bleomycin induced accumulation of lung collagen in mice

Background-Increased production of transforming growth factor p (TGF-/J) seems to have an important role in the pathophysiology of bleomycin induced lung fibrosis. This is attributed to the ability of TGF-/) to stimulate infiltration of inflammatory cells and promote synthesis of connective tissue, leading to collagen deposition. Methods-The study was designed to evaluate the antifibrotic potential of TGF-/8 antibody in mice treated with bleomycin, which is a model of lung fibrosis. Under methoxyflurane anaesthesia, each mouse received intratracheally either 50 u1 sterile isotonic saline or 0f125 units bleomycin in 50 pl. Within five minutes after the instillation, mice received into the tail vein 100 p1 non-immune rabbit IgG, TGF-fl2 antibody, or a combination of TGF-Ih and TGF-8,1 antibodies at various dose regimens. Mice were killed 14 days after the instillation and their lungs processed for morphological and biochemical studies. Results-Administration of 250 pg of TGF-fl2 antibody after instillation of bleomycin followed by 100 ug on day 5 and 100 jg on day 9 significantly reduced the bleomycin induced increases in the accumulation of lung collagen from 445 8 (42.3) pgllung to 336-7 (56.6) pgllung at 14 days. Similarly, the combined treatment with 250 pug TGF-62 antibody and 250 pg TGF-,61 antibody after bleomycin instillation followed by 100 pg of each antibody on day 5 also caused a significant reduction in bleomycin induced increases in lung collagen accumulation and myeloperoxidase activity at 14 days. Conclusions-These results suggest that TGF-fi has an important role in the aetiology of bleomycin induced lung fibrosis; the neutralisation of TGF-I8 by systemic treatment with its antibodies offers a new mode of pharmacological intervention which may be useful in treating lung fibrosis. (Thorax 1993;48:959-966) Interstitial pulmonary fibrosis is a potentially lethal, chronic response of the lung to injury that may result from a wide range of processes.' Regardless of its multifactorial origin, interstitial pulmonary fibrosis is invariably accompanied by an over exuberant repair process, which is characterised by an excessive number of fibroblasts,' an absolute increase in lung collagen content, and abnormality in the ultrastructural appearance and spatial distribution of collagen types.3 Bleomycin represents a group of glycopeptides that are used as chemotherapy in the treatment of cancer.4 The use of bleomycin as an antineoplastic drug is, however, limited because it produces a dose dependent pneumonitis which often progresses to interstitial pulmonary fibrosis in humans.4 Intratracheal instillation of bleomycin in rodents is often used as an animal model of interstitial pulmonary fibrosis as it resembles that seen in humans.5 6 The number of cytokines known to upregulate the inflammatory and fibroproliferative responses of lungs leading to increased extracellular matrix production in the rodent bleomycin model of lung fibrosis is ever increasing.7-10 It is generally accepted that the increased production of transforming growth factor ,B (TGF-ff) is an important component in the pathophysiology of bleomycin induced lung fibrosis for the following reasons. Firstly, TGF-fl is a potent stimulator of extracellular matrix synthesis, although its effects on cell proliferation depend on the presence of other growth factors and culture conditions. 11-13 Secondly, Raghu et al found that TGF-fl caused a twofold to fourfold increase in collagen production and collagen mRNA in fibroblasts cultured from normal and fibrotic human lungs.'4 Thirdly, there is increased expression of TGF-fl gene and cell proliferation in lungs undergoing bleomycin induced pulmonary fibrosis.'