Melior Discovery fibrosis
Pulmonary fibrosis is characterized by alveolar epithelial cell injury and hyperplasia, inflammatory cell accumulation, fibroblast hyperplasia, deposition of extracellular matrix, and scar formation. The end result of this process is the loss of lung elasticity and loss of alveolar surface area leading to impairment of gas exchange and pulmonary function. The disease is further characterized by the presence of chronic inflammatory infiltrates, myofibroblast hyperplasia, and disordered collagen deposition.
The bleomycin model of pulmonary fibrosis is the best characterized, and most widely used model. Direct delivery of bleomycin to the lung (e.g. intratracheal) induces rapidly developing fibrosis after a single administration. Direct pulmonary delivery of bleomycin causes direct damage to alveolar epithelial cells. This is followed by the development of neutrophilic and lymphocytic alveolitis within the first week. After the first week, alveolar inflammatory cells are cleared, fibroblast proliferation is initiated, with synthesis of extracellular matrix. The development of fibrosis in this model can be seen biochemically and histologically by day 14 with maximal responses observed between 21- 28 days.
Figure 1. Bodyweight changes. Animals were weighed twice a week. The Bleomycin-treated group had a significant decrease in body weight after 7 days post-induction and remained smaller than their vehicle/untreated counterparts. Data are mean ± SEM; ****p<0.0001 compared to vehicle control.
Figure 2. Lung hydroxyproline. Hydroxyproline content of lung tissue was measured by colorimetric assay. Bleomycin-treated animals had significantly increased lung hydroxyproline content, demonstrating that pulmonary fibrosis has formed. Data are mean ± SEM; **p<0.01 compared to vehicle control.
These data support the findings that lung fibrosis by administration of bleomycin has been accomplished.
H&E: Hematoxylin and eosin stain
PSR: Picro-Sirius Red Stain
Figure 3. H&E, PSR Staining and Histopathology Score. Hematoxylin and eosin (H&E) and Picrosirius Red (PSR) staining are commonly used histopathology techniques to visualize inflammation and collagen deposit in tissue sections. Pathological alterations were evaluated by an ACVP Board Certified Toxicology Pathologist in blind manner. Interstitial Fibrosis was assessed based on the increase of PSR staining. The subacute interstitial inflammation and Agonal Hemorrhage were evaluated mainly based on the H&E staining. Compared to the lung samples from Vehicle group, significant increases in both interstitial fibrosis and inflammation were observed in the lung samples of Bleomycin group. Data are mean ± SEM; ****p<0.0001, compared to vehicle control.
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