Occipital condyle defects assessed by radiography or CT can be a normal finding in foals.

Age of complete ossification of equine occipital condyles has not been published. Consequently, clinical significance of occipital condyle defects on radiographs or CT scans of young horses remains unknown. The goals of this single-center, retrospective, cross-sectional study were to characterize incidental occipital condyle defects and to define the age of complete ossification. The margin of occipital condyles was classified as regular or with defect(s). Analyses were made on 121 horses, including 106 radiographic and 19 CT studies showing the occipital condyles of horses less than 5 years of age obtained over 6 years in a referral hospital. Neurological signs and outcome were not associated with occipital defects. Horses with regular occipital condyles on radiographs had a median age of 974 days (median interquartile range = 707) compared with 47 days (interquartile range = 106) in the defect group. The odds of finding radiographically regular occipital condyles were 2.6% higher for each additional day of age (P = .011, 95% CI, 0.6-4.7%). In the CT group, univariate analyses demonstrated a significant effect of age on the aspect of occipital condyles (P = .016). Horses with regular occipital condyles were older (median age = 881 days; interquartile range = 1054) than horses with a defect (median age = 109 days, interquartile range = 318). All horses above 156 days (5.1 months) of age and 550 days (18.1 months) of age had regular occipital condyles on radiographic and CT images, respectively. This study describes occipital condyle defects as a potential normal finding in young horses and provides guidelines for interpretation of the occipital condyle ossification process.

The equine asthma model of airway remodeling: from a veterinary to a human perspective.

Human asthma is a complex and heterogeneous disorder characterized by chronic inflammation, bronchospasm and airway remodeling. The latter is a major determinant of the structure-function relationship of the respiratory system and likely contributes to the progressive and accelerated decline in lung function observed in patients over time. Corticosteroids are the cornerstone of asthma treatment. While their action on inflammation and lung function is well characterized, their effect on remodeling remains largely unknown. An important hindrance to the study of airway remodeling as a major focus in asthma research is the lack of reliable non-invasive biomarkers. In consequence, the physiologic and clinical consequences of airway wall thickening and altered composition are not well understood. In this perspective, equine asthma provides a unique and ethical (non-terminal) preclinical model for hypothesis testing and generation. Severe equine asthma is a spontaneous disease affecting adult horses characterized by recurrent and reversible episodes of disease exacerbations. It is associated with bronchoalveolar neutrophilic inflammation, bronchospasm, and excessive mucus secretion. Severe equine asthma is also characterized by bronchial remodeling, which is only partially improved by prolonged period of disease remission induced by therapy or antigen avoidance strategies. This review will focus on the similarities and differences of airway remodeling in equine and human asthma, on the strengths and limitations of the equine model, and on the challenges the model has to face to keep up with human asthma research.

Lung Microbiome Is Influenced by the Environment and Asthmatic Status in an Equine Model of Asthma.

There is evidence that the lung microbiome differs between patients with asthma and healthy humans, but the effect of environmental conditions and medication is unknown and difficult to study. Equine asthma is a naturally occurring chronic airway disease characterized by reversible airway inflammation and bronchoconstriction upon exposure to inhaled antigens. In the present study, we evaluated the effect that environmental conditions and disease status have on pulmonary, nasal, and oral microbiomes. Six asthmatic and six healthy horses were studied while at pasture ("low antigen exposure"), as well as when being housed indoors and fed good-quality hay ("moderate exposure") and poor-quality hay ("high exposure"). At each time point, lung function was recorded; BAL, oral, and nasal rinses were collected; and 16S rRNA gene sequencing was performed. Asthmatic horses developed airway obstruction and inflammation under moderate and high antigen exposure conditions, whereas nonasthmatic horses showed mild inflammation under high antigen exposure, without bronchoconstriction. Lung, oral, and nasal communities clustered by environmental condition, but only lung communities were different between healthy and asthmatic horses. The association between asthma and lung microbiome was strongest in horses under moderate antigen exposure. Pulmonary, oral, and nasal microbiomes are influenced by environmental conditions, but only the pulmonary microbiome differs between horses with and without asthma. This difference, seen mainly when airway inflammation was present in horses with asthma but not in control animals, suggests that the altered lung microbiome in asthma might not be inherent but coincident with inflammation.

