Biobanking of fresh-frozen human colon tissues: impact of tissue ex-vivo ischemia times and storage periods on RNA quality.

BACKGROUND: Biobanking plays an important role in translational cancer research. The impact of tissue ex-vivo ischemia time and storage period on RNA integrity is not well documented.
METHODS: Fresh-frozen colon tissues were collected in Taizhou Hospital of Zhejiang Province in China since 2004. Fifty-one colon cancer tissues with tumor cell content higher than 70 % and matched normal tissues during four storage periods (less than 15 months, 16-20 months, 21-25 months, and 26-40 months) were chosen to detect RNA quality. Fresh colon cancer tissues from 5 patients were cut into pieces and kept at room temperature or on ice for 0.5, 1, 2, and 4 h before snap freezing. RNA integrity was determined by microcapillary electrophoresis by the RNA integrity number (RIN) algorithm.
RESULTS: Sixty-seven percent of normal colon tissues and 94 % of colon cancer specimens yielded RNA with a RIN of ≥7. Matched colon cancer and normal tissues showed significant difference in RNA quality. RNA remained stable in colon cancer tissues kept at room temperature and on ice for up to 4 h, and long-term storage of banked colon specimens did not negatively influence RNA quality (RNA with RIN of ≥7 banked less than 15 months, 83 %; 16-20 months, 78 %; 21-25 months, 77 %; 26-40 months, 90 %).
CONCLUSIONS: Frozen colon tissues yield high-quality RNA in approximately 80 % of specimens. Ex-vivo ischemia times and storage periods did not adversely affect RNA quality. This study showed that standard operation protocols and the maintenance of high-quality tissue repositories were the keys to translational medicine research.