Cytotoxicity of Dimethyl Sulfoxide on Human Hematopoietic Stem Cells at Different Temperatures

Abstract

BACKGROUND: Dimethyl sulphoxide (DMSO, a small strongly polarized amphiphilic molecule) is used as a cryoprotector due to its possibility to easily penetrate cell membranes and to form strong H-bonds with water molecules, preventing by that arising of aqueous crystals. AIMS: We have investigated the vitality of hematopoietic stem cells after incubation at +4°C, +20°C and +37°C for 30 min, 60 min and 24 h in cryoprotective solution with 5% DMSO, and also after deep-freezing at –80°C and subsequent storage for 24 hours at –20°C and +4°C. MATERIALS AND METHODS: The vitality was evaluated counting the number of alive (uncoloured) and dead stem cells (blue coloured) using a staining test with Trypan blue dye. RESULTS: The obtained results disclose that DMSO has a cytotoxic effect which depends on the temperature and the time of cultivation: the cytotoxicity is insignificant at +4°C even for 24 hours; at +37°C about 90% cells remain vital for 1 hour, however after 24 hours they completely die out. CONCLUSION: Comparing the non-frozen cells with the deep-frozen at –80°C and subsequently defrozen cells in identical conditions (24 hours storage at +4°C) reveals that the freezing process causes an additional delayed damaging effect, which leads to death of half of the stem cells..