficacy of mesenchymal stromal cell (MSC) therapy is thought to depend on the intrinsic heterogeneity of MSC cultures isolated from different tissue sources as well as individual MSCs isolated from the same tissue source, neither of which is well understood. To study this, we used MSC cultures isolated from horses. The horse is recognized as a physiologically relevant large animal model appropriate for translational MSC studies. Moreover, due to its large size the horse allows for the simultaneous collection of adequate samples from multiple tissues of the same animal, and thus, for the unique collection of donor matched MSC cultures from different sources. The latter is much more challenging in mice and humans due to body size and ethical constraints, respectively.

METHODS

In the present study, we performed single-cell RNA sequencing (scRNA-seq) on primary equine MSCs that were collected from three donor-matched tissue sources; adipose tissue (AT), bone marrow (BM), and peripheral blood (PB). Based on transcriptional differences detected with scRNA-seq, we performed functional experiments to examine motility and immune regulatory function in distinct MSC populations.

RESULTS

We observed both inter- and intra-source heterogeneity across the three sources of equine MSCs. Functional experiments demonstrated that transcriptional differences correspond with phenotypic variance in cellular motility and immune regulatory function. Specifically, we found that (i) differential expression of junctional adhesion molecule 2 (JAM2) between MSC cultures from the three donor-matched tissue sources translated into altered cell motility of BM-derived MSCs when RNA interference was used to knock down this gene, and (ii) differences in C-X-C motif chemokine ligand 6 (CXCL6) expression in clonal MSC lines derived from the same tissue source correlated with the chemoattractive capacity of PB-derived MSCs.

CONCLUSIONS

Ultimately, these findings will enhance our understanding of MSC heterogeneity and will lead to improvements in the therapeutic potential of MSCs, accelerating the transition from bench to bedside.

Secreted sphingomyelins modulate low mammary cancer incidence observed in certain mammals

Determining mechanisms that naturally protect species from developing cancer is critical in order to prevent and treat cancer. Here, we describe a novel cancer-suppressing mechanism, via the secretion of bioactive factors by mammary cells, that is present in domesticated mammals with a low mammary cancer incidence. Specifically, these bioactive factors induced triple-negative breast cancer cell (TNBC) death in vitro and reduced tumorigenicity in a xenograft TNBC mouse model in vivo. RNA deep sequencing showed significant downregulation of genes associated with breast cancer progression in secretome-cultured TNBC cells. Further in-depth multi-omics analysis identified sphingomyelins as key secreted factors, and their role was confirmed via inhibition of the sphingomyelin signaling pathway. We speculate that secreted sphingomyelins in the mammary gland of mammals with a naturally low incidence of mammary cancer mediate the elimination of cancer cells. This study contributes to the growing list of protective mechanisms identified in cancer-proof species.

Beyond tradition and convention: benefits of non-traditional model organisms in cancer research

Traditional laboratory model organisms are indispensable for cancer research and have provided insight into numerous mechanisms that contribute to cancer development and progression in humans. However, these models do have some limitations, most notably related to successful drug translation, because traditional model organisms are often short-lived, small-bodied, genetically homogeneous, often immunocompromised, are not exposed to natural environments shared with humans, and usually do not develop cancer spontaneously. We propose that assimilating information from a variety of long-lived, large, genetically diverse, and immunocompetent species that live in natural environments and do develop cancer spontaneously (or do not develop cancer at all) will lead to a more comprehensive understanding of human cancers. These non-traditional model organisms can also serve as sentinels for environmental risk factors that contribute to human cancers. Ultimately, expanding the range of animal models that can be used to study cancer will lead to improved insights into cancer development, progression and metastasis, tumor microenvironment, as well as improved therapies and diagnostics, and will consequently reduce the negative impacts of the wide variety of cancers afflicting humans overall.

One health in regenerative medicine: report on the second Havemeyer symposium on regenerative medicine in horses

Regenerative medicine is commonly used in human and equine athletes. Potential therapies include culture expanded stem cells, stromal vascular fraction of adipose tissue, platelet-rich plasma, bone marrow concentrate, or autologous conditioned serum. The purpose of this manuscript is to disseminate findings from a workshop on the development of translational regenerative medicine in the equine field. Five themes emerged: stem cell characterization and tenogenic differentiation; interactions between mesenchymal stem cells, other cells and the environment; scaffolds and cell packaging; blood- and bone marrow-based regenerative medicines; clinical use of regenerative therapies. Evidence gained through the use of regenerative medicine applications in the horse should continue to translate to the human patient, bringing novel regenerative therapies to both humans and horses.

