Effects of CatK deficiency on ECM content in lung. (A) Representative Masson trichome staining of small airways from 3 months old WT and Ctsk-/- - mice shows collagen distribution around airways (blue color; original magnification, ×200). (B) Morphometric analysis of collagen distribution surrounding the airways. (C) hydroxyproline (HYP) and (D) glycosaminoglycan (GAG) contents in lung sections from 1, 2, 3, 6 months old mice. The unit (μg/mg) indicates the HYP and GAG contents per mg protein. Morphometric analyses were performed using Openlab software. A/Pbm means the staining area divided by the perimeter of airway basement.