Thermodynamics of custom-designed labware and an automated cryostorage system for human reproductive cells and...

Human reproductive cells and tissues (eggs and embryos) are cryopreserved using vitrification for long-term storage at cryogenic temperatures (<-150 °C). Current equipment and processes, including data handling, are primarily manual. The central concern with any cryogenic storage system is the maintenance of specimen-level temperatures and prevention of excursions that could damage or destroy the cells and tissues. Automation and digital specimen management have recently become available to repositories storing human cells and tissues (Investigational Device (IDV)). To characterize the IDV and its components during normal operation and extreme conditions, a series of experiments were undertaken. These experiments compared the IDV labware with current industry conventional devices (CD). Vitrified single-cell mouse embryos served to determine the highest safe temperature when left in ambient conditions for the IDV labware and CD. The results show that the IDV maintains temperatures well below critical during normal storage conditions and extreme automation conditions. When exposed to ambient temperatures, the CD labware warmed significantly (P < 0.001) faster to reach -100 °C (mean ± SD;165.0 ± 4.4 s) than the IDV components (693.5 ± 33.2 s), even with a lower starting temperature. The highest safe temperature for the model embryos was determined to be -80 °C with 100% of the IDV (n= 11) and CD (n= 12) embryos developing to the expanded blastocyst stage on day 5. The mean (±SD) time for the IDV components to reach safe temperature was 1002.25 ± 82.54 s, which was significantly greater than CD (251.63 ± 12.79 s; P ≤ 0.001). The IDV can maintain a safe temperature for human reproductive cells and tissues during normal usage. In the event of mishap and exposure to ambient temperatures, components of the IDV provide a safer specimen environment than CD by extending the time cells and tissues are kept at safe temperatures before returning to a cryogenic environment. Here, we demonstrate that transient exposure of mammalian embryos, in both the IDV and CD, to temperatures above the glass transition (T_g) did not inhibit development to the expanded blastocyst stage. Further studies to determine the impact of time, and not just transient exposure to temperatures above T_g on mammalian cells and tissues for both the IDV and CD are warranted.