Equine pegiviruses cause persistent infection of bone marrow and are not associated with hepatitis

Pegiviruses frequently cause persistent infection (as defined by >6 months), but unlike most other Flaviviridae members, no apparent clinical disease. Human pegivirus (HPgV, previously GBV-C) is detectable in 1–4% of healthy individuals and another 5–13% are seropositive. Some evidence for infection of bone marrow and spleen exists. Equine pegivirus 1 (EPgV-1) is not linked to disease, whereas another pegivirus, Theiler’s disease-associated virus (TDAV), was identified in an outbreak of acute serum hepatitis (Theiler’s disease) in horses. Although no subsequent reports link TDAV to disease, any association with hepatitis has not been formally examined. Here, we characterized EPgV-1 and TDAV tropism, sequence diversity, persistence and association with liver disease in horses. Among more than 20 tissue types, we consistently detected high viral loads only in serum, bone marrow and spleen, and viral RNA replication was consistently identified in bone marrow. PBMCs and lymph nodes, but not liver, were sporadically positive. To exclude potential effects of co-infecting agents in experimental infections, we constructed full-length consensus cDNA clones; this was enabled by determination of the complete viral genomes, including a novel TDAV 3’ terminus. Clone derived RNA transcripts were used for direct intrasplenic inoculation of healthy horses. This led to productive infection detectable from week 2–3 and persisting beyond the 28 weeks of study. We did not observe any clinical signs of illness or elevation of circulating liver enzymes. The polyprotein consensus sequences did not change, suggesting that both clones were fully functional. To our knowledge, this is the first successful extrahepatic viral RNA launch and the first robust reverse genetics system for a pegivirus. In conclusion, equine pegiviruses are bone marrow tropic, cause persistent infection in horses, and are not associated with hepatitis. Based on these findings, it may be appropriate to rename the group of TDAV and related viruses as EPgV-2.

Transmissible hepatitis in horses (Theiler’s disease) has been known for 100 years without knowledge of causative infectious agents. Recently, two novel equine pegiviruses (EPgV) were discovered. Whereas EPgV-1 was not associated to disease, the other was identified in an outbreak of acute serum hepatitis and therefore named Theiler’s disease-associated virus (TDAV). This finding was surprising since human and monkey pegiviruses typically cause long-term infection without associated clinical disease. Whereas no subsequent reports link TDAV to disease, the original association to hepatitis has not been formally examined. Here, we studied EPgV-1 and TDAV and found that their natural history of infection in horses were remarkably similar. Examination of various tissues identified the bone marrow as the primary site of replication for both viruses with no evidence of replication in the liver. To exclude potential effects of other infectious agents, we developed molecular full-length clones for EPgV-1 and TDAV and were able to initiate infection in horses using derived synthetic viral genetic material. This demonstrated long-term infection, but no association with hepatitis. These findings call into question the connection between TDAV, liver infection, and hepatitis in horses.

The mesenchymal stromal cell secretome impairs methicillin-resistant Staphylococcus aureus biofilms via cysteine protease activity in the equine model

Mesenchymal stromal cells (MSCs) from various species, such as humans, mice, and horses, were recently found to effectively inhibit the growth of various bacteria associated with chronic infections, such as nonhealing cutaneous wounds, via secretion of antimicrobial peptides. These MSC antimicrobial properties have primarily been studied in the context of the planktonic phenotype, and thus, information on the effects on bacteria in biofilms is largely lacking. The objectives of this study were to evaluate the in vitro efficacy of the MSC secretome against various biofilm-forming wound pathogens, including the methicillin-resistant Staphylococcus aureus (MRSA), and to explore the mechanisms that affect bacterial biofilms. To this end, we used equine MSCs, because the horse represents a physiologically relevant model for human wound healing and offers a readily translatable model for MSC therapies in humans. Our salient findings were that the equine MSC secretome inhibits biofilm formation and mature biofilms of various bacteria, such as Pseudomonas aeruginosa, S. aureus, and Staphylococcus epidermidis. Furthermore, we demonstrated that equine MSC secrete cysteine proteases that destabilize MRSA biofilms, thereby increasing the efficacy of antibiotics that were previously tolerated by the biofilms. In light of the rise of antibiotic-resistant bacterial strains as an increasing global health threat, our results provide the rationale for using the MSC secretome as a complementary treatment for bacterial skin infections in both humans and horses.

