Blood mitochondrial DNA as a biomarker of clinical outcomes in idiopathic pulmonary fibrosis

Idiopathic pulmonary fibrosis (IPF) is a chronic, progressive fibrosing interstitial pneumonia of unknown aetiology [1] with aging being one of the major risk factors [2]. Several aging-related changes, such as the overproduction of mitochondrial reactive oxygen species, low adenosine triphosphate production, reduced mitochondrial biogenesis, and inadequate mitochondrial DNA (mtDNA) repair [3] have also been reported in the IPF lungs [4, 5] and in a bleomycin-induced mouse model [6]. Plasma cell-free DNA, including mtDNA, is released from dying cells into the circulatory system in response to injury [7]. Since circulating mtDNA contains CpG-rich sequences similar to bacterial DNA, disengaged mtDNA can activate the innate immune system by functioning as a damage-associated molecular pattern [8] and contribute to the stimulation of the pro-fibrotic pathway [9]. Footnotes This manuscript has recently been accepted for publication in the European Respiratory Journal . It is published here in its accepted form prior to copyediting and typesetting by our production team. After these production processes are complete and the authors have approved the resulting proofs, the article will move to the latest issue of the ERJ online. Please open or download the PDF to view this article. Conflict of interest: Dr. Yoon has nothing to disclose. Conflict of interest: Dr. Choi has nothing to disclose. Conflict of interest: Dr. Kim has nothing to disclose. Conflict of interest: Dr. Kim has nothing to disclose. Conflict of interest: Dr. Song has nothing to disclose.