Expression of heat shock protein 47 in chronic hypersensitivity pneumonitis

Abstract

Hypersensitivity pneumonitis is one of the interstitial lung diseases caused by the inhalation of organic substances and certain inorganic chemicals.However, little is known about the pathophysiology of chronic hypersensitivity pneumonitis. Chronic hypersensitivity pneumonitis has often been misdiagnosed as idiopathic pulmonary fibrosis (IPF) which was often difficult in differential diag-nosis, both clinically and histopathologically. Heat shock protein 47 (HSP47), a collagen-specific molecular chaperone, is essential for biosynthesis and secretion of collagen molecules. In this study, the expression of HSP47 in the lung tissues was evaluated to elucidate pathogenic differences involving HSP47 in chronic hypersensitivity pneumonitis and IPF. We reviewed surgical lung biopsy specimens of 14 patients with chronic hypersensitivity pneumonitis and 20 with IPF and assigned a score for the expression of HSP47. The expression of HSP47 was noted predominantly in fibroblasts and epithelial cells in active fibrotic areas which were thought to be the active sites at the forefront of ongoing fibrosis, while the expression was low in areas of dense fibrosis. HSP47 expression in fibrotic lesions showing cen-trilobular distribution was considered one of the histologic characteristics of chronic hypersensitivity pneumonitis when compared with IPF. The expression level of HSP47 in chronic hypersensitivity pneumonitis was similar to that of IPF. The present findings suggest that enhanced HSP47 expression is a common pathogenetic pathway to chronic hypersensitivity pneumonitis and IPF, regardless of the etiology, suggesting that underlying fibrogenic mechanisms similar in the two conditions.