These findings are supplemented by the results of a study of 153 adrenal tissue samples (normal adrenal gland and various adrenal tumor tissues) stored at -80°C for up to 27 years. Samples exhibited an ‘‘acceptable’’ or ‘‘excellent’’ tissue morphology, with no correlation between the quality of RNA and time of storage. Similarly, RNA quality did not degrade in liver tissue samples after seven years at -80°C and -150°C; neither in brain autopsy tissue samples stored at -70°C for 15 years.
Measurement values after 12 years of storage did not differ from baseline values for more than half of analytes. Fifteen analytes exhibited high correlation between baseline and 12-year values, while the recovery rate of analytes with weak correlation did not drop under 70%.
DNA and miRNA – A study of serum samples from the Janus Serumbank revealed that even after 40 years, serum samples stored at -25°C are viable for whole-genome sequencing and SNP calling, as well as qPCR and small RNA sequencing, with 650 unique miRNAs detected, on average, in each sample.
Serum levels of other analytes, however, may be substantially altered over time; the study revealed a 26.4% increase in potassium levels and a 59.4% decrease in bilirubin levels after storage for 25 years.
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