MicroRNA-221 is overexpressed in the equine asthmatic airway smooth muscle and modulates smooth muscle cell proliferation.

Airway wall remodeling, including hyperplasia and hypertrophy of smooth muscle (ASM) cells leading to an increased smooth muscle mass, is considered central to asthma. However, molecular pathways responsible for ASM remodeling remain poorly understood. MicroRNAs (miRNAs) have emerged as key regulators of inflammatory and repair processes affecting the lungs and can downregulate protein expression by inhibiting target mRNA translation. We therefore hypothesized that miRNAs are involved in ASM remodeling in asthma by modulating ASM proliferation. We have analyzed the expression of miRNAs in bronchial smooth muscle from asthmatic horses during disease exacerbation and remission and from controls. Their involvement in ASM cell proliferation was then studied. Our results shown that miR-26a, miR-133, and miR-221 were upregulated in ASM from horses with asthma exacerbation compared with asthma remission and controls. MiR-221 induced cell hyperproliferation and reduced the expression of contractile gene markers in ASM cells. These changes were associated with the decreased mRNA expression of cell cycle regulatory genes (p53, p21, and p27). In conclusion, we demonstrated for the first time an upregulation of miR-221 in asthmatic airway smooth muscle and confirm the involvement of miR-221 in ASM cell proliferation by regulation of the cell cycle arrest genes. Targeting miR-221 network genes may represent a novel approach for the treatment of ASM remodeling in asthma.

Insights into animal models for cell-based therapies in translational studies of lung diseases: Is the horse with naturally occurring asthma the right choice?

Human asthma is a widespread disease associated with chronic inflammation of the airways, leading to loss of quality of life, disability and death. Corticosteroid administration is the mainstream treatment for asthmatic patients. Corticosteroids reduce airway obstruction and improve quality of life, although symptoms persist despite treatment in many patients. Moreover, available therapies failed to reverse the lung pathology present in asthma. Animal models, mostly rats and mice, in which the disease is experimentally induced, have been studied to identify new therapeutic targets for human asthma. Alternative animal models could include horses in which naturally occurring asthma could represent an important step to test therapies, potentially designed around mouse studies, before being translated to human testing. Horses naturally suffer from asthma, which has striking parallels with human asthma. Severe equine asthma (SEA) is characterized by reversible bronchospasms and neutrophil accumulation in the lungs immunologically mediated mainly by Th2. Moreover, the pulmonary remodelling that occurs in SEA closely resembles that of human asthma, making the equine model unique for investigation of tissue repair and new therapies. Cell therapy, consisting on mesenchymal stromal cells (MSCs) and derivatives (conditioned medium and extracellular vesicles), could represent a novel therapeutic contribution for tissue regeneration. Cell therapy may prove advantageous over conventional therapy in that it may repair or regenerate the site of injury and reduce the reaction to allergens, rather than simply modulating the inflammatory process.

Maintenance of contractile function of isolated airway smooth muscle after cryopreservation.

Isolated human airway smooth muscle (ASM) tissue contractility studies are essential for understanding the role of ASM in respiratory disease, but limited availability and cost render storage options necessary for optimal use. However, to our knowledge, no comprehensive study of cryopreservation protocols for isolated ASM has been performed to date. We tested several cryostorage protocols on equine trachealis ASM using different cryostorage media [1.8 M dimethyl sulfoxide and fetal bovine serum (FBS) or Krebs-Henseleit (KH)] and different degrees of dissection (with or without epithelium and connective tissues attached) before storage. We measured methacholine (MCh), histamine, and isoproterenol (Iso) dose-responses and electrical field stimulation (EFS) and MCh force-velocity curves. We confirmed our findings in human trachealis ASM stored undissected in FBS. Maximal stress response to MCh was decreased more in dissected than undissected equine tissues. EFS force was decreased in all equine but not in human cryostored tissues. Furthermore, in human cryostored tissues, EFS maximal shortening velocity was decreased, and Iso response was potentiated after cryostorage. Overnight incubation with 0.5 or 10% FBS did not recover contractility in the equine tissues but potentiated Iso response. Overnight incubation with 10% FBS in human tissues showed maximal stress recovery and maintenance of other contractile parameters. ASM tissues can be cryostored while maintaining most contractile function. We propose an optimal protocol for cryostorage of ASM as undissected tissues in FBS or KH solution followed by dissection of the ASM bundles and a 24-h incubation with 10% FBS before mechanics measurements.

