Extracellular DNA in cord blood plasma and applications in cord blood banking for sample identification

Human cord blood (CB) units donated for transplantation require testing for various markers in blood and plasma aliquots. Although the identity link between the CB unit and the labeled aliquots with the same identifiers can be confirmed by HLA-DNA assays, these methods have not been used for CB plasma. We have previously reported that viral DNA sequences are present in the CB plasma of carrier babies and now hypothesize that human genomic DNA may also be present in CB plasma.

The aim of the study was to determine whether human genomic DNA is also present in CB plasma in quality and quantity able to support human genetic identification by short tandem repeat analysis (STR).

The presence of extracellular DNA (EC-DNA) in CB and adult peripheral blood plasma was confirmed by HLA-DR polymerase chain reaction (PCR) and real-time PCR of Alu (SB2) genes. High concentrations were seen in CB plasma (0.131 ng/mL vs. adult 0.005 ng/mL; p < 0.001). EC-DNA increased over time while CB was stored at room temperature; this increase was associated with decreasing cell viability. STR-PCR of EC-DNA showed good signal strength and accurate allele calling so that linkage between the infant donor, the collected CB unit, and CB plasma aliquots could be established.

This study demonstrates that infant-derived EC-DNA is present in CB plasma and provides a useful tool for the unambiguous confirmation of plasma aliquot identity, as routinely used in CB banking, by the use of a sensitive and highly accurate DNA assay.