Regulatory T cells (Tregs) are required for human amnion epithelial cell (hAEC)-mediated repair of bleomycin-induced lung injury in Rag1
mice. (A) Administration of bleomycin into Rag1
-/- mice resulted in a significant increase in tissue-to-airspace ratio. A small reduction was observed following hAEC administration alone. Tissue-to-airspace ratio was lowest in the Treg + hAEC group, and this was significantly lower compared with groups given either Tregs or hAECs (*P <0.05, **P <0.01, ***P <0.001). (B) Representative images of hematoxylin-and-eosin-stained lung sections were taken at 200× magnification (scale bar = 100 μm). (i) Saline, (ii) saline hAECs, (iii) bleomycin, (iv) bleomycin hAECs, (v) CD45+ bleomycin saline, (vi) CD45+ bleomycin hAECs, (vii) Tregs bleomycin saline, (viii) Tregs bleomycin hAECs. (C) At day 14, bleomycin administration significantly increased total lung collagen content. Co-administration of Tregs and hAECs significantly reduced lung collagen content in comparison with control groups given hAECs or Tregs alone (*P <0.05, **P <0.0001). (D) Macrophages were identified by F4/80 staining and were quantified at day 7. Bleomycin administration resulted in a significant increase in macrophage numbers, but administration of hAECs alone had no significant effect. The number of macrophages in the lungs was reduced only in the Treg + hAEC group (**P <0.01).