Method for freezing aggregates of pluripotent stem cell-derived cardiomyocytes

1. A method of freezing an aggregate of pluripotent stem cell-derived cardiomyocytes, or preparing a frozen aggregate of pluripotent stem cell-derived cardiomyocytes, comprising:

(i) immersing an aggregate of pluripotent stem cell-derived cardiomyocytes in a cryoprotective solution for 5 to 60 minutes at 2 to 24° C.; and

(ii) freezing the aggregate immersed in the cryoprotective solution at −60 to −150° C.,

wherein the aggregate has a diameter of 50 to 5000 μm;

wherein the cardiomyocytes show a viability of 80% or more 3 days after the aggregate is thawed.

2. The method of claim 1 , wherein the aggregate is immersed in the cryoprotective solution for 10 to 30 minutes.

3. The method of claim 1 , wherein the aggregate is immersed in the cryoprotective solution at 2 to 10° C.

4. The method of claim 1 , wherein the aggregate is frozen at −70 to −90° C.

5. The method of claim 1 , wherein the aggregate has a diameter of 50 to 2000 μm.

6. The method of claim 1 , wherein the pluripotent stem cell-derived cardiomyocytes express GFP-calmodulin-myosin light chain fragment-binding protein.

7. The method of claim 1 , wherein the pluripotent stem cell-derived cardiomyocytes are cells obtained by the method comprising:

(1) culturing pluripotent stem cells in a medium containing a WNT signaling activator and a PKC activator; and

(2) culturing the cells obtained by the step (1) in a medium containing a WNT signaling inhibitor, a Src inhibitor, and an EGFR inhibitor.

8. The method of claim 1 , wherein the cryoprotective solution comprises DMSO or glycerol.