ABSTRACT
OBJECTIVE: To study the effect of anti-type IV collagenase single-chain antibody scFv (3G11) on bleomycin (BLM)-induced pulmonary fibrosis. METHODS: C57BL/6 mice were divided into six groups (blank, saline control, BLM, low-dose treatment, intermediate-dose treatment, and high-dose treatment), the animal model of pulmonary fibrosis was induced with 400 ng/g intratracheal BLM. The day that treatment groups were injected with BLM was marked Day 0. Then at Days 1 - 7, scFv (3G11) was injected once intraperitoneally each day with three dosage [low-dose treatment (15 microg/g), intermediate-dose treatment (30 microg/g) and high-dose treatment (45 microg/g)]. At Day 21, 6 mice of each group (saline control, BLM, intermediate-dose treatment) were sacrificed and pathomorphological changes of left lungs evaluated with HE stained sections. Meanwhile, 6 mice of each group (blank, saline control, BLM, low-dose treatment, intermediate-dose treatment, and high-dose treatment) were sacrificed, the content of hydroxyproline was detected to measure the degree of collagen deposition. Macrophages were extracted from murine abdominal cavity and primarily cultured. And the inhibition of matrix metalloproteinase (MMP)-2 and MMP-9 excretion by different concentrations of scFv (3G11) (0, 15, 30, 45, and 60 micromol/L) was determined by gelatin zymography. RESULTS: By image analysis, the degree of fibrosis in the lungs of treated group was lighter than that of the BLM group. The percentages of the area of interalveolar septum (45.3% +/- 3.2%) and the number of nucleated cells (451 +/- 47) of treated group were remarkably reduced as compared with the BLM group (59.0% +/- 3.0%, 599 +/- 42, both P < 0.01). The content of hydroxyproline of the intermediate-dose treatment group [(0.82 +/- 0.05) microg/mg] and high-dose treatment group [(0.80 +/- 0.03) microg/mg] was lower than that of the BLM group [(0.92 +/- 0.07) microg/mg, P < 0.05, P < 0.01]. The result of gelatin zymography demonstrated that the excretion of MMP-2 and MMP-9 by macrophage was inhibited by scFv (3G11) at the concentration of 15 micromol/L. CONCLUSION: Single-chain antibody directed against type IV collagenase might inhibit the development of bleomycin-induced pulmonary fibrosis.
