Cell-free DNA(cfDNA) is a kind of small amount DNA that is out of cell, it was found and reported on 1940s by scientists. cfDNA is also called circulating DNA when it exists in plasma or serum. We also can find that there is a small group fetus cfDNA from maternal blood during pregnancy, this kind of fetus cfDNA can be called cell-free fetal DNA (cff-DNA). The research of circulating DNA in human blood has become one of the hot topic on bio-medical and clinical diagnosis regions. With the development of Next-Generation Sequencing(NGS), we can carry out cfDNA quantifiable research from genomics level.
There are several aspects of cfDNA in scientific research and medical application: Noninvasive prenatal testing(NIPT), cancer detection and monitoring and organ transplantation, etc.
The Noninvasive prenatal testing (NIPT) commonly refers to fetal chromosome screening and detection or genetic diagnosis through analyzing the cell-free fetal DNA from maternal plasma or serum. After collecting the peripheral blood of pregnant women, the extracted cell free fetal DNA was sequenced using the next generation high-throughput sequencing technology and analyzed with bioinformatics method. The NIPT is a noninvasive method to test the fetal chromosomal abnormalities disease, mainly Down’s syndrome (Trisomy 21), Edward’s syndrome (Trisomy 18) and Patau’s syndrome (Trisomy 13) and other common copy number variant diseases with high sensitivity, high accuracy and other advantages such as no risk of spontaneous abortion.
Tumors are somatic mutations that only exist in tumor cells. When the tumor cells die, they release their own DNA fragments into the blood circulation, which is circulating tumor DNA(ctDNA). Several studies have shown that ctDNA in the blood can be used as a specific molecular marker for tumor detection and prognostic monitoring.
In sports medicine research field, researchers have found that sports(e.g. marathon, weightlifting, boxing and cycling) by increase of free radical damage organ, caused the DNA rupture, in turn cause more cfDNA appears in blood, therefore cfDNA content in plasma is considered to be the most promising to become new monitoring indicator of overtraining.