The Effect of Glycerol as a Cryoprotective Agent in the Cryopreservation of Adipose Tissue

Background: Long-term preservation of adipose tissue is crucial for clinical applications. Researchers should consider both efficiency and biosafety when choosing a cryoprotective agent (CPA) for adipose tissue preservation. Glycerol has been applied as a nontoxic CPA for multiple tissues but not adipose tissue. We aimed to evaluate the efficacy of glycerol as a CPA for adipose tissue cryopreservation.Methods: Fresh human adipose tissues were obtained from ten patients who underwent liposuction and divided into 1 ml samples. Each sample was randomly mixed with 1 ml of CPA: 60 to 100% glycerol, 0.25 mol/L trehalose or DMSO+FBS and cryopreserved in -196 °C liquid nitrogen for one month. After thawing and elution, the tissues were immediately evaluated for activity and structural integrity in vitro. Then, 0.2 ml of each sample was transplanted subdermally to the nude mouse dorsum and harvested after one month for histological examination to assess the effect of the cryopreserved fat in transplantation.Results: After cryopreservation, the samples treated with DMSO+FBS, trehalose, and 60% and 70% glycerol had a more integrated structure than the samples in other groups. Tissues preserved with 70% glycerol had the highest tissue activity, close to that of fresh tissues. Adipose-derived stem cells (ADSC) viability, proliferation and differentiation capability were also better in 70% glycerol group. In vivo analysis showed that tissue preserved with 70% glycerol had superior retention rates and structural integrity. Compared to the DMSO+FBS and trehalose groups, the glycerol group showed lower inflammation.Conclusion: Glycerol (70%) is efficient in adipose tissue cryopreservation. Glycerol-based CPAs, which are nontoxic and show biosafety, are a promising solution for clinical tissue cryopreservation.

Cryopreservation of Cyanobacteria and Eukaryotic Microalgae Using Exopolysaccharide Extracted from a Glacier Bacterium

Exopolysaccharide (EPS) has been known to be a good cryoprotective agent for bacteria, but it has not been tested for cyanobacteria and eukaryotic microalgae. In this study, we used EPS extracted from a glacier bacterium as a cryoprotective agent for the cryopreservation of three unicellular cyanobacteria and two eukaryotic microalgae. Different concentrations of EPS (10%, 15%, and 20%) were tested, and the highest concentration (20%) of EPS yielded the best growth recovery for the algal strains we tested. We also compared EPS with 5% dimethyl sulfoxide (DMSO) and 10% glycerol for the cryopreservation recovery. The growth recovery for the microalgal strains after nine months of cryopreservation was better than 5% DMSO, a well-known cryoprotectant for microalgae. A poor recovery was recorded for all the tested strains with 10% glycerol as a cryoprotective agent. The patterns of growth recovery for most of these strains were similar after 5 days, 15 days, and 9 months of cryopreservation. Unlike common cryopreservants such as DMSO or methanol, which are hazardous materials, EPS is safe to handle. We demonstrate that the EPS from a psychrotrophic bacterium helped in the long-term cryopreservation of cyanobacteria and microalgae, and it has the potential to be used as natural cryoprotective agent for other cells.