First report of equine parvovirus-hepatitis-associated Theiler's disease in Europe

BACKGROUND

Equine parvovirus-hepatitis (EqPV-H) has been proposed as the aetiological cause of Theiler's disease, also known as serum hepatitis. EqPV-H-associated Theiler's disease has not been previously reported in Europe.

OBJECTIVES

To determine whether EqPV-H infection was associated with a 2018-2019 outbreak of Theiler's disease in four horses on a studfarm.

STUDY DESIGN

Descriptive case series.

METHODS

The medical records of four horses from the same farm diagnosed with fatal Theiler's disease were examined retrospectively. Information collected included a clinical history, physical examination findings, tetanus antitoxin exposure, serum biochemistry and necropsy reports. Liver tissue from all four horses was tested for EqPV-H using PCR and in situ hybridisation (ISH) assays.

RESULTS

Three of the horses had a history of recent (7-11 weeks) tetanus antitoxin administration. Liver tissue from all four horses tested positive for EqPV-H with PCR. In situ hybridisation revealed a widespread distribution of viral nucleic acid in hepatocytes in one case, and a more sporadic distribution in the remaining three cases.

MAIN LIMITATIONS

Case controls were not available from the farm in question given the retrospective nature of analysis.

CONCLUSIONS

This case series documents the first reported EqPV-H-associated Theiler's disease in Europe and the first use of ISH to visualise the viral nucleic acid in liver tissues of horses with Theiler's disease.

Tropism, pathology, and transmission of equine parvovirus-hepatitis

Equine parvovirus-hepatitis (EqPV-H) has recently been associated with cases of Theiler's disease, a form of fulminant hepatic necrosis in horses. To assess whether EqPV-H is the cause of Theiler's disease, we first demonstrated hepatotropism by PCR on tissues from acutely infected horses. We then experimentally inoculated horses with EqPV-H and 8 of 10 horses developed hepatitis. One horse showed clinical signs of liver failure. The onset of hepatitis was temporally associated with seroconversion and a decline in viremia. Liver histology and in situ hybridization showed lymphocytic infiltrates and necrotic EqPV-H-infected hepatocytes. We next investigated potential modes of transmission. Iatrogenic transmission via allogeneic stem cell therapy for orthopedic injuries was previously suggested in a case series of Theiler's disease, and was demonstrated here for the first time. Vertical transmission and mechanical vectoring by horse fly bites could not be demonstrated in this study, potentially due to limited sample size. We found EqPV-H shedding in oral and nasal secretions, and in feces. Importantly, we could demonstrate EqPV-H transmission via oral inoculation with viremic serum. Together, our findings provide additional information that EqPV-H is the likely cause of Theiler's disease and that transmission of EqPV-H occurs via both iatrogenic and natural routes.

Effects of orally administered raltegravir in cats with experimentally induced ocular and respiratory feline herpesvirus-1 infection

OBJECTIVE

To determine the effects of orally administered raltegravir in cats with experimentally induced ocular and respiratory feline herpesvirus-1 (FHV-1) infection.

ANIMALS

14 healthy 6-month-old unvaccinated specific pathogen-free cats.

PROCEDURES

On day 0, all cats were experimentally inoculated by topical application of 0.1 mL of a solution containing 10⁶ plaque-forming units of FHV-1 strain FH2CS to the inferior conjunctival fornix of each eye. Cats were randomly assigned to receive either raltegravir (80 mg; n = 7) or lactose (250 mg; vehicle; 7), PO, every 12 hours for 14 days beginning on day 1. Cats were assigned clinical ocular and respiratory disease scores every other day from days 0 to 30. Conjunctival swab specimens were collected for detection of FHV-1 by virus isolation and real-time PCR assay at 3-day intervals from days 0 to 30. Confocal microscopy was performed on days 0 and 10 to assess corneal epithelial leukocyte infiltration. The assessed variables and duration of FHV-1 shedding were compared between the 2 treatment groups.

RESULTS

Cats in both groups developed moderate to severe conjunctivitis and ulcerative keratitis characteristic of FHV-1 infection. Median duration of FHV-1 shedding was shorter and signs of ocular and respiratory disease were less severe for raltegravir-treated cats than for vehicle-treated cats. However, the mean conjunctival FHV-1 titer and corneal epithelial leukocyte count did not differ between the 2 groups.

CONCLUSIONS AND CLINICAL RELEVANCE

Results suggested orally administered raltegravir might be effective for alleviation of ocular and respiratory signs of FHV-1 infection in cats. (Am J Vet Res 2019;80:490-497).

What Do We Know About Hepatitis Viruses in Horses?

