Factors contributing to development of complex regional pain syndrome (CRPS) are not fully understood. This study examined possible epigenetic mechanisms that may contribute to CRPS after traumatic injury. DNA methylation profiles were compared between individuals developing CRPS (n = 9) and those developing non-CRPS neuropathic pain (n = 38) after undergoing amputation following military trauma. Linear Models for Microarray (LIMMA) analyses revealed 48 differentially methylated cytosine-phosphate-guanine dinucleotide (CpG) sites between groups (unadjusted P's < 0.005), with the top gene COL11A1 meeting Bonferroni-adjusted P < 0.05. The second largest differential methylation was observed for the HLA-DRB6 gene, an immune-related gene linked previously to CRPS in a small gene expression study. For all but 7 of the significant CpG sites, the CRPS group was hypomethylated. Numerous functional Gene Ontology-Biological Process categories were significantly enriched (false discovery rate-adjusted q value <0.15), including multiple immune-related categories (eg, activation of immune response, immune system development, regulation of immune system processes, and antigen processing and presentation). Differentially methylated genes were more highly connected in human protein–protein networks than expected by chance (P < 0.05), supporting the biological relevance of the findings. Results were validated in an independent sample linking a DNA biobank with electronic health records (n = 126 CRPS phenotype, n = 19,768 non-CRPS chronic pain phenotype). Analyses using PrediXcan methodology indicated differences in the genetically determined component of gene expression in 7 of 48 genes identified in methylation analyses (P's < 0.02). Results suggest that immune- and inflammatory-related factors might confer risk of developing CRPS after traumatic injury. Validation findings demonstrate the potential of using electronic health records linked to DNA for genomic studies of CRPS.
Complex regional pain syndrome after traumatic injury is associated with differential DNA methylation profiles, particularly in immune-related genes.
aDepartment of Anesthesiology, Vanderbilt University Medical Center, Nashville, TN, United States. Mr. Shaw is now with Department of Anesthesiology and Pain Medicine, University of Alberta, Edmonton, AB, Canada
bDivision of Genetic Medicine, Department of Medicine, Vanderbilt Genetics Institute, Vanderbilt University Medical Center, Nashville, TN, United States
cDepartment of Anesthesiology, Clare Hall, University of Cambridge, Cambridge, United Kingdom
dDepartment of Anesthesiology, Duke University Medical Center, Durham, NC, United States
eDepartments of Medicine and Biomedical Informatics, Vanderbilt University Medical Center, Nashville, TN, United States
*Corresponding author. Address: Vanderbilt University Medical Center, 701 Medical Arts Building, 1211 Twenty-First Ave South, Nashville, TN 37212, United States. Tel.: (615) 936-1821. E-mail address: Stephen.Bruehl@vumc.org (S. Bruehl).
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S. Bruehl and E.R. Gamazon contributed equally to this manuscript.