It has been reported that bone marrow-derived mesenchymal stem cells (BM-MSC) can differentiate into pulmonary epithelial and pulmonary endothelial cells. Some animal studies showed that BM-MSCs differentiate into bronchial cells and type 2 pneumocytes in rats with pneumonia and improve the fibrosis that occur after administration of bleomycin. Based on the findings, it is considered that mesenchymal stem cell therapy can help regenerate the damaged lung as well as BPD that cause lung inflammation, fibrosis, deficiency of type 2 pneumocytes, and so on.