Lung tissue repair can be divided into three main phases:
1. Inflammation The initial response to lung injury involves inflammation. This phase is characterized by the rapid influx of immune cells to the site of injury. Macrophages release cytokines and chemokines that recruit other immune cells, such as neutrophils, to the damaged area. These cells work together to clear dead cells and pathogens, setting the stage for the next phase.
2. Proliferation During the proliferation phase, there is an increase in the activity of alveolar epithelial cells and fibroblasts. Type II pneumocytes proliferate and differentiate into type I cells to restore the epithelial layer. Fibroblasts produce ECM components like collagen and elastin to rebuild the structural framework of the lung. This phase is critical for restoring the lung's architecture and function.
3. Remodeling The final phase, remodeling, involves the maturation and reorganization of the newly formed tissue. Excess ECM is degraded by matrix metalloproteinases (MMPs), and the lung tissue gradually returns to its normal state. This phase can be prolonged in cases of chronic injury or disease, leading to fibrosis and impaired lung function.
