Mary Grace Murray

"Circulating cell-free serum mtDNA as a novel noninvasive biomarker for Eosinophilic Esophagitis"

Introduction: Eosinophilic esophagitis (EoE) diagnosis and management rely upon endoscopy with tissue biopsy. Identification of noninvasive biomarkers of EoE may reduce the need for repeated endoscopy. Circulating mitochondrial DNA (mtDNA) is has been explored as a biomarker in various cancers as well as in patients with inflammatory bowel disease; however, the relationship between circulating mtDNA and EoE disease status remains elusive. 

Methods: Serum was isolated from blood samples obtained from human subjects undergoing esophagogastroduodenoscopy (EGD) for known or suspected EoE. All patients met various clinical criteria for endoscopy, including chronic abdominal pain, chronic diarrhea, reflux symptoms, nausea, dysphagia, history of esophageal food or foreign body impaction, and failure to thrive. EoE and gastroesophageal reflux disease (GERD) were diagnosed according to current clinical guidelines. Patients who met clinical criteria of EoE with histologic presence of ≥15 esophageal mucosal eosinophils (eos) per high-powered field (hpf) were classified as Active EoE. EoE patients who demonstrated resolution of histologic inflammation and eosinophilia (<15 eos/hpf) upon follow up EGD were designated as Inactive EoE. Subjects with a history of gastroesophageal reflux who demonstrated esophageal inflammation but did not meet histologic criteria for EoE were designated as GERD. Normal subjects include those who reported symptoms warranting endoscopy despite proton pump inhibitor treatment, but lacked a previous diagnosis of EoE, GERD, inflammatory bowel disease, celiac disease, or any other intestinal disorders. Nucleic acids were isolated from a standard volume of serum using Qiagen QIAamp Circulating Nucleic Acid Kit. The mitochondrially-encoded ND1 gene was amplified using qPCR. Copy numbers of ND1 were calculated using a standard curve of known copies of ND1. 

Results: Increased copies of circulating ND1 were found in patients with active EoE (n=56) as compared to normal (n=53; p=0.0095), to inactive EoE (n=47), and GERD (n=8) as shown in Figure 1.

Conclusions: Our findings indicate that higher levels of mtDNA are detectable in the serum of patients with Active EoE as compared to inactive EoE, normal patients, as well as those with GERD, a differing esophageal inflammatory condition with similar clinical presentation to EoE. A larger sample size may lead to significant differences between active and inactive EoE patients that would allow us to determine an appropriate cut point for mtDNA level in the serum. It is our hope that the development of mtDNA as a noninvasive biomarker for EoE will reduce the need for patients to undergo endoscopy for preliminary diagnosis and or monitoring of active vs inactive EoE disease status.