Circulating bronchoepithelial cells expressing mRNA for surfactant proteinA in patients with pulmonary fibrosis

There are several unsolved clinical findings in patients with idiopathic pu lmonary fibrosis (IPF); (i) predominance of fibrosis in the lower lung fiel ds, (ii) digital clubbing, and (iii) patchy distribution of pulmonary fibro sis. To explain these unsolved problems, we hypothesized that regenerated o r premature bronchoepithelial cells may circulate in the blood in patients with IPF. To prove this, we performed the reverse transcriptase-polymerase chain reaction (RT-PCR) for cytokeratin 19 (CK19) and pulmonary surfactant protein A (SPA) in peripheral blood in patients with IPF and pulmonary fibr osis associated with collagen vascular disorders. In addition, 20 patients with chronic pulmonary emphysema as a disease control and 19 normal volunte ers were also evaluated for the existence of circulating bronchoepithelial cells. RT-PCR analysis showed that CK19 was expressed in 12 of 38 blood samples (3 1.6%) of IPF and pulmonary fibrosis associated with collagen vascular disor ders, seven of 20 (35.0%) blood samples of chronic pulmonary emphysema, and four of 19 (21.1%) blood samples of normal volunteers. mRNA for SPA was po sitive in eight of 38 (21.1%) blood samples of IPF. In contrast, SPA expres sing cells were not detected in any blood samples obtained from patients wi th chronic pulmonary emphysema or normal volunteers. This evidence suggests that there were some circulating bronchoepithelial c ells expressing mRNA for SPA in peripheral blood of patients with IPF and p ulmonary fibrosis associated with collagen vascular disorders.