Adherence to treatment recommendations and short-term outcome of pleasure and sport horses with equine asthma.

Treatments for mild forms of equine asthma are extrapolated from those recommended for severe equine asthma (heaves), but little is known about owner's adherence to recommendations and treatment efficacy. The objective was to determine which recommendations are implemented by owners and their perception of the clinical response to treatment. Medical records of 43 horses diagnosed with moderate asthma between 2010 and 2012 were retrieved from the Université de Montréal database. Treatments and perceived responses were recorded by telephone survey, 2 to 35 months after diagnosis. All 33 owners who completed the survey attempted to decrease exposure to dust and half had also administered medication. Twenty-four owners (73%) described a > 50% improvement in the clinical signs. There was no association between a specific treatment and outcome. A majority of owners of pleasure and sport horses with equine asthma perceived improvement when limiting exposure to hay and barn dust (alone or with medications).

Respect des recommandations de traitement et résultats à court terme pour les chevaux d'agrément et de sport atteints d'asthme des équidés. Les traitements pour des formes bénignes d'asthme des équidés sont extrapolés de ceux recommandés pour le traitement de l'asthme des équidés grave (emphysème chronique), mais on en sait encore peu à propos de l'observance des recommandations par les propriétaires et de l'efficacité du traitement. L'objectif consistait à déterminer quelles recommandations sont mises en oeuvre par les propriétaires et leur perception de la réponse clinique au traitement. Les dossiers médicaux de 43 chevaux diagnostiqués avec un asthme modéré entre 2010 et 2012 ont été récupérés de la base de données de l'Université de Montréal. Les traitements et les réactions perçues ont été consignés lors d'un sondage par téléphone, de 2 à 35 mois après le diagnostic. Les 33 propriétaires qui ont répondu au sondage avaient tenté de réduire l'exposition à la poussière et la moitié avaient aussi administré des médicaments. Vingt-quatre propriétaires (73 %) ont décrit une amélioration de > 50 % des signes cliniques. Il n'y avait aucune association entre un traitement spécifique et un résultat. La plupart des propriétaires possédant des chevaux d'agrément et de sport atteints d'asthme modéré ont perçu une amélioration lorsqu'ils limitaient l'exposition à la poussière de foin et de grange (comme seule mesure ou avec des médicaments). lorsqu'ils limitaient l'exposition à la poussière de foin et de grange (comme seule mesure ou avec des médicaments).(Traduit par Isabelle Vallières).

Neutrophil extracellular traps are downregulated by glucocorticosteroids in lungs in an equine model of asthma.

BACKGROUND: Severe neutrophilic asthma is poorly responsive to glucocorticosteroids (GC). Neutrophil extracellular traps (NETs) within the lungs have been associated with the severity of airway obstruction and inflammation in asthma, and were found to be unaffected by GC in vitro. As IL-17 is overexpressed in neutrophilic asthma and contributes to steroid insensitivity in different cell types, we hypothesized that NETs formation in asthmatic airways would be resistant to GC through an IL-17 mediated pathway. METHODS: Six neutrophilic severe asthmatic horses and six healthy controls were studied while being treated with dexamethasone. Lung function, bronchoalveolar lavage fluid (BALF) cytology and NETs formation, as well as the expression of CD11b and CD13 by blood and airway neutrophils were evaluated. The expression of IL-17 and its role in NETs formation were also studied. RESULTS: Airway neutrophils from asthmatic horses, as opposed to blood neutrophils, enhanced NETs formation, which was then decreased by GC. GC also tended to decrease the expression of CD11b in blood neutrophils, but not in airway neutrophils. IL-17 mRNA was increased in BALF cells of asthmatic horses and was unaffected by GC. However, both GC and IL-17 inhibited NETs formation in vitro. CONCLUSION: GC decreased NETs formation in vitro and also in vivo in the lungs of asthmatic horses. However, airway neutrophil activation during asthmatic inflammation was otherwise relatively insensitive to GC. The contribution of IL-17 to these responses requires further study.

