Researchers at Berkeley Engineering, California, successfully revived human heart tissue after it had been preserved in a subfreezing, supercooled state for 1 to 3 days. However this was only possible thanks to their new supercooling technique, isochoric freezing, which prevented any cell-damaging ice from forming even at below-freezing temperatures. This particular technique stores samples at a constant volume in a rigid isochoric chamber, using less energy than other freezing methods such as isobaric freezing.
For this study the researchers used a cardiac tissue grown from adult stem cells, using the heart-on-a-chip system that was developed in Healy’s lab in 2015. The cardiac tissue beats at a rhythm comparable to the human heart, with the systems micofluidic channels replicating the way the cells are exposed to nutrients and drugs.
The heart-on-a-chip was then submerged in a rigid chamber, filled with a common organ preservation solution at a more chilling three degrees celcius. At three different time intervals of 24 hours, 48 hours and 72 hours they removed the heart cells from the solution, and returned them to a more normal average body temperature of around 37 degrees celcius.
Their findings were promising, with examinations of the heart tissue showing that the supercooling had not effected the structural integrity of the heart tissue, beat rate or waveform, with no significant differences between each individual time interval. Additionally, they found that spontaneous beating resumed for up to 65% to 80% of the human heart muscle chips that had been supercooled for up to three days, as well as remaining responsive to isoproterenol, a medication that results in an increased heart rate.
Initial studies on this new method of supercooling have showed promising results for the preservation of human tissues and organs. Looking to the future, this tool could be extremely useful within the medical field, helping to overcome current challenges where in unfortunate circumstances, donor organs have to be discarded.
This is due to the fact that currently there is an inability to preserve them long enough to reach patients in need. The viability of a donor heart, for instance, is measured in hours, greatly limiting the number of potential recipients who could benefit from a lifesaving transplant. However, this new method of supercooling that has been recently discovered would help to combat the issue, allowing donors to be safely stored and preserved for a much longer period of time.