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Increased type I procollagen mRNA transcripts in the lungs of mice during the development of bleomycin-induced
S Shahzeidi1, P K Jeffery, G J Laurent
1Dept of Thoracic Medicine, National Heart and Lung Institute, University of London, UK.
Abstract:
In this study, in situ hybridization has been used to investigate the localization of type I procollagen messenger ribonucleic acid (mRNA) in normal lung, and in the lungs of mice during the development of bleomycin-induced pulmonary fibrosis. Lung fibrosis was induced by a single intratracheal instillation of bleomycin sulphate (6 mg.kg-1 body weight), and tissues examined at times up to 35 days thereafter. Tissue transcripts of alpha 2(I) procollagen mRNA were visualized after hybridization with 35S-labelled riboprobes. Hybridization signals were associated with alveolar interstitial cells throughout the normal lung, with additional areas of dense hybridization signals observed subpleurally. Three days following administration of bleomycin, there was no apparent change in the pattern of hybridization. By 10 days, foci of intense hybridization signals indicative of gene activation were observed associated with individual cells in the alveolar interstitium. At 21 days, the increase in hybridization signals appeared to be associated with greater numbers of cells rather than highly activated cells. These results demonstrate that procollagen genes are normally expressed in the mouse lung, and that during bleomycin-induced pulmonary fibrosis hybridization signals increase, suggesting that both enhanced gene expression by individual cells and increased numbers of cells expressing the type I procollagen gene are involved in the pathogenetic mechanism.
Insights
This study reveals that type I procollagen gene expression increases in mouse lungs during bleomycin-induced pulmonary fibrosis. Both enhanced gene activity in individual cells and a higher number of expressing cells contribute to lung fibrosis development.
Area of Science:
- Pulmonary Medicine
- Molecular Biology
- Pathology
Background:
- Pulmonary fibrosis is a debilitating lung disease characterized by excessive collagen deposition.
- Type I procollagen is a key component of the extracellular matrix and its overproduction contributes to fibrosis.
- Understanding the cellular and molecular mechanisms of procollagen gene expression is crucial for developing therapeutic strategies.
Purpose of the Study:
- To investigate the spatial and temporal expression patterns of type I procollagen mRNA in normal mouse lungs.
- To examine the changes in type I procollagen mRNA localization during the development of bleomycin-induced pulmonary fibrosis.
- To elucidate the cellular mechanisms underlying increased procollagen production in lung fibrosis.
Main Methods:
- In situ hybridization was employed to visualize type I procollagen mRNA transcripts in lung tissue.
- A mouse model of bleomycin-induced pulmonary fibrosis was established.
- Lung tissues were analyzed at various time points (up to 35 days) post-bleomycin administration.
Main Results:
- Type I procollagen mRNA was detected in alveolar interstitial cells and subpleural regions of normal lungs.
- Following bleomycin instillation, increased hybridization signals indicative of gene activation were observed in alveolar interstitial cells by day 10.
- By day 21, the elevated signals were associated with a greater number of cells expressing the procollagen gene, rather than solely increased activity per cell.
Conclusions:
- Procollagen genes are constitutively expressed in normal mouse lungs.
- Bleomycin-induced pulmonary fibrosis involves both increased expression of type I procollagen by individual cells and an expansion of the procollagen-producing cell population.
- These findings highlight the dynamic cellular responses contributing to the pathogenesis of lung fibrosis.