Theiler disease (serum hepatitis or idiopathic acute hepatic necrosis) has long been suspected to have a viral etiology. Four viruses have been described in association with hepatitis in horses. Further investigation suggests equine pegivirus and Theiler disease-associated virus (a second pegivirus) are neither hepatotropic nor pathogenic. Nonprimate hepacivirus (NPHV) causes subclinical disease in experimental models and has been associated with hepatitis in some clinical cases. Equine parvovirus-hepatitis (EqPV-H) experimentally causes subclinical-to-clinical liver disease and is found in the vast majority of Theiler disease cases. EqPV-H is likely of clinical significance, whereas the significance of NPHV is unknown.

Viral testing of 10 cases of Theiler's disease and 37 in-contact horses in the absence of equine biologic product administration: A prospective study (2014-2018)

Background

A novel equine parvovirus (EqPV‐H) was recently discovered in the equine liver with Theiler's disease.

Objectives

To determine the prevalence of EqPV‐H infection in naturally occurring Theiler's disease cases and in‐contact horses in the absence of historical equine biologic product administration.

Animals

Ten cases of Theiler's disease from 6 separate properties were included in the study, based on the criteria of acute onset of clinical signs of liver failure with laboratory or histopathologic findings characteristic of Theiler's disease and no history of receiving an equine biologic product within the preceding 4 months. In addition, 37 in‐contact horses from 4 of the 6 properties were screened for EqPV‐H infection and hepatitis.

Methods

In prospective case series, cases were diagnosed with Theiler's disease by the attending veterinarian and were tested for EqPV‐H by PCR of liver or serum. In‐contact horses were assessed via serum chemistry and PCR at the attending veterinarian's discretion. Hepatitis was defined as serum gamma‐glutamyltransferase activity above reference interval. The association of EqPV‐H with hepatitis was determined by Fisher's exact test.

Results

Nine of 10 (90%) Theiler's disease cases and 54% of tested in‐contact horses were EqPV‐H positive. Hepatitis was significantly associated with EqPV‐H infection (P = .036).

Conclusions and Clinical Importance

Although further study is required to identify EqPV‐H as the causative agent of Theiler's disease, EqPV‐H appears strongly associated with cases of fatal Theiler's disease and subclinical hepatitis in horses in contact with those cases. The prevalence of EqPV‐H infection on affected properties can be high.

Viral testing of 18 consecutive cases of equine serum hepatitis: A prospective study (2014-2018)

Background

Three flaviviruses (equine pegivirus [EPgV]; Theiler's disease–associated virus [TDAV]; non‐primate hepacivirus [NPHV]) and equine parvovirus (EqPV‐H) are present in equine blood products; the TDAV, NPHV, and EqPV‐H have been suggested as potential causes of serum hepatitis.

Objective

To determine the prevalence of these viruses in horses with equine serum hepatitis.

Animals

Eighteen horses diagnosed with serum hepatitis, enrolled from US referral hospitals.

Methods

In the prospective case study, liver, serum, or both samples were tested for EPgV, TDAV, NPHV, and EqPV‐H by PCR.

Results

Both liver tissue and serum were tested for 6 cases, serum only for 8 cases, and liver only for 4 cases. Twelve horses received tetanus antitoxin (TAT) 4‐12.7 weeks (median = 8 weeks), 3 horses received commercial equine plasma 6‐8.6 weeks, and 3 horses received allogenic stem cells 6.4‐7.6 weeks before the onset of hepatic failure. All samples were TDAV negative. Two of 14 serum samples were NPHV‐positive. Six of 14 serum samples were EPgV‐positive. All liver samples were NPHV‐negative and EPgV‐negative. EqPV‐H was detected in the serum (N = 8), liver (N = 4), or both samples (N = 6) of all 18 cases. The TAT of the same lot number was available for virologic testing in 10 of 12 TAT‐associated cases, and all 10 samples were EqPV‐H positive.

Conclusions and Clinical Importance

We demonstrated EqPV‐H in 18 consecutive cases of serum hepatitis. EPgV, TDAV, and NPHV were not consistently present. This information should encourage blood product manufacturers to test for EqPV‐H and eliminate EqPV‐H–infected horses from their donor herds.

