Serum levels of genomic DNA of α1(I) collagen are elevated in scleroderma patients

Recent studies have indicated that various nucleic acids are present in human sera, and attracted attention for their potential as novel disease markers in many human diseases. In this study, we tried to evaluate the possibility that DNA and RNA of collagens exist in human sera, and determined whether their serum levels can be useful biomarkers in scleroderma patients. The RNA or DNA of collagens were purified from sera, and detected by polymerase chain reaction or quantitated by real‐time polymerase chain reaction. Among approximately 18 360 bases of full‐length α1(I) collagen DNA, various regions were detected by polymerase chain reaction in human sera. However, α2(I) collagen DNA, α1(I) collagen RNA or α2(I) collagen RNA were not detectable. α1(I) Collagen DNA in sera was quantitative using our method. The levels of serum α1(I) collagen DNA were significantly increased in scleroderma patients compared with healthy control subjects or systemic lupus erythematosus patients. According to the receiver–operator curve analysis, serum α1(I) collagen DNA levels were shown to be effective as a diagnostic marker of scleroderma. Furthermore, when we determined the association of serum α1(I) collagen DNA levels with clinical/laboratory features in scleroderma patients, those with elevated α1(I) collagen DNA levels showed significantly higher prevalence of pitting scars/ulcers. In summary, elevation of serum α1(I) collagen DNA levels in scleroderma patients may be useful as the diagnostic marker, reflecting the presence of vasculopathy.