GDF11 and pulmonary fibrosis: Finally, sorted lung MSCs were enriched for many transcripts which could play a role in myofibroblast differentiation and fibrosis including those encoding CD105/endoglin, part of the TGF-β receptor complex; the TGF-β family protein Gdf11 [39,40]; the TGF-β antagonists Gremlin, Lefty1 and BMP-binding endothelial regulator [41,42]; SMADs 2 and 3; NFATc3, a transcription factor involved in TGF-β1 signaling in airway smooth muscle [43]; and osteopontin which has been shown to be required for TGF-β expression and lung fibrosis in bleomycin- [44] and OVA-treated mice [45].