Title:The Assessment of Cryopreservation Conditions for Human Umbilical Cord Stroma-Derived Mesenchymal Stem Cells towards a Potential Use for Stem Cell Banking
VOLUME: 8 ISSUE: 1
Author(s):Deniz Balci and Alp Can
Affiliation:Department of Histology and Embryology, Ankara University School of Medicine, Sihhiye, 06100 Ankara, Turkey
Keywords:Cell bank, cryopreservation, human umbilical cord stroma, mesenchymal stem cells, slow freezing, osteoblasts, cellular therapies, Dimethyl sulfoxide (DMSO).
Abstract:Human umbilical cord stroma-derived mesenchymal stem cells (hUCS-MSCs) are considered as a remarkable
and promising stem cell source to be potentially used in cellular therapies. While no graft rejection has been reported in
the recipient organism even in xeno-transplantation studies, attenuate tumor cell growth and gene transfers have been experimentally
shown. In this study, we have demonstrated a reliable, reproducible and efficient cryopreservation method of
hUCS-MSCs resulting in one of the highest cell survival rates reported so far. Conventional, computer-controlled multistep
slow freezing (MSSF), and vitrification methods were comparatively tested using cell permeable [dimethylsulfoxide
(DMSO), ethylene glycol] and impermeable [trehalose, sucrose, hydroxyethyl starch (HES), human serum albumin] cryoprotectant
agents (CPAs). After determining the ice nucleation point for each solution, latent heat evolution was suppressed
during freezing, followed by a cooling process to –40°C at 1°C/min or 0.3°C/min. The efficiency of the cryopreservation
techniques used was determined by cell viability and proliferation assays, the expression of cell surface markers,
cytoskeletal proteins and chromosome alignments. The cell survival rate was found to be highest (87±5%) by MSSF with
sucrose (0.1 M) +DMSO (10%) at 1°C/min freezing rate. In this group, no significant difference was noted before and after
the cryopreservation in cell morphology, cytokeratin, vimentin, and α-smooth muscle actin profiles and the expressions
of CD105, CD90, CD73, CD29 and HLA-DR. Second highest cell survival ratio (85±6%) was obtained in DMSO (10%)
alone at 1°C/min freezing rate. Interestingly, poor (18±15%) cell survival rates were obtained after vitrification. Cumulatively,
results indicated that MSSF favors the other freezing protocols with an addition of sucrose or DMSO alone depending
on the freezing rate used.
