TGFB1 and bronchopulmonary dysplasia: Recent work on stem-cell therapy has also highlighted the pathogenic role of TGF-β signaling, where application of bone marrow mesenchymal stem cells (via the intravenous route), with concomitant erythropoietin administration (via the intraperitoneal route) led to improved alveolarization in a hyperoxia-based mouse model of BPD.