Interstitial pulmonary fibrosis is thought by many to develope as a direct result of leukocytic response to a primary lung cell injury. Previous studies have demonstrated that continuous propranolol treatment, or a single subcutaneous injection of a low dose of bleomycin, results in a fibrogenic response of the alveolar lung parenchyma. This response is characterized by increased connective tissue, in the absence of a leukocytic infiltrate, alveolitis, or even significant pulmonary cell damage. The low term goal of the proposed project is the characterization of these models, and the investigation of this fibrogenic response which occurs apparently without the accepted scheme of events, particularly a noticeable leukocytic infiltrate.
The specific aims of this project include a precise morphologic and morphometric characterization of the models, using standard techniques including Weibel's techniques coupled with video technology at the electron microscope. The second major aim is the visualization of the process of fibrogenesis, as clarified by the absence of major tissue damage. Newly synthesized collagen will be labelled by the use of 3H-proline, and then quantified and localized, using biochemical and autoradiographic methods. This will be accomplished in saline-treated controls, as well as in both models. The proliferative capacity of fibroblasts isolated from bleomycin- treated animals will be assayed by 3H-thymidine incorporation, and their collagen synthesizing ability will be determined through 3H- proline incorporation, in parallel to the in vivo study. These results will allow comparisons between the two models and the controls. The amounts and distribution of collagen subtypes I and III will be determined in both models and controls, by the use of gel separation and immunocytochemical means. This, when coupled with the 3H-proline incorporation studies, will address the question of new collagen deposition vs. degradation, as well as a possible shift in the type I/type III ratio in fibrogenesis. Some possible pathogenic mechanisms will be investigated in both models as well. The influence of the 8-adrenergic system will be investigated by measuring cAMP/cGMp levels in isolated pulmonary fibroblasts and macrophages. Leukocyte influence will be tested by inducing leukopenia in the animals prior to drug treatment. The influence of alveolar macrophages and/or their products will be blocked using a cyclooxygenase inhibitor. Finally, the participation of undergraduate women has been maximized in the proposed project, and is considered essential.
| Smith, D M; Smith, S K (1997) Ultrastructural changes in the synthetic and secretory patterns of pulmonary surfactant following pilocarpine in vivo. Histol Histopathol 12:343-8 |
