Compatible solutes improve cryopreservation of human endothelial cells

Dimethyl sulfoxide (DMSO) is till now a widely used cryoprotective agent for cryopreservation of cells. Since high concentrations of DMSO have detrimental effects on cell functioning the aim of this study is to reduce the DMSO concentration by using compatible solutes (CS). These are small organic osmolytes that microorganisms synthesize and accumulate to counteract stress factors. Three CS, hydroxyectoine, ectoine and L-proline were investigated as cryoprotective agents for the cryopreservation of the human endothelial cell line HPMEC-ST1.6R. They were either supplemented to freezing or to cell culture medium. L-proline was the most effective CS, the efficiency of recultivation was improved by more than 100 percent. A combination of L-proline and ectoine in the cell culture medium resulted in an improvement by 63 percent. Our results show that L-proline and ectoine could be used as additional CPAs to improve the cryopreservation of human endothelial cells in the presence of low DMSO concentration.