Cellular response of adipose derived passage-4 adult stem cells to freezing stress.

A differential scanning calorimeter technique was used to generate experimental data for volumetric shrinkage during cooling at 20 degrees C/min in adipose derived adult stem cells (ASCs) in the presence and absence of cryoprotective agents (CPAs). By fitting a model of water transport to the experimentally determined volumetric shrinkage data, the membrane permeability parameters of ASCs were obtained. For passage-4 (P4) ASCs, the reference hydraulic conductivity Lpg and the value of the apparent activation energy ELP were determined to be 1.2 X 10(-13) m3/Ns and 177.8 kJ/mole, respectively. We found that the addition of either glycerol or dimethylsulfoxide (DMSO) significantly decreased the value of the reference hydraulic conductivity Lpg(cpa) and the value of the apparent activation energy ELp(cpa) in P4 ASCs. The values of Lpg(cpa) in the presence of glycerol and DMSO were determined as 0.39 x 10(-13) and 0.50 X 109-13) m3/Ns, respectively, while the corresponding values of ELp(cpa) were 51.0 and 61.5 kJ/mole. Numerical simulations of water transport were then performed under a variety of cooling rates (5-100 degreesC/min) using the experimentally determined membrane permeability parameters. And finally, the simulation results were analyzed to predict the optimal rates of freezing P4 adipose derived cells in the presence and absence of CPAs.