Mini Review

Development of Cystic Fibrosis Animal Models

Yonta Tiakouang Henri¹, Qingtian Wu¹, Gang Zhao², Wenhua Bao^1*, Lei Liu¹, Pengxia Zhang^3* and Xia Hou^1*

¹Department of Biochemistry and Molecular Biology, Jiamusi University School of Basic Medicine, China

²Department of Pharmacology, Jiamusi University Hospital of Stomatological, China

³Department of Respiratory, The first Affiliated Hospital of Jiamusi University, China

Submission: October 25, 2019;Published: November 20, 2019

*Corresponding author: Hou Xia, Department of Biochemistry and Molecular Biology, Jiamusi University School of Basic Medicine, China, Zhang Pengxia, Department of Biochemistry and Molecular Biology, Jiamusi University School of Basic Medicine, China

How to cite this article: Yonta Tiakouang Henri, Qingtian Wu, Gang Zhao, Wenhua Bao, Lei Liu, Pengxia Zhang, Xia Hou. Development of Cystic Fibrosis Animal Models. Arch Anim Poult Sci. 2019; 1(2): 555559. DOI: 10.19080/AAPS.2019.01.555559

Abstract

Cystic fibrosis (CF) is a multiorgan-affected genetic disorder, induced by the mutations of cystic fibrosis transmembrane conductance regulator (CFTR). The mechanism of CF related phenotypes is still unknown and the research resources from CF patients are limited. It is impossible to full process CF in patients. The animal models are indispensable during CF research. To date, six CF animal models were generated. However, animals are not as same as human beings, each animal model has its advantages and disadvantages.

Keywords: Animal models; Cystic fibrosis; CFTR

Abbreviations: CF: Cystic Fibrosis; CFTR: Cystic Fibrosis Transmembrane Conductance Regulator; MI: Meconium Ileus

Introduction

Cystic fibrosis (CF) is one of the most common recessive genetic disorders in the world, which affects multiple organs, including lung, pancreas, liver, reproductive system and other orangs [1,2]. CF is resulted from mutations of cystic fibrosis transmembrane conductance regulator (CFTR), a cAMP/PKA-regulated chloride channel at the apical membranes of epithelial cells lining the airways and other epithelial tissues [3].

To date, there is no cure for CF, although treatment is improved [4]. Furthermore, the mechanism of many CF related phenotypes is still unclear, such as CF related diabetes and CF related liver disorders. To understand the full process of CF in patients is impossible [5,6]. Therefore, the animal models are indispensable and have made significant contributions in CF research. The use of animal models brought a better understanding of the human physiology.

The inaccessibility of human organs was made possible in animal models. Shortly after the discovery of the CFTR gene in 1989, several groups set out to generate CF animal models with mutations in the CFTR locus [7]. This has open doors to many scientific new areas and contributed in the understanding of CFTR protein expression across the body.

Although animal models have limitations and do not easily recapitulate the human disease, their contribution has been the best tools in understanding the pathophysiologic process of human diseases.

Until now, six CF animal models have been reported: mice, rat, pig, ferret, sheep and rabbits [5,6,8]. In this review, we will summarize the development of CF animal models briefly.

CF animal models

CF Mice

To generate mouse strains with mutations in the CFTR locus using the homologous recombination technology and mouse embryonic stem cells pioneered by Mario Capecchi et al. between 1980 and 19867. Several loss of function, or “knock-out” models were made by interrupting the mouse CFTR coding region; Hippomorphic mutations (Cftrtm1Hgu ** Ex10 I); F508del mutations; and Other point mutations (Cftrtm2Hgu G551D R and Cftrtm3Hgu G480C (H&R)). An important addition to the CF mouse family is a conditional CFTR deletion that can be created by cell specific expression of the recombinase [9].

These genetically modified mice allow the contribution of different cell lineages to CF pathology to be better understood. Comparative CF pathology in human and mouse CF mutants in different organs give us more information about the use of animal models in CFTR gene research [10]. Here are some differences between Human tissues and mouse models tissues respectively. CF mice does not show obvious obstructive, lethal mucus plugging, spontaneous inflammation and tissue remodeling in CF mice lung, which is the most important part of a CF animal model [10].

