In pulmonary fibrosis, there is an increased proliferation and fibroblast differentiation into collagen producing myofibroblasts. The overgrowth, hardening and scarring of tissue is attributed to the excess deposition of extracellular matrix including collagen, proteoglycan and glycoproteins.
Under normal physiological condition, there is a controlled synthesis, deposition and degradation of the extracellular matrix, while in pulmonary fibrosis, abnormal extracellular matrix accumulation is a critical part of pathogenesis.