The purpose of this study was to assess the availability of low-molecular-weight (low-MW) hyaluronan (HA) as a cryoprotectant for cellular cryopreservation. To clarify whether low-MW HA is cryoprotective, we evaluated the effect of HA concentration (0-5% w/w) in a cryoprotectant solution on cell membrane integrity after freeze-thaw. A test sample was created using human dermal fibroblast monolayers incubated in a culture dish for 24 h (37°C, 5% CO2). Sodium hyaluronate (MW 3×104-5×104) dissolved in medium served as the cryoprotectant solution. Samples were immersed in the solution for 2 h at 0-4°C. They were frozen at a cooling rate of 3°C/min from 4 to –80°C, cooled further to below –185°C, and then thawed. Cell membrane integrity after thawing was evaluated using a trypan blue exclusion assay. The sample and freezing procedures were repeated in subsequent experiments, while the conditions of the solution immersion with respect to the sample varied. Next, to clarify whether the cryoprotective action of HA is intra- or extracellular, we performed three experiments. The first studied the dependence of membrane integrity after freeze-thaw on preliminary incubation time (0.75-24 h at 37°C) with a sample immersed in the solution (5% w/w HA). In the second, membrane integrity of thawed samples that were initially frozen in a medium instead of solution, by removing extracellular HA following a preliminary 6-h incubation period, were evaluated. Thirdly, we investigated cellular uptake of fluorescein isothiocyanate-labeled HA (MW 105, 1% w/w) after a preliminary 6-h incubation period under fluorescent microscopy (without freeze-thaw). The results show that HA had a cryoprotective effect, and that this cryoprotective action was intracellular. Therefore, low-MW HA proves to be a promising cellular cryoprotectant.
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CELL MEMBRANE INTEGRITY;
HUMAN DERMAL FIBROBLAST MONOLAYERS;
PRELIMINARY INCUBATION TIME
Document Type: Research Article
Publication date: March 1, 2010
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CryoLetters is a bimonthly international journal for low temperature sciences, including cryobiology, cryopreservation or vitrification of cells and tissues, chemical and physical aspects of freezing and drying, and studies involving ecology of cold environments, and cold adaptation
The journal publishes original research reports, authoritative reviews, technical developments and commissioned book reviews of studies of the effects produced by low temperatures on a wide variety of scientific and technical processes, or those involving low temperature techniques in the investigation of physical, chemical, biological and ecological problems.