Exercise modifies the innate immune response in equine bronchial epithelial cells

Peer reviewe

Identification of pro-fibrotic macrophage populations by single-cell transcriptomic analysis in West Highland white terriers affected with canine idiopathic pulmonary fibrosis.

Canine idiopathic pulmonary fibrosis (CIPF) affects old dogs from the West Highland white terrier (WHWT) breed and mimics idiopathic pulmonary fibrosis (IPF) in human. The disease results from deposition of fibrotic tissue in the lung parenchyma causing respiratory failure. Recent studies in IPF using single-cell RNA sequencing (scRNA-seq) revealed the presence of profibrotic macrophage populations in the lung, which could be targeted for therapeutic purpose. In dogs, scRNA-seq was recently validated for the detection of cell populations in bronchoalveolar lavage fluid (BALF) from healthy dogs. Here we used the scRNA-seq to characterize disease-related heterogeneity within cell populations of macrophages/monocytes (Ma/Mo) in the BALF from 5 WHWTs affected with CIPF in comparison with 3 healthy WHWTs. Gene set enrichment analysis was also used to assess pro-fibrotic capacities of Ma/Mo populations. Five clusters of Ma/Mo were identified. Gene set enrichment analyses revealed the presence of pro-fibrotic monocytes in higher proportion in CIPF WHWTs than in healthy WHWTs. In addition, monocytes-derived macrophages enriched in pro-fibrotic genes in CIPF compared with healthy WHWTs were also identified. These results suggest the implication of Ma/Mo clusters in CIPF processes, although, further research is needed to understand their role in disease pathogenesis. Overexpressed molecules associated with pulmonary fibrosis processes were also identified that could be used as biomarkers and/or therapeutic targets in the future

MafB-restricted local monocyte proliferation precedes lung interstitial macrophage differentiation.

peer reviewedResident tissue macrophages (RTMs) are differentiated immune cells that populate distinct niches and exert important tissue-supportive functions. RTM maintenance is thought to rely either on differentiation from monocytes or on RTM self-renewal. Here, we used a mouse model of inducible lung interstitial macrophage (IM) niche depletion and refilling to investigate the development of IMs in vivo. Using time-course single-cell RNA-sequencing analyses, bone marrow chimeras and gene targeting, we found that engrafted Ly6C+ classical monocytes proliferated locally in a Csf1 receptor-dependent manner before differentiating into IMs. The transition from monocyte proliferation toward IM subset specification was controlled by the transcription factor MafB, while c-Maf specifically regulated the identity of the CD206+ IM subset. Our data provide evidence that, in the mononuclear phagocyte system, the ability to proliferate is not merely restricted to myeloid progenitor cells and mature RTMs but is also a tightly regulated capability of monocytes developing into RTMs in vivo

Un modèle murin de la surdominance polaire ?

peer reviewe

The expression microarray: A potentially useful tool for the understanding of the immune response to a stress caused by exercise in horses

Malgré de multiples études, les interrelations entre l’exercice, le stress et la réponse immune sont peu définies. Or, la compréhension de ces interrelations pourrait jouer un rôle très important dans l’amélioration de la santé et des résultats sportifs des athlètes. En effet, l’exercice peut être reconnu comme un stress. Il induit des modifications de l’équilibre homéostatique qui peuvent à leur tour altérer la réponse immunitaire de l’hôte et donc sa susceptibilité aux maladies. L’adrénaline est la molécule essentielle de tout processus de stress. La technologie des microdamiers, outil majeur d’investigation transcriptomique, permet l’étude de l’expression génique de l’ensemble du génome. Son utilisation devrait donc permettre de mieux caractériser et définir les interrelations entre l’exercice, le stress et la réponse immune. Cette revue recense les interrelations connues entre la réponse immune à un stress adrénergique d’une part et la réponse immune à l’exercice d’autre part. Elle considère en outre la contribution potentielle des microdamiers à une meilleure compréhension des effets d’un stress, et plus particulièrement celui lié à l’exercice, sur l’immunité

Genetic engineering in the mouse: from functional genomics to zootechnical applications

