Microtubular discontinuities as acquired ciliary defects in airway epithelium of patients with chronic respiratory diseases
A critical relationship exists between ordered ciliary ultrastructure and optimal mucociliary clearance in the respiratory airways. Structurally defective cilia derived from heritable syndromes or from epithelial cell injury may promote or exacerbate chronic disease processes. A lesion of airway epithelial cilia characterized by microtubular discontinuities and previously associated with primary ciliary dyskinesia (PCD) has been documented in other forms of chronic airways diseases, including cystic fibrosis (CF). Nasal cilia obtained by curettage of the inferior nasal turbinate from 89 patients without CF but exhibiting symptoms favoring PCD were evaluated by transmission electron microscopy. Of the 89 patients in the study group, 19 (21.4%) were diagnosed with PCD. Among the PCD patients, 16 (84.2%) exhibited microtubular discontinuities. Nine patients from this group without ultrastructural evidence of PCD also exhibited these defects, however. Furthermore, seven of eight nasal biopsy specimens from patients with CF in a separate disease control group exhibited microtubular discontinuities. Microtubular discontinuities were quantitatively negligible among control groups of healthy human subjects and individuals experimentally and naturally subjected to acute airway injury. These data provide evidence that ciliary microtubular discontinuities represent acquired ciliary defects reflective of chronic airway disease injury and are not components of a primary structural abnormality in PCD.