The Contribution of Oxidative Stress and Inflamm-Aging in Human and Equine Asthma.

Aging is associated with a dysregulation of the immune system, leading to a general pro-inflammatory state of the organism, a process that has been named inflamm-aging. Oxidative stress has an important role in aging and in the regulation of immune responses, probably playing a role in the development of age-related diseases. The respiratory system function physiologically declines with the advancement of age. In elderly asthmatic patients, this may contribute to disease expression. In this review, we will focus on age-related changes affecting the immune system and in respiratory structure and function that could contribute to asthma occurrence, and/or clinical presentation in the elderly. Also, naturally occurring equine asthma will be discussed as a possible model for studying the importance of oxidative stress and immun-aging/inflamm-aging in humans.

COMPARISON OF THORACIC ULTRASONOGRAPHY AND RADIOGRAPHY FOR THE DETECTION OF INDUCED SMALL VOLUME PNEUMOTHORAX IN THE HORSE.

Small volume pneumothorax can be challenging to diagnose in horses. The current standard method for diagnosis is standing thoracic radiography. We hypothesized that thoracic ultrasonography would be more sensitive. Objectives of this prospective, experimental study were to describe a thoracic ultrasound method for detection of small volume pneumothorax in horses and to compare results of radiography and ultrasound in a sample of horses with induced small volume pneumothorax. Six mature healthy horses were recruited for this study. For each horse, five 50 ml air boluses were sequentially introduced via a teat cannula into the pleural space. Lateral thoracic radiographs and standardized ultrasound (2D and M-mode) examinations of both hemithoraces were performed following administration of each 50 ml air bolus. Radiographs and ultrasound images/videos were analyzed for detection of pneumothorax by four independent investigators who were unaware of treatment status. Sensitivity, specificity, positive predictive values, negative predictive values, and agreement among investigators (Kappa test, κ) were calculated for radiography, 2D and M-mode ultrasound. Comparisons were made using a chi-squared exact test with significance set at P < 0.05. Two-dimensional (84%) and M-mode (80%) ultrasound were more sensitive than radiography (48%) for pneumothorax detection (P = 0.02 and P = 0.04, respectively). Specificity and positive predictive values were similar for all three imaging modalities (P = 1). Agreement between investigators for pneumothorax detection was excellent for 2D ultrasound (κ = 1), very good for M-mode ultrasound (κ = 0.87), and good for radiography (κ = 0.79). Findings from this experimental study supported the use of thoracic ultrasonography as a diagnostic method for detecting pneumothorax in horses.

Neutrophil-Derived Exosomes: A New Mechanism Contributing to Airway Smooth Muscle Remodeling.

