Circulating nucleic acids in blood of healthy male and female donors.

The analysis of circulating nucleic acids (cirNAs) in blood provides helpful information for medical diagnostics (1). Thus, there has been intensive investigation of the factors influencing nucleic acid concentrations in plasma and serum, such as changes in DNA concentrations in serum and plasma during storage of blood samples (2) and the influence of blood processing on cell-free DNA quantification (3)(4)(5). Recent observations demonstrated that cirNAs are found not only free in blood plasma but also bound to the cell surface (6). Physiologic factors determining cirNA concentrations in blood remain to be elucidated. In the present study, we compared the concentration of cell-surface–bound and cell-free cirNAs in blood samples from 15 healthy men and 20 healthy women. Venous blood (8 mL) was collected into 13-mL tubes (cat. no. 55.459; Sarstedt) containing 2 mL of sterile phosphate-buffered saline (PBS) containing 50 mmol/L EDTA. The samples were stored at 4 °C and treated within 4 h after blood collection. Plasma was collected after low-speed centrifugation …