In this research project, we performed optical coherence tomography (OCT) analysis in pulmonary fibrosis model mice to develop a novel imaging technique in a respiratory system diagnostic. Eight units/kg bleomysin (BLM) or PBS was directly administered by tracheal intubation into C57BL/6N and secretoglobin (SCGB) 3A2 KO mice. The trachea and lung were analyzed at 1, 7, 14, and 28 days after BLM administration. First, cilia of trachea were observed by OCT in the mice one day after BLM administration. The motility of cilia was imaged as light signals and detected changes of signals in wild type mice (control). In comparison to control, the motility decreased in KO mice. The motilities decreased by BLM. Second, the normal lung surface and tissue were visualized as uniform reflected intensities in the OCT images. Fibrotic lung was visualized as nonuniform signals, which regions increased with lapse of time after BLM administration. The fibrotic foci and the emphysema-like pulmonary alveoli were visualized as dark signals and round higher reflected light signals at 28 days after BLM administration respectively.

These results suggest that a pathological condition of pulmonary fibrosis can be detected by OCT technique. Therefore OCT may be a novel useful technique for diagnosis of respiratory disease.