Cell Culutring, Harvesting & Preservation:

Kinoshita (US 2023/0380417) discloses a storage method for HCECs or their precursor cells by culturing the cells in a medium that contains a ROCK inhibitor and in which the content of epidermal growth factor (EGF) is less than a concentraiton that will cause a transformation are harvested at a timing when any one or plurality of conditions (a)-(d) have been met and then placing the cells in a suspension state and then preserved. (a) morphology: immediately after the HCECs has shifted from a spindle fibroblast-like shape having irregular elongated projections to a tessellated shape whose major axis-minor axis ration incluidng the projections is close to 1, until immediately before boundaries between tehe cells become indistinct. (b) during a period when the expression of CD44 becomes equalto or less than half a maximum value observed aft the most recent subculturing until this expression level reaches a plateau. (c) cell density: when the cell density of the HCECs is not less than 900 cells/mm2 and not more than 2500 cells/mm2 and (d): when the number of culturing days since the most recent subculturing is not less than 4 days and not more than 14 days. The inventors discovered that if the cells are harvested immediately after a timing when the destiny of the cell population to be differentated as funcitonal human corneal endotheial cells had been decided which was also a timing when the proliferation viability was still high and then placing theis populaiton in a suspension state, then it was possible to preserve functional HCECs while maintaining a hihg survival rate.