Respiratory Animal Models in the Common Marmoset (Callithrix jacchus)

Animal and Cell Culture Models for Cystic Fibrosis: Which Model Is Right for Your Application?

Over the past 30 years, a range of cystic fibrosis (CF) animal models have been generated for research purposes. Different species, including mice, rats, ferrets, rabbits, pigs, sheep, zebrafish, and fruit flies, have all been used to model CF disease. While access to such a variety of animal models is a luxury for any research field, it also complicates the decision-making process when it comes to selecting the right model for an investigation. The purpose of this review is to provide a guide for selecting the most appropriate CF animal model for any given application. In this review, the characteristics and phenotypes of each animal model are described, along with a discussion of the key considerations that must be taken into account when choosing a suitable animal model. Available in vitro systems of CF are also described and can offer a useful alternative to using animal models. Finally, the future of CF animal model generation and its use in research are speculated upon.

High expression of acidic chitinase and chitin digestibility in the stomach of common marmoset (Callithrix jacchus), an insectivorous nonhuman primate

Chitin is a polymer of N-acetyl-D-glucosamine (GlcNAc) and a main constituent of insects' exoskeleton. Insects are rich in protein with high energy conversion efficiency. Recently, we have reported that acidic chitinases (Chia) act as digestive enzymes in mouse, pig and chicken (omnivorous) but not in dog (carnivorous) and bovine (herbivorous), indicating that feeding behavior affects Chia expression levels, and determines chitin digestibility in the particular animals. Common marmoset (Callithrix jacchus) belongs to New World monkey family and provides a potential bridge between mouse models and human diseases. Common marmoset is an insectivorous nonhuman primate with unknown expression levels and enzymatic functions of the Chia homologue, CHIA. Here, we report that common marmoset highly expresses pepsin-, trypsin- and chymotrypsin-resistant CHIA in the stomach. We show that CHIA is most active at pH 2.0 and degrades chitin and mealworm shells into GlcNAc dimers under gastrointestinal conditions. Although common marmoset and crab-eating monkey (Old World monkey) have two CHIA genes in their genomes, they primarily express one gene in the stomach. Thus, this study is the first to investigate expression levels and enzymatic functions of CHIA in a New World primate, contributing to the understanding of dietary adaptation and digestion in this taxon.

Viral Diseases of Common Marmosets

Common marmosets are highly susceptible to several viral pathogens that exist as latent or subclinical infections in their natural reservoir hosts but cause severe disease or death when interspecies transmission occurs. Examples of such viruses in marmosets are herpes simplex virus infections, parainfluenza virus 1 infections, and measles acquired from humans, Saimiriine herpesvirus 1 infection after transmission from squirrel monkeys, and infections with lymphocytic choriomeningitis virus originating from mice. Other relevant viral infections causing spontaneous disease in common marmoset colonies include cowpox virus infections and paramyxovirus saguinus infections. Callitrichine herpesvirus 3 is a newly recognized lymphocryptovirus that is associated with the development of intestinal lymphoproliferative disease in common marmosets. Most viral pathogens causing disease in common marmosets are potential zoonotic agents, and protective measures should be implemented when handling these small New World monkeys.

Spontaneous lung pathology in a captive common marmoset colony (Callithrix jacchus)

Data on spontaneous pathology are substantially scarce for common marmosets, compared to other laboratory animals, but is essential for the interpretation of histological findings in the context of toxicological and experimental studies. Especially if common marmosets are used as experimental animals in respiratory research, detailed knowledge on the spectrum, occurrence, and incidence of spontaneous histopathological pulmonary lesions in this non-human primate species is required. In this study, lung tissue of 638 common marmosets from the marmoset colony of the German Primate Center was examined histologically. The analysis revealed a high incidence of predominantly mild and multifocal interstitial pneumonia (32.99 %) of unknown etiology in most cases. Only few marmosets exhibited lobar pneumonia (1.41 %) and bronchopneumonia (0.94), which were mainly caused by bacterial pathogens such as Bordetella bronchiseptica and Klebsiella pneumoniae. Lung immaturity and atelectasis were common histological findings in newborn marmosets. Typical background lesions included anthracosis (8.15 %), hemosiderosis (1.72 %), extramedullary hematopoiesis (11.6 %), mineralization (10.97 %), and inflammatory cell foci (10.34 %). In addition, three cases of pulmonary arteriopathy (0.47 %) and 1 case of foreign-body granuloma (0.16 %) were detected in the marmoset study cohort. The high prevalence of circulatory disturbances (congestion, edema, hemorrhage) and changes in air content (secondary atelectasis, alveolar emphysema) could partly be explained by euthanasia-related artifacts or agonal changes. The present study provides a comprehensive overview of the range and incidence of spontaneous pulmonary histopathology in common marmosets, serving as valuable reference data for the interpretation of lung lesions in toxicological and experimental marmoset studies.

Morphology and staining behavior of neutrophilic and eosinophilic granulocytes of the common marmoset (Callithrix jacchus)

Common marmosets (Callithrix jacchus) are frequently used as translational animal models for human diseases. However, a comparative study of cytological and histochemical detection methods as well as morphometric and ultrastructural characterization of neutrophils and eosinophils in this species is lacking. Blood samples of house dust mite sensitized and allergen challenged as well as lipopolysaccharide (LPS) challenged marmosets were analyzed with different cytological and histological staining methods. Furthermore, cell size and number of nuclear segments were compared between neutrophils and eosinophils. Electron microscopy was performed to characterize the ultrastructure of granulocytes. Of all applied cytological stains, three allowed differentiation of eosinophils and neutrophils and, thus, reliable quantification in blood smears: May-Grünwald-Giemsa stain, Congo Red and Naphthol AS-D Chloroacetate-Esterase. For histology, Hematoxylin-Eosin (H&E) could not demonstrate clear differences, whereas Sirius Red, Congo Red, and Naphthol AS-D Chloroacetate Esterase showed capable results for identification of eosinophils or neutrophils in lung tissue. Morphometry revealed that marmoset neutrophils have more nuclear segments and are slightly larger than eosinophils. Ultrastructurally, eosinophils presented with large homogeneous electron-dense granules without crystalloid cores, while neutrophils were characterized by heterogeneous granules of different size and density. Additionally, sombrero-like vesicles were detected in tissue eosinophils of atopic marmosets, indicative for hypersensitivity-related piecemeal degranulation. In conclusion, we provide a detailed overview of marmoset eosinophils and neutrophils, important for phenotypic characterization of marmoset models for human airway diseases.

Lessons from the analysis of nonhuman primates for understanding human aging and neurodegenerative diseases

Animal models are necessary tools for solving the most serious challenges facing medical research. In aging and neurodegenerative disease studies, rodents occupy a place of choice. However, the most challenging questions about longevity, the complexity and functioning of brain networks or social intelligence can almost only be investigated in nonhuman primates. Beside the fact that their brain structure is much closer to that of humans, they develop highly complex cognitive strategies and they are visually-oriented like humans. For these reasons, they deserve consideration, although their management and care are more complicated and the related costs much higher. Despite these caveats, considerable scientific advances have been possible using nonhuman primates. This review concisely summarizes their role in the study of aging and of the mechanisms involved in neurodegenerative disorders associated mainly with cognitive dysfunctions (Alzheimer's and prion diseases) or motor deficits (Parkinson's and related diseases).