A Heterotopic Xenograft Model of Human Airways for Investigating Fibrosis in Asthma.

Limited in vivo models exist to investigate the lung airway epithelial role in repair, regeneration, and pathology of chronic lung diseases. Herein, we introduce a novel animal model in asthma-a xenograft system integrating a differentiating human asthmatic airway epithelium with an actively remodeling rodent mesenchyme in an immunocompromised murine host. Human asthmatic and nonasthmatic airway epithelial cells were seeded into decellularized rat tracheas. Tracheas were ligated to a sterile cassette and implanted subcutaneously in the flanks of nude mice. Grafts were harvested at 2, 4, or 6 weeks for tissue histology, fibrillar collagen, and transforming growth factor-ß activation analysis. We compared immunostaining in these xenografts to human lungs. Grafted epithelial cells generated a differentiated epithelium containing basal, ciliated, and mucus-expressing cells. By 4 weeks postengraftment, asthmatic epithelia showed decreased numbers of ciliated cells and decreased E-cadherin expression compared with nonasthmatic grafts, similar to human lungs. Grafts seeded with asthmatic epithelial cells had three times more fibrillar collagen and induction of transforming growth factor-ß isoforms at 6 weeks postengraftment compared with nonasthmatic grafts. Asthmatic epithelium alone is sufficient to drive aberrant mesenchymal remodeling with fibrillar collagen deposition in asthmatic xenografts. Moreover, this xenograft system represents an advance over current asthma models in that it permits direct assessment of the epithelial-mesenchymal trophic unit.

Mitotic asynchrony induces transforming growth factor-ß1 secretion from airway epithelium.

We recently proposed that mitotic asynchrony in repairing tissue may underlie chronic inflammation and fibrosis, where immune cell infiltration is secondary to proinflammatory cross-talk among asynchronously repairing adjacent tissues. Building on our previous finding that mitotic asynchrony is associated with proinflammatory/fibrotic cytokine secretion (e.g., transforming growth factor [TGF]-ß1), here we provide evidence supporting cause-and-effect. Under normal conditions, primary airway epithelial basal cell populations undergo mitosis synchronously and do not secrete proinflammatory or profibrotic cytokines. However, when pairs of nonasthmatic cultures were mitotically synchronized at 12 hours off-set and then combined, the mixed cell populations secreted elevated levels of TGF-ß1. This shows that mitotic asynchrony is not only associated with but is also causative of TGF-ß1 secretion. The secreted cytokines and other mediators from asthmatic cells were not the cause of asynchronous regeneration; synchronously mitotic nonasthmatic epithelia exposed to conditioned media from asthmatic cells did not show changes in mitotic synchrony. We also tested if resynchronization of regenerating asthmatic airway epithelia reduces TGF-ß1 secretion and found that pulse-dosed dexamethasone, simvastatin, and aphidicolin were all effective. We therefore propose a new model for chronic inflammatory and fibrotic conditions where an underlying factor is mitotic asynchrony.

Extracellular cyclophilin levels associate with parameters of asthma in phenotypic clusters.

OBJECTIVE: Leukocyte persistence during chronic (quiescent) phases of asthma is a major hallmark of the disease. The mechanisms regulating these persistent leukocyte populations are not clearly understood. An alternative family of chemoattracting proteins, cyclophilins (Cyps), has recently been shown to contribute to leukocyte recruitment in animal models of allergic asthma. The goals of this study were to determine whether Cyps are present in asthma patients during the chronic phase of the disease and to investigate whether levels of Cyps associate with clinical parameters of disease severity. METHODS: Nasal wash samples from an urban cohort of 137 patients of age 6-20 years with physician-diagnosed asthma were examined for the presence of cyclophilin A (CypA), cyclophilin B (CypB), as well as several other classical chemokines. Linear, logistic, or ordinal regressions were performed to identify associations between Cyps, chemokines, and clinical parameters of asthma. The asthma cohort was further divided into previously established phenotypic clusters (cluster 1: n = 55; cluster 2: n = 31; and cluster 3: n = 51) and examined for associations. RESULTS: Levels of CypB in the asthma group were highly elevated compared to nonasthmatic controls, while a slight increase in Monocyte Chemotactic Protein-1 (MCP-1) was also observed. CypA and MCP-1 were associated with levels of eosinophil cationic protein (ECP; a marker of eosinophil activation). Cluster-specific associations were found for CypA and CypB and clinical asthma parameters [e.g. forced expiratory volume in 1 second (FEV(1)) and ECP]. CONCLUSIONS: Cyps are present in nasal wash samples of asthma patients and may be a novel biomarker for clinical parameters of asthma severity.