DPP4 and pulmonary fibrosis: Although other means of DPP-4 inhibition that do not involve endothelial cells could have promoted the observed anti-fibrotic effects, we strongly believe in the clinical significance of endothelial DPP-4 in fibrotic disorders such as pulmonary fibrosis after systemic endotoxemic injury, in which vascular damage and activation of endothelial cells play a significant role.