The results indicated that positive expression of COL1, mRNA and protein expression of MMP-9/TIMP-1 in lung tissue was increased in the neonatal mice exposure to hyperoxia induced BPD group than in control, but reduced in MSCs, EPO, particularly MSCs+EPO group in comparison with BPD mice (P<0.05). Here, MMP9 is linked to bronchopulmonary dysplasia.