Evaluation of topical ophthalmic ganciclovir gel for the treatment of dogs with experimentally induced ocular canine herpesvirus-1 infection

OBJECTIVE To determine the in vitro half maximal effective concentration (EC₅₀) of ganciclovir for canine herpesvirus-1 (CHV-1) and to evaluate the efficacy of ganciclovir ophthalmic gel in dogs with experimentally induced ocular CHV-1 infection. ANIMALS 10 specific pathogen-free adult Beagles. PROCEDURES Cytotoxicity and EC₅₀ of ganciclovir for CHV-1 were determined during in vitro experiments. During an in vivo experiment, dogs with experimentally induced ocular CHV-1 infections received 1 drop of 0.15% ganciclovir (ganciclovir group; n = 5) or artificial tear (control group; 5) ophthalmic gel in both eyes 5 times daily for 7 days, then 3 times daily for 7 days. For each dog, ophthalmic and confocal microscopic examinations were performed at predetermined times to determine severity of ocular disease and inflammation. Conjunctival swab specimens were collected at predetermined times for PCR assay analysis to determine CHV-1 shedding. RESULTS No in vitro cytotoxic effects were observed for ganciclovir concentrations ≤ 500μM. The EC₅₀ of ganciclovir for CHV-1 was 37.7μM. No adverse effects associated with ganciclovir were observed during the in vivo experiment. Mean ocular disease and inflammation scores for the ganciclovir group were significantly lower than those for the control group. Mean duration of CHV-1 shedding for the ganciclovir group (0.4 days) was significantly shorter than that for the control group (6.2 days). CONCLUSIONS AND CLINICAL RELEVANCE Topical administration of 0.15% ganciclovir ophthalmic gel was well tolerated and effective in decreasing clinical disease scores, ocular tissue inflammation, and duration of viral shedding in dogs with experimentally induced ocular CHV-1 infection.

Differential signaling pathway activation in 7,12-dimethylbenz[a] anthracene (DMBA)-treated mammary stem/progenitor cells from species with varying mammary cancer incidence

A natural variation exists in the susceptibility to mammary cancer among wild and domestic mammalian species. Mammary stem/progenitor cells (MaSC) represent a primary target cell for transformation; however, little is known about the intrinsic response of these cells to carcinogenic insults. Polycyclic aromatic hydrocarbons (PAH), such as 7,12-dimethylbenz[a]anthracene (DMBA), are abundantly present in the environment and have been linked to the development of mammary cancer in humans and rodents. We treated MaSC from equine (mammary cancer-resistant) and canine (mammary cancer-susceptible) species with DMBA and assessed cytochrome P450 metabolic activity, DNA damage and viability. Our notable findings were that MaSC from both species showed DNA damage following DMBA treatment; however, equine MaSC initiated cell death whereas canine MaSC repaired this DNA damage. Follow-up studies, based on genome-wide transcriptome analyses, revealed that DMBA induced activation of both the intrinsic and extrinsic apoptotic pathways in equine, but not canine, MaSC. Based on these findings, we propose a hypothetical model in which undergoing apoptosis in response to an oncogenic event might contribute to a lower incidence of mammary cancer in certain mammalian species. Such a mechanism would allow for the elimination of DNA-damaged MaSC, and hence, reduce the risk of potential tumor-initiating mutations in these cells.

Transcriptome profiling of alphaherpesvirus-infected cells treated with the HIV-integrase inhibitor raltegravir reveals profound and specific alterations in host transcription

Anti-microbial compounds typically exert their action by directly interfering with one or more stages of the pathogen's life cycle. However, some compounds also have secondary effects on the host that aid in pathogen clearance. Raltegravir is a human immunodeficiency virus (HIV)-integrase inhibitor that has been shown to alter the host immune response to HIV in addition to its direct antiviral effect. Interestingly, raltegravir can also directly inhibit the replication of various herpesviruses. However, the host-targeted effects of this drug in the context of a herpesvirus infection have not been explored. Here, we used felid alphaherpesvirus 1 (FHV-1), a close relative of human alphaherpesvirus 1 (HHV-1) that similarly causes ocular herpes, to characterize the host-targeted effects of raltegravir on corneal epithelial cells during an alphaherpesvirus infection. Using RNA deep sequencing, we found that raltegravir specifically boosts the expression of anti-angiogenic factors and promotes metabolic homeostasis in FHV-1-infected cells. In contrast, few changes in host gene transcription were found in uninfected cells. Importantly, we were able to demonstrate that these effects were specific to raltegravir and independent of the direct-acting antiviral effect of the drug, since treatment with the DNA polymerase inhibitor phosphonoacetic acid did not induce these host-targeted effects. Taken together, these results indicate that raltegravir has profound and specific effects on the host transcription profile of herpesvirus-infected cells that may contribute to the overall antiviral activity of the drug and could provide therapeutic benefits in vivo. Furthermore, this study provides a framework for future efforts evaluating the host-targeted effects of anti-microbial compounds.