Intestine phenotypes, such as Meconium ileus, chronic malabsorption, failure to thrive. While the CF mouse lacks a spontaneous lung, pancreatic, and liver phenotype, CF mice show liver impairment only after 12 months or older with high fat diet [11]. It has provided a wealth of insight into the biological underpinnings of CFTR-deficient epithelia in other organs such as the intestine, and lessons learned from CF mice have laid a rich foundation for other CF animal models.

Nevertheless, mouse model presented several important biologic divergences with Human. This bring researchers to look for more animal models such as rats, ferrets, pigs and sheep, with the intention of creating physiological conditions that are more related with Human physiology.

CF Rat

Rat models gene disruption successfully generates a CF animal model that recapitulates some aspects of human disease, such as CF rat lung is spontaneously infected. The CF rat has normal mucociliary clearance at birth 12. Also, CF rat does not show any liver problem [12].

CF Ferret

Ferret is one of the laboratory-friendly animals and genetically closer to human beings than rat and mice. CFTR-knockout CF ferret model was generated in 2008 by using adeno-associated virus gene-targeting methods [13]. CF ferret manifest multiple defects similar to human, including airway pathological changes; impaired pancreatic, liver, and vas deferens disease [14].

Approximately 75% CF ferret shows meconium ileus (MI) at birth and dead in 24 hours after birth, which is only 15% in human [15]. GI is a main reason for neonate of both human and ferret, which is obviously higher than in human newborns. Furthermore, CF ferrets require special care with high maintenance costs [16].

CF Pig

Pig owns similarities with humans than other animals mentioned in the previous article. CF pig was set up in 2008 in University of Iowa [17,18]. In the past ten years, CF pig models contributed valuable data to CF research. CF pig manifests most human being like phenotypes than other animal models CF animal models, mainly including lung, pancreas, intestine, hepatobiliary, and vas deferens lesions [19-21]. Symptoms onset in CF pig are earlier than human being [22]. For seriously GI problem, 100% intestinal impact after birth of CF pig. CF pig need special treatment and with a very high cost [18,23].

CF Zebra fish

CFTR of zebra fish is similar to that of human [24]. However, physiological structure of zebra fish is too far from human being’s, e.g. zebra fish has no lungs. Even though, zebra fish also serve as a model for CF research, such as inflammation induced by CFTR knockout [25].

CF sheep

CF sheep model was produced by Fan’s group in 2018 by CRISPR/Cas9 transgenic methods. CF sheep also show multiple organ impairment, however, all CF lambs died in three days after birth because severe manifestation of multiorgan [26]. It is still unclear the prospect of CF sheep in CF study.

CF Rabbit

Rabbit is laboratory-friendly animal with cheaper maintaining cost and many human-like phenotypes. CFTR gene of Rabbit is most closed human being’s than every other animal that are involved in CF model generation. However, like mice and rat, the anatomical structure of rabbit is little far from human, such as no submucosal gland in rabbit [23]. Dr. Sun and Dr. Chen’s groups set up CF rabbit in 2014 by CRISPR/Cas9 knockout experiments (unpublished) [8].

CF rabbit shows major phenotypes similar to CF patients, including spontaneous polymicrobial infections in the airway, and gastrointestinal disease. CF rabbit can survive more than one month and easy to be maintained. The CF rabbit model may be used as a good tool for understanding CF pathogenesis and the therapy of CF disorder.

Conclusion

The study of biologic systems requires the selection of a faithful model to which perturbations can be investigated, quantified, and related to disease processes. In CF, this is complicated by the multi-system nature of this disease. In recent years, the advances in genetic engineering of relevant species that fully recapitulate the human disease have matured alongside the development of highly sophisticated in vitro model systems that can compartmentalize various microenvironments.

Animal models come with their own cellular/organ physiology, which may differ from humans. It is beneficial from CF animal models during understanding pathogenesis and the development of therapeutics for this life-threaten disease. Together these arms provide unprecedented flexibility in experimental design, allowing scientists to ask questions previously thought inaccessible in the laboratory.

Relating these studies in the laboratory to experimentally driven clinical trials in CF subjects, will greatly enhance the field’s understanding of clinically important targets for therapy. These innovations are revealing more about the pathogenesis of CF than ever thought possible and are redirecting efforts along new lines of thought.

Author contributions

Xia Hou, Pengxia Zhang were responsible of the project and designed the experiments; Yonta Tiakouang Henri, Qingtian Wu,   Gang Zhao, Wenhua Bao, Pengxia Zhang and Xia Hou wrote the paper.

Conflict of interests

The authors declare no competing interests.

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