SOX2 Expression and Regulation in Pulmonary Aplasia/Agenesis.

Background: Pulmonary agenesis is characterized by the absence of bronchi and lung parenchyma and it differs from pulmonary aplasia by the presence of rudimentary bronchial buds. SOX2 expression is observed during the normal course of lung development. The objective of this study is to investigate the expression of SOX2 and its regulation in the residual airway epithelium of pulmonary agenesis/aplasia.

Methods: Six cases of pulmonary agenesis/aplasia aged between 12 and 37 weeks of gestation and 6 age-matched controls were studied. Immunochemistry was performed using primary antibodies against SOX2, BMP4, FGF9, FGF10, TTF1, SHH, and beta-catenin.

Results: In sections of bronchi or trachea from lung agenesis or aplasia, the residual epithelium shows a high nuclear expression of SOX2 and an absence of expression of BMP4 as in the esophagus whereas in control cases, the airway epithelium shows an absence of expression of SOX2 and a high expression of BMP4. There were no differences between control and agenesis/aplasia cases concerning the expression of FGF9, FGF10, SHH, TTF1, and beta-catenin.

Conclusion: The expression of SOX2 and BMP4 is strongly altered in pulmonary agenesis/aplasia. Thus, these proteins appear to regulate tissue-specific proliferative activity during early lung development.