Equine mesenchymal stromal cells from different tissue sources display comparable immune-related gene expression profiles in response to interferon gamma (IFN)-γ

Mesenchymal stromal cells (MSC) have the therapeutic potential to decrease inflammation due to their immunomodulatory properties. They can be isolated from various tissue sources such as bone marrow, adipose tissue, and blood, but it is unknown how the tissue source of origin affects the responses of MSC to inflammatory stimuli. Here, we conceptually addressed this question by evaluating the immune-related gene expression profiles of equine MSC from different tissue sources in response to interferon gamma (IFN-γ) stimulation, with the goal to determine if there is a preferable MSC source for clinical application in an inflammatory environment. The salient findings from this initial study were that the baseline expression of all immune related genes analyzed, with the exception of prostaglandin-endoperoxide synthase 2 (PTGS2), was variable in MSC depending on tissue source. Following IFN-γ stimulation, however, gene expression profiles became more similar across all tissue sources, suggesting that MSC from different sources will likely respond similarly in an inflammatory environment when used clinically.

The secretome of adipose-derived mesenchymal stem cells protects SH-SY5Y cells from arsenic-induced toxicity, independent of a neuron-like differentiation mechanism

Arsenic exposure through contaminated food, water, and air causes irreversible neural damage and affects millions of people worldwide. Several studies have demonstrated that the secreted factors (secretome) from mesenchymal stromal/stem cells (MSCs) can promote neural recovery after several forms of injury including stroke and neurodegenerative diseases. The present study was conducted to determine if the secretome from adipose-derived MSCs (ADSCs) prevents arsenic damage to SH-SY5Y cells. To this end, human neuroblastoma cells (SH-SY5Y) were pre-treated with the secretome from ADSCs and then challenged with different concentrations of arsenic. After various doses and exposure times, the extent of neuronal injury was assessed using MTT reduction and LDH release assays as well as LIVE/DEAD staining. These data demonstrate that the ADSC secretome protects SH-SY5Y cells from arsenic-induced toxicity. Previous reports have shown that the secretome of MSCs can induce neuroblast differentiation and mature neurons are less susceptible to chemical-induced toxicity. In the current study, proliferation assays, neurite length assessment, and quantitative RT-PCR of differentiation markers indicated that the ADSC secretome does not induce SH-SY5Y differentiation into a mature neuron-like phenotype. In contrast, our results demonstrated that soluble factor(s) in the ADSC secretome enhance SH-SY5Y cell substrate-dependent adhesion. The present study is the first to illustrate that the secretome from ADSCs protects SH-SY5Y cells from arsenic-induced toxicity. Additionally, we showed that protection against arsenic toxicity is not dependent on SH-SY5Y cell differentiation into a mature neuron-like phenotype, but involves soluble factor(s) in the secretome that appear to enhance cell survival by an adhesion-dependent mechanism.

BB-Cl-Amidine as a novel therapeutic for canine and feline mammary cancer via activation of the endoplasmic reticulum stress pathway

Background

Mammary cancer is highly prevalent in dogs and cats and results in a poor prognosis due to critically lacking viable treatment options. Recent human and mouse studies have suggested that inhibiting peptidyl arginine deiminase enzymes (PAD) may be a novel breast cancer therapy. Based on the similarities between human breast cancer and mammary cancer in dogs and cats, we hypothesized that PAD inhibitors would also be an effective treatment for mammary cancer in these animals.

Methods

Canine and feline mammary cancer cell lines were treated with BB-Cl-Amidine (BB-CLA) and evaluated for viability and tumorigenicity. Endoplasmic reticulum stress was tested by western blot, immunofluorescence, and quantitative reverse transcriptase polymerase chain reaction (qRT-PCR). Canine and feline mammary cancer xenograft models were created using NOD scid gamma (NSG) mice, and were treated with BB-CLA for two weeks.

Results

We found that BB-CLA reduced viability and tumorigenicity of canine and feline mammary cancer cell lines in vitro. Additionally, we demonstrated that BB-CLA activates the endoplasmic reticulum stress pathway in these cells by downregulating 78 kDa Glucose-regulated Protein (GRP78), a potential target in breast cancer for molecular therapy, and upregulating the downstream target gene DNA Damage Inducible Transcript 3 (DDIT3). Finally, we established a mouse xenograft model of both canine and feline mammary cancer in which we preliminarily tested the effects of BB-CLA in vivo.

