Immunohistochemical and gelatin zymography studies for matrix metalloproteinases in bleomycin-induced pulmonary fibrosis

The role of various matrix metalloproteinases (MMP) and tissue inhibitor of metalloproteinases-2 (TIMP-2), and the gelatinolytic activities of MMP inv olved in the process of bleomycin-induced pulmonary fibrosis in rabbits wer e investigated, Male Japanese white rabbits were intubated with tracheal tu bes under anesthesia, and bleomycin hydrochloride in sterile saline or only sterile saline was administered through the tracheal tubes, The animals we re killed 1, 3, 7, 14 and 28 days after the administration of bleomycin (n = 3) or saline (n = 2). Light microscopic immunohistochemistry for MMP-1 (i nterstitial collagenase), MMP-2 (gelatinase A), MMP-9 (gelatinase B) and TI MP-2 was performed. The gelatinolytic activities of lung tissue homogenates were studied by gelatin zymography. In the early stages, the gelatinolytic activity of MMP-9 was predominant. MMP-9 localized in the infiltrating neu trophils, macrophages, bronchial and bronchiolar epithelial cells, The alve olar epithelial basement membrane was frequently disrupted in the early sta ges, where MMP-9 possibly contributed to the disruption. In the late stages , the gelatinolytic activities of the latent and active forms of MMP-2 were predominant, and MMP-2 localized in the regenerated alveolar epithelial ce lls in addition to the bronchial epithelial cells. MMP-2, especially its ac tive form, possibly plays a role in alveolar epithelial cell regeneration, The localization of MMP-1 was similar to that Of MMP-9, TIMP-2 localized in the epithelial cells and in some fibroblasts in fibrotic lesions, TIMP-2 p ossibly plays a role in extracellular matrix deposition in balance with MMP .