Objective   To investigate the effects of thrombopoietin (TPO) on proliferation and collagen synthesis in pulmonary fibroblasts induced by TGFβ1.

  Methods   Cultured human embryonic lung fibroblasts (HFLs) were treated with recombinant human TGF-β1 to induce myofibroblast differentiation. Different concentrations of recombinant human TPO were applied individually or in combination. Cell proliferation rate was determined using the CCK8 assay. Q-PCR and immunofluorescence assay were employed to examine the mRNA and protein expression of α-smooth muscle actin (αSMA) and type I collagen (COL1)A2.

  Results   TGFβ1 treatment induced HFL transdifferentiation to myofibroblasts was determined by the expression of αSMA, a myofibroblast-specific marker. Cell proliferation increased during the induction. COL1 gene and protein expression were upregulated by TGFβ1 induction (P < 0.05). The TGFβ1-induced mRNA and protein expression of αSMA and COL1A2 was decreased by TPO treatment (P < 0.05), as determined by reverse transcription quantitative polymerase chain reaction and immunofluorescence analysis, respectively. The inhibitory rate showed a dose dependent effect within a certain TPO concentration range. The CCK8 assay demonstrated that TPO downregulated the TGFβ1-induced proliferation (P < 0.05). Furthermore, the expression of heme oxygenase- 1 (HO- 1) was downregulated in TGFβ1- induced lung fibroblasts, and these effects were attenuated by TPO administration (P < 0.05).

  Conclusions   TPO can inhibit the TGFβ1-induced proliferation and differentiation of human lung fibroblasts. These effects may be mediated in part by HO-1-related signaling pathways.