Temporal patterns of circulating cell-free DNA (cfDNA) in a newborn piglet model of perinatal asphyxia

Perinatal asphyxia is a severe medical condition resulting from oxygen deficiency (hypoxia) at the time of birth, causing worldwide approximately 680,000 newborn deaths every year. Better prediction of severity of damages including early biomarkers is highly demanded. Elevated levels of circulating cell-free DNA (cfDNA) in blood have been reported for a range of different diseases and conditions, including cancer and prematurity. The objective of this study was to validate methods for assessing cfDNA in blood and cerebrospinal fluid (CSF) and to explore temporal variations in a piglet model of neonatal hypoxia-reoxygenation. Different cfDNA extraction methods in combination with cfDNA detection systems were tested, including a fluorescent assay using SYBR Gold and a qRT-PCR-based technique. Newborn piglets (n = 55) were exposed to hypoxia-reoxygenation, hypoxia-reoxygenation and hypothermia, or were part of the sham-operated control group. Blood was sampled at baseline and at post-intervention, further at 30, 270, and 570 minutes after the end of hypoxia. Applying the fluorescent method, cfDNA concentration in piglets exposed to hypoxia (n = 32) increased from 36.8±27.6 ng/ml prior to hypoxia to a peak level of 61.5±54.9 ng/ml after the intervention and deceased to 32.3±19.1 ng/ml at 570 minutes of reoxygenation, whereas the group of sham-operated control animals (n = 11) revealed a balanced cfDNA profile. Animals exposed to hypoxia and additionally treated with hypothermia (n = 12) expressed a cfDNA concentration of 54.4±16.9 ng/ml at baseline, 39.2±26.9 ng/ml at the end of hypoxia, and of 41.1±34.2 ng/ml at 570 minutes post-intervention. Concentrations of cfDNA in the CSF of piglets exposed to hypoxia revealed at post-intervention higher levels in comparison to the controls. However, these observations were only tendencies and not significant. In a first methodological proof-of-principle study exploring cfDNA using a piglet model of hypoxia-reoxygenation variations in the temporal patterns suggest that cfDNA might be an early indicator for damages caused by perinatal asphyxia.