A subsequent study has reported that the MMP-9/TIMP-1 ratio plays an important role in the progression of BPD, and it was observed that Mn (III) tetrakis (4-benzoic acid) porphyrin chloride can effectively decrease the MMP-9/TIMP-1 ratio in a rat model (29). This evidence concerns the gene MMP9 and bronchopulmonary dysplasia.