From the farm to the lab: the pig as a new model of cystic fibrosis lung disease

Downregulation of Aquaporins (AQP1 and AQP5) and Na,K-ATPase in Porcine Reproductive and Respiratory Syndrome Virus-Infected Pig Lungs

Aquaporins (AQPs) and Na,K-ATPase control water transport across the air space-capillary barrier in the distal lung and play an important role in the formation and resolution of lung edema. Porcine reproductive and respiratory syndrome virus (PRRSV) infection usually causes pulmonary inflammation and edema in the infected pig lungs. To investigate the possibility that PRRSV infection may cause altered expression of AQPs and Na,K-ATPase messenger RNA (mRNA) levels and protein expression of AQP1, AQP5, and Na,K-ATPase in the PRRSV-infected pig lungs were detected. Quantitative real-time PCR (qRT-PCR) analysis showed markedly decreased mRNA levels of AQP1 and AQP5 and Na,K-ATPase in the PRRSV-infected pig lungs compared to those of uninfected pig lungs. Western blot studies also revealed significantly reduced levels of AQP1, AQP5, and Na,K-ATPase proteins in the PRRSV-infected pig lungs. In addition, immunohistochemical (IHC) analysis showed decreased protein expression of AQP1 and AQP5 in the endothelial cells of the capillaries and venules and secretory cells of terminal bronchiole and the alveolar type I cells, respectively. The expression of Na,K-ATPase in the basolateral membrane of alveolar type II cells presented great reduction in the PRRSV-infected pig lungs. To further understand the reduction of these proteins, the ubiquitination of AQP1 and Na,K-ATPase was examined in uninfected and PRRSV-infected pig lungs. The results showed that there is no difference of ubiquitination for these proteins. Thus, our results suggest that PRRSV infection may induce downregulation of these proteins and cause impairment of edema resolution by failed water clearance in the infected pig lungs.

An American Thoracic Society Official Research Statement: Future Directions in Lung Fibrosis Research

BACKGROUND

Pulmonary fibrosis encompasses a group of lung-scarring disorders that occur owing to known or unknown insults and accounts for significant morbidity and mortality. Despite intense investigation spanning decades, much remains to be learned about the natural history, pathophysiology, and biologic mechanisms of disease.

PURPOSE

To identify the most pressing research needs in the lung fibrosis community and to provide a roadmap of priorities to investigators, funding agencies, patient advocacy groups, and other interested stakeholders.

METHODS

An ad hoc international working group of the American Thoracic Society with experience in clinical, translational, and bench-based research in fibrotic lung diseases was convened. The group used an iterative consensus process to identify successes and challenges in pulmonary fibrosis research.

MEASUREMENTS AND MAIN RESULTS

The group identified five main priority areas in which substantial resources should be invested to advance our understanding and to develop novel therapies for patients with pulmonary fibrosis. These priorities include develop newer models of human lung fibrosis, engage current and new stakeholders to provide sustained funding for the initiatives, create a global infrastructure for storing patient-derived materials, establish collaborative preclinical and clinical research networks in fibrotic lung disease, and create a global lung fibrosis initiative that unites these multifaceted efforts into a single virtual umbrella structure.

CONCLUSIONS

Despite recent advances in the treatment of some forms of lung fibrosis, many gaps in knowledge about natural history, pathophysiology, and treatment remain. Investment in the research priorities enumerated above will help address these shortcomings and enhance patient care worldwide.

Efficient gene delivery to pig airway epithelia and submucosal glands using helper-dependent adenoviral vectors

Airway gene delivery is a promising strategy to treat patients with life-threatening lung diseases such as cystic fibrosis (CF). However, this strategy has to be evaluated in large animal preclinical studies in order to translate it to human applications. Because of anatomic and physiological similarities between the human and pig lungs, we utilized pig as a large animal model to examine the safety and efficiency of airway gene delivery with helper-dependent adenoviral vectors. Helper-dependent vectors carrying human CFTR or reporter gene LacZ were aerosolized intratracheally into pigs under bronchoscopic guidance. We found that the LacZ reporter and hCFTR transgene products were efficiently expressed in lung airway epithelial cells. The transgene vectors with this delivery can also reach to submucosal glands. Moreover, the hCFTR transgene protein localized to the apical membrane of both ciliated and nonciliated epithelial cells, mirroring the location of wild-type CF transmembrane conductance regulator (CFTR). Aerosol delivery procedure was well tolerated by pigs without showing systemic toxicity based on the limited number of pigs tested. These results provide important insights into developing clinical strategies for human CF lung gene therapy.Molecular Therapy-Nucleic Acids (2013) 2, e127; doi:10.1038/mtna.2013.55; published online 8 October 2013.

Primary bronchial epithelial cell culture from explanted cystic fibrosis lungs

Lung disease is responsible for more than 95% of morbidity and mortality in cystic fibrosis. The exact pathogenesis of cystic fibrosis lung disease remains poorly understood. Experimental models are therefore vital for use in research. Animal models and immortalized cell lines both have inherent limitations. Explanted lungs removed from people with cystic fibrosis at the time of transplantation represent a potentially valuable but technically and logistically challenging source of primary cystic fibrosis bronchial epithelial cells. In this study, pieces of segmental bronchus from explanted lungs were treated with patient-specific antimicrobials prior to isolation of bronchial epithelial cells. Cultured cells were characterized by their morphology under light microscopy, cytokeratin and hematoxylin-eosin staining, and electrophysiological profile. Primary bronchial epithelial cells were successfully cultured from 15 of 22 patients attempted. The cells exhibited typical epithelial morphology, staining for cytokeratin, lack of responsiveness to forskolin treatment, and remained viable after storage in liquid nitrogen. Seven unsuccessful cultures failed due to early infection with bacteria known to colonize the airways pretransplant. The results show that primary bronchial epithelial cell culture is possible from explanted cystic fibrosis lungs. This provides an important cellular model to elucidate the pathogenic mechanisms in cystic fibrosis lung disease and to investigate potential therapeutic targets.