Allergic rhinitis: A disease remodeling the upper airways?

The nasal and bronchial mucosa present similarities and differences. Remodeling is defined as "model again or differently, reconstruct" and is present in the airways of most if not all asthmatic patients. Even though inflammation is similar in allergic rhinitis and asthma, the pathologic extent of nasal remodeling in patients with rhinitis seems to be far less extensive than that in the bronchi of asthmatic patients. Epithelial damage is only minimal, and the reticular basement membrane does not appear to be largely pseudothickened. Moreover, the demonstration of fibrogenic growth factors in the nasal mucosa of patients with allergic rhinitis is lacking because of the paucity of studies. The reasons why remodeling appears to be less extensive in the nasal mucosa than in the bronchial mucosa are still unclear, but 2 hypotheses can be put forward. On one hand, the cytokine production of smooth muscle cells might partly explain differences in remodeling of the 2 sites of the airways. On the other hand, the genes of the embryologic differentiation might persist in the nose and bronchi or might be re-expressed in asthma and rhinitis. Because the nose is of ectodermal origin and the bronchi of endodermal origin, these genes might also govern remodeling patterns. More studies are urgently required to better characterize nasal remodeling in patients with rhinitis. A better understanding of nasal and bronchial remodeling might help to identify new pathways and new therapeutic strategies to reduce long-term remodeling in asthma.