Neutrophils infiltrate the airways of patients with asthma of all severities, yet their role in the pathogenesis of asthma and their contribution to airway remodeling is largely unknown. We hypothesized that neutrophils modulate airway smooth muscle (ASM) proliferation in asthma by releasing bioactive exosomes. These newly discovered nano-sized vesicles have the capacity to modulate immune responses, cell migration, cell differentiation, and other aspects of cell-to-cell communication. The aim of the study is to determine whether bioactive exosomes are released by neutrophils, and, if so, characterize their proteomic profile and evaluate their capacity to modulate ASM cell proliferation. Exosomes were isolated from equine neutrophil supernatants by differential centrifugation and filtration methods, followed by size-exclusion chromatography. Nanovesicles were characterized using electron microscopy, particle size determination, and proteomic analyses. Exosomes were cocultured with ASM cells and analyzed for exosome internalization by confocal microscopy. ASM proliferation was measured using an impedance-based system. Neutrophils release exosomes that have characteristic size, morphology, and exosomal markers. We identified 271 proteins in exosomes from both LPS and unstimulated neutrophils, and 16 proteins that were differentially expressed, which carried proteins associated with immune response and positive regulation of cell communication. Furthermore, neutrophil-derived exosomes were rapidly internalized by ASM cells and altered their proliferative properties. Upon stimulation of LPS, neutrophil-derived exosomes can enhance the proliferation of ASM cells and could therefore play an important role in the progression of asthma and promoting airway remodeling in severe and corticosteroid-insensitive patients with asthma.

Peripheral Airway Smooth Muscle, but Not the Trachealis, Is Hypercontractile in an Equine Model of Asthma.

Heaves is a naturally occurring equine disease that shares many similarities with human asthma, including reversible antigen-induced bronchoconstriction, airway inflammation, and remodeling. The purpose of this study was to determine whether the trachealis muscle is mechanically representative of the peripheral airway smooth muscle (ASM) in an equine model of asthma. Tracheal and peripheral ASM of heaves-affected horses under exacerbation, or under clinical remission of the disease, and control horses were dissected and freed of epithelium to measure unloaded shortening velocity (Vmax), stress (force/cross-sectional area), methacholine effective concentration at which 50% of the maximum response is obtained, and stiffness. Myofibrillar Mg(2+)-ATPase activity, actomyosin in vitro motility, and contractile protein expression were also measured. Horses with heaves had significantly greater Vmax and Mg(2+)-ATPase activity in peripheral airway but not in tracheal smooth muscle. In addition, a significant correlation was found between Vmax and the time elapsed since the end of the corticosteroid treatment for the peripheral airways in horses with heaves. Maximal stress and stiffness were greater in the peripheral airways of the horses under remission compared with controls and the horses under exacerbation, potentially due to remodeling. Actomyosin in vitro motility was not different between controls and horses with heaves. These data demonstrate that peripheral ASM is mechanically and biochemically altered in heaves, whereas the trachealis behaves as in control horses. It is therefore conceivable that the trachealis muscle may not be representative of the peripheral ASM in human asthma either, but this will require further investigation.

Evolution of in vitro antimicrobial resistance in an equine hospital over 3 decades.

This study identified antimicrobial resistance patterns of commonly isolated bacteria at the Equine Hospital of the Université de Montréal between 2007 and 2013, and compared the results with the resistance patterns observed in tests performed in previous decades in the same hospital. A total of 396 antimicrobial susceptibility tests were analyzed by the Kirby-Bauer method during the period 2007 to 2013 and compared to 233 and 255 tests completed in 1986 to 1988 and 1996 to 1998, respectively. The most common bacteria were Streptococcus equi subsp. zooepidemicus (S. zooepidemicus) and Escherichia coli. Except for resistance of coagulase-positive staphylococci to trimethoprim-sulfamethoxazole, there was no overall increase in resistance observed between 1986 to 1988 and 2007 to 2013 for antimicrobials reported for all 3 periods. However, between 1996 to 1998 and 2007 to 2013, there was an increase in in vitro resistance to enrofloxacin for E. coli and Enterobacter spp., and to ceftiofur for Enterobacter spp. and coagulase-positive staphylococci. No increase in resistance was observed for S. zooepidemicus and no isolate was resistant to penicillin.

