Effect of nebulized 25D and 1,25D on lipofibroblast (a) and alveolar epithelial type II cell (b) differentiation markers. 2 weeks of daily administration of different doses of 25D and 1,25D from postnatal day 0 to 14 resulted in significantly increased protein levels of PPARγ and C/EBPα (a), with maximal increases seen with 100 ng/kg of 25D and 1 ng/kg of 1,25D. *p < 0.05 versus control. n = 4. Similarly, SP-B and leptin receptor (b), two key ATII cell differentiation markers, protein levels increased with 100 ng/kg of 25D and 1 ng/kg of 1,25D. *p < 0.05 versus control. n = 4. Effect of nebulized 25D and 1,25D on key alveolar differentiation markers was also confirmed by immunofluorescence staining of the 25D- and 1,25D-exposed lung sections (c). Compared to the controls, significantly increased expression of VDR, lung mesenchymal differentiation marker PPARγ, and lung epithelial differentiation markers p180 and SP-B were seen with both 25D and 1,25D. n = 4