Long-term hypothermic preservation of cardiomyocytes in vitro

Introduction: Solid organ transplantation as well as the evolving field of tissue engineering necessitate the long-term storage of cells, tissues and organs. Hypothermia is the most commonly applied method to conserve cells and organs. We set out to investigate and compare the capability of different commercially available solutions to conserve cardiomyocytes at hypothermic conditions for extended time periods.

Materials: Cardiomyocytes were isolated from neonatal Sprague Dawley rats and subjected to hypothermic storage at 4°C for up to 5 days in various storage solutions. Cellular viability and metabolic activity were assessed after 1 day of rewarming by immunofluorescent live cell staining, flow cytometry and time-lapse video microscopy with contractility analysis.

Results: After 5 days of hypothermia and 1 day of recovery, cardiomyocytes incubated in cell culture medium, St. Thomas II, HTK-Bretschneider, ChillProtecPlus® and CoolStar® did not show any spontaneous contraction and exhibited viability of 2%, 4%, 6%, 11% and 13%, respectively. In contrast, cells stored in Hypohtermosol-FRS® and ChillProtec® exhibited spontaneous synchronous contraction and showed viability rates of 74% and 81%, respectively.

Discussion: Cardiomyocytes are generally known to have a relatively short ischemia time, thus limiting the time span for heart transplantation and storage of tissue-engineered myocardial constructs. Here, we demonstrate successful preservation of cardiomyocytes for up to 5 days at hypothermia and show that the storage solution has a great impact on cell survival.