Évolution de l'antibiorésistancein vitrodans un hôpital équin pendant 3 décennies. L'objectif était d'identifier les patrons de résistance aux antimicrobiens des bactéries fréquemment isolées à l'Hôpital Équin de l'Université de Montréal de 2007 à 2013, pour ensuite les comparer aux données observées au cours des dernières décennies dans le même hôpital. Trois cent quatre-vingt-seize antibiogrammes faits à l'aide de la méthode Kirby-Bauer ont été analysés et comparés aux 233 et 255 ayant été effectués en 1986­1988 et 1996­1998, respectivement. Les bactéries les plus fréquentes étaient Streptococcus equi subsp. zooepidemicus (S. zooepidemicus) et Escherichia coli. Pour les antibiotiques testés pendant les 3 périodes de l'étude, il n'y pas eu d'augmentation de la résistance observée entre 1986­1988 et 2007­2013, à exception de celle des staphylocoques à coagulase positive au triméthoprime-sulfaméthoxazole. Cependant, entre 1996­1998 et 2007­2013, une augmentation de la résistance à l'enrofloxacin a été observée pour E. coli et Enterobacter spp., ainsi qu'une augmentation de la résistance au ceftiofur pour Enterobacter spp. et les staphylocoques à coagulase positive. Aucune augmentation de résistance n'a été observée pour S. zooepidemicus et aucun isolat n'était résistant à la pénicilline.(Traduit par les auteurs).

Contribution of SRF, Elk-1, and myocardin to airway smooth muscle remodeling in heaves, an asthma-like disease of horses.

Myocyte hyperplasia and hypertrophy contribute to the increased mass of airway smooth muscle (ASM) in asthma. Serum-response factor (SRF) is a transcription factor that regulates myocyte differentiation in vitro in vascular and intestinal smooth muscles. When SRF is associated with phosphorylated (p)Elk-1, it promotes ASM proliferation while binding to myocardin (MYOCD) leading to the expression of contractile elements in these tissues. The objective of this study was therefore to characterize the expression of SRF, pElk-1, and MYOCD in ASM cells from central and peripheral airways in heaves, a spontaneously occurring asthma-like disease of horses, and in controls. Six horses with heaves and five aged-matched controls kept in the same environment were studied. Nuclear protein expression of SRF, pElk-1, and MYOCD was evaluated in peripheral airways and endobronchial biopsies obtained during disease remission and after 1 and 30 days of naturally occurring antigenic exposure using immunohistochemistry and immunofluorescence techniques. Nuclear expression of SRF (P = 0.03, remission vs. 30 days) and MYOCD (P = 0.05, controls vs. heaves at 30 days) increased in the peripheral airways of horses with heaves during disease exacerbation, while MYOCD (P = 0.04, remission vs. 30 days) decreased in the central airways of control horses. No changes were observed in the expression of pElk-1 protein in either tissue. In conclusion, SRF and its cofactor MYOCD likely contribute to the hypertrophy of peripheral ASM observed in equine asthmatic airways, while the remodeling of the central airways is more static or involves different transcription factors.

Airway collagen and elastic fiber content correlates with lung function in equine heaves.

The consequences on lung function and inflammation of alterations in the extracellular matrix affecting the peripheral airway wall in asthma are largely unknown. We hypothesized that remodeling of collagen and elastic fibers in the peripheral airway wall leads to airway obstruction and contributes to neutrophilic airway inflammation. Animals used were six heaves-affected horses and five controls. Large peripheral lung biopsies were obtained from horses with heaves in clinical remission (Baseline) and during disease exacerbation and from age-matched controls. The area of collagen and elastic fiber content in the lamina propria was measured by histological staining techniques and corrected for airway size. Collagen type 1 and type 3 content was further assessed from additional horses after postmortem lung samples by immunohistochemistry. The collagen breakdown products proline-glycine-proline (PGP) and N-acetylated-PGP (N-α-PGP) were also measured in bronchoalveolar lavage fluids (BALF) by mass spectrometry. Compared with controls, heaves-affected horses had an increase in collagen (P = 0.05) and elastic fiber contents (P = 0.04) at baseline. Collagen types 1 and 3 content was also significantly increased in diseased horses (P = 0.015) when both collagen types were combined. No further change in collagen content was observed after a 30-day antigenic challenge. Airway collagen at baseline was positively correlated with pulmonary resistance in asthmatic horses (r(2) = 0.78, P = 0.03) and elastic fiber content was positively associated with pulmonary elastance in controls (r(2) = 0.95, P = 0.02). No difference between groups was appreciated in PGP and N-α-PGP peptides in BALF. Increased airway wall collagen and elastic fiber content may contribute to residual obstruction in the asthmatic airways.