Conclusion

We propose that our established mouse xenograft models will be useful for the study of mammary cancer in dogs and cats, and furthermore, that BB-CLA has potential as a novel therapeutic for mammary cancer in these species.

Electronic supplementary material

The online version of this article (10.1186/s12885-018-4323-8) contains supplementary material, which is available to authorized users.

The secretome from bovine mammosphere-derived cells (MDC) promotes angiogenesis, epithelial cell migration, and contains factors associated with defense and immunity

Treatment of bovine mastitis with intramammary antibiotics is common, yet several concerns exist including failed efficacy for individual hosts or pathogens and the inability of approved drugs to revert mastitis-induced tissue damage to healthy tissue capable of returning to full milk production. These issues, in addition to aspects of public health such as accidental antibiotic residues in saleable milk and the potential for antimicrobial resistance, support the need to find alternative therapies for this costly disease. This study shows that the secretome, or collective factors, produced by mammosphere-derived cells (MDC) promotes angiogenesis, epithelial cell migration, and contains proteins associated with immunity and defense; all of which are necessary for healing damaged mammary gland tissue. Furthermore, we found that the MDC secretome remains effective after freezing and thawing, enhancing its therapeutic potential. Our results provide a foundation for further characterization of the individual secreted factors and the rationale for using the MDC secretome as a complementary treatment for bovine mastitis.

Effect of a Histone Demethylase Inhibitor on Equine Herpesvirus-1 Activity In Vitro

Equine herpesvirus type 1 (EHV-1) is a ubiquitous and highly contagious pathogen that causes a range of disease severities with outbreaks of notable economic impact. Given the limitations in immune protection of current vaccines and the limited effectiveness of antiviral drugs on EHV-1 infections in vivo, improved treatment measures are needed to control disease. The use of drugs that alter the epigenetic state of herpes simplex virus genome has been shown to limit viral primary infection and reactivation both in vitro and in vivo. Therefore, we tested the hypothesis that maintaining a repressive epigenetic state on the EHV-1 genome in the host equine cell would decrease viral load during lytic infection. Equine fetal kidney cells (EFKCs) or isolated peripheral blood leukocytes were treated in vitro with (a) the nucleoside analog ganciclovir; (b) the histone demethylase inhibitor OG-L002; (c) both ganciclovir and OG-L002; or (d) dimethyl sulfoxide (DMSO, vehicle control); and then infected with a clinical EHV-1 isolate. Treatment of EFKCs with ganciclovir (mean 22.3 DNA copies per cell, p = 0.0005), OG-L002 (mean 25.6, p = 0.005) or both ganciclovir and OG-L002 (mean 7.1, p = 0.0001) resulted in decreased EHV-1 viral load at 24 h post-infection (hpi) in comparison with DMSO (mean 42.0), with greater impact using the combined treatment. Further, EHV-1 gene expression at 3 hpi decreased when EFKCs were infected in the presence of ganciclovir (p = 0.04) and combined treatment of ganciclovir and OG-L002 (p = 0.0003). In contrast, under similar conditions, neither ganciclovir nor OG-L002 suppressed EHV-1 infection in leukocytes. Differences between cell types, drug penetrance, or drug turnover, may have contributed to the distinct effects observed in this study.

New Paradigms for the Study of Ocular Alphaherpesvirus Infections: Insights into the Use of Non-Traditional Host Model Systems

Ocular herpesviruses, most notably human alphaherpesvirus 1 (HSV-1), canid alphaherpesvirus 1 (CHV-1) and felid alphaherpesvirus 1 (FHV-1), infect and cause severe disease that may lead to blindness. CHV-1 and FHV-1 have a pathogenesis and induce clinical disease in their hosts that is similar to HSV-1 ocular infections in humans, suggesting that infection of dogs and cats with CHV-1 and FHV-1, respectively, can be used as a comparative natural host model of herpesvirus-induced ocular disease. In this review, we discuss both strengths and limitations of the various available model systems to study ocular herpesvirus infection, with a focus on the use of these non-traditional virus-natural host models. Recent work has demonstrated the robustness and reproducibility of experimental ocular herpesvirus infections in dogs and cats, and, therefore, these non-traditional models can provide additional insights into the pathogenesis of ocular herpesvirus infections.

