Fig. 1

a The evaluation of severity of acute lung injury in different intratracheal injection of LPS concentrations. The lung imaging feature of four intratracheal injection LPS concentrations: 4.0, 4.5, 5.0 and 7.0 mg/kg, n = 20 for each group (upper). The survival rate of ALI rat of four intratracheal injection LPS concentrations (lower). b The hematoxylin and eosin stain of lungs after acute lung injury (200×). Most alveolar walls were fractured on the first day post injury (D1). On day 2 and 3, alveolar spaces were filled with a mixed neutrophilic and monocytic infiltrate, alveolar wall capillaries were congested. Alveolar hemorrhage was visible. Alveolar walls were lined with cuboidal epithelial cells which were proliferating AEC2s. On days 5 and 7, the formation of alveolar wall was recovered. Scale bar = 100 μm. c Immunofluorescence analysis of AEC1s in the rat lung after acute lung injury. Immunostaining for AQP5 (green) was performed on lung tissue from Normal (N), D1 (Day 1), D2 (Day 2), D3 (Day 3), D5 (Day 5) and D7 (Day7) days after injury. Scale bar = 100 μm. d The immunofluorescence analysis of AEC2s in rat lung after ALI. Immunostaining for pro-SPC (green) was performed on lung tissue from days 1, 2, 3, 5 and 7 after ALI. Arrowhead indicates proSPC positive AEC2s. Scale bar = 100 μm. e The cellular kinetics of AEC1s after ALI (The dose of LPS is 4.5 mg/kg in ALI rat model). Rat lung cell suspensions were incubation with anti-AQP5 antibody, the percentage of AQP5 positive cells was analyzed by flow cytometry analysis (left). *P = 0.026 (compared with sham group). The variance of percentage of covering surface of AEC1s after ALI (analyzed by Image J, Version 1.2). *P < 0.05 (compared with normal control) (middle). The flow cytometry analysis of AEC2s after acute lung injury. The rat whole lung cell suspensions were incubation with anti-proSPC antibody, the percentage of proSPC positive cells was analyzed. *P = 0.012 (right)