Cryopreserved cord blood mononuclear cells in DMSO are healthy for at least 6 hours after thawing

Abstract

Purposes: We investigated the impact of time, storage temperature, and dimethyl sulfoxide (DMSO) on the viability of HSCs, as well as on apoptotic changes in thawed CB.

Materials & methods: Thirteen units of cryopreserved CB were thawed and half of each sample was stored at room temperature (RT) and the other half at 4℃, without removing or diluting DMSO. Flow cytometry was employed to enumerate total nucleated cells (TNCs), total/viable CD34+ cells, and early/late apoptotic cells using anti-CD45, anti-CD34, and annexin V(AnV), 7-amino actinomycin D(AAD) staining, respectively.

Results: In CBs stored at 4℃ there were no significant changes in numbers of TNCs, total/viable CD34⁺ cells, or early/late apoptotic cell up to 48 h. However, the numbers of these cells declined significantly at RT. Total and viable CD34⁺ cell counts did not change for up to 6 h at RT but viable CD34+ cells decreased significantly after 24 h, and total CD34+ cell after 48 h. Early and late apoptosis tended to increase with time at RT, and numbers of viable CD34+ cells and early apoptotic cells differed significantly between RT and 4℃ after 48 h.

Conclusions: There are no significant changes of viability and apoptosis in CBs stored in DMSO at 4℃ until 48 h after thawing, while at RT, there are no significant changes of total/viable CD34+ cell counts or in the proportion of apoptotic cells for at least 6 h after thawing.

Keywords: Apoptosis; Cord blood; Cryopreservation; Dimethyl sulfoxide; Viability.