First demonstration of equid gammaherpesviruses within the gastric mucosal epithelium of horses

Horses commonly develop gastric mucosal ulcers, similar to humans, a condition known as equine gastric ulcer syndrome (EGUS) that can lead to poor performance and lost training time and care expenses. Unlike humans, however, an infectious bacterial cause of ulcers has not been conclusively identified. Herpesviruses, while well-established causative agents of diseases such as cold sores, genital lesions, and certain types of cancer, have also been implicated in the development of a subset of gastric ulcers in humans. The presence of equid herpesviruses in the gastrointestinal tract and their potential contribution to EGUS has not been evaluated. Here, we provide the first evidence of equid gammaherpesviruses 2 and 5 (EHV-2 and -5) within the epithelium of the gastric mucosa of horses. These viruses were initially detected by a nested PCR screen of gastric tissue samples obtained from client- and university-owned horses with and without ulcers; however, no association with EGUS was found in this limited sample set. We then validated a highly sensitive in situ hybridization (ISH) assay and used this assay to characterize the distribution of these viruses in necropsy gastric tissue samples from five racehorses. Analyses revealed frequent EHV-2 and EHV-5 co-infections within the gastric mucosal epithelium, regardless of the ulcer status. These results are the first to demonstrate the presence of equid gammaherpesviruses in the gastric mucosa of horses and warrants further investigation to determine the contribution of these viruses to the development of EGUS and/or other gastrointestinal diseases.

Conserved and variable: Understanding mammary stem cells across species

Postnatal mammary gland development requires the presence of mammary stem and progenitor cells (MaSC), which give rise to functional milk-secreting cells and regenerate the mammary epithelium with each cycle of lactation. These long-lived, tissue-resident MaSC are also targets for malignant transformation and may be cancer cells-of-origin. Consequently, MaSC are extensively researched in relation to their role and function in development, tissue regeneration, lactation, and breast cancer. The basic structure and function of the mammary gland are conserved among all mammalian species, from the most primitive to the most evolved. However, species vary greatly in their lactation strategies and mammary cancer incidence, making MaSC an interesting focus for comparative research. MaSC have been characterized in mice, to a lesser degree in humans, and to an even lesser degree in few additional mammals. They remain uncharacterized in most mammalian species, including "ancient" monotremes, marsupials, wild, and rare species, as well as in common and domestic species such as cats. Identification and comparison of MaSC across a large variety of species, particularly those with extreme lactational adaptations or low mammary cancer incidence, is expected to deepen our understanding of development and malignancy in the mammary gland. Here, we review the current status of MaSC characterization across species, and underline species variations in lactation and mammary cancer through which we may learn about the role of MaSC in these processes. © 2017 International Society for Advancement of Cytometry.

Antimicrobial peptides secreted by equine mesenchymal stromal cells inhibit the growth of bacteria commonly found in skin wounds

BACKGROUND

The prevalence of chronic skin wounds in humans is high, and treatment is often complicated by the presence of pathogenic bacteria. Therefore, safe and innovative treatments to reduce the bacterial load in cutaneous wounds are needed. Mesenchymal stromal cells (MSC) are known to provide paracrine signals that act on resident skin cells to promote wound healing, but their potential antibacterial activities are not well described. The present study was designed to examine the antibacterial properties of MSC from horses, as this animal model offers a readily translatable model for MSC therapies in humans. Specifically, we aimed to (i) evaluate the in vitro effects of equine MSC on the growth of representative gram-negative and gram-positive bacterial species commonly found in skin wounds and (ii) define the mechanisms by which MSC inhibit bacterial growth.

METHODS

MSC were isolated from the peripheral blood of healthy horses. Gram-negative E. coli and gram-positive S. aureus were cultured in the presence of MSC and MSC conditioned medium (CM), containing all factors secreted by MSC. Bacterial growth was measured by plating bacteria and counting viable colonies or by reading the absorbance of bacterial cultures. Bacterial membrane damage was detected by incorporation of N-phenyl-1-naphthylamine (NPN). Antimicrobial peptide (AMP) gene and protein expression by equine MSC were determined by RT-PCR and Western blot analysis, respectively. Blocking of AMP activity of MSC CM was achieved using AMP-specific antibodies.

RESULTS

We found that equine MSC and MSC CM inhibit the growth of E. coli and S. aureus, and that MSC CM depolarizes the cell membranes of these bacteria. In addition, we found that equine MSC CM contains AMPs, and blocking these AMPs with antibodies reduces the effects of MSC CM on bacteria.

CONCLUSIONS

Our results demonstrate that equine MSC inhibit bacterial growth and secrete factors that compromise the membrane integrity of bacteria commonly found in skin wounds. We also identified four specific AMPs produced by equine MSC. The secretion of AMPs may contribute to the value of MSC as a therapy for cutaneous wounds in both horses and humans.