Muscular hypertrophy (MH) in cattle is a condition occuring in various breeds and often referred to as “double muscling”. Affected individuals are characterized by a mean 20% increase of skeletal muscle mass. This trait has been selected for in some breeds, especially in the Belgian White and Blue breed, and has attracted considerable attention from geneticists. The mode of inheritance has been characterized as autosomal and recessive (Hanset & Michaux, 1985 a et b). A positional cloning approach has localized MH to the centromeric tip of bovine chromosome 2 (Charlier et al., 1995). Inactivation of the Growth and Differentiation Factor 8 (now referred to as Myostatin - MSTN) in the mouse (McPherron et al., 1997) resulted in a dramatic increase of skeletal muscle mass as a result of combined muscular hyperplasia and hypertrophy. Using a positional candidate approach, Grobet et al. (1997, 1998) demonstrated that MH in cattle is due to loss of function alleles of MSTN. MSTN is a member of the TGF- superfamily of growth and differentiation factors (McPherron et al., 1997). As in cattle, naturally occurring loss of MSTN function in mice (Szabo et al., 1998), sheep (Clop et al., 2006), dogs (Mosher et al., 2007) and humans (Schuelke et al., 2004) result in a spectacular muscular hypertrophy. Consequently, MSTN has become a major research topic in muscle biology either for fundamental research or for more applied purposes. For unravelling some aspects of its biology, for exploring new avenues for palliating muscle wasting conditions or for developing new zootechnical strategies, MSTN over-expression as well as inhibition has been performed in various mouse models (Bogdanovitch et al., 2002; Zimmers et al., 2002; Lee, 2007). Engineering of MSTN in the mouse was carried out in our unit for achieving either its post-natal or male-specific muscular inactivation. Post-natal inactivation has been performed using a conditional knock-out approach (Grobet et al., 2003). The third exon of MSTN, mainly coding for the bioactive domain of the protein, has been flanked by two loxP sites in the same orientation. Post-natal and muscle-specific genomic inactivation was achieved by use of a trangene expressing the Cre recombinase under the MCK promoter. This resulted in a skeletal muscle mass increase of the same magnitude as found in the constitutive knock-out. This demonstrated clearly that post-natal manipulation of MSTN can still have a major effect on muscle development. For modelizing a male-specific muscular hypertrophy, the MSTN latency associated propeptide (previously demonstrated as having MSTN dominant-negative properties; Lee & McPherron, 2001) was inserted on the murine Y chromosome under a muscle-specific promoter (Pirottin et al., 2005). This first successful targeting of the Y chromosome in live mice allowed the expression of a male-specific muscular hypertrophy. This model demonstrated the feasibility of a novel production system in cattle, combining superior beef ability in bulls without impeding dairy production in cows of the same lineage. The MSTN story depicted here is a clear example of the contribution of mouse genetic engineering to fundamental research as well as to more applied model development.Myostatin engineerin

Clonage positionnel et ingénierie génétique de la myostatine, le gène responsable du caractère culard chez les bovins

Double-muscling in cattle is a generalised hypertrophy of skeletal muscle resulting from a hyperplasia of the myofibers. Using a positional cloning strategy, we have identified the gene underlying double-muscling, namely myostatin, and causal loss-of-function mutations therein. Myostatin is a novel member of the TGF-beta superfamily of growth and differentiation factors. Using conditional gene targeting in a murine model, we have demonstrated that post-natal muscle specific inactivation of the myostatin gene causes full-blown double muscling. This demonstrates the potential value of myostatin antagonist whether to promote muscle regeneration in patients suffering from muscle wasting disease, or to enhance meat production in livestock species. Finally, by targeting a myostatin transinhibitor on the Y chromosome, we have demonstrated in the mouse the feasibility of a more efficient cattle production system combining superior beef production abilities for bulls and dairy abilities for cows.Le caractère culard chez le bovin est une augmentation généralisée de la masse des muscles squelettiques faisant suite à une hyperplasie des fibres musculaires. En utilisant des méthodes classiques de clonage positionnel, nous avons démontré que le caractère culard du bovin est dû à des mutations induisant une perte de fonction de la myostatine, un membre de la superfamille des facteurs de croissance et de différenciation de type TGF-? . Les outils de ciblage et d’inactivation conditionnelle de gènes chez la souris nous ont ensuite permis de montrer que l’inactivation postnatale et muscle-spécifique de la myostatine suffisait à induire une hypertrophie musculaire comparable à celle observée lors de l’inactivation constitutive du même gène, ouvrant ainsi la porte à l’utilisation d’inhibiteurs de la myostatine chez l’adulte, tant dans le domaine des productions animales qu’en médecine humaine. Enfin, en insérant un transinhibiteur de la myostatine sur le chromosome Y, nous avons montré en modèle murin la faisabilité d’un nouveau mode d’élevage bovin où les caractères viandeux et laitiers ségrégeraient au sein d’une même race, respectivement chez les mâles et les femelles

Increased hypoxia-inducible factor 1alpha expression in lung cells of horses with recurrent airway obstruction.

ABSTRACT: BACKGROUND: Recurrent airway obstruction (RAO, also known as equine heaves) is an inflammatory condition caused by exposure of susceptible horses to organic dusts in hay. The immunological processes responsible for the development and the persistence of airway inflammation are still largely unknown. Hypoxia-inducible factor (Hif) is mainly known as a major regulator of energy homeostasis and cellular adaptation to hypoxia. More recently however, Hif also emerged as an essential regulator of innate immune responses. Here, we aimed at investigating the potential involvement of Hif1-alpha in myeloid cells in horse with recurrent airway obstruction. RESULTS: In vitro, we observed that Hif is expressed in equine myeloid cells after hay dust stimulation and regulates genes such as tumor necrosis factor alpha (TNF-alpha), interleukin-8 (IL-8) and vascular endothelial growth factor A (VEGF-A). We further showed in vivo that airway challenge with hay dust upregulated Hif1-alpha mRNA expression in myeloid cells from the bronchoalveolar lavage fluid (BALF) of healthy and RAO-affected horses, with a more pronounced effect in cells from RAO-affected horses. Finally, Hif1-alpha mRNA expression in BALF cells from challenged horses correlated positively with lung dysfunction. CONCLUSION: Taken together, our results suggest an important role for Hif1-alpha in myeloid cells during hay dust-induced inflammation in horses with RAO. We therefore propose that future research aiming at functional inactivation of Hif1 in lung myeloid cells could open new therapeutic perspectives for RAO