Bleomycins are a family of compounds produced by Streptomyces verticillis. They have potent tumour killing properties which have given them an important place in cancer chemotherapy. They cause little marrow suppression, but pulmonary toxicity is a major adverse effect. The mechanisms of cell toxicity are well described based on in vitro experiments on DNA. The bleomycin molecule has two main structural components: a bithiazole component which partially intercalates into the DNA helix, parting the strands, as well as pyrimidine and imidazole structures, which bind iron and oxygen forming an activated complex capable of releasing damaging oxidants in close proximity to the polynucleotide chains of DNA. This may lead to chain scission or structural modifications leading to release of free bases or their propenal derivatives. The mechanisms are well described based on in vitro experiments on DNA, but how they relate to intact cells in whole animals is more tenuous. Bleomycin is able to cause cell damage independent from its effect on DNA by induction lipid peroxidation. This may be particularly important in the lung and in part account for its ability to cause alveolar cell damage and subsequent pulmonary inflammation. The lung injury seen following bleomycin comprises an interstitial oedema with an influx of inflammatory and immune cells. This may lead to the development of pulmonary fibrosis, characterized by enhanced production and deposition of collagen and other matrix components. Several polypeptide mediators capable of stimulating fibroblasts replication or excessive collagen deposition have been implicated in this, but the precise role of these in bleomycin-induced fibrosis is yet to be demonstrated. Current therapy for bleomycin-induced lung damage is inadequate, with corticosteroids most often used. Given the mechanism of action described above, antioxidants and iron chelators might be beneficial. Although, studies to date are equivocal and there is insufficient evidence to promote their use clinically. Novel drugs are currently being developed and it is hoped these may be more useful.

The observation that pulmonary inflammatory lesions and bleomycin (BLM)-induced pulmonary fibrosis spontaneously resolve in young mice, while remaining irreversible in aged mice, suggests that impairment of pulmonary regeneration and repair is associated with aging. Since mesenchymal stem cells (MSCs) may promote repair following injury, we postulated that differences in MSCs from aged mice may underlie post-injury fibrosis in aging. The potential for young-donor MSCs to inhibit BLM-induced pulmonary fibrosis in aged male mice (>22 months) has not been studied. Adipose-derived MSCs (ASCs) from young (4-month) and old (22-month) male mice were infused 1-day following intratracheal BLM administration. At 21-day sacrifice, aged BLM mice demonstrated lung fibrosis by Ashcroft score, collagen content, and αv-integrin mRNA expression. Lung tissue from aged BLM mice receiving young ASCs exhibited decreased fibrosis, matrix metalloproteinase (MMP)-2 activity, oxidative stress, and markers of apoptosis vs. BLM controls. Lung mRNA expression of TNFα was also decreased in aged BLM mice receiving young-donor ASCs vs. BLM controls. In contrast, old-donor ASC treatment in aged BLM mice did not reduce fibrosis and related markers. On examination of the cells, young-donor ASCs had decreased mRNA expression of MMP-2, insulin-like growth factor receptor, and AKT activation compared to old-donor ASCs. These results show that the BLM-induced pulmonary fibrosis in aged mice could be blocked by young-donor ASCs and that the mechanisms involve changes in collagen turnover and markers of inflammation.

D Di iv ve er rs se e c ce el ll lu ul la ar r T TG GF F--β 1 1 a an nd d T TG GF F--β 3 3 g ge en ne e e ex xp pr re es ss si io on n i in n n no or rm ma al l h hu um ma an n a an nd d m mu ur ri in ne e l lu un ng g This procedure was technically simple, providing excellent resolution. TGF-β 1 and TGF-β 3 messenger ribonucleic acid (mRNA) transcripts were detected in a wide variety of cells. In human lung, mRNA for both isoforms was localized to bronchiolar epithelium and alveolar macrophages. TGF-β 1 , but not TGF-β 3 mRNA was detected in mesenchymal and endothelial cells. In murine tissue, TGF-β 1 , mRNA was localized to bronchiolar epithelium, Clara cells, mesenchymal cells, pulmonary endothelium and alveolar cells, including macrophages. TGF-β 3 mRNA was similarly distributed but not detected in endothelium.In summary, using a nonisotopic technique in lung tissue, we have detailed the cells expressing the transforming growth factor-β 1 and β 3 genes in human and murine lung. There was widespread expression of these cytokines in normal lung consistent with autocrine or paracrine roles in regulating cellular turnover, immune defence and matrix protein metabolism.

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Background-Intratracheal instillation of bleomycin into mice leads to deposition of collagen in the lung and fibrosis, but the mechanism for this is poorly understood. Enhanced collagen gene expression, increased collagen synthesis, decreased collagen degradation, and proliferation of fibroblasts have all been proposed as possible contributors. To obtain information on the activity of collagen producing cells at an early stage in the development of pulmonary fibrosis in situ hybridisation was used to detect and localise products of the type III procollagen gene. In addition, assay of type III procollagen gene expression was performed using dot-blot analysis of lung RNA extracts. Methods-Lung fibrosis was induced in mice by intratracheal instillation of bleomycin sulphate (6 mgikg body weight) and tissues were examined after three, 10, 21 and 35 days. RNA-RNA hybridisation was accomplished with riboprobes labelled with sulphur-35 which were generated from a 1-7 kb mouse procollagen al(III) cDNA. In situ hybridisation was performed on sections fixed in paraformaldehyde and embedded in paraffin wax and steady state values of type III procollagen mRNA were assayed by dot-blot analysis of total lung RNA extracted by guanidium isothiocyanate.