A Nucleic Acid Quality Control Strategy for Frozen Tissues from a Biobank of High-Risk Pregnancy

The preservation of placental and fetal tissues will contribute to studying the pathogenesis of high-risk pregnancy diseases. However, few studies have focused on the effects of different preservation methods and cold ischemia time (CIT) on the quality of nucleic acids. An available quality control (QC) strategy will be beneficial to evaluate these effects for high-risk pregnancy biobanks.

We established an evaluation strategy of nucleic acid QC by analyzing total RNA and genomic DNA (gDNA). Through this strategy, the effects of CIT, cryoprotectants (CPAs), and freeze/thaw cycles on the yield and integrity of placental RNA were analyzed. In addition, the effects of CIT on the yield and integrity of fetal DNA were determined.

For placental samples, there was no significant difference in RNA integrity (CIT <2 hours). After several freeze/thaw cycles, the RNA quality number values of placental samples in the CPA-free group and in the RNasin (TRIzol) group were decreased. For fetal samples, the DNA integrity of different organs (CIT <24 hours) was completely satisfactory, but it declined with the extension of CIT. Furthermore, different organs had different tolerances to cold ischemia, and the rank was as follows: skin, heart, liver, and placenta. In addition, the content of medium-length (600 bp) and long (1310 bp) fragments of gDNA were mainly reduced with the extension of CIT.

The RNA integrity of placental tissue was affected by CIT significantly. It is recommended that placenta should be cryopreserved within 2 hours (4°C) from isolation. To ensure DNA quality of fetal tissues, the samples are suggested to be frozen within 24 hours (4°C) from isolation. On the contrary, if samples have a long CIT, skin is superior to other organs in the aspect of biobanking donor's genetic information.