Inhibition of bleomycin-induced pulmonary fibrosis by bone marrow-derived mesenchymal stem cells might be mediated by decreasing MMP9, TIMP-1, INF-γ and TGF-β.

Abstract

The study was aimed to investigate the mechanism and administration timing of bone marrow-derived mesenchymal stem cells (BMSCs) in bleomycin (BLM)-induced pulmonary fibrosis mice. Thirty-six mice were divided into six groups: control group (saline), model group (intratracheal administration of BLM), day 1, day 3 and day 6 BMSCs treatment groups and hormone group (hydrocortisone after BLM treatment). BMSCs treatment groups received BMSCs at day 1, 3 or 6 following BLM treatment, respectively. Haematoxylin and eosin and Masson staining were conducted to measure lung injury and fibrosis, respectively. Matrix metalloproteinase (MMP9), tissue inhibitor of metalloproteinase-1 (TIMP-1), γ-interferon (INF-γ) and transforming growth factor β1 (TGF-β) were detected in both lung tissue and serum. Histologically, the model group had pronounced lung injury, increased inflammatory cells and collagenous fibres and up-regulated MMP9, TIMP-1, INF-γ and TGF-β compared with control group. The histological appearance of lung inflammation and fibrosis and elevation of these parameters were inhibited in BMSCs treatment groups, among which, day 3 and day 6 treatment groups had less inflammatory cells and collagenous fibres than day 1 treatment group. BMSCs might suppress lung fibrosis and inflammation through down-regulating MMP9, TIMP-1, INF-γ and TGF-β. Delayed BMSCs treatment might exhibit a better therapeutic effect. Highlights are as follows: 1. BMSCs repair lung injury induced by BLM. 2. BMSCs attenuate pulmonary fibrosis induced by BLM. 3. BMSCs transplantation down-regulates MMP9 and TIMP-1. 4. BMSCs transplantation down-regulates INF-γ and TGF-β. 5. Delayed transplantation timing of BMSCs might exhibit a better effect against BLM.