Inhaled corticosteroids modulate the (+)insert smooth muscle myosin heavy chain in the equine asthmatic airways.

RATIONALE: Overexpression of the (+)insert smooth muscle myosin heavy chain (SMMHC) isoform could contribute to airway bronchospasm by increasing the velocity of contraction. Whether the (+)insert isoform is present in the small airways and its expression is reversible in asthma are unknown. OBJECTIVES: To determine the anatomical location and the expression kinetics of the (+)insert SMMHC isoform in airways of horses with heaves and to evaluate its modulation in response to disease status. METHODS: We evaluated the (+)insert SMMHC isoform in the airways of horses with heaves during disease exacerbation and remission, and in controls. The expression kinetics of the SMMHC (+)insert was then assessed at multiple time points in two studies: first, in horses with heaves treated for a 1-year period with antigen avoidance alone, inhaled corticosteroids alone or both; second, in horses with heaves before and after a 30-day natural antigen exposure. Gene expression analysis was assessed by quantitative PCR and protein expression was confirmed by targeted mass spectrometry. MEASUREMENTS AND MAIN RESULTS: The (+)insert SMMHC isoform was significantly increased in central and peripheral airways, but not in the trachea of heaves-affected horses in clinical exacerbation when compared horses with heaves in remission and controls. Both corticosteroid administration and antigen avoidance led to a significant reduction of the (+)insert expression in the airways. The (+)insert SMMHC isoform was not significantly increased in airways after 1 month of antigenic re-exposure. CONCLUSIONS: The (+)insert SMMHC expression is increased throughout the bronchial tree in horses with heaves and reversible by corticosteroids administration and antigen avoidance.

Towards personalized medicine for the treatment of equine asthma.

Although horses with asthma share similar clinical signs, the heterogeneity of the disease in terms of severity, triggering factors, inflammatory profile, and pathological features has hindered our ability to define biologically distinct subgroups. The recognition of phenotypes and endotypes could enable the development of precision medicine, including personalized, targeted therapy, to benefit affected horses. While in its infancy in horses, this review outlines the phenotypes of equine asthma and discusses how knowledge gained from targeted therapy in human medicine can be applied to evaluate the potential opportunities for personalized medicine in equine asthma and to suggest avenues for research to advance this emerging field.

Comparative study of the bronchodilator efficacy and adverse effects of salbutamol and hyoscine butylbromide in horses with severe asthma.

BACKGROUND: Salbutamol and hyoscine butylbromide (HBB) are commonly used bronchodilators in horses with severe asthma (SA). OBJECTIVE: To compare the bronchodilation potency, duration, and adverse effects of salbutamol and HBB in SA. ANIMALS: Six horses in exacerbation of SA. METHODS: The effects of inhaled salbutamol (1000 µg) and HBB (150 mg, IV) were compared in a randomized, blinded, crossover experiment. Lung function, intestinal borborygmi and heart rate were assessed before and sequentially until 180 minutes after drug administration, and analyzed with 2-way repeated-measures ANOVA and Dunnett's multiple comparison tests. RESULTS: Both treatments caused a similar improvement in lung function. Pulmonary resistance and reactance returned to baseline values within 30 minutes after HBB administration, whereas salbutamol improved reactance until 180 minutes (mean improvement at 180 minutes of 0.040 Kpa/L/s, 95% CI = 0.004 to 0.076; P = .02 for salbutamol and of 0.009 Kpa/L/s, 95% CI = -0.028 to 0.045; P = .98 for HBB for the resistance at 3 Hz and of 0.040 Kpa/L/s, 95% CI = 0.007 to 0.074; P = .01 for salbutamol and of 0.009 Kpa/L/s, 95% CI = -0.024 to 0.042; P = .97 for HBB for the reactance at 7 Hz). From 5 to 30 minutes after HBB administration, the heart rate accelerated (mean increase of 3.3 beats per minute, 95% CI = -6.6 to 13.1; P = .92 for salbutamol, and of 13.0 beats per minute, 95% CI = 3.6 to 22.4; P = .002 for HBB at 30 minutes) and the gut sounds decreased (mean reduction of 1.3, 95% CI = -0.1 to 2.8; P = .09 for salbutamol and of 2.8 for the gastrointestinal auscultation score, 95% CI = 1.4 to 4.3; P < .0001 for HBB at 30 minutes). CONCLUSIONS AND CLINICAL IMPORTANCE: Both drugs have a similar bronchodilator potency but with a longer duration for salbutamol. Gastrointestinal and cardiovascular effects were noted only with HBB, suggesting the preferential use of salbutamol to relieve bronchoconstriction in horses with asthma.

