An object of the present invention is to provide a novel therapeutic agent for pulmonary fibrosis for which no effective drug therapy has been established at present. The present invention is a therapeutic agent for pulmonary fibrosis, comprising mesenchymal stem cells. The pulmonary fibrosis is preferably normal interstitial pneumonia (UIP) or idiopathic pulmonary fibrosis (IPF). Further, it is preferable that the mesenchymal stem cells are derived from adipose tissue or from another family.
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