Improvement of previously disrupted differentiation-specific protein expression and defective skin barrier function in postnatal Abca12−/− skin. A–J: Immunolabeling for differentiation-specific molecules confirmed improved keratinization during maturation of the grafted Abca12−/− skin. Intense kallikrein 5 (KLK5) immunostaining (A and B, white arrows), in situ transglutaminase 1 (TGase1) activity labeling (C and D) and loricrin immunolabeling (E and F, white arrows) were seen throughout the granular layers in mature grafted Abca12−/− skin, compared with their sparse distribution in the Abca12−/− neonatal skin (see Figure 2, B, D and F). Increased loricrin and KLK5 immunolabeling intensity was confirmed by Western blot analysis using epidermal extracts from mature grafted Abca12−/− skin (K). Mature grafted Abca12−/− skin showed intense profilaggrin/filaggrin labeling in the granular layer (H), similar to the mature grafted wild-type skin (G). Diffuse profilaggrin/filaggrin staining in the entire cornified layers observed in Abca12−/− neonatal skin (see Figure 2H) disappeared in mature grafted Abca12−/− skin. Expression of desmoglein 1 (DSG1), unassociated with keratinization, was not altered in the grafted skin (I and J). Western blotting with anti-profilaggrin/filaggrin antibody revealed that normal conversion of profilaggrin to filaggrin was restored in mature Abca12−/− epidermis (K). Nuclear stain: propidium iodide, red; original magnification ×40; Scale bars = 20 μm. L: The barrier function in the transplanted skin was assessed by measuring transepidermal water loss (TEWL). The Abca12−/− neonates (red bar, left) showed significantly greater TEWL than the wild-type neonates (blue bar, left) showed (*P < 0.001). TEWL levels of mature Abca12−/− epidermis three weeks after the skin graft (red bar, right) were significantly decreased as compared with levels of Abca12−/− neonatal skin (red bar, left) (**P < 0.001), and was similar to levels of mature wild-type skin three weeks after the skin graft (blue bar, right). (Abca12−/− neonates, n = 3; wild-type neonates, n = 3; mature Abca12−/− skin, n = 3; mature wild-type skin, n = 3). KLK5, kallikrein 5; proFLG, profilaggrin; FLG, filaggrin; 4FLG, filaggrin tetramer; 3FLG, filaggrin trimer; 2FLG, filaggrin dimer; 1FLG, filaggrin monomer.