Severe asthma in horses is associated with increased airway innervation.

BACKGROUND: Altered innervation structure and function contribute to airway hyperresponsiveness in human asthma, yet the role of innervation in airflow limitation in asthma in horses remains unknown. HYPOTHESIS: To characterize peribronchial innervation in horses with asthma. We hypothesized that airway innervation increases in horses with asthma compared with controls. ANIMALS: Formalin-fixed lung samples from 8 horses with severe asthma and 8 healthy horses from the Equine Respiratory Tissue Biobank. Ante-mortem lung function was recorded. METHODS: Blinded case-control study. Immunohistochemistry was performed using rabbit anti-s100 antibody as a neuronal marker for myelinating and non-myelinating Schwann cells. The number and cumulative area of nerves in the peribronchial region and associated with airway smooth muscle were recorded using histomorphometry and corrected for airway size. RESULTS: Both the number (median [IQR]: 1.87 × 10-5 nerves/µm2 [1.28 × 10-5 ]) and the cumulative nerve area (CNA; 1.03 × 10-3 CNA/µm2 [1.57 × 10-3 ]) were higher in the peribronchial region of horses with asthma compared with controls (5.17 × 10-6 nerves/µm2 [3.76 × 10-6 ], 4.14 × 10-4 CNA/µm2 [2.54 × 10-4 ], Mann-Whitney, P = .01). The number of nerves within or lining airway smooth muscle was significantly higher in horses with asthma (4.47 × 10-6 nerves/µm2 [5.75 × 10-6 ]) compared with controls (2.26 × 10-6 nerves/µm2 [1.16 × 10-6 ], Mann-Whitney, P = .03). CONCLUSIONS AND CLINICAL IMPORTANCE: Asthma in horses is associated with greater airway innervation, possibly contributing to airway smooth muscle remodeling and exacerbating severity of the disease.

Low levels of microRNA-21 in neutrophil-derived exosomes may contribute to airway smooth muscle hyperproliferation in horses with severe asthma.

OBJECTIVE: Neutrophilic inflammation is associated with the degree of airway obstruction in severe equine asthma (SEA), but the contribution of these leukocytes to bronchial remodeling remains ill defined. Neutrophils could cause structural alterations of the airways by the release of exosomes, a type of cell-derived nanoparticles that can modify the biology of local and distant cells. Neutrophil-derived exosomes have been shown to increase airway smooth muscle (ASM) cell proliferation in humans and horses. Therefore, this study aimed to identify neutrophil exosomal microRNAs (miRs) implicated in the regulation of ASM biology in SEA. ANIMALS: 6 horses with SEA and 6 healthy controls. METHODS: The expression of selected miRs in exosomes from peripheral neutrophils was studied by quantitative PCR. The effects of miR-21 transfection in ASM cells were evaluated by gene expression analysis and proliferation studies. RESULTS: The miR-21 was downregulated in neutrophil exosomes from SEA horses, and it attenuated the proliferation of ASM cells stimulated with lipopolysaccharide. CLINICAL RELEVANCE: The lower level of miR-21 in neutrophil-derived exosomes could contribute to ASM hyperproliferation, which could, in turn, promote the thickening of the bronchial wall in SEA.