SMN1 and bronchopulmonary dysplasia: In the ATII cells of BPD rats, the co-expression of surfactant protein C (SPC) and alpha-smooth muscle actin (a-SMA) can be observed, along with characteristic ultrastructural changes of EMT, including vacuolization of some ATII cells and a significant increase in actin microfilaments (Yang et al., 2014).