ABSTRACT
Following severe injury, the lung can be repaired in a limited number of ways anatomically, of which functional repair eventually depends. Conducting airways undergoing necrotizing lesions that denude surfaces must be relined with stem cells arising largely from residual basal cells or from necks of tracheal and bronchial glands. These cells must migrate and differentiate into ciliated, goblet, and nonciliated secretory cells (Clara) if functional healing is to occur. However, if factors necessary for normal differentiation of these regenerating cells are absent, a squamous phenotype develops, resulting in functional impairment owing to loss of cilia, mucous secretion, secretions of Clara cells, water and chloride homeostasis, and impairment of neural functions of nerve endings and neuroendocrine cells present in normal conducting airway epithelium (1).
