The purpose of this study was to determine the late decline in viability of fat cells over time for fat tissue stored at −15°C and −70°C after harvest from abdominal liposuction. A total of 16 females were recruited for this study. The viability of fat cell specimens was measured after freezing for 1, 3, 7, 14, 28, and 56 days. A number of viable mature adipocytes were evaluated by fluorescence microscopy after staining with fluorescein diacetate and propidium iodide. The glycerol-3-phosphate dehydrogenase activity was measured in lipoaspirates before digestion and the XTT reduction assay was performed. In addition, the XTT reduction assay was also performed on isolated lipocytes and preadipocytes.
The viability of mature adipocytes was very low for both the −15°C and −70°C samples after 1 day of freezing (13.3% ± 7.4% and 12.6% ± 6.3%, respectively). There was no statistically significant difference between the samples stored at the 2 temperatures. The GPDH activity of the lipoaspirates frozen, for 1 day, at −15°C and −70°C was 25.1% ± 10% and 28.7% ± 11%, respectively. For the XTT test, the fractional enzyme activity of the lipoaspirates frozen, for 1 day, at −15°C and −70°C was 30.0% ± 10.9% and 36.1% ± 12.3%, respectively. In addition, the adipocytes had low activity from day one: 15.4% ± 7.2% at −15°C and 11.5% ± 5.6% at −70°C. Furthermore, the preadipocytes had a low activity of 8.0% ± 6.0% at −15°C and 8.6% ± 3.8% at −70°C. At 8 weeks, there were few viable mature adipocytes and the activity of the cells was very low by XTT and GPDH testing.
The results of this study showed that the viability of adipocytes declined rapidly after frozen storage for 1 day at both −15°C and −70°C, and decreased gradually in storage after 8 weeks; at which time only approximately 5% of the fat cells were alive. These findings suggest that the present fat preservation storage techniques using a −15°C freezer or a −70°C deep freezer are both inadequate to maintain the viability of fat cells.